Acc. pump adj. for 98,99 wr's

5 replies to this topic
  • tbronco

Posted June 10, 2001 - 07:31 PM


I thought I'd share this with you guys.

I've been drawn in by all the carb tweaking that's been going on. After a little thought I came up with a simple, externally adjustable way to limit the travel of the accelerator pump.

it's a simple tapered shaft that fits into a hole in the carb body. A cam is attached to the shaft to contact the black plastic belcrank, stopping it from running through it's full stroke. The cam has a profile that allows adjustment from full stroke to no stroke in a little more than 30 deg.

I took a Faber Castell "uni ball micro" pen, and cut it off about 2.5 in. from the top.

Trimmed off the sharp corner of the end plug with a knife so it will bottom nicely in the hole.

Then dry fit the shaft (pen) in the hole to get an idea of where to locate the cam, and the profile needed.

I formed the cam from a scrap piece of soft plastic ~.375" thick. Any material easy to work will do. Just drill a hole the size of the pen shaft so it fits very tightly.

Now PATIENTLY whittle, cut, sand, etc. the cam profile testing fit, trim, test, trim,... Until you're happy with it. I ended up with adjustment from 0 to full squirt in about 30 deg.

To finish up I poked a stiff piece of wire through the outer end of the pen shaft. It works as a lever to twist the whole thing in place on the bike.

It appears to work as intended, at least before I put the carb back on. I won't be able to do live testing for a few more days. (I'm out of service for routine maint.)

The materials I used are not likely to hold up over time. Heat and fuel will likely take their toll in a few rides. But, I hope it will hold up long enough to get a good feel for is effect.

If anyone's still with me, I can try to get pic's and specific measurements.

98 WR400 Dualsport!

  • Ynahg

Posted June 11, 2001 - 04:49 AM


An image says more than 1000 words....

'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

  • tbronco

Posted June 11, 2001 - 10:28 AM


not this time

[This message has been edited by tbronco (edited 06-11-2001).]

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  • tbronco

Posted June 11, 2001 - 10:30 AM


OK, here they are.

Please excuse the poor quality, I had to use a camcorder for the images.




[This message has been edited by tbronco (edited 06-11-2001).]

[This message has been edited by tbronco (edited 06-11-2001).]

  • James_Dean

Posted June 11, 2001 - 10:33 AM



Yes, a picture will help. The '98/'99 carburetor is the same version as all the new KTM and Suzuki FCR carbs. Your ideas could help more than just WR riders.


  • tbronco

Posted June 11, 2001 - 03:12 PM


I didn't know that. -may be worth building one with Al, a little more permanent.

98 WR400 Dualsport!


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