Stock cdi ?

[swheels]

Iv'e heard that there's no rev limit to the stock cdi.Ok put i put my thermos exhaust can on then took a little test run.Well going down a hill you can really hear the rpm's pick up.It sounded like if id stayed on the gas the motor would have kept reving.When does the rev limiter kick in.I know the exhaust could have a great deal on the engine performance.I can't see how it could affect how much the engine revs unless it's to restrictive.Is there free rpms in the exhaust?

[The Nutty Professor]

I would think so. A restrictive exhaust pushes gas pressure back or at least causes the pulses to smack into each other. I would think this would push back on the exhaust charge in turn slowing the piston. Less revs?

[Blitz$M.Inc.$]

ok, the stock cdi has no limit that i know of
ive revved my motor in second before till it just wouldnt anymore
any/every thing you can do to help the motor rev higher will give more power/speed
i have noticed on my bike, when i went to 17/28 gearing, my top speed became related to whatever my rpms were
in order to get my top end higher i had to get the motor to rev higher
the big valve head with its greater breathing ability really helped alot, i think i got another 1k out of that, and consequensly a higher top speed and all round rpm performance
my exhaust was ready for the big time already pimp11

[#84]

the stock cdi has no rev limit, i put a mycron 3 on my bike and i have had it to 10k rpm on the stock cdi. didnt want to push it any farther. i dont see how an exhaust system could raise your max rpm, on a 2 stroke yes. however thats only due to the expansion chamber which creates an area of low pressure. hook a tac up to it and test the different exhaust systems.

[redryderaus]

I'm still amazed that even with all the 4T exhaust tuning information freely available on the internet some people still insist that a 4T exhaust is just a pipe with a can on the end. If a properly tuned 4T exhaust can't improve performance then why do top race teams spend many thousands of dollars developing and testing their 4T exhausts to extract maximum performance from their engine? Why do they then go through the process again if they change cam/porting/etc? 2T's aren't the only things that benefit from a properly tuned exhaust.

Stock CDI's fitted to chinese bikes may not have a rev limiter, but due to poor design and/or cheap components the CDI/ign coil/ign lead may have a noticeable rpm limit after which the CDI just can't keep up. I've witnessed a dyno run with a Lifan 125cc powered bike that would misfire quite badly once it hit 8600rpm. The ignition monitor (part of the dyno) clearly showed the coil was missing over 30% of the required sparks.

Cheers,

red