Monthly Archives: January 2012

Working on the conversion – loctite and #@^&% rubber gaskets


Yeah some more time to do stuff.


Also I got loctite and a gasket for between the air cleaner back plate and the conversion ring to the Mikuni carb.



So the air cleaner had to come off again.



Because these bolts needed loctite. I received some very good advise on When these bolts ever come loose they end up in the carb and then.. in the cylinders. Better to locktite them really good. :)



I also put the new gasket in place.



Loctite on the bolts now. One the bolts wouldn’t come off. The metal ring that’s in the backplate started turning so I couldn’t get is out.

So I put some loctite in the hole where the bolt goes.



Nice new gasket in place.



I put loctite on the breather bolts too.



And everything loctited back in place.



Aircleaner finished.



Slowly I’m getting there now. :)

So far I have not put the rocker covers back on. There is a reason for this. I wanted to put oil in the rockerboxes before I started the engine.  Since I took all the oil out there’s no oil in the engine now. In a minute I will put oil back in the oiltank. At the time I start the engine however there is no oil in the engine. This has to be pumped through it by the oil pump. It will take a while before oil is pumped around everywhere. Especially to the rockerbox it takes a while. The oil has to be pumped through the pushrods up there. So I wanted to pour some oil there as short as possible before I start the engine. Well this is about as late as it gets.




This is the rubber gasket that comes between the rockerbox and the inner rocker cover.


It seemed just a tiny bit too big somehow. When it was ok at one side


this would happen at the other side.


The inner rocker cover.


Here I put the inner rocker cover on. It looked like it was ok to me.



Ok now I pour some oil in the rocker cover and near the pushrods.



The second gasket, the one that comes between the inner and outer rocker cover was even harder to put in place. The cover has to be pushed between the ridges. And it would not stay in at all. This was a mayor pain the ass that I spend about an hour on. There was no way the gasket stayed in place and I could put the outer rocker cover on. I ended up putting oil on the gasket to see if it would stick a bit. That worked a little bit. Then I decided to lie the gasket on the inner cover and try to push the gasket in place while putting the outer rockercover on.


I cleaned the outer cover with break cleaner first.


Then I put it on pushing the gasket in place with my fingers and in some cases with a screwdriver. I thought I pulled it off.



But this is what I found after bolting the cover down.



And there was more. I got quite frustrated here. This was one of the most annoying things so far.



Then I thought of something. I have a grease gun in the shop. I applied grease on the inner cover and just glued the gasket down with that. HA !!


That worked. I forgot to take picture for a while but the is how it ended up.



Look ! No gasket sticking out on the rear cylinder.



Or on the front one.



With the cylinders in place some wiring had to be connected again.





The VOES connector.





The wiring harness was still loose.



Time to tie it down with tie wraps.



That’s better. Cleared the wiring from the cylinder.



And the battery is full too !

Unfortunately I had to leave now for the holiday of a friend.

Working on the conversion – Day 12 – Some more ignition, coil and cables


Next thing to do is to put the cables from the ignition in the Deutz connector to hook it up to the wiring harness.


The instruction that came with the ignition explained wich wire goes where.

To my suprise there were only 4 wires instead of the 5 that came from the original one. I missed the black on on this. Acoording to the workplace manual the black wire is the ground. Hmmm….

Ah.. that explains it :)

Ok on with the wires and the connector then.

The wires have to go in the proper hole in this rubbery piece. This then slides in the connector.

The rubber in the connector here. The brown and blue wire don’t go in this connector but in a seperate connector that came with the ignition.


The green locking piece keeps the wires in place.


For the empty hole there was a white stud like the one already covering the other unused hole.



The second connector works just like the other one it only has 2 holes.



I’ve put some tape on the wires to add some protection.



The 2 wire connector clicks into this one wich has also 2 wires, a blue and a brown one. They’re protected by a shell. This wire has to be routed from under the engine to the coil. The blue wire is the wire for the second coil. The brown one can be used for a tach. I don’t have one but I’ll keep it in case I ever get one.

