First, with the cam cover removed ...
And second with the head off, revealing a nice dirty piston.
Golly, that is a big one, as it were. It's bigger than the last piston I looked in the face, which was on my 2.25 petrol Land Rover. And I thought they were big. The engine I fettled before that was a Rover 3.5 V8 in my trialler, and they were tiny in comparison.
On the advice of a complete stranger (and Internet acquaintance, this time), I will need a lot of heat to shift the rusty bits, so I have taken out the valves and set the workshop out ready for a session of heat'n'hammer later this week. I will also lap the valves in, as there is evidence that they aren't sealing too well, and therefore harming the compression. I haven't lapped valves for a long time. Should be fun.
The last Yamaha I had in pieces (= the last Yamaha I had 30+ years ago) was a 2 stroke twin!
ReplyDeleteStrangely I recently found the "old" pistons removed from it with my antique collection of Mecano.
It never ran properly and then someone stole it - good riddance I said!
If you'd put the pistons back in the bike, it might have run better :)
ReplyDeleteRichard
ReplyDeleteYou are a veritable genius - you should write an update sequel to ZMM!
It actually had an airleak into the crankcase....
Ah. Common cause of two-stroke stoppages. Bad luck.
ReplyDeleteMy sequel is coming along. Working title is "Karate and the Art of Breaking Expensive Bits".