I've been having issues with my 650cc 500 R starting and running. I noticed today since it was dark out that I am actually getting a spark between the b+ terminal and the output to the distributor on my ignition coil. I'm trying to figure out what may be causing this, I'm thinking maybe points or capacitor in the distributor might be messed up and causing too much resistance back feeding the system or something. Spark plugs look fine so I dont think the issue is there. Maybe the coil itself? I had another ignition coil in there before and had no start issue so I dont think it's that unless both are bad. I have a 123 ignition kit on it's way anyways, but itll be here in a few weeks, and I would like to get it running in the mean time if possible. Anyone have a similar experience or suggestions? Thanks.

Hi,
This is almost certainly a crack across the insulated top of the coil. Even if the lead is disconnected it should not arc across the coil. Try a new oil.



Robert G8RPI.

I replaced the coil. Short at the b+ terminal is gone. But I'm still stuck with a no start condition. I seem to be getting spark at the spark plugs when I pull the wires and hold them near ground and try to start it. I know I am getting fuel, when I take the intake off the carb I can see it. I know there isnt anything blocking air, so I am a bit stumped as to the no start condition. Only thing left may be low or no compression. I am going to get a compression gauge and check. I will report back my findings as soon as I get them. Anyone know the appropriate psi for compression, I didnt see it in the 126 Workshop manual?

SpyderJava said:

Anyone know the appropriate psi for compression,

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I can’t find a figure for the 650 but I’d guess the c/r would be close to the figure for the 594 which shows in the 126 manual as 7.5:1 therefore cylinder psi would be 7.5 x 14.7psi = 110 on a new engine. Dependant on engine wear, if it were mine, any reading below about 85-90psi would indicate to me there was a reason to open the engine for examination.

As you appear to have checked everything else is it possible that this is another case of incorrect tappet clearances? These engines are very intolerant of incorrect clearances.

So I upgraded to the 123 ignition. Fixed most of my issues. Just had a problem starting while hot. The new carburetor came in now things are running good. Thank you all for your help.