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WR450SM

07 need help! using wideband O2 to fix stutter / jetting

21 posts in this topic

Help me guys,

My 07 WR450 wont pull a wheelie without stuttering, stumbling, or misfirng when I try to hold the bike at balance point.

I have searched TT and other sources for the last 6 months and tried nearly every jet combination out there trying to fix the stutter at 1/8 to 1/4 throttle.

I have had Eddie's help from the jetting forum, but so far we haven't solved the problem. Here is the link to the jetting discussion:http://www.thumpertalk.com/forum/showthread.php?t=623653

I am wondering if this might not be jetting, even though jetting does influence the problem. What I mean is, changing jetting can make the problem worse or better, and even make it happen at different RPM or throttle position...but jetting has not been able to make the problem go away.:thumbsup: The other thread has lots of info from the wideband O2 sensor that I put on the bike to diagnose the carb circuits and effects on my stutter symptoms.

I am running the bike with the TPS unplugged already, and still having the problem....so no easy fix there unfortunately.

My latest theory is the stock pipe or more directly the tailpipe which was removed at the dealership before I bought the bike. Not just the restrictor, they trashed the whole tail pipe, All I have is the spark arrestor inside the can and the end cap with nothing inside. Could this cause some weird exhaust resonance / reversion / funky situation that is causing the bike to run like it does?

On the trottle it is awesome, but at steady speed it is killing me with this misfire.....Do you guys have any other ideas? I really want to enjoy this bike...but so far all I have gotten is :thumbsup:

Thanks,

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Looks like you two are on the right path. when I jet a bike, I first get the pilot circuit right. I then get the main jet right. Numbers you would want are between 12.5 and 13.5 A.F. You did confirm float height is right?

Then to do the needle, the bike must be under load. I mark the throttle with tape and place marks on the tape at 1/8, 1/4, 3/8's and so on. Find a long road that is a stead incline. In 3rd or 4 fourth gear, hold the throttle at 1/8, record the A/F for about 10 seconds. Stop the recording, do it again at 1/4 and so on. Get the average A/F for each session, throw out any numbers that are way different (caused by the AP or other things).

These numbers will paint the needle setup. Using them, you can then find a needle that will bring them in line. Chances are, you will pick the corrct needle the first time and omnly have yo move the clip once or twice to nail the needle setting.

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Thanks William,

I already had the throttle marked, but the rest of the procedure is a bit different from what I have been doing. I think your way is going to be more accurate than testing on a flat road.

I have not checked float height, might be a good idea to confirm.

On the AFR.... when the bike is stutttering the readings are between 12.5 and 13.5. That is what has me wondering. I understand that if the cylinder is not burning fuel every power stroke then the O2 will read falsely richer than true AFR. That info points me to richen the needle variables, however with the 3 new needles I bought from Sudco , the stutter is reduced the more I lean the clip position. Unfortunately I run out of needle clip slots before the problem goes away completely (it is best with the clip in positon 1 = closest to flat end of needle).

I am thinking I need a new needle with the same straight diameter, but different L1 dimension so that I can get the clip position dialed in. I was thinking somethin like a EVN, but Sudco only has EVQ as the closest. Honestly I am getting tired of the needle change routine, but at least I am learning alot about tuning the FCR.

In the end, I am hoping for a bike that rides properly, and whatever number on the O2 that acheives it, is OK with me.

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If the stutter occurs at say less than five K, the issue may not be only the jetting. The cams in these bikes have a lot of duration and overlap. At lower engine speeds, you can get a fair amount of 'blow back', similar to what used to happen in two strokes before reed valves. An air fuel mixture gets sucked in, some gets blown back out, picks up more fuel charge and gets sucked in at the beginning of the next intake stroke. Once the revs get up there, the velocity of the charge 'packs' the air and fuel against the valve and tends not to blow back.

I believe when a needle is 'not on the chart' it is because of overlap, ie, Needle one on clip 4 is the same as needle two on clip 2 sort of thing.

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WR450SM,

I'm learning a lot from your posts. Did you ever try that 110 MAJ? I left mine out also...

have you given any thought about using an aftermarket emulsion tube? like in the Zipty kit?

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WR450SM,

I'm learning a lot from your posts. Did you ever try that 110 MAJ? I left mine out also...

have you given any thought about using an aftermarket emulsion tube? like in the Zipty kit?

I didn't install the 110 MAJ - what I read from Eddie on the jetting forum said that it was only helpfull if you disable ACV in the cut postition, which he did not reccomend. I think he likes to disable ACV in the open position when he does the mod.

I don't know much about the Zip Ty emulsion tube. Is it something that they sell separately? At this point I would try just about anything to get this thing sorted out.

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I didn't install the 110 MAJ - what I read from Eddie on the jetting forum said that it was only helpfull if you disable ACV in the cut postition, which he did not reccomend. I think he likes to disable ACV in the open position when he does the mod.

I don't know much about the Zip Ty emulsion tube. Is it something that they sell separately? At this point I would try just about anything to get this thing sorted out.

When I emailed JD about the MAJ, he said not to bother with it, because something about not much air from it gets to the emulsion tube on the newer carb so messing with the MAJ didn’t do much. I could be miss quoting him.

