White Bros XR4 Rev Kit

[mtngoat]

Jay Peters http://www.justxr.com/info/xr4report.html raves about this mod. Seems to make sense that an EPA bike would have retarded timing and a timing advance mod would really work well. I'm not so sure that disabling the rev limiter (or setting it 2K RPM higher) is so great, but the improved advance curve is appealing.

Anyone try the product??

 

[Wolf]

After reading that article I am curious myself. Let me know if you find any info.

 

[mtngoat]

So far, all I have is the price, $329.

The catalog information is pretty weak, making a bigger deal out of extending the rev limit than discussing the advance curve. No dyno testing either, which is unusual for White Bros products.

Jay seems to be pretty informed. I spoke with him last week and he's apparently tried just about every XR4 mod I've ever heard.

Someone out there tried this???

 

[John K]

OK, now it's time for me to throw in a bit of wild speculation and heresay! Please don't by any means take this as gospel !! Awhile back I can vaguely remember a comment along the lines of the XR4 Rev Kit that is sold by certain aftermarket retailers here in Australia as being an XR600 CDI unit. Off hand I don't even know if the plug is the same? Or if there is an adaptor lead? Or if it's just innacurate.... but I'd sure be interested to find out... anybody else know?

 

[penguin]

I would not waste my money on the rev kit, it is mostly a lot of hype. You would get more performance out of a big bore kit for about the same price. Honda put a rev limiter in the ignition for a reason, you spin the XR4 too high and bad things start happening. ask a DRZ400 owner what happens if you try and rev the motor too high :eek:

 

[Wolf]

I am a little reluctant to go into the engine or change anything on the rev limiter. I don't want to loose the reliability of my XR and that is the main reason I like it.....but I am still curious.

 

[Ol'89r]

Rev kit.

mtngoat.

I have installed one of these on a customers XR. The engine was modified with a cam, ported head, Mikuni pumper carb, WB head pipe and silencer. The bike ripped. Made good mid range power and rev'd to the moon. The XR engines make good power up top if you let them rev. They seem to hold together pretty good also.

IMO, the most noticeable mod was the Mikuni pumper.

 

[mtngoat]

Thanks Terry

I thought you'd know.;) Had a lead on a two month old Mikuni and lost it. I'm leaning that direction, but I want to try the rev kit too. WIsh WB would dyno it.

 

[weekendtoy]

Penguin what happens when you rev a DRZ motor too high?You hit the rev limiter?Most dynos show the DRZ motor making power right to 10k.

 

[penguin]

ask the DRZ owners who have gotten the hi rev ignition kits....they blow up, just like the DR350's before them. Unless you want to do serious modifications to the valve train on many of the 4 stroke trailbikes, you are courting disaster if you try and rev them past their designed limits. You can believe it or not but I have 30 years of riding and wrenching to back me up. Unless you fancy yourself a factory pro, a lot of the hopup parts are wasted on us normal human beings. :silly:

 

[Handl-it]

It would be interesting to see a dyno chart with this rev kit. I would think that very little usable power would be had up high. But there could be gains in mid range with the advance curve. For the money the Mikuni carb is awesome! I gave mine the altitude test this weekend and I am happy!

 

[mtngoat]

I agree. I'm a lot more interested in the advance curve than the rev limit. I'll try to talk to their techs. Ideally, I'd want the curve and leave the rev limit alone or set it lower. Maybe it's adjustable. But, I also believe the Honda valve train can take it and is more robust than Suzuki (no bash intended, just my confidence in Honda engineering).

 

[mtngoat]

Spoke to the White Bros tech folks. Apparently, stock XR4 ignition curve is very retarded, especially thru mid-range RPM for EPA compliance. The kit makes the curve linear (flat), which should really improve mid-range response, IMHO. The rev limit is not adjustable. The kit still has not been dyno'd and no apparent plans to do so. The tech had ridden before/after application and claims significant improvement, consistent with Jay Peter's observation. This mod is most popular with the TRX400 quad. No reports of blown motors due to high reving.

The tech agreed to send me the owner's manual. If there's any more good info there, I'll post.

 

[mtngoat]

Sorry, bad prior post

Oops, sorry to controvert my last post, but I received more info and talked with Gary Jones in White Bros. R&D and I'm getting a different and IMO a more accurate assessment of the kit.

Gary did R&D on this kit and played with different curves. He says the modified curve isn't that different and this kit is more about extending rev limits than changing curves. To take full advantage of the rev limit really requires a cam change to enable breathing at higher RPMs. He doesn't recommend it for a stock engine. Personally, I want more low and mid-range performance for my riding. This won't help me there.

This really "syncs" with Ol89r's experience.

 

[Wolf]

Re: Sorry, bad prior post

Originally posted by mtngoat
[B

. Personally, I want more low and mid-range performance for my riding. This won't help me there.

[/B]

.....Pumper Carb:cool:

 

[motoman393]

Hello all...I had a 97' XR400 (I still do because it is sooo much fun to ride) but anyway I only come to this site but about every week (I mostly goto thumpertalk.com) since I have a YZ426 now!

