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Friday, 19 April 2024

FH - followers, pistons and barrels

 With the little QR50 out of the way and the FH back on the bench, we can get on with the build. The barrel has been painted for a while, the bottom end is in the bike, there's no primary or timing side and no pistons. Off we go:

First step is to fit a circlip to each piston; the gudgeon pins come out with some mild warming and are refitted just as easily. As you can see, I've put a large rag under the pistons as I don't want a circlip in the crankcase at this stage, and the pins go back in and the circlips go on without any drama.


Next, we can refit the reground cam followers. I've ground the radius back into these such that they now have no wear grooves. The retaining screws and pins (with the missing ball) have been refitted:


Next, we fit the ring compressors - these are just strips of tin held in place with ty-wraps. These were cut for the SQ4 and are not really long enough for these larger pistons. You'll see the wood - these are to prevent the pistons rocking about when the barrel goes on.


Before the wood strips go in, we squirt oil all over both small ends. 

The wood strips are wide enough to completely stabilise the pistons while we put the barrel on, but first we use Threebond 1215 to apply the base gasket to the barrel, to keep it out the way. This wasn't ideal as I was forever wiping gasket goo off my gloves -  it would have been better to have the gasket, goo down, on the crankcase and apply the goo to the upper side after the barrel was over the rings.


After a lot of fiddling, swearing and anguish the barrel went down. The compression rings were not too bad but the three piece oil control rings, with their thin 'rails' were a pain to get in as they popped out of the compressors before they were caught by the barrel.

They went in eventually, and we can retain the barrels with four nuts.



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