high rpms?

[1965 honda]

what kinda rpms do you guys think im hittin on my 400. my mods are listed below.

[TYayo420]

a 250ex stock revs out at 8700 rpm's so ima say roughly maybe with your mods, 10,000

[GPracer2500]

On a 400EX the stock CDI ends the show at 9100rpm. If you've got an aftermarket CDI then the increase in revs will depend on what CDI it is. I think most give you about an extra 1000revs. The Big Gun has no limit. Some high end CDIs have adjustable rev limiters (MSD's is 8750 - 12500).

There's probably no reason to go beyond 10,000 on most builds. And anything above stock will probably want stronger valve springs or at least schedualed replacement of the stockers if you spend a lot of time way up there. This is even more important if you're also running an aftermarket cam. I ran a WB CDI and a WB Track cam and all my (stock) valve springs where beyond their service limit after a while.

[TYayo420]

hmm this article said 250 ex has a 8700rpm stock CDI rev limiter, i thought there would be a bigger gap that that

http://www.atvconnection.com/Features/ATV_Reviews/2000-Honda-250ex-review.cfm

[underpowered]

Originally posted by TYayo420
hmm this article said 250 ex has a 8700rpm stock CDI rev limiter, i thought there would be a bigger gap that that

http://www.atvconnection.com/Features/ATV_Reviews/2000-Honda-250ex-review.cfm

and what does a 250ex have to do with a 400ex??? jsut wondering why you keep bringing it up.

but yeah stock rev limit is 9100, so unless you have an aftermarket CDI you are hitting 9100RPM. and like GP said, much higher than that really stresses the valve train and the stock valves and springs should be replaced with HD aftermarket units. personally i run a stock CDI, tried an aftermarket on and did not not ever use the extra RPM's. IMO an aftermarket CDI is not worth it unless you pound the stock on as it is

[TYayo420]

Originally posted by underpowered
and what does a 250ex have to do with a 400ex??? jsut wondering why you keep bringing it up.


Because a 400ex and a 250ex have a 200cc difference n size obviously, so i figured the 400 would have a couple hundred more RPM's due to its gearing diff and engine size...

[underpowered]

Originally posted by TYayo420
Because a 400ex and a 250ex have a 200cc difference n size obviously, so i figured the 400 would have a couple hundred more RPM's due to its gearing diff and engine size...


yes, but in general a larger engine will turn lower RPM's usually than a smaller engine. the larger engine has a heavier rotating mass so they usually run slower. i mean look at car engines. a little 4 banger will kit 9k but a big block is lucky to see 6k in stock form. bigger does not mean higher RPMS

9100-8700=400. last time i checked, 400 was more than a few hundred.