Some shot of how I put the wire on the bike. I start under the engine and route the wire behind the primary case.


Up behind the battery holder.




And there is is.




I decided to keep it under the frame and guide it along the wiring harness under the tie wraps.


All the way to the front cylinder where the coil comes.



I used some tie wraps to keep the Deutsch connectors in place.





And I cut the ends.



Now I put the coil in place. The bracket is locked later by the bolt that also keeps the tank to the frame.


At this time I remembered to put the battery on a loader. When I will start the bike later (hopefully) the starter engine has to have enought power to turn the cylinders. This will be harder after the conversion since the compression is higher now. A full battery can help then.




So here another shot of the coil and the cables that have to be connected to it. The black ends connected to the original coil have to be cut and stripped. The brown wire also has to be cut and stripped. The brown one for the tach I will tuck in the protective shielding for later use.


For cutting and stripping I had this tool. It will also help with crimping the connectors on.



Cutting the first black connector.


Eh yeah. With the ignition came this bag of stuff.


In the bag were three of these. The bits have to be put on the wires.



Here I cut the blue wire to proper length and stripped the end.


Here the connector is in place. It slides over the wire and has to be crimped on with the wire stripper/crimping tool. I’ve tucked the brown wire here. Basically I put the end of it back into the shielding and pushed it almost all the way in. This way I can alway pull it back out if I ever need it.




Stripped both other wires here. Also I cut off the shield to make room for the red connectors.


This is how you crimp the connector on. I knew I made a shot of this :)



On the coils ends there are 3 rings. The one next to the nut is of the self locking type.


I put the connector between the 2 normal rings. This made sense for me. Don’t know why.



And there. The coil with the 3 wires.


Working on the conversion – Day 11 – carb, ignition and coil

I’m a bit behind with writing about what I did so I’ll try to catch up today.

This day I went on with the carburetor and ignition module.


After all the pissing about with the VOES and in particular bending it’s metal bracket there is now room for the carb. I tried putting the carb in the rubber sleeve but that wouldn’t go in so I put some grease on the sleeve.



This is the side that had to go in.

Here the carb is in place. In this pic it shows that the VOES is bend upwards and almost touches the carb. Also the vacuum hose between the VOES and the carb is in bend but in almost a circle. It’s a bit tight but it’s in place.


Here there’s 2 hoses coming from the back of the motor mount here. The one on the left is the gasline that comes from the carb and the right one is the vacuum hose that comes from the VOES. The vacuum hose will be connected to the tank later. It’s needed to prevent a vacuum in the tank that would make no fuel coming out of it.

Also the choke cable is in place here.

I’m not very happy with the fit of the choke cable here. It’s a bit to long to make it fit so it has to be in a bend to make it fit.

I looked in the carb holding the throttle open to see how it fit. There’s a few millimeters of room left between the carb and the manifold. Pushing the carb further in was not possible but since the carb is well inside the sleeve I think it ok like this.

Next are the breather bolts. They had some stuff in the threads wich I think was loctite. I used breakcleaner and this metal thingy to  clean them.

Now it’s time to put the air cleaner on.

Here I’m pushing the air cleaner and the conversion ring that’s on it onto the carb. It does slide a bit further but a gap remains between the head and the backplate. I think that because the carb doesn’t slide all the way in the sleeve and the conversion ring make the whole carb stick out more than the cv carb did. The backplate is from plastic so it can bend a bit. So I went on to see how things would look when installed.

The backplate put in place by the breather bolts.

The backplate in place. As can be seen heren the backplate bend a bit. Between the backplate and the head there are 2 rings. I’m thinking of getting 2 extra actually but forget them when I was at my Indie but I will get them later.

Now the 2 breather tubes are in place. They will put the oil blowby into the carb.

And the aircleaner is in place.


The foam from the aircleaner seems to fill the gap that’s there because of the bend backplate so maybe it will work ok but I’m not overly exited about this.