I’m a total noob to this stuff, so you are probably best ignoring me. But, I saw this today… and thought it would be a real pisser to go obsessive over needles if your flow out of the emulsion tube wasn’t getting atomized very well.

http://www.factorypro.com/products/F...u_hi_disp.html

The factory pro website says zipty is one of their distributors.

The zip-ty mod is you send them the carb with $100 and they send it back without your $100. The pictures of their jet kit include what looks like the parts and tools to drill and tap the MAJ, and a new emulsion tube. I just figure that their carb service would include that stuff too…It says call for details, satisfaction is guaranteed. Call them up pick their brain too.

http://www.ziptyracing.com/products/product_detail.aspx?id=MTUxOQ==

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That is good info, I knew Zip Ty did some sort of an AP fix, but not much more than that. After looking at the links, I am interested in the factory pro emulsion tube, but it looks like they only sell in a jet kit, which ZipTy only shows for the 06 and earlier WR's. I'll make a few phone calls tomorow and see what else I can learn.

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I talked to both Factory Pro and Zip Ty about the problem I am having. FP designed their custom emulsion tube to provide finer atomization of the fuel coming through the main circuit at any throttle operning. They will sell the tube direct under part #125K for $30.

Zip Ty only sells a jet kit for 03-06 WR's. The kit includes FP emulsion tube and a titanium needle along with a couple of jets and spare needle clips. The interesting thing that the guy from Zip Ty said was that my problem is not a needle problem at all. He was certain that itwas an accelerator pump issue.

How do I fix this problem with AP adjustments?

I already have a 45 leak jet and the AP arm o-ringed, but I have not changed the pump timing screw setting or taken the airbox out to watch the spray pattern (if it hits the slide or not).

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The guy at ZipTy was wrong, no nice way to put it. You are at (or nearly at) steady throttle. The AP has no effect on small or gentle throttle changes.

If you change the emulsion tube to any design other than what you have now, your needle may also have to be changed. did you try a new stock on tube for your carb?

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William,

I haven't had much time to actually work on the bike in the last couple of days. I have gone back into reserarch mode!

I should have asked the Zip Ty tech guy for his theory on why the AP would effect the steady throttle condition. My mind went to some sort of siphonig effect where fuel was pulled through the AP system, but I think it was just false hope:confused:

I have annother FCR from a Honda CRF 450 that I may rob the needle jet (emulusion tube) out of just to compare. Other than that I will be buying annother needle to try. One with a leaner clip position like the EVQ since the DMM, DMP and EMN didn't seem to have any desirable effect. EVQ is still richer on staight diameter than my origional non-adj NFNT or the GYTR AIS kit DTR.

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Bump.......It's still not running correctly. I bought a JD kit and have tried nearly every needle clip position in both needles, and it still stutters!!!

Can anyone help?

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I saw those on TT yesterday, JD posted them in annother thread. I'm going to give him a call today to get his take on fixing the problem.

Thanks

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Hey, I had the exact same problem after installing the factory pro kit. I have the TPS disconnected and it helps a little, but the problem was still there. I jetted and changed everything out in the carb until I finally changed the needle. As it turns out the brand new Factory Pro needle was bent. After installing the original needle, the bike ran like a dream. It doesn't take much of a bend to make the bike run rough. you will have to take the needle and roll it across a very flat surface to spot a bend or use a dial micrometer and some sort of fixture.

I wrote Factory Pro about the bent needle and they never responded, so after a few weeks, I had to open a dispute through PayPal. Factory Pro finally responded, but so far they are not taking any responsibility for sending damaged parts. How is that for customer service?

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I would borrow a coil/sparkplug lead from another bike and see if that solves it.

A buddy had one go bad and it was very difficult to find.

They get pretty hot and sometimes go bad.

I had a stutter on my 07 WR250 at lower speeds and I blocked off the ACV and it seemed to help.

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Here is the latest..... I have talked with a couple of tech reps from Vortex and Dynatek about ignition differences between their products and the Yamaha CDI. With the programmable CDI you get more spark energy and obviously the advantage of custom timing maps to suit your individual bikes needs.

I also talked to James Dean of JD jetting , and we are both thinking that it is an internal mapping problem with the Yamaha CDI, perhaps even intentional. It is very hard to believe that Yamaha has not noticed this problem, since it has been there since the 400's like 8 years ago.

The plan of action is to get a programmable CDI and do some back to back dyno runs on JD's dyno. Hopefully we can find an absolute answer to the problem that seems to plague all street ridden WR's to some extent or annother. I will certainly post an update as things progress.

Thanks for all of your imput guys, even the jetting suggestions.....been there and done that, have the datalogs from the WB O2 to prove it.

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I’ll be very interested in the out come of your testing… keep us posted.

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I too, will be very interested in the results. Being a very slow old man, I tend to be in that annoying throttle range fairly often and am sick the slow speed snap/crackle/pop. If I wanted it, I'd eat cereal.

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I recall a bike that a bike that I worked on and was hard to start. It had a stutter problem, but accelerated fine. The bike was a kick start only and would take about 20 kicks to get it to start instead of 1 or 2, but still would start and idle and accelerate ok. As it turned out, one of the cams was 1 tooth off alignment from the last valve adjustment. Once the cam was put into alignment, the bike started great, and the stutter problem was also fixed.

Since your bike is electric start, you may not notice a starting problem. You may want to verify the cam chain alignment and it only takes 10 minutes to do. If you do it yourself, it doesn't cost you anything either.

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