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Post by racedad on Apr 16, 2019 21:38:24 GMT -5
I'm in need of a little help. just installed a 100cc BBK. all seemed good until driving. when I get to 48-48mph it starts studdering, like its hitting a rev limiter. It has a performance cdi and I've changed jets 3 times. I'm a little confused now. More or less jet?? or what?
Dave
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Post by jackrides on Apr 17, 2019 11:41:33 GMT -5
Rpm before and after? Top speed before? Tried putting the old cdi back on?
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Post by FrankenMech on Apr 17, 2019 13:50:41 GMT -5
Stuttering is usually either fuel or ignition as you surmise. It could be that 'performance' CDI which are often crap so try the OEM CDI or a new or known good stock CDI as mentioned above. It could also be the coil or spark plug/wire. Try restricting the air filter air intake a little and see if the problem gets worse or better. This may help you narrow the problem down.
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Post by racedad on Apr 17, 2019 13:59:45 GMT -5
thanks for the tips. not sure on rpm sounded a little higher. coil and plug are new. gonna try a little restriction of air and see what happens
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Post by FrankenMech on Apr 17, 2019 14:06:55 GMT -5
Where China parts are concerned new does not always mean good. LOL
Good luck!
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Post by GrumpyUnk on Apr 26, 2019 7:46:41 GMT -5
From limited experience, 'performance' CDI units may offer worse performance than stock. I have watched tests done by youtube presenters and the trend is that they do little to help, and in many cases make starting the engine more difficult. YMMV
I'd go stock. You may be running into ignition breakdown, or misfire due to limited(restricted?) fuel supply flow. If you have a tachometer, does the rpm indication start to flutter, (which I would interpret as ignition breakdown or intermittent misfire)?
You might try to test if the problem occurs immediately(shortly after getting warmed up), or occurs after things have reached their 'high' temperature limit(after running for 1/2 hour or so at higher speeds). A quick check, shortly after startup, might leave enough fuel in the float bowl for a good run without symptoms if it was a fuel limit problem, and a cool run might limit heat related problems in the ignition(fuzzy coil, CDI, etc). Now that it is all clouded up with options, try re-installing the stock CDI, and test again.
tom
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Post by jdaley1847 on Jun 16, 2019 17:31:33 GMT -5
Performance cdi are garbage. Hard starting, backfire, low power, cutting out, surge, and pinging. The only ones that I've found that work correctly are the Ncy stock replacement ones or the stock cdi. All others are a waste of money.
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Post by jdaley1847 on Jun 16, 2019 17:52:44 GMT -5
Oh also do not use a spark plug that is resistor type, you will have power loss, hard starting and cutting out. Personal experience. So if the plug number has an r in it, throw it away.
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Post by pinkscoot on Jun 16, 2019 19:25:26 GMT -5
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