Next thing is the ignition module. I’ve bought this Daytona Twin Tec 1005S EX because it has some nice features. Single or dual fire, multi spark, 7 different advance curves and a configurable rev limiter. With a $100 cable that I do not have (yet) it’s even possible to create custom maps on a computer and load those up to the module.

Single fire means that instead of both spark plugs fire at the same time only the cylinder that it in the compression stroke will fire when it’s ready. A special single fire coil is needed for this and I got one with the kit.

When multispark  is switched on the module will create a few sparks close after each other when the motor is started of driving slowly, effectively creating a long spark effect. This will create a better burning of the gas and fuel mixture in the cylinder.

Switching between the different settings can be done by the 4 wheels.

To install the module the wires have to be fed through a hole in the engine case to the bottom of the engine. I put some tape around the wires here to make the wires stay together and prevent the tubing from getting stuck of damaging.


Putting the cable in the hole.


Here the cable comes out at the bottom.

Now the module is in place with the hose protecting the wires. I took off the tape so I can put the Deutsch connector on.

This is the other stuff that came with the ignition. The single fire coil, some wires and connectors. On the right the old coil with the bracket it’s attached to the bike with.

Taking the bracket of the original dual fire coil.

And the coil joins the other stuff that came off my bike.

And the new dual fire coil has a bracket. The new coil has 3 connectors instead of the 2 from the old one. This is because there are actually 2 coils inside the housing. Both have a + and they share the -.


Working on the conversion – Day ehhm 10 – Put stud in head before assembly

I’ve Learned a lesson today.

 I didn’t have much time the last week to do anything. So yesterday I had a few hours and went at it. Slowly I’m getting there now. Only a few more things to do.
Put the front motormount back on, install the carb and ignition. After that I can put the tank on and try to start my baby up !
The engine is kept to the frame by a few motormounts. One of them is put to the front cylinder head by 2 screws. On the sportster the screws are 3/8″ but on a Thunderstorm head the bolts are 7/16″ so a bit bigger.
To make the Thunderstorm head and the mount work together the  2 holes in the motormount have to be drilled a little bigger to 7/16″.
Here a picture with the 2 holes in the front of the head and the motormount behind it. This is not an old picture. You’ll see why in a minute.
Here my friend is drilling the mount.
I have 2 of these bolts to go into the head. Here i’m putting the one for the left side of the head together.
WTF ??? That doesn’t fit between the frame and the head !
I looked on pictures of my bike when I was taking it apart. Turns out that in this hole there was a stud, not a bolt.
Sigh…. This is… pretty dumb..
I gave it some thought, then some curses and then..  came to the conclusion that the head had to come off again and a stud had to come where the bolt couldn’t go.
So I took of the manifold, mid motormount, rockerbox and cylinder head, hence the first picture.  While taking off the head I noticed that one of the pushrod cover seals had twisted a bit when I put on the head before. That would most likely have caused an oil leak later on. So I guess I had some good and bad luck at the same time discovering this. :-)
So Mark went off to the Indie’s shop and bought a longer version of the first 7/16″ bolt.
And dear friend Mr Anglegrinder made the bolt into a stud.
2 nuts twisted tight to each other helped out in making it a bit of a screw again so it could be screwed into the head.
Et voila, a head with a stud.
This is much better.
Now the motormount fits.
On the other side of the head a bolt can be used.
This all took a whole afternoon and early evening. Driving back and forth through town to the Indie for a screw took most of the time on this day. Anyway time to leave for something to eat.
So for all viewers that are planning a conversion of head swap; remember to put the stud in before you install the head ok ?
And read this, twice (or three times even) :

Working on the conversion – Day 9 – Maybe screwed up the VOES and made gas cables

My last post ended when I changed the orientation of the VOES. This should have to make the Mikuni fit in the manifold.

Well it didn’t with me.





The vacuum hose from the VOES to the carb only fits when the hose is orientated to the left like here. But the VOES is still in the way. It sticks out too much preventing the Mikuni from sliding into the manifold.


