REV Limiter???

[400exUtah]

I recently installed a Big Gun Race Series Exhaust System on my 400ex. I LOVE the added power! However, I need your help! I went to the Little Sahara Sand Dunes of Utah the day after Thanksgiving and noticed that my 400ex wanted to go faster, but couldn't:( I felt like I could go faster in 4th gear than 5th. I still have my front sprocket geared down a tooth, but I'm not so sure that would be the problem. I had my 400ex re-jetted and it runs great, quick response, awesome power especially in 3rd gear. I just felt like I was going through the different gears way too quickly, and didn't have as much top-end power.

My questions to you are:

How much of a difference does a REV Limiter make?

Should I go back to the stock front sprocket? (my problem is I like the quicker power climbing hills and going off jumps).

Is there anything else I should consider?

THANKS FOR YOU HELP GUYS!!

Put your stock 15 tooth sprocket back on....when I dropped to a 14 tooth I didn't care much for it,, had NO 1st gear and very little 4th,,but that's on a track with the hammer down,,,14 tooth sprockets are more for trail riding and climbing. Not dunes or MX tracks.

Put the 15 back on and I bet you'll be happy,,plus save ya some money..

[400exUtah]

Thanks Rico! Great to hear from you:cool:

I'm all for saving money, but would be happy to spend the $100 if the REV Limiter really makes a difference.

Looks like I'll have to put the stock sprocket back on. I just love beating my friend up sand mountain when we get to the really steep part. I'll have to change the sprocket back and go from there.

I purchased my 400ex from a guy who only owned it for 2 months, and never rode it. The previous owner was the one who put the smaller sprocket on the front. When I change it back to the stock sprocket, will I have to adjust the rear axle at all to tighten up the chain? Or are there other "TRICKS" I should know about?

THANKS

You'll have to tighten your chain up some,,but no biggy. Rev limiter,,,I'd leave the stocker in there,,,I just sold mine cuz it made the bike impossible to start. I think you'll like the change to the 15 tooth and be happy with that. Don't waste the money on the CDI.

[kc 300EX]

The best thing to do would probably be to get the 15 tooth sprocket, and if you dont like it, or it doesnt do what you want, then maybe it would be time to invest in the CDI, but of course try the cheaper idea first, you can get one of those cheesy front sprockets from Rocky Mountain for like 7 bux

[cbrown400ex]

i have the wb cdi box on mine. I have never had any problem out of it. Although it hasn't gotton that cold here yet. I have switched back and forth and could notice some, very little, difference. It is no where close to the difference that a pipe and a jet kit makes. If you have the xtra $100 bucks to spend go for it. At least you will be able to decide for yourself. CJ

[400exUtah]

THANKS GUYS:)

I still have the stock front sprocket. I will go ahead and put it back on the front and give it a try.

Any other ideas or suggestions are very welcome!

[Glamis400ex]

I'll continue to beat the dead horse here. I also had the WB CDI on my 400ex. It was a mofo to start, at least it was on my quad, your mileage may vary.

I have spoken to the folks at Duncan Racing, and they recommended I take off the WB CDI. It does nothing to a stock motor, even a modded motor for that matter. The 400ex quits making HP at 8000rpm and the meat of the rpm is between 2500-6000 or so. So....all your'e doing is ringing it's friggin neck by making the motor rev faster........absolutely no benefit what-so-ever. Just my 2 cents, call Duncan Racing and they'll tell ya the same thing.

I noticed no inprovement with the WB CDI.

No flame intended here, so don't even start.

Cheers,

Glamis

[hippy440]

if the temp falls below 50 mine wont start with the wb cdi on it if i plug the stock cdi in it starts up instantly..dont waste your money!!! :(

[cbrown400ex]

It has gotten well below 50 an mine starts every time. It has only been on about 3 months, I don't know how long the wb rev box was on my before my ex b/c I bought it used. Time may be a factor in it eventually making it hard to start. I will have to agree that one doesn't gain that much from the box. Slightly more top end,but think about how long you ride wide open in 5 gear. There are plenty other $100 dollar acc. that make more of a difference. What i meant was you sounded like money wasn't an issue so why not buy it. If your anything like me you like having misc. parts around just so you can tinker with them and say that you've tried them. My 2 cents. CJ

Dont waste your money on a higher cdi!!! I used to think they would make a difference. they dont give you any more usable power. Get a flywheel advance key for 15$.

[400exUtah]

This is great to hear such great advise. Pardon my knowledge here, but I don't know what a fly wheel advance key is. Will you please explain that one to me?

THANKS guys!

[400exdad]

In my opinion the timing advance key is a pretty cheesy little device that does seem to work. What I mean is that it is simply a regular key that has been machined on one side above the point where it sits in the groove of the crankshaft. When you put the flywheel on, you turn it till it hits the machined edge of the new key and tighten it up. The cheesy part is that it is now thinner than original (above the crank groove) and is more likely to bend or break. There is also a gap on the "backside" of the key between it and the flywheel (slop??). Alot of folks use them. The other day I read that you cannot use your flywheel "ticks" anymore, if you have a key, to set your valves with since it is now "advanced". I don't think I will use one, but then again I don't race and need everything I can get to whip the competition into submission! :devil

Well I just sold my white bros CDI the other day. I guess you might see some minor changes but not much. The bike started fine with it in for about 7 months,,then it just one day wouldn';t start and after that point there was a 80% chance it wouldn't start everytime I wanted to ride. So the way I looked at it was I just put a $120 part on my bike that keeps it from starting. Huh,,,,,i can't except that,,so the stocker is now back on and will stay on,,,and I don't plan on putting a different advance timing key on it either..

Oh and cold weather didn't matter, it wouldn't start this summer when it was 80%-90% outside.

[Tommy 17]

thats what i heard about a 400ex that it increases the timming or sumtin so much that it won't start well in the cold... mayb u guys should just run them in the summer or when its over 50 outside. i am leaving my stock one on too like rico. it won't make that much of a dif.

[hippy440]

buy the timing key it's cheap:D

[400exUtah]

Welp, I just finished installing the stock front sprocket back on my 400ex. I tightened everything back up, serviced the chain, replaced the sand paddle tires with the stock knobbies and fired up the big gun race series exhaust. After she warmed up I took off and screamed through all the gears.

Of course I'll have to try it out at the dunes, but for now all I can say is you all were right!!!!!!!!! I love the stock gearing! I felt like I got much better performance out of my pipe with the stock front sprocket. MUCH better top end. I'm sure I'll be pleased at the dunes as well.

Thanks for saving me $100:)

[Sweet400EX]

I heard on this site once that instead of buying a CDI box, that you could take one off of a Honda XR250R. does anyone know about this?

400exutah,,,your welcome and glad we could help,,,and as for the 250 cdi box that's what I heard but your still gonna cause your bike to not start and who want's that....

[Sweet400EX]

so basically just forget the whole CDI box thing, causee it doesnt do anything helpful anyways???

[400exUtah]

To me it sounds like you are much better off withourt a CDI box if you live in an area that experiences weather below 50 degrees, and you don't like ringing your wheeler's neck. From what I can tell, save the $100:)

[Wheelie]

What jets are you running? Jetting has a big influence on top end performance.