WJPez said:
I reset the gap to .002" again and turned the bike over 360' before rechecking where the gap had increased to a massive .058"!!! I reset the gap again and turned the engine over 720' and rechecked the gap, all was ok. The bike started and appeared to run ok but I did not take it for a ride. What have I done wrong?
Hi Wayne,
Nothing that can't be fixed!
I'd just start from the start again and I'm pretty sure everything will work okay.
Like the guys above said, engine needs to be stone cold. And make sure you've got the
right TDC. And make sure the adjusters nuts are cinched up nice and tight. Check gap again after you have tightened adjusters.
One place you went wrong was turning 360º and checking gap again. (Of course this may have accidentally put you back on the right track). The CG engine is a bit tricky as it has no overlap in the valve timing; exhaust shuts at TDC and inlets opens also at TDC. As such you can be at TDC with both valves shut(ish), but be 360º away from TDC on the compression stroke (which is where you check valve clearance). Remember, camshaft turns at half the speed of the crankshaft, so it takes two revolutions of the crank, 720º, to complete one valve cycle.
When you got the .058" reading I suspect you were at TDC on the compression stroke, after having wrongly set the valve clearance 360º previous .There may be enough ramp on that little lobe that you're .050" odd off the base circle at TDC for both inlet and exhaust.
To make doubly sure you've got TDC on the compression stroke, go through a couple of cycles. take out the spark plug and put something like a screwdriver in the cylinder. Maybe put some tape on it so you don't scratch anything inside. Turning the engine slooowly (making sure the screwdriver doesn't bind) watch the screwdriver go down and get pushed back out of the hole. When it stops going any higher but hasn't yet gone down - that's TDC. But which one? Watch the valves, and keep turning. (I like to turn the engine by putting the bike in top gear with the back wheel off the ground, and turn the back wheel in the direction as if you're going down the road). You want the one where the inlet valve is shutting as the piston starts making its way from BDC to TDC.
This is the TDC where you do your measuring.
Keep going past TDC and both valves will be shut for ages, until the exhaust valve starts to open close to the bottom of the stroke. The next time the screwdriver is coming up, the exhaust valve is closing and at TDC it is shut. Immediately after this the inlet valve starts to open. Even though both valves are shut, this is
not the TDC to be checking the valves at!
Hope I'm not teaching Grandma how to suck eggs, and good luck with it.
Stan
