motorman Posted March 4, 2011 Report Share Posted March 4, 2011 Hi guys, I'm tearing my hair out here ! Have a 77 Ossa MAR 250 which won't rev out. I've tried everything plugs , carburetion , cleaned the exhaust, sent the Motoplat unit away to Spain for repair and testing. Engine is totally rebuilt on new seals and bearings. Everything in tip top condition , but it will only run cleanly to about 3/4 throttle and then misfires and won't rev out. Any ideas ? Cheers. Quote Link to comment Share on other sites More sharing options...
breeze Posted March 4, 2011 Report Share Posted March 4, 2011 Sounds like it's running too rich (4 stroking) maybee the main jet was increased over time to compensate for the crank seals passing air? and now it is not drawing in air you are left with too rich at top end. Quote Link to comment Share on other sites More sharing options...
motorman Posted March 5, 2011 Author Report Share Posted March 5, 2011 Sounds like it's running too rich (4 stroking) maybee the main jet was increased over time to compensate for the crank seals passing air? and now it is not drawing in air you are left with too rich at top end. Quote Link to comment Share on other sites More sharing options...
darmst6829 Posted March 5, 2011 Report Share Posted March 5, 2011 Hi guys, I'm tearing my hair out here ! Have a 77 Ossa MAR 250 which won't rev out. I've tried everything plugs , carburetion , cleaned the exhaust, sent the Motoplat unit away to Spain for repair and testing. Engine is totally rebuilt on new seals and bearings. Everything in tip top condition , but it will only run cleanly to about 3/4 throttle and then misfires and won't rev out. Any ideas ? Cheers. I have the same problem on an early 4 speed Bultaco, fresh rod kit, piston, seals everything. My next step is to try a different carb. I will let you know how it turns out. Dave Quote Link to comment Share on other sites More sharing options...
darmst6829 Posted March 20, 2011 Report Share Posted March 20, 2011 I have the same problem on an early 4 speed Bultaco, fresh rod kit, piston, seals everything. My next step is to try a different carb. I will let you know how it turns out. Dave New carb, same problem. Going into the ignition now..... Quote Link to comment Share on other sites More sharing options...
darmst6829 Posted March 26, 2011 Report Share Posted March 26, 2011 OK, I figured out my Spanish motorcycle problem! Bad Italian points! The points looked good and the gap was correct but after changing them the bike behaved as it should and I saw 60mph on the speedometer! I would have never guessed from the symptom I was experiencing that that was the problem. Dave Quote Link to comment Share on other sites More sharing options...
motorman Posted April 7, 2011 Author Report Share Posted April 7, 2011 OK, I figured out my Spanish motorcycle problem! Bad Italian points! The points looked good and the gap was correct but after changing them the bike behaved as it should and I saw 60mph on the speedometer! I would have never guessed from the symptom I was experiencing that that was the problem. Dave Thanks for the info , mine is fitted with Motoplat , haven't got round to changing the carb jetting yet. will let you know the result, Cheers Robin Quote Link to comment Share on other sites More sharing options...
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