Then I thought of bending the metal bracket a bit. Making both 90 degree angles smaller would make the VOES stick out less. Just enough to make the carb fit.

Unfortunately I decided to pry the retainer ring from the VOES to separate it from the bracket so I could bend the metal easier.



And then this happened. I broke the VOES apart. It turns out the ring can not be pried off. All I did was pull it apart.

I did put it back together and bent the bracket with the VOES in. I’m not sure if the VOES is broken now though.

After some thinking I ordered a new one to be sure.


Here I’ve put the VOES back. The carb does fit now but I forgot to make a picture of it I just found out.

Next thing then.

The CV carburetor takes the gas cables from the front side of the bike. With the Mikuni this is different.



As can be seen here on a picture (I took before the VOES was in place) the gas cables have to come from the left side of the bike. So the cables have to be routed from the gashandle along the front of the bike to the left and then back to the right side under the tank.

My Indie didn’t have gas cables in that length in stock so I bought some that I could fit myself.


I did a test fit to see how long the cables have to be. They have to be routed like this.



The outer cables have to be about 10 cm longer.




The cables come with these parts to make it complete. An elbow, outer and inner cable and two small notches, one for each end to the cable.



To install the cable the handle has to come loose by first taking out this screw.



And then this one.



Then the notch goes into the handle. The outer cable and elbow have to be off here.



Now the elbow and outer cable can be put on the inner cable. I lubed the inner cable with silicone spray first. Silicone is a good lubricant and it repels water too.



And the cable is done.

Sorry for the poor quality of some of the pictures. I didn’t notice that they weren’t very good only when I came home.


Working on the conversion – Day 8 – Mikuni HRS 42


Over the year before I ordered all the parts I have been reading a lot about 1250 conversions and in my mind I was making a list of parts that I wanted to have. One of them was a Mikuni HSR 42 carberator.

 The sportster originally comes with a CV carburetor. It’s a fine carb according to most sportster riders and I guess they’re right. There are a few minor things I don’t like though. I think it reacts a bit slow to throttle response. Sometimes I jank on the throttle and it takes 1-2 seconds before the engine reacts by revving up. Maybe it takes less time but it does feel like 1-2 seconds to me.

Over the past year I read quit a lot about the Mikuni carburetor. Apparently they react instantly to the throttle.  Another advantage seems to be that jets can be changed without taking the whole carb off the bike like it is necessary with the CV. So my curiosity was awakened and I added one to my order at NRHS.

