99WR400 owner seeks jetting info

I just got this 99WR400. its in great shape. Stock pipe. WR timing. I did the Taffy mod on the accelerator pump shaft per posts on this forum with .5sec duration .6mm gap.

What Im trying to find is a good jetting setup for sea level both with and without the 'octopus' and maybe a link on how to remove all those hoses and move to the YZ setup if anyone has it bookmarked.

So far I found theres a 172 main, 10mm float instead of the stock 9 and who knows what other mischief in there.

where did you buy yours?

Its a non-CA. model I bought in New Hampshire. I was going to set all the jetting back to stock and go from there unless someone had a good setup suggestion

Check this thread:

Jetting d-base

Indy_WR450 has the setup you need.

I saw that when I searched for jetting infos, but it seems to be all 450 specific. AFAIK the 400 has a different carb. =(


keep us posted. I'm very curious about your setup. I too have a 99wr400.

Cheers and good luck.

read my jetting at the bottom of this post. that's at sea level and plenty have been pleased with it.

it's with the standard euro pipe which is muffled but not like the USA version! if you run open then go up +5MJ and keep the rest the same.

as for de-octopuss-boy that IS going a long way back! we do have info in the archive maintenance so you'll find it there if anywhere.

YZ timing works well with this jetting. indeed it is for the YZ timing that i offer it too you. i suggest you go for the YZ timing. everyone else did and was happy.



i think it was 158MJ, 160MAJ, EMM needle on clip 4 or 5, 35PJ, 45PAJ, starter jet i can't remember, APJ at .6mm, YZ timing,

From my archives:

A cut and paste of Clark's write up. You can probably ignore the jetting, it does not seem to apply anymore.

Also: How to remove the WR carb Octopus if you dareMore on Jetting and YZ timing

by Clark

There are a few jetting differences between the YZ and the WR. The YZ uses a 175 main jet stock and the WR a 168, the YZ uses a DVR needle and the WR a DTM both use a 45 pilot jet. The WR uses a more complicated slow speed start circuit with a lot of complicated vacuum hoses, and two start air jets. The WR secondary start jet cuts out as soon as the engine starts and generates manifold vacuum. Thats what the vacuum module on the side of the WR carb does, remember I live in the USA.

The DVR YZ needle is way leaner than the WR needle at and just off idle, this is why so many compaints are made about the bike pooping on deceleration with the YZ needle, because it goes from WOT to lean in a heartbeat. NEVER RUN THE (YZ) DVR NEEDLE IN A WR WITHOUT THE YZ CAM TIMING YOU WILL OVERHEAT THE ENGINE AND RUN WAY HOT.

Heres how the needles stack up from richer to leaner DTM, DTP, DVN, DVP, DVR.

What I have found to work best is to use the YZ cam timing, a DVP needle (YAMAHA PART # 5BE-14916-DP) (#3 or #4 clip from the top), 48 pilot jet, idle screw 2 to 2.25 turns out, 178 to 185 main depending on altitude. The 180 is a good all around choice. ___________ ___________

If you have a WR and want to eliminate the vacuum module and extra hoses which I tend to knock off and cause a vacuum leak read on.

Parts required: 1) a YZ pilot air jet #100, 2) a YZ start jet #65. Available from Yamaha look at the YZ parts listing, 3) A couple of small automotive vacuum line rubber/plastic blocking caps.

Remove the carburetor

Remove the vacuum module from the left side of the carburetor and all associated vacuum hoses.

Plug the exposed vent port on the INTAKE AIR HORN side of the carb with a standard rubber/plastic automotive vacuum plug cap. Plug the exposed secondary start air jet input--on the left side of the carb with a second vacuum plug cap.

Remove the carburetor float bowl and change the start jet in the carb from a #60 to the YZ #65; reinstall the float bowl.

Change the #1 Pilot air jet from a #75 to the YZ #100--note this air jet is behind the air horn on the bottom. Remove the air horn via two screws look at the carb there will be two air jets on the bottom its the one on the left, reference your manual this is easy. Carefully reinstall the air horn using the two screws.

Be sure to make any other jeting changes you may have in mind at this time.

Reinstall the Carb in the Bike.

Now connect the hot start button vacuum line (the longest vacuum line)directly to the vacuum port on the HEAD INTAKE MANIFOLD.


This eliminates a lot of stuff from the left side of the carb, eliminates multiple vacuum connections (sources of vacuum leaks), saves a little weight and works just fine. My bike is an easy staring machine.

Hope this is of benefit


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