What causes high RPM misfire or sputter ?

[Jayraye39]

got a new problem. bike runs normal all through the low and mid range power but as soon as I get to 6000rpm or just before getting on the pipe. the bike starts to sputter or missfire. fuel is not the problem and my magnet hasnt moved and the magnito itself looks fine. It did it yesterday twice. this morning went to go start it and I got nothing. Tried for an hour to start it but it would not start. I changed the plug still wouldnt start. so I changed my CDI from the Catnip back to the stock CDI and it fired right up. went for a ride and same problem 6000rpm it starts to sputter and cut.out. I disconnected the cutoff switch and wired the cdi dirrect to the magnito. but still the same problem. Bike also idles perfectly. no spike in revs so its not an air leak. WTF im at a loss for words. Think my Magnito it going out. or are both CDIs bad????????

 

[GW's Motorized]

What did your old plug's burn look like? Your mixture could be getting off and it might be 4 stroking

 

[Chainlube]

Sounds like a bad coil, if you have a spare, swap it.

I've had a few bad coils.

 

[Jayraye39]

def not 4 stroking its more like spark cut off. or a fouling plug but only at high rpm

 

[Jayraye39]

found it!!!!! since i did a little more port work lastnight by widening exhaust and intake to their absolute max width. I did not take into consideration that my spark plug gap was still set to an earlier time when i had way less modds on my motor. with the excessively high RPMs that I'm running now the spark plug gap was too wide at high RPM it would not ignite causing it to sputter that sputtering is what blew out my catnip CDI it is now trash when I ran it with the stock CDI it did the same thing sputtered up top thankfully I caught it in time before it blew up the stock CDI I just now closed the spark plug gap to 0.03 and it runs like a champ and with the extra port workI can already feel in the midrange that its faster then before. . however with the stock cdi im not so sure my top speed will be any better. since they dont retard the curve up high. But now that extra power makes my clutch slipp as soon as the pipe hits. bout to go do a speed run and see what she does. but im going to be in the market for a lightning CDI and a super clutch unfortinately

 

[DAMIEN1307]

closed the spark plug gap to 0.03

Closed to 0.03 ????????, your kidding me, right???...lol.

 

[GW's Motorized]

0.03 ????????, your kidding me, right???...lol.

Yeah, that sounds pretty wide. I gap mine to .025

 

[DAMIEN1307]

Yeah, that sounds pretty wide. I gap mine to .025

Makes me wonder how wide the gap was before he closed it down to 0.030...It's not like these motors of ours are HEI...lol.

 

[Jayraye39]

no 0.003

 

[Jayraye39]

damn near touching