Today was the first time I looked at it closely and did some stuff on it in order to install it.
The first thing Dr. Mark had to do was to transplant the enrichener cable from the CV carb to the Mikuni.
This is the CV with the choke cable still attached. It is the cable coming from the right side of the carb. The cable is screwed into the CV by a plastic screw.
The cable is off the CV now.
The choke cable has to go in the place where the black plastic starter nut is on the Mikuni. The spring and plunger that are on the cable now are to be replaced by similar parts that come with the Mikuni. Now the black starter nut has to come off.
Turning the starter nut here.
This is 5 minutes later when I found the nut and spring again that popped away when the nut came loose. The plunger was still in the carb. If you’re ever going to do this put your hand before the nut in order to catch the spring.
The spring and plunger have to be put on the CV choke cable.
CV choke cable with Mikuni spring and plunger. The black nut that came off the Mikuni only came to keep the spring and plunger in the card. It is not to be used.
With the Mikuni came a bag with screws. The instruction sheet said they were there to replace the allenhead screws that were in the carb. I decided to replace the allenheads with the philips. Reason is that I do have a philips screwdriver in my toolroll when I go out riding and I don’t carry the tiny size allenwrench with me.
Halfway replacing the bolts of the bottom of the carb.
After I changed out the screws I thought that it might be nice for the viewers to have a look of the inside where the jets are so I opend the carb up and took some pics.
Here the bottom is off. The fuel will be in here.
The jets.
The carb from the bottom side. In front of the carb are the extra jets that came with it, 2 pilot jets size 25 and 30, and 2 mains 160 and 165.
For now I left the 30 and 165 in it. This is the richest jetting. I read that during the break in of the engine it’s dangerous to have a mixture of air and gas that is too lean. It will make the engine run hotter than with a rich jetting. Heat is something to be kept at a minimum during the break in. To  be sure about the jetting I asked around at which you can read here :
and I emailed Dan at NRHS who also recommended me to use the 30 and 165. Well actually Dan and Rico at xlforum recommended 27.5 Pilot and a 162.5 main but I don’t have those.
Here I’m taking the bolts on the top of the carb off.
Here I take a peek into the carb now the lid is off. The black screw inside the carb holds a retainer that in its turn holds the needle in place. The needle is difficult to see but it’s the light half round thingie left of the retainer screw. I suppose that replacing of taking out  a needle would involve loosing the retainerscrew and take the needle out with a pair of pliers.
Here another shot of the needle and retainer.
Here the carb is closed again and the enrichener cable is in place.
Next I had to fit the Screaming Eagle aircleaner of the CV to the Mikuni.
The Mikuni comes with an adapter kit to make it fit to a standard Sportster aircleaner.
The donor and the new owner.
The airfilter backplate comes off after removing 3 allenhead screws.
And it’s ready to be transplanted.
This is the adapter. The rubber ring slides over the intake of the Mikuni while the metal ring is screwed to the backplate of the aircleaner.
Here it’s screwed to the backplate. I’ve reused the gasket from the CV here. I know.. i know.. I’ll get a new one 😉
This is the backplate with the adapter behind it so the intake is a bit smaller than with the CV.
After this I put the gas line to the carb.
Next is the VOES.
In the instructions it said to change the orientation of the VOES. Normally the cable to the carb is oriented to the left. It has to be changed the below. Here the VOES is still screwed to the motor mount by the way.
In order to change the orientation
this retaining ring has to come loose a bit.
I’m using a crewdriver for that here.
Now it looks like this, pointing downwards instead of to the left. After I put the motor mount back to the bike and tried to put the VOES back it turned out not to fit like that.
Here I changed the orientation around because the VOES line wouldn’t fit otherwise.
Now I ran into trouble because the Mikuni wouldn’t fit. But more about that later.

Working on the conversion – Day 7 – Rockerbox, manifold and oil filter



I had an hour or 2 today so I went on with putting my 1250 conversion together. Next was the rear rockerbox.



First I cleaned the gasket with some break cleaner.



The rockerbox had some oil and dust on it.



So I cleaned the rockerbox with break cleaner too. In particular the bits where gaskets or seals are going to be I cleaned very thoroughly.



The rear rockerbox is a bit of a pain to get in place. Taking out the intake pushrod makes it a lot easier. It can be put back in when the rockerbox is in place but not bolted on.

This is starting to look like an engine again, isn’t it :)



Next the manifold. This is the manifold as it came off my bike when it still was an 883. The rubber seals were damaged a bit and stuck to the manifold.



The heads came without these two bolts so I took them of of my old 883 heads.




Here the manifold all cleaned and with new rubber seals.



I noticed these flanges had a letter on them. One had an ‘r’ and the other a ‘f’. I assumed that meant ‘front’ and ‘rear’.



Apparently it doesn’t. Because this what happened when I tried to fit the ‘f’ to the front head. Didn’t fit. Now I do have Thunderstorm heads so maybe they have a different fit or something. Luckily the ‘f’ did fit nicely on the rear cylinder and the ‘r’ on the front.



I put together some bits out of my toolbox to be able to put some force on the bolts here. Otherwise they can’t be reached properly. I know there’s a special tool that can be bought but “We don’t need no stinkin special tools” :)

Keeping the manifold, flanges and seals together and have them properly aligned when fastening the bolts under an angle was a bit of a pain but still doable.



Here the manifold is in place ! :)




Next my bike had no oil filter yet. I bought 2 cheap ones earlier together with a 5 liter can of dino oil for the break in. I put some oil on the black ring first.



