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 xlforum.net 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 xlforum.net 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.