Spring is here and I procrastinated. PLEASE HELP!

Well I put it off all winter and now riding season is upon us here in Western PA. I have a '00 WR400 with WR timed cams, gray wire cut and the airbox lid removed. I have the new GYTR baffle ordered which should be here soon! LOL

I am definately going to do the BK mod. Can anyone give me ballpark complete jetting recommendations after this mod is completed to speed my setup/testing time? My altitude here is about 1000 feet with an average springtime temp. of approximately 60 degrees F. with average humidity.

I also hate to open up this can of worms again, but I'm considering YZ cam timing. I ride primarily loamy singletrack with alot of roots/some rocks. I'm considering some harescramble racing this year and am about 200 pounds without gear. I am probably of average riding skill. What are your opinions?

If you do recommend YZ timing are there any durability problems with this mod? Are there any jetting changes recommended? Please help so I can ride soon. :)


i too am from western pa.

if you wanna race a harescrambles series that isn't too rough, try hopps switchback raceway. ( link to track's web page )

i race there all the time. it's like 2 mi. from my house.

as for the yz timing, i too ran wr timing in my wr all the last 2 seasons, and finally was gonna go to yz timing this spring, but decided to go ahead with the 03 yz450 cam swap while i was at it. that way i gain auto decompression with it (not a problem starting the bike, jsut a convenience and a creature comfort.)

no jetting changes REQUIRED, but some people on this board will recommend you some if you wanna go to yz jetting, too, which i hear has it's advantages as much as the timing does. but then again, i imagine some people would insist you need to change jets when you swap handle bars positions or run different psi in tires. lol :):D :D

if you wanna go the cheap way, just turn the stock exhaust cam one tooth counterclockwise i believe. you can doa search to be sure. i asked that question about a month ago and got the exact directions, so just run a search and you should find it.

happy roosting. maybe see you on the local trails sometime.

pm me if you wanna hook up to ride.

racer36 :D


I don't know my jetting off the top of my head but as for the YZ timed cam, I love it. The mod is easy enough if you're any handy and yields big results. My favorite riding is tight twisty singletrack and double track up in the mountains (all conditions--slick and sticky) and have never had an issue with power delivery. This may be because prior to my WR I spent many years riding a pipey, top-end monster 250 2-stroke. Some people complain about the power delivery, I guess it depends on your skill level and what you're used to riding.


The YZ timing didn't affect my bike's ability to lug through the difficult stuff in the low end of the power band. My bike is now set up as a wide ratio YZ so my jetting will not apply. Your jetting will not only depend on altitude and temp but also the flow of exhaust, you're not going to recieve the full benifit of YZ timing with an insert of any type. I understand the insert is nessary for your application, its just that jetting also depends on how well the bike breathes.

Thanks for the suggestions. I am probably going to use the YZ timing unless someone gives me a strong reason not to. (ie. - significant loss of low end, durability problems, jetting problems etc.)

What I really need are jetting suggestions for the following parameters - '00 WR 400, BK mod, YZ cams, lid removed, new GYT-R insert with stock pipe, gray wire cut, 60 degrees avg. spring temperature, 1000 feet altitude, average humidity.

Right now my jetting is completely stock except for a slightly richer main. The throttle response is crappy since I haven't done the BK mod yet, but I plan on it this week. Any suggestions to get me started are appreciated.

Thanks XRRACER, I probably will come out to check out your local track. My sister lives in Butler. I was also thinking about doing the flat track race at the County fair. I saw it last year and it looked pretty fun.

Anyone? Anything?

sorry, check my last statement. you need to turn it one tooth, CLOCKWISE. you need to start with 14 pins tween the timing marks and twelve o'clock, and end up with 13 pins tween them.

sorry if you went ahead and did it on my retarded instructions. i just had it backwards. :):D

oh, and my bro has a 98 YZ 400.

way more power everywhere i thought. much better for racing. that's why i am changing mine this season. not sure if jetting has much to do with it. his bike don't got a flywheel weight either, it's a yz.

and it had aftermarket boingers (suspension) -PR2- when he got it, so it rides much smoother than mine, too.

hope it actually helped this time.

racer36 :D

Don't worry, I haven't done anything with the cams yet. I've been glued to Fox news. I did receive my new GYT-R baffle though. I just ordered it a week ago. If anyone is still on backorder, call Chaparral. They don't sell it through the accessory division. You will need to call the dealership section. Check the website at www.chaparralmotorsports.com for the phone number for the Yamaha DEALERSHIP.

I still haven't gotten to it since we have our first baby due shortly and I've been busy. I might get to it this week, then again maybe not. Any suggestions for jetting yet? At least a ballpark main jet and pilot. Thanks.

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