’01 FCR Accelerator Pump



5 replies to this topic
  • Hick

Posted December 07, 2000 - 01:18 PM

#1

If you haven’t heard, the accelerator pump has been redesigned for ’01 for the YZ (and the WR too I’m sure). The few tests I’ve read or heard about reported an improvement in throttle response off of idle, this was attributed to the new pump design.

Apparently most dealers have a partial fiche for ’01 part numbers. I called NCY and this is what I found:

3TJ-14293-40-00: 2001 Accelerator Pump Cover
3TJ-14293-40-00: 2000 Accelerator Pump Cover
(they must be identical)

5BE-14940-18-00: 2000 Pump Diaphragm (STD, options 15, 17, & 19)
5JG-14940-07-00: 2001 Pump Diaphragm (STD, options 06, & 08)

I tried to order one but it isn’t available yet. I plan on buying this part (heck, its only $15) when it is available to see what the difference is, I imagine the metal button is longer to reduce the stroke, and seeing what effect this has on my ’00 YZ’s throttle response.

A poor man’s P-38?

  • James_Dean

Posted December 07, 2000 - 10:30 PM

#2

I'll be waiting for a report on the '01. The 3 other optional pump diaphrams for the 2000 were ordered MONTHS ago at my local dealer and never came in. Don't know why.

  • Hick

Posted December 08, 2000 - 07:24 AM

#3

Yeah, I was wondering what happened with that. Hopefully I’ll be able to get the standard ’01 part since it is, well, standard.

The parts mgr. at NCY said it would probably be a month before it was avail., although I'm sure that was just a wild guess...

[This message has been edited by Hick (edited 12-08-2000).]

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  • James_Dean

Posted December 10, 2000 - 12:02 PM

#4

Dirt Rider magazine - Jan '01 pg. 126 - "The cam that drives the accelerator pump has been remapped to improve throttle response." I take this to mean it probably pumps less volume. The spring in the pump body and the nozzle outlet hole size limit the spray speed (flow rate).

The stock accelerator pumps on '98 -'00 models have about 3mm(.115") of stroke. The P-38 accel pump cover from Factory R&D reduces the stroke to about 1/2 this amount. They sell a few versions with different stroke lengths for the KTM, Suzuki, and Yamaha. The Yamaha version uses the least stroke because it revs quicker.

It would be interesting to know what the '01 YZ/WR426 pump stroke is.

James

  • mikeolichney

Posted December 10, 2000 - 01:47 PM

#5

Originally posted by James Dean:
Dirt Rider magazine - Jan '01 pg. 126 - "The cam that drives the accelerator pump has been remapped to improve throttle response." I take this to mean it probably pumps less volume. The spring in the pump body and the nozzle outlet hole size limit the spray speed (flow rate).

The stock accelerator pumps on '98 -'00 models have about 3mm(.115") of stroke. The P-38 accel pump cover from Factory R&D reduces the stroke to about 1/2 this amount. They sell a few versions with different stroke lengths for the KTM, Suzuki, and Yamaha. The Yamaha version uses the least stroke because it revs quicker.

It would be interesting to know what the '01 YZ/WR426 pump stroke is.

James


I had a faulty carb on my 01 (see $6k paperweight discussion). One of the things the dealer tried was to tap the bottom cover of the carb and install a screw and locknut over the pump. I didn't look at the internal mechanism, but the dealer claimed that this would provide an adjustable stop for the accel pump. Turning the screw in would limit the pump travel and reduce the fuel squirt. It didn't fix the fouling problem mine had but it sounds like you could play with this stop to see if you could get better throttle response.

  • James_Dean

Posted December 10, 2000 - 09:01 PM

#6

Thought about doing that. Unfortunately, to do it right the screw needs to be perfectly square, have a large face on its end, and the threads need to seal the gas. An o-ring seal would be best. Otherwise it will leak and the diaphram could slip to the side of the pump rod.

The P-38 would not have solved your problem, but it's good to hear your mechanics were looking at everything.





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