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Discussion Starter · #1 ·
So, my '70 Olympique 299 single is giving me more grief than normal. Here's the problem; from idle the engine backfires just before the clutch engages and won't rev up. Now here is the background; typically this machine runs well but will occasionally foul a plug, put a new one in and it would be good for a good while. This season it seems to foul the plug more often. The engine will idle perfectly and run at speed then after slowing to an idle it will pop once or twice then rev out but get worse the longer you ride to the point where it won't rev up at all after coming to an idle and a plug change only makes a temporary improvement.

To me it seemed like the timing was too advanced or the ignition advance was sticking so I put the engine on the bench to check things out. I only pulled the recoil horn and the outer half of the shroud off. The advance seemed to move freely and springs back, points looked good and were set at about 0.018". However at full advance the points started to open at approx 0.280" before top dead center which is way earlier than the 0.150-0.170" spec I found online. Okay, so I adjusted the stator plate so the points started to open at about 0.160", put the engine back in and test drove it for about 5min. It started, idled and ran good.

Today, took it back out for a ride, but after about 15 min it started to do the same thing again, a plug change only made a very temporary improvement. I find it strange that it idles good and if you can get it to rev up it runs good at 10mph and up.

Sorry for the long post but I wanted to give as much info as I could to describe the situation. I appreciate any help anyone may have to offer. Thanks in advance!
 

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Did you clean the points with a thin piece of cardboard sprayed with ether or equivalent to make sure of good contact. Make sure coil wire is in good shape too. Trim plug end & reassemble it to cap. I presume you timed it with the advance lever held to max. as well?
 

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Discussion Starter · #3 ·
Didn't clean the points. By coil wire do you mean plug wire? Yes I timed it with advance held to the max. If I pull the engine again I will pull the flywheel so I can get a better view of things. Thanks 70-335 for your reply and advice.
 

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Yes plug wire & if you get deeper check the bottom end of plug wire as well & also make sure no other small wires rubbing or pinched behind stator plate as well.
 
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