00wr400 jetting mistry

4 replies to this topic
  • miked

Posted December 17, 2000 - 07:43 PM


I purchased a used 00 wr400f about a month ago. The guy was motorcrossing it. He had a local dealer rejet the carb. The bike runs fine, no hesitation, pulls well all the way up to rev limit. I live in Indiana elevation 0-1,000 feet. The bike has a two piece uni filter, top removed, white e pipe without the end plate. WR timing. I am working on it now, checking the valves, and I took the carb apart for cleaning and general inspection. I found the carb to be as follows:

00 wr stock setting____________Mine
main 165_____________________165
Pilot 42______________________38
starter 65______________________65
needle obdrs-3_________________OBDTL-3
Pilot screw 1 5/8_______________1 1/2

Question #1: My Plug reading is slightly rich?
I put a new plug in, ran it through a field three times, pulled the plug. A little rich?
How can it be rich?

Question: Has anyone heard of an OBDTL needle. It has OBDT stamped on it at the top and then a blank space, then the letter "L"?

Question: How can this bike be running rich with a 165 main and smaller 38 pilot with the pilot screw at 1 1/2?

The bike runs fine, but after reading the forum, I was compelled to check mine. I expected a large main and pilot, and possible the needle at #4. I felt I would change the needle to the DTM with a 172 main and 45 pilot. But now that I see what's in it, it seems that these changes would only make the bike richer which it dosnt need?

Any ideas?

[This message has been edited by miked (edited 12-17-2000).]

  • James_Dean

Posted December 17, 2000 - 08:13 PM



OBDTL is one step richer on the straight diameter than a stock '99WR needle - OBDTM.

This is the first time I have seen anyone use the L other than myself. It was for evaluating the richer option EML - with a 2.705mm straight diameter before the taper starts. I found it to be rich just off idle and not anywhere else. This explains the small (38) pilot jet in your bike. The main jet is not important unless you were only riding at full throttle and shut down at speed from a long run. If you are running rich 0-1/8 throttle, it is likely from the L.

There is nothing wrong with this setup. A bigger main might give you more top end (172-178). The #3 clip position is a good choice.

If it starts to foul plugs, think about switching to a leaner DTM, DTN, or DVP in that order. The bigger pilot jets work well with these and help to reduce stalling at low speeds.


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  • miked

Posted December 17, 2000 - 08:29 PM


Thanks James,
That explains my plug readings. I felt it must have been my needle, but I have not seen anything on that needle in my book or on the forum. Do you think my bike would benefit from making the change to the DTM needle, 172 main and 45 pilot over what I have. I appreciate the quick responce. I was planning to go to the Yam shop. Need a 185 shim.

  • James_Dean

Posted December 17, 2000 - 10:09 PM



DTM and DTL are very close to the same. It is difficult to say you would be able to notice this change.

The pilot sounds small, but if it runs good and doesn't have a problem with stalling there is little reason to change at this point. ( if it ain't broke, don't fix it! )

It's hard to know without riding and comparing in your specific conditions.


  • Boit

Posted December 17, 2000 - 10:58 PM


If you simply remove the plug after riding the bike for a few minutes, you aren't coming close to getting an accurate plug reading. The proper procedure is to warm the bike up thoroughly, and then try to find a hill with a slight grade(incline). Accelerate thru the gears and when you get into 3rd, roll the throttle on to full tilt and let the engine get near redline. Here's the tricky part....when the engine is near the rev limiter with the throttle wide open, pull in the clutch, hit the kill button, and hold the throttle wide open. Keep the throttle open until the engine stops spinning, while at the same time, you get the bike stopped and yank the plug out. (It's really smart to do all this so that you end up near your truck and/or toolbox). This will give you the best indication of how the "overall" jetting is. There are some opinions that this isn't even applicable to today's fuels but, it's better than nothing. As a reference, I switched from VP C-12 to Sunoco Standard fuel and my plug went from a nice tan to a light gray color and the engine runs great on either fuel with the same jetting. In my opinion, a rider should get a "feel" for how the engine runs...and is supposed to run. Generally, if the engine starts easily, has good throttle response,makes good power, doesn't have any unusual stalling or hiccups, doesn't run hot, doesn't smoke, doesn't foul plugs, doesn't misfire or blubber in the mid to upper RPM range, the jetting is pretty damn close. Educating oneself on one's own machine pays dividends over the long haul. Avoid blowhards like my neighbor who tried to convince me that.."You gotta match your octane to the petcock vapor pressure....." Yeah, right!


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