Question about 2010 Yamaha WR250F

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Jetting for a 2010 wr 250f

What do you recommend for the jet for trail and motocross style riding, i already have a FMF powercore on it! Do you thing i should open the airbox as well

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I recommend that you don't open the air box unless you put a bigger jet in it because if your ratios arent right you will blow it up real quick

Posted on Feb 20, 2013

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Posted on Jan 02, 2017

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SOURCE: i have a 98 yz125,

I would first make sure the power valve is decarboned and moves smoothly. Jetting is trial and error as so many things can affect the mix. Temp. humidity, gas quality, oil ratio etc. Tht being said you can make small changes and keeping a log with results. First write down baseline settings. Include main jet and pilot jet numbers found stamped on the jets and needle number. You don't say where it is you are trying to get power. 125s have poor bottom mid power, it is all on top for racing. Don't change and race or you may keep going when you should stop and melt something. Try to test at the altitude where you will race and read the plug often, cleaning or changing the plug between tests. Be alert for the surging feel of lean mix with racing idle do not let this continue. Remember 0 to 1/4 throttle, pilot and needle base width. 1/4 to 1/2 throttle controlled by needle mid taper. 1/2 to 3/4 throttle needle tip and main. 3/4 to full is the main jet. Find out the stock settings and make sure to start near there. I don't know about a spes pipe but pro circuit has charts for jetting and maybe a support line. I really feel you will get more from a clean powervalve, repack the silencer, clean airfilter and maybe v-force reed. Gearing can offer some options. I just read about a James Dean jet kit for cr250 that puts more power in the low mid. I might try that for my bike. Good luck, just remeber " too lean, too long- too bad"

Posted on Apr 06, 2011

Motoxpartson
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SOURCE: Just bought a 2001 WR 426. Has an FMF pipe, no air

Hard to give accurate info with out seeing the bike with jetting but I would suggest take a reading from the fuel air screw if the bike running better with the fuel air screw in carbi at 2.5 turns out or more then definitely increase pilot jet up 1 or 2 sizes if you get the bike to run well between one - two turns out on the fuel air screw that is where your jetting should be
I wouldn't be concerned with main jet at all - it should be fine for wide open throttle unless you feeling power loss when you open it right up
also if you are getting backfire or popping when de accelleration that also hints toward lean pilot so a size or two change in pilot jet would be worth trying

Posted on May 25, 2011

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Need 3000 ft elevation jetting for 2002 yz250 with fmf SST pipe and fmf spark arrestor


Hey Anon,
Proper and correct jetting is something that can only be achieved in person by a REAL MECHANIC that KNOWS how to "read" a spark plug,,,With the mods you mentioned.. you need to know the stock jet sizes..a close guess would be reduce the main jet by two or three steps and lower the needle one clip position... oil mix should be at least 32:1....or better yet 28:1.. KEEP the oil mixture and jet the carb for performance....( I see TOO MANY IDIOTS that instead of jetting a carb correctly just reduce the oil ..some as low as 50:1(INSANE) just to keep from fouling plugs.).. then WONDER why their engine doesn't last long... hahaha????
YOU > BE SMART!!

Aug 25, 2013 | 2005 Yamaha yZ 250 F

1 Answer

Just bought a 2001 WR 426. Has an FMF pipe, no air box lid. Main is a #165 and pilot is a #42.these are stock jets according to shop manual. My elevation is 2500-3000 Ft. Any ideas on jetting?


Hard to give accurate info with out seeing the bike with jetting but I would suggest take a reading from the fuel air screw if the bike running better with the fuel air screw in carbi at 2.5 turns out or more then definitely increase pilot jet up 1 or 2 sizes if you get the bike to run well between one - two turns out on the fuel air screw that is where your jetting should be
I wouldn't be concerned with main jet at all - it should be fine for wide open throttle unless you feeling power loss when you open it right up
also if you are getting backfire or popping when de accelleration that also hints toward lean pilot so a size or two change in pilot jet would be worth trying

Jan 20, 2011 | 2001 Yamaha WR 426 F

1 Answer

I was wondering what kind of jets and needles I should put in my 99 yamaha banshee after I just rebuilt it. It is bored 80 over, has fmf pipes. what would be a good jet to start with?


whatever a professional manual or pro sez-jets are a delicate thing cause you cud end up rebuildin again--the web n fixya has books or getta hold of a motocrosser

Aug 26, 2010 | 2003 Yamaha YZ 125

1 Answer

FUEL RATIO


For motocross racing..50:1 gas:oil mix. For trail riding and sand pits,..try 40:1.

Mar 15, 2010 | 2003 Suzuki RM 125

1 Answer

I was recently riding down and enduro trail when i laied my 2003 WR-250F over and when i attempeted to started it, i had little to no compression. When i inspected it i found a fouled spark plug, and so i...


Take out your spark plug, but plug it into the plug-wire. Let the bottom of it dangle against the head and try to kick it. If no spark, problem with that, if it sparks, you may have a cracked head or piston/rings problems. This will at least rule one thing out.

Nov 06, 2009 | 2003 Yamaha WR 250 F

1 Answer

2003 Kawasaki KLX300R - Severe lack of power.


This bike was designed to be trail "friendly." I would recommend a different model for what you are looking for. A lot of money in to this will not give you what a stock 250 two stroke or even a 250 four stroke motocross bike will.

Aug 07, 2009 | 2003 kawasaki KLX 300 R

1 Answer

Mpg on 2003 yz250


depends alot on your, riding style, final gearing, terrain, and to an extent even jetting/temperature/humidity/etc.

I have figured 2.5-3 hours of average riding based on 2.1 gallon tank for trail type riding. If your really aggressive/heavy on the throttle, you may get closer to 2.

if you ride with quads, get them to bring a small container of premix for you. try not to run out tho.........no gas=no oil.

May 22, 2009 | 2003 Yamaha YZ 250

1 Answer

New slip-on FMF Powercore 4 on 02' TT-R250


i looked up in the book for jets for your bike,i diden't see any.you could try to drill out the jet but they are brass.and very fragile.unless you are a machinest.also did you upgrade your air filter to go along with your new exhaust?

Apr 13, 2009 | 2002 Yamaha TT-R 250

2 Answers

Crf 150f backfire


change the jetting...youcan contact FMF for thier setup recommendations for running that pipe with the bike...very common problem and jetting will take care of alot of the issue

Mar 31, 2009 | 2003 Honda CRF 150 F

1 Answer

Jetting a 2001 YZ426


will a 1989 yz426 motor fit in all years

Mar 20, 2009 | 2001 Yamaha YZ 426 F

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