87 KLF300 timing issue

[bdl1801]

I just bored out my 87 Bayou 300 .020 over and installed a new oversized piston and had the valves vacuum checked. With everything back together and after setting timing and cleaning carb I am having a problem with it trying to start. When the engine turns over it will pop as if it is trying to fire off but will not run. I have about 125lb compression I have fire and I sprayed fuel in carb with these it should at least try to run. The only thing I can think of is a timing issue. I have lined the cam sprocket up with klf300 and set accordingly to the to the T mark on the alternator rotor. I have taken it off and double checked it twice I have even set it one camchain link forward and then aft of the correct Top setting at the camsprocket. I have set the valves to spec. When I turn the engine over by hand the valves open and close like they should at the right interval and the piston is at top dead center when aligned with the T mark and cam sprocket are in there right positions. Can I use a timing light when I try to start the engine and check for correct timing? I read something about a timing advance not sure how that works. Is there a sure way to check exactly when the engine fires?

[DirtDemon]

Check the flywheel key, if it sheared off, the flywheel will spin on the shaft and not stay lined up and you will get spark, but it won't be at the right time. To check and see when you are getting spark, pull the plug ground it against the motor and witht he key and kill switch on, turn the motor slowly with a breaker bar and socket by the flywheel nut. Try to keep it steady, it will want to pop a bit when the piston passes TDC on the compression stroke. The plug should fire just before TDC if the timing is right.

[bdl1801]

The crank key appears to be good and holding its position. I hooked up a timing light and turned it over with starter and the timing fired off at the F mark. I just ohm tested the igniter unit and found it did not meet spec. I figured with a bad igniter unit I would not have spark at all. What exactly does this Igniter unit do?

Edited March 25, 2010 by bdl1801