Then I put it here in the very clean spot that remained after I took the filter off earlier using the cut up bottle.





Here the filter is in place. The special oil filter tool I bought to get filters off and on more easy didn’t fit on this filter.

That’s probably the reason it was on sale.

That was it for this time. I didn’t want to but I had to go :-/




Working on the conversion – Day 6 – Almost broke stuff


I was a bit behind with posting the work I did so I’m posting now what I did on the 31th of December. Only did a little bit of work this day. My time was used up by driving to my indie twice and I had to leave early to do shoppings for New Year :-)

After some thinking about the squishband and valve to piston clearance tests I decided that both were ok. The squishband looked alright the first time we did the clay tests and in my opinion the second, valve to piston test only, gave me confidence that things are like they should be. Also the smoothness of the engine when I was turning the rearwheel was reassuring.

So today I wanted to install the cylinders and heads for the last time and continue the buildup. Still I had to arrange for the adapter for the 3/8″ torquewrench to the 1/2″  socket. I went to a toolshop near my workplace that turned out to be closed due to it being both saturday and New Year’s eve. Then I called my indie, Michel from in Rotterdam, up and asked if he sold one. He didn’t but he told me I could borrow one from him for the day ! How’s that for customer service ?! :)

I’ve said before that this guy is worth his weight in gold and this proves it again.



So I jumped in my car drove 20 minutes to his shop and got this adapter. When I left he said I could take my time and return it next week also if I needed it longer.



Wrench and the adapter that made it usable. At this point I should have honored the 1 page manual that came with it a read, but I didn’t.


New Year’s eve was a very cold day. So have to mention something. I’m very happy with this little heater :) Helped my hands stay functional through a very cold day in my workshop.

Ok back to work.


On the NRHS website they state that the heads must be torqued in steps from 9 ft-lbs, 14 ft-lbs, 22 ft-lbs, 35 ft-lbs,  42 ft-lbs. Also they advise to oil the head bolts.

So I put some oil in the screw, set the torque wrench to 9 ft-lbs and started wrenching in the pattern that’s mentioned in an earlier post.

The torque wrench I had been working with a while ago was one that when the set torque was reached it started rattling and didn’t allow to tighten stuff up more. Strange thing.. this wrench didn’t do that. I kept turning it until what I knew for sure was more than 9 ft-lbs but no rattle. To make sure all bolts were tightened the same I did so on the other screws but no rattle. I started thinking the the wrench was broken. Since the wrench’s lowest setting was actually 10 ft-lbs I set it to 14 now. Maybe this would cause the rattle.


At 14 no rattle. Then I set the wrench to 22, 35 and 42 and went over all the screws. Still no rattle. When I set it to 42 and started turning I reached a point that was very much near the force it took to unscrew the bolt when I was taking the cylinders apart.

Time to read the instruction sheet. Turns out this wrench only gives a very modest click when torque has been reached ! So I pulled at 42 and suddenly heard the click. It was so gentle that I hadn’t noticed it before. Pfewwww Luckily I stopped and didn’t pull through. This could have caused serious damage had I not been so carefull.



After the required torque has been reached the Workplace manual tells to give the screw an extra quarter turn.






Drip some oil into the pushrod tubes to lube the tappets and maybe get some oil on the cams. I decided not to open the camcase again to put lube on the cam lobes although some people recommended that. This is second best I thought 😉



The pushrods put in.



Bolting the rocker box on. First the 4 black bolts.



Nice shot of the beehive springs. This shot is here for no particular reason. I just thought it looked nice.



Next are the 3 metal colored bolts. I kept these in a piece of cardboard to make sure to put everything back in the right place.



Put some oil on them.



Bolt them down.



And then I had to leave. The misses started calling that I had to come home for New Year. I went to my indie to return the adapter and went home to get pissed for New Year… ehm well….



Working on the conversion – Day 5 – Cylinders, squishband and valve to piston clearance


This day I encountered some difficulties. And learned some things.

