rebuilt engine

I've just put a new piston in a freshly replated bore (don't lose your drain bolt whilst riding - it gets expensive!) and have noticed a couple of things the bike does that it didn't do before.

a) It doesn't tick over as reliably. Even when holding it on part throttle it will sometimes just 'pop' and die. Never did this before the rebuild.

:) Sometimes (but not all the time) When trying to start it, it won't kick all the way through the stroke, but stops half way as though I've come up against compression again.

Bear in mind that I've had the bike for 18 months so know it quite well, and these things didn't happen before the rebuild.

Only thing I can think of is that originally I didn't change to YZ timing until the bike was 6 months old (and therefore well run in). I've set it up with YZ timing with the new piston, so maybe it will settle down when I've done a few meetings?

Just to make sure! ( not doubting your ability sir ) New gaskets and a torque wrench used at build-up? Ring end gap done? Valve shims at spec? No leakage at carb. junction or aitrbox? ( need to eliminate the obvious first )

Gey back to us sson, we will try our best.

Take, care.

Yes, those cam bearing caps are a soft material. it is possible to have them seize or gall after improper assembly.

I noticed after rebuilbing my 426 that it has taken about 7-10 gallons of fuel for the thing to get back to normal.

It starts easier now and stalls less...


New gaskets - check

torque wrench used at build-up - check

Ring end gap done - new rings, ends positioned as per the manual

Valve shims at spec - check

No leakage at carb junction or aitrbox - carb wasn't removed, just disconnected from head. Seems to be back in place OK

It seems fine when it's running, it's just these two little things that make me a bit nervous!!


[ November 05, 2001: Message edited by: MXH ]

You might also consider taking the carb apart and give it a good cleaning, then go from there.

MXH, what is the weather like over your way? In Montreal this time of year we average 5-10 deg. C. It takes considerably longer to get the bike up to operating temps and yes I am jetted lean as I did not update my summer jetting to winter yet.

Can this explain your lean condition?

As for the weird compression I am experiencing something along that line. As SFO said the break- in may have something to do with it. My compression seems to be getting better the more I ride ( I have about 8 hours on the new piston / rings ) If your valves are well set and timed and the valve caps are properly torqued as Thronco mentioned I would not worry.

Take care and good luck. Let us know what happens.

Just my .02 cents Canadian ( or .0125 US ! ) :)

[ November 05, 2001: Message edited by: Hugh LePage ]

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