YZ Timing Revisited/Slow Going

Hate to bring this topic up again but I want to hear from the hard core trail riders. How is this mod in the slow nasty stuff, single track trails, rocks roots and steep climbs. What do you like better for this stuff(yz or wr timing) and why?

Already have yz pipe(BMP system), just wandering about switching.....TW

I'm glad you are asking this question because this is exactly what I had on my mind when I logged on tonight! You see a friend just bought a used (only 10 hours!) WR400 today and we test rode it at my shop today (in a field) and we were remarking how much better the torque was at low to mid engine speeds than his 2001 yz 426 was. We have yet to ride it on the trails yet but I'm sure for woods it will be much better, though the power will be missed during the occasional drag race. Up until now I have been told there was no noticable loss of power at low revs but I know better now!

Your ridin' bud Kurt

I just did mine in the last two weeks, so I think my impressions are still pretty fresh. The first riding I did after the conversion was the Prarie City CC last weekend. There were some medium-slow rocky whoop sections, I found the new power delivery a little abrupt and fatiguing on this terrain. I also had installed stiffer springs front and rear, so this probably contributed to the fatigue factor also. For most of the riding I do the extra power in the mid to high is worth the compromise.

I didn't think I lost anything down low, it just hits harder and picks up rpm's faster. With stock gearing a WR is going to feel like it has more down low because 1st and 2nd gear are so much lower than a YZ.

there is no doubt i lost a bit of torque down low on my 250F, and for steep, rocky hill climbs, the WR timing was much easier to work with. But, after time, i got used to the YZ timing. It's only a 250 anyway, so even with the YZ timing, it's still not going to rip my arms out.

Found i could do wheelies from 1st gear really easy with WR timing, and could control them no worries, but with the YZ timing, it was a bit harder to get used to.

When you are taking off slowly in, say 3rd gear WFO, you can feel the engine gradually picking up revs until mid range where the bike starts accellerating much harder until it screams.

I have lost some down below, no question about it.

Doc, I totally agree with you!!!! I think that my bike is FASTER with the YZ timing but I lost some throttle control along the way. I feel that the WR426 is plenty fast in stock form and many guys never need all the (drag-race) power. For the first time I've actually hit the rev limiter now that my bike is yz timed. As soon as I get around to it im gonna change back to WR spec. The loss of bottom end isnt all that noticeable as much as the loss of throttle control. krusty.gif

[ January 26, 2002: Message edited by: Dan Lorenze ]

[ January 26, 2002: Message edited by: Dan Lorenze ]

[ January 26, 2002: Message edited by: Dan Lorenze ]

Thanks for the replies, I need some more though, lets keep this thing going......TW

why don't you time the cams like me and get all the bottom end and all the top end. no loss, just gain, gain, gain!!


what are taffy timed cams??? :)

there's a company at clearwater, florida that makes variable camwheels. falicon crankshafts. with a high degree of care you time the cams to open at the perfect moment. the timing;is available. getting someone who knows what they're doing is another.

[url=http://www.thumpertalk.com/bike/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=32&t=000351&p=]http://www.thumpertalk.com/bike/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=32&t=000351&p=[/ur l]

sorry i can't make the link work but feed the words "torque" or "more torque" in the search. ok?


[ January 27, 2002: Message edited by: Taffy ]

[ January 27, 2002: Message edited by: Taffy ]


I felt some loss of low end response. This to me was better for the really tight stuff, it makes the bike less snappy at low R's, kind of smoothed it out. If power is really needed for a steep climb, out of a slow section, the displacement of the blue beast makes up for the slight loss of HP.

Everywhere else the bike performs better, compared to WR timing. I wished I would have done the mod sooner.


Just finished re-timing and test riding around the block a few times. Very impressive power. Way stronger in the midrange and top end and very smooth. It might be a bit of a handfull now in the really tight going because it has so much more power. Will have to wait for the snow to go away to see. The best part is that this is with the stock - very quiet - exhaust, and if you don't like it, it will take less than 1 hour to change it back.

[ January 29, 2002: Message edited by: Woodzi ]

I agree with Bill. YZ timing has smoother power down low, more hit in the midrange. YZ timing revs MUCH faster.

If you have good throttle control, I wouldn't worry much. If you're a lazy rider meaning you can't or don't want to finese the throttle, stick with WR timing.

I ride snotty trails in Southern Ohio-YZ timed WR400, e-series, jetted, DSP box, etc. Personally I worry more about handling/suspension than power on the trails. The YZ timing will be able to lug down low quite wellprovided you['ve jetted the bike correctly. When I was too rich, stalling was a problem when chugging/YZ timing.

