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swells454

TPS/jetting stumble??!!

10 posts in this topic

I have an '04 WR450 and I have a terrible stumble when riding in any gear from approx. 1/8 to 1/2 throttle.

I started w/ the jetting since it was stock when I bought it but had a GYTR performance tip installed. It stumbled like this when I bought it.

I installed the JD Jetting kit, blue needle 3rd position.

I put in a 168 main jet, 48 pilot, 40 leak jet & #70 starter jet. Airbox unchanged and fuel screw is 1.75 turns out.....the stumble got more pronounced but still idles great and has tons of power w/ no noticable bog just like before.

I live in Michigan...alt. is approx. 600 msl-2000 msl. Temp is avg. 65-80 deg f.

After reading several other posts I decided to adjust my TPS. The Range says .58-.78 VDC output. I was at .55 so I adjusted to .77. I heard the idle increase as I did this. The stumble was still there...seems to be just as bad as before. I unplug the TPS and the thing rips....NO STUMBLE anywhere! :thumbsup:

It runs the way I think it should now, but I'm worried it may screw something up long term if I leave it unplugged. Am I asking for trouble here...like by burning up my exhaust valves or something 'cuz the CDI mapping is wrong at certain RPM's now? Anyone have any experience or input w/ this?

Thanks for any help guys.

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Hey I do the same thing with my 03 but I unplug when I'm home were I ride dirt roads and some street, (steady speed) then plug in when I travel up north for some real riding, (runs great in the trail) I don't ride much at home but when I do its much better unplugged. I would love to just leave it unplugged if it won't hurt anything. :thumbsup:

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TPS unpluged won't hurt the valves. You go from a 3-D map to a 2-D map. RPM vs timing only instead of RPM vs throttle position vs timing.

Have you tweeked the accelerator pump linklage. It made a big difference on mine.

Also, reduce the leak jet to 35 or less, especially with cold weather coming on.

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TPS unpluged won't hurt the valves. You go from a 3-D map to a 2-D map. RPM vs timing only instead of RPM vs throttle position vs timing.

Have you tweeked the accelerator pump linklage. It made a big difference on mine.

Also, reduce the leak jet to 35 or less, especially with cold weather coming on.

At last , some one has explained the link with TPS. However, leak jet and accelerator pump linkage won't affect constant throttle openings. Maybe that TPS is only there to get the bike past emissions, it seems to be a PITA.

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Great..I'm heading North for the next week so maybe I'll experiment w/ leaving it unplugged for now and take some of the other advice when I get back home.

Thanks for the input! :thumbsup:

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How good (or bad) is the OEM CDI anyway ?

Maybe compared to the Vortex ?

Can we, owners of WR´s get into the program of the OEM CDI the mapping ?

Either the TPS or the ignition computer must be broken in this case.

What tools do Yamaha dealer shops have to repair or adjust the CDI ?

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are you talking about riding on the road or on the trails? have you tried the red JD needle? our altitude and temps are almost the same and i don't run the blue needle till it's in the 40's.

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I'm riding mostly all trails w/ some fire roads thrown in. This is where I notice it the most and it's more annoying than anything. I ran the blue needle mostly 'cuz that's what the JD kit said to start with. Maybe I'll try dropping the red needle in (I'm assuming it's richer?). What position do you run the red needle in?

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the blue needle is the richer of the two. that's why i use it in the winter. i've had my best luck with the clip in the middle groove.

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