Question about 2003 Yamaha YZ 250

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Carb problem how do i adjust my carb on my 2001 yamaha blaster that is bored over 30 or do i need a bigger carb or better reeds i have carbon fiber reeds in a hot rode crankshaft i have stock exhaust still on it i keep trying to kick it over and it wont unless i spray carb cleaner in it then it will turn over but not for long then it boggs out when i rev the engine a few times what can be the problem what do i need to fix it

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  • Yamaha Master
  • 767 Answers

With the symptons I think you need to clean the carburator , it seems it doen't get the fuel at all, thts why you hve to spray the carb cleaner to start it !
Remove the bowl of the carb and see if theres fuel coming in once you switch the petcock to 'ON' postion, if it is coming thn prolly the float is too tight (whn the bowl was fitted) thus not allowing the fuel into the float chamber, you will need to adjust the float.
Check the condition of the bowl inside if it has the rusty powderish residue, it will require cleaning and blowing off the jets both the poilet and main jets.
Good luck.

knight (Yamaha Seca XJ750A 1981)

Posted on Apr 17, 2009

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1 Answer

Restricted exhaust


its a case of see if it fits in the right places , then you mite need the carb jets increasing and airfilter replcing with a K n N type to get more fuel and air in to cope with unrestricted exhaust ! Does the engine have reed valves infront of the carb ? could do with opening to max amd fit fiber reeds ! have fun P...

Dec 15, 2013 | Yamaha Motorcycles

Tip

How to tune / de-restrict a 2 stroke


2 strokes in lower ccs are usualy slow, so heres a list of things you can do to de-restrict and tune your 2 stroke.

1) Get a racing exhaust, Key part too most 2 strokes is a good exhaust, this will remove some restrictions. Gianelli, Big One, fmf and many others are available on ebay or your local bike shop.

2) Big Bore kit, adding a big bore kit can give up to 30% more performance, and will usualy de-restrict the bike. search ebay for (Bike Model) (year) Big Bore kit. it will come usualy with everything you need for the upgrade.

3) Carbon Reed Valves, are a key part too your acceleration, also removing the little cages that stop them opening all the way and replacing with big washers is another good step, make sure theres nothing for your reeds to nock on when removing the cage.

4) Boost Bottle, a boost bottle will help 2 strokes with no reed valves more then reeded bikes but will give alot more low and high end performace. search ebay for (bikes cc) boost bottle.

5) Jets, are a key thing when getting a bore kit or race exhaust. you MUST change the jets if you change exhaust, get bigger ones if you get an exhaust go a few sizes over and check the spark plug if its a brown tan/ grey collor you got it all right, if its black it means you have to much fuel so go smaller, and if its white it usualy means not enough fuel. you can buy jets from any motorcycle shop usualy around $1 a peice. you onyl need to change the Main jet.

6) Air Filter, you dont need it on most bikes but it could add extra acceleration, measure your carbeurator intake and search it on ebay for a K&N style filter, Power filter.

7) Restrictors in the intake, some 2 strokes have restrictors between the carb and the cylinder, it is key to remove these or drill them out to the size of the carb/ cylinder hole size.

8) Sprockets, if your lucky enough to have a chain and sprockets, its a nice trick to change sprockets on your bike.
For Top Speed - Bigger front sprocket & smaller rear sprocket
For Acceleration - Smaller front sprocket & bigger rear sprocket
by bigger or smaller i mean more or less teeth on the sprocket. if you go for speed your acceleration will lack and vice versa if you go for acceleration you will loose top speed.

9) Electical Restriction, Some bikes are restricted in the CDI, if yours does not want to reach a good RPM search up CDI, de-restriction. usualy it involves cutting a wire between the CDI and engine. and will unlock that slow engine into a screaming 2 stroke.


If you follow all these steps your 2 stroke will no longer be restricted and slow and will be the fastest arround.

on Feb 16, 2010 | Motorcycles

1 Answer

Yamaha blaster. yfs200 carb problem?


Hey Anon, sounds like you may have done something wrong when reassembling your Blaster... When you "cleaned" the carb, you may have reassembled it incorrectly.. This sounds serious!!.... this situation is difficult to diagnose on-line.. I wish you were near me.. . (North Alabama) .. I am a 40+ years Yamaha Factory tech... I could fix it...

Jul 16, 2017 | K&L Boating

1 Answer

I want more power in my bike. i have v force 3 reeds but not enought wat can i do on my carb wish size of jets can i use to have more power and wish is the better fuel ratio to mix.


the way u can get more power that u can really feel is to do two things, bore the engine out for a bigger piston size and port the engine, 2 stroke engines respond well to these changes, consult a shop on the job, it is not something an amatuer can do, u need specail skills and equip, the carb will also have to be rejetted.

Jan 08, 2010 | 2004 Suzuki RM 125

2 Answers

What size jet would i need if ive got a 70cc big bore kit on a standard carb ??


I believe the standard starting place is to go 2 jet sizes bigger, but I would check with the manufacturer of the big bore kit to make sure. Hope this helps

Oct 26, 2009 | 2000 Yamaha XV 125 - S

1 Answer

2001 blaster losses power under a load.


check the compression and if thats good, remove the air filter and try to start. or possible air fuel jet needs adjusting.

May 06, 2009 | Yamaha YZ 250 Motorcycles

1 Answer

Low power stumble at idle to low rpm


try placing the reed spacer between .reed assembly & cylinder, also try an adjustable ignition stator plate, set at +4, k & n air filter, open air box.replace T.O.R.S. eliminator system w/ a cap & cable, and idle air screw install kit, also a pipe tuned for more torque(bottom -end/mid range) blasters dont have a lot of power on bottom end and the engine needs to rev to hit power band.cylinder porting,240 bigbore kits, & +4mm stroker crank assemblies are good performance options.

Feb 22, 2009 | 2003 Yamaha YZ 250

2 Answers

Low power from low to middle rpm


Two strokes exhuast is very important for low end volumetric efficiancy. Check for cracks leaks and even crushed expansion chamber will effect low end performance.

Feb 09, 2009 | 2003 Yamaha YZ 125

2 Answers

Very low end power


Replace the reeds, Clean the carb jets and adjust mixture screws.


Please rate this a fixya

Feb 06, 2009 | 2003 Yamaha YZ 250

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