98 honda trx450s spark problem

hi guy need help on this one my trx450 start good idle good when i rev it it 4000 i lose the spark and it miss and back fires what could be the problem run fine till up to 4000 rpm but will some time go to 5500 no problem

Originally Posted by lamhound hi guy need help on this one my trx450 start good idle good when i rev it it 4000 i lose the spark and it miss and back fires what could be the problem run fine till up to 4000 rpm but will some time go to 5500 no problem

Are you sure it's a spark problem and not a fuel flow problem at high rpm?

I would start with the CDI and/or the pickup. Ajmboy has a good point too, what makes you think that it is losing spark? You may just need to clean the carb and/or adjust the floats or something.

no its not the carb when i put my volt meter on the input side of the coil i can see the volt start at 40volt @ 1500rpm the 210volt @ 3900rpm then nothing till it droppers back into the 3000 rpm range then i got volt again or when i put my timing light on the same thing light flashes till 4000 rpm then noting like it would have a rpm limiter i got a friend coming over with the same Honda i will try swapping the cdi i will keep you posted
thanks

CDI box. they are usually reliable....

i change out cdi from friends quad guess what runs very good will hit 7000 rpm now. phone Honda dealer wants $400.00 for new one but found a used one at a bike recyclers for 40.00 so got my finger crossed it works thank for the reply so on till next time
thank eh
mike

Right on, good luck with the used CDI. If you have any problems with it, try Service Honda, they have OEM Honda parts for quite a bit less than what your dealer is probably asking.