2008 WR/YZ450 Timing Map

I've been doing some research on my WR450 "stutter" issue. So far, I've found lots of statements that the grey wire is a CDI map-limiter to "de-tune" the WR for several reasons: trail-power, emissions, and lower rev's for dB's.

Reasons vary some, but the common response seems to be that when you cut the grey wire, you access the YZ timing map in the CDI. OK, fine.........

IF this is the case, what's the mechanical difference between the YZ's and WR's that would make them run different (other than the needle)?:)

Cam shafts, exhaust system.

Even if you cut the grey wire, it is still a WR CDI and not a YZ one. It merely is running a different map inside of a WR CDI.

Cam timing, exhaust, and air box configuration.

All '03-'05 models had the '03-'05 YZ intake cam and a special WR exhaust cam that was essentially a YZ cam with advanced timing.

The '06 used the same intake as the '06 YZF, but also had a different exhaust cam.

The '07 and up models use both cams designed for the WR. Part of this is certain to be emissions related.

IF this is the case, what's the mechanical difference between the YZ's and WR's that would make them run different (other than the needle)?:D

The cams, flywheel weight, wide ratio gearbox.

Even if you replaced the cams and ignition on the WR, it'd still have a less pronounced "hit" compared to YZ because of the gaps between gears and the heavier flywheel. And thats ok though because for its intended purpose the WR (when piped and uncorked) has way more power than most mortals can use.:)

I think my stutter went away when I installed a yz head pipe. its really hard to tell but it might be gone. but I might just be riding it different. YMMV.

Maybe a stupid question, but does the CDI in the WR have anything to do with the charging/lighting/starting circuit directly? Does the rectifier/regulator have anything to do with ignition directly?

I'm also looking at the 2 diodes that the WR has on it. Do they clip the AC power to DC for the battery?

I think my stutter went away when I installed a yz head pipe. its really hard to tell but it might be gone. but I might just be riding it different. YMMV.

Yeah I have no more stutter since I installed the YZ exhaust system.

It was only really mild on my bike to start with but it has all but disapeared :thumbsup:

I did a slip-on FMF pipe, so what's the difference between the YZ head pipe and the WR head pipe?

I did a slip-on FMF pipe, so what's the difference between the YZ head pipe and the WR head pipe?

the diameter of the tube... 38mm vs 45mm.

Thank's Demo.....:thumbsup:

Thank's Demo.....:thumbsup:

thank you too...

FYI

i had put bad info about the 08 yz head pipe having a 41.5mm outlet. mine that I got off of ebay had a 45mm outlet. and when I looked up the yamaha midpipe gasket, the 07 and 08 use the same mid pipe gasket. so tribalbc was correct.

on my leovince slip-on I just removed tha gasket and slipped the head pipe in. My slip-on is basically the same for WR and YZ other then the WR has that gasket and a different quite insert. the leovince guys warrened me that with the bigger head pipe the bike would be louder.

but please don't get mad at me if the head pipe doesn't fix the issue. it is possible that it's still doing it and that I'm just not feeling it. I only have 2 rides on the pipe. althought last ride it occured to me that the miss was missing and I tried to reproduce the surging and it was not noticable. it may have been missfiring but I sure didn't feel it at the rear wheel.

eitherway I think the YZ head pipe is a rad upgrade for the WR. they are titainum and you can pick them up in the $100 to $150 range.

there was even a post about using it with the stock WR silencer with the YZ gasket.

No problem! Thanks for the update. Here's where I'm going with this.

It looks like the WR is set up with massive emission-control settings that jack things up. The YZ is a race bike that avoids all that. From what I've been able to put together, the WR has the following differences from the YZ other than the obvious gearing, shocks, etc...:

1-milder cams

2-smaller exhaust system

3-AIS

4-dual-map CDI

5-heavier flywheel

6-different stator

7-rectifier/regulator

8-two diodes

9-different carb needle

Of the 9 items listed above, #5 is good for momentum at low RPM and probably has bigger magnets for electrical. #6 & #7 are for lighting and battery. #8 are for converting AC to DC (again lighting/battery).

That leaves #1, 2, 3, 4, &9 for the stutter. The majority here and elsewhere seem to agree that the AIS (#3) just adds air to the exhaust pipe for emissions, so it's out. Jury is still out for 100% of the exhaust change-out (#2) since most have at least opened up the muffler, so we'll set it off to the side for now.

That just leaves #1, 4, &9. If you cut the grey wire, It's supposed to access the YZ map. If that's really the case, then #4 is out.

Cams and carb. That's what's left!:thumbsup:

I'm starting to think that the YZ map is not very compatible with the lazy cams in the WR, and questionable jetting only make it worse......:worthy:

No problem! Thanks for the update. Here's where I'm going with this.

It looks like the WR is set up with massive emission-control settings that jack things up. The YZ is a race bike that avoids all that. From what I've been able to put together, the WR has the following differences from the YZ other than the obvious gearing, shocks, etc...:

1-milder cams

2-smaller exhaust system

3-AIS

4-dual-map CDI

5-heavier flywheel

6-different stator

7-rectifier/regulator

8-two diodes

9-different carb needle

Of the 8 items listed above, #5 is good for momentum at low RPM and probably has bigger magnets for electrical. #6 & #7 are for lighting and battery. #8 are for converting AC to DC (again lighting/battery).

That leaves #1, 2, 3, 4, &9 for the stutter. The majority here and elsewhere seem to agree that the AIS (#3) just adds air to the exhaust pipe for emissions, so it's out. Jury is still out for 100% of the exhaust change-out (#2) since most have at least opened up the muffler, so we'll set it off to the side for now.

That just leaves #1, 4, &9. If you cut the grey wire, It's supposed to access the YZ map. If that's really the case, then #4 is out.

Cams and carb. That's what's left!:worthy:

actually I think #9 the needle is out. mine still had the stutter after a JD needle install. #4 is also a little iffy, JD worked with one of the guys on this board to fix the issue on a dyno and the X-10 ignition did fix the stuter but only on one of the 10 maps. so its not a mater of deffective ignition.

The learning I have from reading the thumper talk posts on about this subject, is that people have moved or lowered the stutter with: jetting, TPS sensor and changing the ignition (or all of the above). None of which seems to be the smoking gun.

The ignition uses the RPM and the TPS to choose how much advance the ignition gets. At some mid point of throttle position and RPM the ignition might be making a large change in timing. Or if they don’t(or can't) have enough hysteresis and it could be oscillating.

:thumbsup:

Other guys would know better then me, but I wouldn’t be surprised to find that the YZ has the same stutter… but because the YZ has less compression braking, that it is not as noticeable to the rider as it is on the WR.

7-rectifier/regulator

8-two diodes

#6 & #7 are for lighting and battery. #8 are for converting AC to DC (again lighting/battery).

You're wrong here.

The rectifier/regulator is for converting AC to DC for the battery, and limiting the voltage. The diode pair #8 is there to isolate the neutral switch from the clutch safety switch, so that the CDI does not see a ground at the neutral signal pin every time you pull in the clutch.

Thanks Grayracer...I actually missed puting the (?) on #8 and mixed up a capacitor with a diode anyway.:worthy:

It's hard to concentrate on this when my work phone keeps ringing....:thumbsup:

Still, I don't think that either the regulator/rectifier and diodes play a part in the stutter so they're moot.

As I said, I'm starting to really think that the YZ map (cut grey wire) is not very compatible with the "lazy" cams in the WR, and questionable jetting only make it worse......

.

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