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81 dt175 won't rev up past 7k


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ok , well today i got that restricter out of the exhaust , without a rotary tool . there was alot of chiseling and the plasma cutter took care of the bulk of the cutting . even tho it's badly out of tune i can already feel more oomph . i also checked the timing and it was dead on . it still doesn't rev up tho .

How did you test the timing, with a strobe? Have you solved the problem yet??

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i think i've just about got it , it runs up to redline and the plug looks pretty good . only thing thats still weird about it is when you rev it way up a tiny bit of gas trickles out the over flow , the float height is already 2mm below stock level so i can only assume the vibration of the engine up that high is vibrating the float valve open slightly . it doesn't leak a drop at low rpm or idle . not much i can do about that aside from putting a piece of hose over the overflow tube in the carb bowl to raise it up some , but i'd rather not . i'm running a 140 main now and it seem to like it a whole lot more . and as for timing there's a line on the flywheel and one on the case , you hit it with the strobe gun at 3k like the manual says , it was dead on .

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i think i've just about got it , it runs up to redline and the plug looks pretty good . only thing thats still weird about it is when you rev it way up a tiny bit of gas trickles out the over flow , the float height is already 2mm below stock level so i can only assume the vibration of the engine up that high is vibrating the float valve open slightly . it doesn't leak a drop at low rpm or idle . not much i can do about that aside from putting a piece of hose over the overflow tube in the carb bowl to raise it up some , but i'd rather not . i'm running a 140 main now and it seem to like it a whole lot more . and as for timing there's a line on the flywheel and one on the case , you hit it with the strobe gun at 3k like the manual says , it was dead on .

Glad to hear you got it sorted BS, might be a bit of blowback through the reed valve at those high revs, I think this could possibly introdue a bit of back pressure that could cause the overflow, and anyway since youre after max performance why not fit some boyesen reeds...Or of course as you have said it might be vibration thing with the float valve

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