The instant snap is what sold me. There's no waiting for the bike to rev anymore!

The best thing I can say is try it out, use YZ jetting specs and experiement on the trails. If you don't like it, change it back. Only you will be able to tell if it's right for you and your riding area. I'm not changing mine back ever, however the extra 26cc's on your bike could turn the beauty into the beast in short order!

Thanks people, I think I'll give it a try to see how I like it. Instant snap would be great for logs also. I'll have to look into the jetting more, I'm installing a YZ exhaust with BMP end cap. mcarp, I wish I had the extra 26cc, but it's just an old warn out 99 WR400.

My bad, I guess I'm getting used to all the 426 questions :)

Yep, give it a try and see how you like.

I think the whole bottom end issue depends on other mods, especially the exhaust pipe. Both Bill and I use WB tapered headers w/ E-series cans...power everywhere and a rather strong bottom end.

Other folks I've noticed (not on this thread, but in the past) that noticed little to no decrease in bottom end also had either a YZ or aftermarket low-end type pipe.

Apples to Apples with similar mods except timing will most likely result in slightly less bottom end with much more mid and top. The difference is more how fast the motor revs once you get past, oh maybe around 3,000-3,500 rpm. Just the spot you want to be in to torque over logs


The lower gearing of the WR vs. YZ also give more of a "tractor" effect which feels like there's more bottom end. Not really, it's just gearing...

Taffy may be the ultimate cam timing knowledge base on TT. I may just try one his combo'sone of these days...

Hm...I seemed to gain in the bottom end. Power delivery very smooth, screams when I want to, also goes slow and chugs well, just like a John Deer. My .02



i agree about the equal bottom end and better and better as you climb the revs.

i also agree about the pipes and what we do with them. in my case i noticed no change in the jetting on the day i did it. i found ways of improving the bike later but it didn't do anything wrong the day i did it.

i think i told this story at the time but i wanted to see how you changed the timing so i had a look see and the next thing i know the dots wouldn't line up. it's 9pm on a saturday and i post a help thread.

in the end i ran out to the bike and put it right or to YZ timing whichever. rode it 100m w/o helmet. seemed ok. raced the next day, came something like 6/102 all in my first ever season of dirtbiking.

flywheel weights help (10oz), juice clutches also and oddly enough the positioning of the gearlever right on your toots.

i hate leaving unfinished business and not testing the DMM needle and playing with the cam timing is starting to haunt me.

i'm convinced that by rocking the cams i would have found DRZ type power. i've been here two years and i can't see anyone except a bike shop mechanic joining in. in which case they'll keep quiet about the numbers they find anyway!!!!


my advice is just try it out.its a very simple modification and its cheap.i like it both ways it just really depends on where im going to go riding at.i change my timing back in forth all the time.it might take 1 or 2 hours your first time.i can drive my bike into my garage with wr timing and drive it back out with yz timing in under 30.

I must have done something wrong when I tried YZ timing on my 99 WR. My bike ran like crap when I did it (this was at least a half a year ago-I put it back to WR timing almost immediately.) Here's what I did--could someone please tell me if I screwed up somewhere:

-Set the piston to TDC, lined up index marks on the cam wheels so they were lined up with the edge of the head

-The count between the top dots was 13 pins before I made the change

-I left the cam chain on the intake (rear) side as is

-I loosened the exhaust side and rotated the cam 1 tooth clockwise and put the camshaft back in place.

-There was then 12 pins between the dots on the cam wheels.

-Put it all back together and tested how it ran.

When I ran it to check it out, it sputtered, missed, popped, backfired and was totally unacceptable. It seems like most people just adjust the cam and go with no changes to the carb. Just to round out the info, I'm at sea level, avg temp is around 80F , I have a 45 pj, 100 pilot air jet, 200 main air jet, 180 main (which I have recently changed to a 175 and it's a lot crisper), DTM needle 4th clip position, fuel screw setting vary depending on conditions but its usually at around 1-1/2 turns out.

I'd really like to have the quicker revving and harder hit of YZ timing, but it just doesn't seem to work for my bike.

Thought you might want to hear from someone who rides Michigan single track-the more challenging the better. YZ timing is superior to wr timing in every way. Once I put the e-series pipe and header on w/ 5 discks for low end, it cured all my problems over stock. I'm not sure on the grey wire , but I cut mine anyway. What I ride on is a range of thick sand, roots, rocks, whoops, very tight trails, some hills and some down logs...I have never felt the power to be to abrupt or fatiguing.

On two tracks and wide open routes, it is a blast.

Hope this helps.


I'm no expert, But it sounds as you did it right. But you needed to rejet.


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