My dad came over to help putting on the cylinder and piston assemblies. He also likes to see me and do stuff like this together and so do I. :-)

This job can’t be done alone I think. NRHS assembled the pistons in the cylinders for me so I don’t have to gap and install the cylinder rings and pistons. This is a bit of a tricky job and requires some tools, a ring compressor for example, I don’t have so I was happy NRHS has this service. So the cylinders and pistons are assembled and installed in one piece.

Also I bought aluminium pushrod bases made by NRHS. The original bases are a bit flimsy and apparently prone to oil leaks. Since the NRHS pushrod bases look really nice too I ordered a pair of them. I actually got them from NRHS for free. The Thunderstorm heads I wanted to have were on back order for 2-3 months so Dan gave the pushrod  bases to me for the waiting time. Again, very nice from Dan.


Her the gastkets are in place. The orginal pushrod bases are kept in place by an allen head nut and the small nobs that stick out right above the tappet holes. The new pushrod bases wouldn’t fit with these still in place so I took one out to see what’s in the holes. Turnes out there’s nothing there so I took out all 4 nobs. This can be done with a pair of pliers.



No more nobs here.

I decided to put the cylinders on now and install the pushrod bases and tubes later when the cylinder heads are put in place.



Here the cylinders and piston are in position. I’ve already pushed the wristpin in when I took this picture. It fits exactly really since I didn’t use lube and the wristpin slid right in but was still tight.

In the mean I’ve had some replies on my on thread from people that use more assembly lube than I did on places like the cam lobes, wristpin, pushrods ends and such. I think they are right in doing so. It never hurts to have some extra lubrication.

I have written down some learned lessons that I will post in a while by the way. Using more lube is one of them. :-)



Here the circlip is in the hole but not fully seated. It has to be seated fully because otherwise it will get out and end up between your cylinder and piston and cause damage to your investment. Notice the bore is still filled up with a rag to prevent flying circlips from entering the engine.



Here the circlip is seated properly.



Now the rag is taken out and the cylinder can be pushed over the piston into the bore.



Here the cylinder is pushed down.



This cylinder has to be kept in place while working on the other cylinder. The two shortest screws can be used to do this. I will be using plastic tube to do this as can be seen in the next shot. I’ve been told it is not forbidden to put some lube in the screws and on the bolts 😉


The rear cylinder is now kept in place by the short screws and some plastic tube. I’ve turned the engine a bit to make the connecting rod stand up vertically.



Wristpin and circlip in place, rag taken out. Pushing the cylinder down will push will rotate the flywheel a bit and push up the already installed pinston. This is the reason we’ve used plastic tubing and the screws to keep the other cylinder in place.


Both in place :-)



Since now the heads can be installed on the cylinders it’s a good time to put the new pushrod covers, it’s gaskets and pushrod bases together. The pushrod bases come with 2 allenhead bolts and rubber gaskets each.

I don’t have radical cams and therefore consider this setup on the safe side of valve to piston contact risks and I expect the squishband to be in order for a well known combination of NHRS cyclinders and Thunderstorm heads.  But knowing how to measure both and also being curious I decided to check the squishband and the valve to piston clearances anyway. I prefer being safe over being sorry and also wanted to do it myself just for the learning experience.

Squishband is the space between the piston and the edge around the combustion chamber in the head. This should be around .030 – .035 inch, or around 0.7 mm for metric people like me. This can be measured using soldering wire. Usually it’s done by taping a few bits of wire on the outside of the head pointing outwards, put the heads on and turn the engine through TDC once. The soldering wire will be flattened. The thickness of the wire will give you the squish clearance. The heads must be taken off again for this of course.

Piston to valve clearance will show if the distance between the piston and the valves is sufficient. Especially at the end of the exhaust stroke where the piston reaches TDC the exhaust will be opened a bit and maybe also the intake valve. Proper clearance would be about .060 or 1.5 mm for metrics.