Anyway about my XR400 that I had:

engine mods were: ported and polished head, flowed head, new rev cam form WB, JE piston higher compression stock bore (11:1 if I remember correctly), WB high rev ignition, new stainless valves, new "harder" valve seats (this combo allowed the XR to rev the moon and not blow up), WB e series exhaust, FMF powerbomb (sounds just like my YZ), bored out carb by 2mm and polished carb

Body mods were: A-Loop seat and tank, Revalved suspension for MX by JM racing, eibach springs and race tech gold valves (in both the front and rear suspension) CR front and rear fenders, RM front # plate! etc etc

Jetting specs: 168 main, 68 pilot, 2 1/4 turns on pilot screw, needle in stock position, float at stock specs! (They didnt have the mikuni pumper when I did this mod so im sure I could get even more HP from this XR if I installed one)

Anyways about the ignition mine lasted about 2 1/2 yrs and then for some reason my bike started running weird...sometimes it would run great down low and sometimes it wouldnt! I spent hours adjusting the carb (float, jetting, etc!) but it didnt help. One day I decided to put the stock ignition and CDI back on, and that was my problem. Something obviously wasnt the working correctly in the ignition and it caused my bike to sputter! I think the WB ignition is a great deal and allows the XR to "run like it should" after putting the stock igniton back on it just wasnt the same, I couldnt lift the front wheel with ease in 4th and 5th gears!

Sorry to blabber on but I think as long as you have the "normal" hop up mods such as: new exhaust airbox snorkel removed, new air filter, rejetted, etc and your ignition is becoming the "bottleneck" in your performance...then this mod will be great! It allows you to have the mid range hit and you eliminate the bog at the bottom (very similar to a YZ)!

Another <$100 mod which gives you awesome snap is a higher compression piston (I had a 11:1 WB JE piston) you dont have to use race gas and you dont have to bore your cylinder! With these mods I could easily smoke 98-99 YZ400's and it was pretty cool to see everyone at the MX track wondering "is that an XR"? Anyways I hope this helps in your decisions, if you have any questions email me at: [email protected]

Garrett

 

[Handl-it]

My Xr is a 98 model 400 and has been the best bike I have ever owned! I can always use more power like the "Toolman" but like to keep it simple. The Mikuni carb makes it start easier and it revs much faster. Power is better across the board, more even with better contol. The power is smooth as before but its there faster. I really think this carb should be the first mod a guy does to the 400, then the rest for more power!

 

[John K]

motoman393:
got any pics of your xr? Love to see and hear more about it.

mtngoat:
I suppose this kinda mod depends on your right hand a bit. I'm not
sure if the unit has any rev limit whatsoever. Perhaps it just relies on
the physical limitations of the motor as so many others so / used to.
Perhaps one of these new twin curve units might be the best bet.

 

[michman]

Well, I just order the Rev kit for my XR and in should be here Friday and I will give you a ride report. So for what I have done to my XR4:
Al Baker 430 kit
Cams
Pumper Carb
Big Gun Exhaust
A-Loop Kit
SRC Fork Brace

Mike

 

[Wolf]

How many miles do you get to a tank ? (A-Loop)

 

[mtngoat]

Motoman, thanks for the feedback.
Michman, looking forward to your review.

My 96 XR4 has the 440 kit, but otherwise has typical (filter, airbox, pipe, jetting) engine-related mods. I'm planning a top end re-work next winter, but I'm not considering a cam unless I need it. My preferred riding calls for more low-mid range. All this considered, I'm having a hard time reaching a conclusion that the Rev Kit is good for my situation. But, the carb is sure looking good!

 

[biker]

I have the pumper carb and XR's Only pipe on my 96 XR 400. It's an awesome setup for what I use it for, mostly mountains and tight trails. What do you guys think about the SRC fork brace. Is there a noticable difference in the handling?

 

[motoman393]

John K,

Yeah I have a few pics on my wesite http://www.scorpius.spaceports.com/~mx393 I just uploaded my site last night and there arent many pics of the XR400 (maybe 3 or 4) but I will be adding some in the next week! The pics are all old thats why there is a FMF exhaust and stock header (now it has fmf powerbomb header and WB e series)

XR Wolf,

I can go about 2 hrs (on a MX track) with my Aloop! When I goto the trails I can do 2 20mile loops back to back and it almost hits reserve! I think the tank size is 2.2 gallons (which is .6 gallons less than stock) but boy does the ALOOP make a difference in how well the XR handles! Later,

Garrett

 

[mtngoat]

biker, I ride mostly mtn trails with lots of rocks. The SRC noticeably improves handling for me. It takes a lot fork flex out. Do a search on it. Lots of good posts. Follow instructions to a tee, if you do it.

 

[Wolf]

The fork brace really helps. I find myself hanging on the inside of a berm/rut more, since the bike actually turns more accurately. I am trying to get used to that and steer a little less.