suspected cdi problem

[ross46]

Hello all, my bike for the last month or two won't rev past 12k? I have tried in every gear and it revs up, holds at 12k and then a couple of seconds later will cut the revs back to about 9k? Is this a problem with the cdi? It is a blue M cdi and used to rev to 14k, what could be causing this? Thankyou all, ross

[Miles]

If its not restricted on the electronic side of things I would have a look at the carbs.

I believe that the main jet is the final factor in determining the amount of fuel from 3/4 to full throttle so might need a carb clean.

Odd that it holds and then drops though

[ross46]

I've just installed a dynojet kit and it hasn't changed, I know its not restricted because it used to rev that high and the carbs have just been cleaned, only thought I have left is to try restricting the airflow to richen it up, was wondering if part of the cdi has been damaged somehow?

[ross46]

Right, tried restricting the airflow by placing tape over the intake of the airbox, 1/4 and a 1/3 until it wouldn't ride properly in low revs and its still doing the same thing, hits 12k holds, sounds like its hit a rev limiter and cuts it back to 9-10k? Could it be the cdi? Or anything else? Any help appreciated

[RedexRobB]

Does it actually slow to 9k or does the bike sound the same and the rev counter shows 9k?

[ross46]

Doesn't slow down, bike sounds the same and the needle drops to 9k then I shift, I've been looking at the cdi's page and it says that some will restrict to about 12,500 unless wired with resistors? Are their resistors present with a blue M cdi?

[RedexRobB]

no the blue CDI's are not restricted. the rev counter picks its signal up off one of the coils iirc, so may be worth checking the wiring to make sure theres a clean contact.

[ross46]

Ok, been a while but I still can't get it to rev past 12.5k, I've changed the cdi, checked the black wire from coil to tacho and all the contacts are clean, what else could it be? Thanks

[ross46]

i know this is an oldish thread but this problem is still present?! i have checked all the parts of the tacho wiring as per manual, checked the tacho itself and its fine, changed out the blue cdi for a known working one, same problem, this is driving me nuts, it still hits 145 on the clock but the revs just sort of stays at 12~12.5k. any ideas? could it be related to the cam chain and pick up coil as when my cam chain was on its way out (chain out of tolerance and cam tensioner plunger butted up against casing) it decided that it would only rev to 10k on the clock but still do 130mph? any help appreciated as this little niggle is driving me nuts!!