2017/09/10 – Recovering from the interior ride (more greasy fingers)

Yeah, I haven’t written up the interior ride yet, partly because my head is wrapped up in fixing the bike. I lost the rear brake (master wouldn’t hold pressure), that was easily fixed by swapping in the master from the kick-start bike… but the motor is more of a problem…

Cylinder head, nearly ready for removal. (Starting to think I’ve seen this view entirely too often.)

It was sounding “off”, sort of a “chuff”-ing noise (at idle, ran fine at speed), and harder to start. Compression test showed it down to about 90psi instead of 120 when I put it together last time. (Those are low, there is an auto-decompression system.)

It _might_ have just been dirt. I don’t have enough knowledge to know what a normal build up would be, but this seems excessive for six months:

Will pull and clean the piston/rings, but the cylinder _seems_ fine.

Fortunately the machine shop finished the valve job on my spare cylinder head. Wish I had a new set of rings on hand though (and may have to wait for some new shims).

I _did_ manage to get the rings free of the old/original piston. If you remember, that was what caused my grief during the spring rebuild when I tried to swap engines, and then (after learning that the e-start conversion was hard) just swapped cams and the carb. On re-assembly the bike wouldn’t start and I was pulling my hair out. Turns out the rings has suddenly stuck to the piston and there was basically no compression (35 psi, 50+ with oil squirted into the cylinder. So I swapped in the cylinder and piston from the kick-start motor… and just finally got the rings out of the old piston.

OK. Definitely looks like the rings were the main cause of the loss of compression, and I’m going to blame that on dirt, although perhaps they are just getting tired and need to be replaced. Top ring was moving a bit (e.g. one side), 2nd ring seemed to simply be stuck.

Sticking rings.