When I got to a toolshop for some soldering wire all they had was wire that had only 50% tin and some other harder metal in it. I couldn’t remember anything about about percentages of tin being necessary but started worrying about the soldering wire maybe being too hard. The head are made from aluminium, not exactly the hardest metal around, and I got afraid that if the soldering wire was too hard it might damage the head. Then I thought of the clay I was going to buy for the valve pockets anyway and decided to use that also for checking the squishband.



We cut the rivets off the gaskets to make sure the gaskets fit between the head and cylinder.



Here the clay is visible. Some round bits on the edges of the piston to measure the squish and, i know now, *too much* in the valve pockets.



Here we’re putting the front head on.



Putting on the rear head. The wire that comes off the head goes to a heat sensor that’s used on Buell motorcycles. On my Sportster it is not used and therefore I cut it.



Cut the wire from the temp sensor here.



Before heads could be torqued down we installed the NRHS pushrod bases. I reeeaaally like them :-)


The pushrods can be put in the tubes. Longest one on the exhaust side.



Next is the rockerbox.



Cleaned thoroughly with breakcleaner to make the gasket seal good.



Some lube on the bolts.



Left of the rear pushrodbase there’s a bolt that holds a metal thing that in it’s place holds the two oil lines in place. This bolt popped off and was nowhere to be found. I took the front sprocket cover off to see if it was there. Never found the bolt again.


At this point I forgot to make pictures until we took the cylinder heads off.

We bolted the heads down in the order that was specified in the Workplace manual. I think I already wrote down earlier in the part were I was taking the stuff off what the proper order was. I didn’t to it using my torque wrench. The torque wrench I bought online turned out to have a 3/8″ connector and the 12 star socket I bought earlier had a 1/2″ intake. So I needed to get an adapter but didn’t want to go and look for it in shops while my father was here to help me.

Now it was time for the rear wheel to be turned. And it wouldn’t. Well a bit and then it got stuck. I pulled pretty hard and it wouldn’t move. My impression was that the cylinder got stuck against something. We were wondering what could be wrong and took a break for a coffee discussing what could be the problem.

After the coffee we decided to give it another carefull try and this time the wheel could be turned ! That’s odd… We forgot about measuring the clearances and got talking and thinking and turning the rear wheel a few more times. It turned smooth now just like you would expect a bike like the Sportster to turn when in 5th gear with the plugs out.

Suddenly I thought it might have been the tappets. Most likely they were fully extended when I put everything together and bolted the head down. We started turning, or trying to do that, right after. Some reading later the NRHS website and and  also learned that after bolting the head down the tappets need a few minutes to bleed down before the rearwheel is to be turned over.

Now I also know that I’ve put to much clay in the valve pockets. Actually I stuffed them with it. This sure didn’t help either.

All in all the measurements we were trying to make were not very trustworthy we decided. The main reason for this is the fact that we turned the backwheel a few times instead of just one. Also we were using too much clay. I also think the clay we were using was a bit too sticky because it stuck to my fingers badly and we found considerable bits clay on the valves.


This is what the clay in the front cylinder looked like. The bit that were to measure the squishband looked good I thought but the pieces in the valves are partially gone and stuck to the valves and in the other pocket there’s a lot pushed aside.



The rear cylinder looked better in my opinion.



This is the front head with clay stuck to the valves.

We did measure the squishband pieces and they were ok. They we a bit under 1 mm so ok we thought.

So what to do now ? Do another test ? Or maybe one only for the valve to piston clearance ? The rear cylinder looked ok’ish and after the coffeebrake the engine turned over nicely so it seemed ok. We decided to to a second test only for the valve to piston clearance and use less clay.

So we cleaned up the piston, head and valves, put clay in the valvepockets put against it’s wall instead of filling the whole pocket with it.


Here’s the result of 1 cylinder. The amount of clay is ok on the left side. The clay on the other side stuck to the valve again. This really convinced me that the clay was too sticky.



Other cylinder same thing.

It was already getting really late so we decided to call it a day and think things over a bit.