FCR carb tuning


well done! your results seem to be solidyfying the settings needed.

you don't & shouldn't presume anything with a 175MJ. it might turn out that the MAJ doesn't move from No 230 at all. guess you'll just have to buy one to find out!!



Good show and your more precise methods are in agreement with my seat of the pants observations. 230 MAJ and a 172MJ for roll on performance. The only difference in my setup was the needle I was using a EKP #4 and the 100 Pilot air jet. Tried to order the adjustable PAJ from Sudco but they are out and the units are on back order. Wonder if its the WR thumpertalk crowd?

Good work Andy


Thank's all,it's great to be able to help out.


Fuel is SHELL OPTIMAX 98 octane pump fuel, exhaust is an AUST made "STAINTUNE" stainless steel 44.4mm Header & muffler (simmilar to YZ)"no resinator", spark arrestor used in dry grassy areas or High fire danger.When switched to yz/race curve It's totaly awsome feels like it could rev to 13,000rpm easily, 150kph power slides are a breeze :):D. I don't think ive ever ridden/driven any thing off road with so much useable power, It's FAN-BLOODY-TASTIC. :D:D:D:D:D



This is GREAT!! :):D:D

This helps us all a great deal. It also confirms the impressions that there is some hidden potential and now gives a better feel for the main air jet effects. What fuel are you using and is the "open exhaust" a like a YZ muffler or? How does it FEEL with the VORTEX/YZ curve close to the rev limit??

Thankyou so much for performing the tests and sharing all this.


(note: - Your PAJ 1 1/4 & PS 1 1/4 works well with #48 in my '00WR also.)

[This message has been edited by James Dean (edited 03-18-2001).]

Andrew and all.

Thanks for your work. I am getting ready to change over to a bigger MAJ. I ordered a 172 MJ today and was looking for some drills to create a 230 MAJ

Here are my questions.

1) What size passageway did you drill out to. 3/32 (2.38) or 7/64 (2.78)

2) The only drill I could find for making a MAJ was a #43 drill. It seems the drill is about a 2.25 size. I guess this will work? Any other suggestions for where to obtain drills? Heck, I live in LA, land of aerospace tools. I should be able to find the right drill if a #43 isn't the best choice?

Thanks for the research.


My Settings, 2000WR, EKN#4, 48PJ, 100PAJ, 3/4 screw out, 168MJ, 200MAJ, DSP tapered header and pipe, lid off.


You are right on the size- #43 is 2.26mm which should be close enough.

Use a 7/64 to open the passage behind to 2.78mm. Be careful of the threads and the depth of bore. Be sure to remove the needle jet before drilling the passage.

Altered the MAJ today on mine and gave it a short run. It revs to the limiter free and easy.

I should just be satisfied with the latest developments but now this raises the question again, what about the "F" taper needles. Clark, you might want to retry the custom FXX needle with the new mods. :)


Previous settings, 2000WR, EKN#4, 48PJ, 100PAJ, 3/4 screw out, 168MJ, 200MAJ, DSP tapered header and pipe, lid off.

I just made the changes of drilling out the main air passage, the main air jet and switching to a 172 MJ.

I drilled out the main air passage to 2.78 and drilled out the PAJ to 2.26 using a #43 drill.

I live in a Southern California neighborhood. So initial impressions are limited to blasting around the block twice.

It now seems "right". The previous settings seemed heavy or rich. Now the bike feels more breathable. Kind of like when somebody takes their asthma medicine and can breathe more deeply. Certainly it seems like it revs easier now.

Hopefully I will get a chance to do some riding this weekend, then I will get a better chance to evaluate, but my initial impressions are that it can't really get much better.

I think when I was drilling, I may have made a small dipple on the far side of the needle bore. This shouldn't make any difference should it?

I did put masking tape around the drill to about 1/4 to 1/2 of an inch from the tip to keep from screwing up the threads.

Thanks Andrew for your testing.


great to hear you've done the MAJ mod,It definately makes a big difference from 3/4 to rev limit.

the dimple you have should not effect performance, if anything it could create some turbulance which may contribute to better atomization of fuel, although very unlikely to effect anything.

i've been running a FMP needle this weekend and had a most enjoyable time, the "F" stands for "F"un. I think a better needle again would be JAMES's FHN or even a FFM for total excitement. I would'nt recomend these needles for racing applications but they are the choice needles for the "F"un factor. as James mentoined in Taffy's thread the "F" needles were not a good choice untill the MAJ mods came into the picture.


Andrew and others,

The FMP#7 matches an FHP#5. I have the FMP#7 in my bike currently and find it pulls extremely hard in the midrange. If you are doing hillclimbs this would be great. Also if you want power more like a KX/CR500 where a higher gear and good throttle control are the faster way to ride. From mild to wild - needles DRS#3- DVP#4/5- EKP#3/4- FHP#4/5, take your pick!

Andrew and I both have a #230 MAJ and increased the airway behind to 2.80mm. As an alternative we might have just removed the main air jet for a similar result.

FHN and FHP - two other options when too much is never enough! :)


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