Question about 2004 Yamaha YZ 125

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When I start bike it rev flat out

Checked carby & reed valves & they look ok

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Idle adjustment, throttle cable, vacuum leak, carburetor. THOROUGHLY CHECK them all

Posted on Nov 26, 2014

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1 Answer

Misfire on Tohatsu outbaord.


one would assume so but as you have not mention if it is a 2 stroke or 4 stroke , that assumption would possibly be wrong
2 strokes use reed valves between the carby and manifold and the crankcase and in outboards these reed valves can split and not function properly especially at higher prms
these reed valves allow fuel mixture in when the piston goes up and shut off when the piston comes down creating a pressure in the crankcase which pushes the mixture up the bypass of the cylinder into the combustion chamber
if these reed valves are not working properly or the crankshaft seal are failed this compression in the sump doesn't occur properly and engine running problems result
IF it is a 4 stroke the soaking the carby in cleaning fluid will only remove 1/2 the problems
It is best to have the carby fully overhauled by an accredited outboard mechanic as there will still be corrosion in the body and mixture passages that cleaning fluid alone will not remove.
have the ignition system checked as it may be an overheating component ( coil --ignition module) that is causing the failure.

Aug 11, 2015 | Boating

2 Answers

04 yamaha yz125 when I start bike it revs flat out, checked carby &; looks ok


Hi, check the throttle slide is at the bottom with just a small gap, if its higher, check your throttle cable, if they are ok you might have some dirt in the jets, youneed to clean the the inside bottom of the carb and blow the jets out with an air line. good luck.

Nov 26, 2014 | 2004 Yamaha YZ 125

1 Answer

Bike was running great on saturday. Went to the races bike started right up when the gate dropped bike won't rev out all the way. Didn't have this problem yesterday. When we got home i cleaned the car


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
YZ250 electrical issue won rev up
YZ250 bad reed Yamaha 2 Stroke
YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

May 19, 2014 | 2007 Yamaha yZ 250

1 Answer

Small pinholes in the reed valves


Yes mate... It is hard to say without seeing the reed valve but I guaranty a dodgy reed valve will make running and tuning the bike a nightmare. Your reeds need to seal perfectly and open and close about 2-3 times a second so if any cracks, holes or damage to them then they will never seal correctly which will allow blow back through the carbi and incorrect air and fuel mix to be sucked into the motor. best solution buy a V force reed kit it replaces the entire cage and reeds just bolts in (4 bolts) I sell them for about $160 delivered, or if your know what you are doing then you can just replace the reed petals with new... About $60 ishwww.motoxpartsonline.com

Feb 21, 2012 | 2004 Yamaha YZ 125

2 Answers

Hello, I recently purchased a 1973 Suzuki TS 185. The bike turns over and starts right up very easily. When the bike idles I can rev it and it seems to work very well in first and second gear. However,...


Check for air leaks. You probably need new crank seals and a new intake manifold. Check your reed valves if you have them and do not hold the throttle wide open if it is bogging you will score the cylinder by running it lean.

Oct 06, 2010 | Suzuki TS 185 Motorcycles

1 Answer

YZ 250 1995 2 stroke have spark,cleaned carby & fuel tank,good compression, mixture 35.1 cannot start my legs going to drop off... Timing has not been touched also use to start & run fine....


If you have a good fat spark and timing is stock, with good compression, your problem is likely fuel/air mixture. Assuming you have good quality fresh fuel/oil. Set air mixture screw one and a half turns out. What is the condition of the reeds and reed holders. Is there a build-up of fuel/oil residue on the piston port skirts or the crankshaft? Check for absolute seal between carby and reed valve manifold. Check for obstructions through airbox inlet, filter and inlet to carby. Ensure the governor is not fouling. The site link below has exploded view diagrams for all components of the bike to see how it all works. Good luck, cheers.

http://www.cmsnl.com/yamaha-yz250g1-1995_model10278/partslist/

Jul 15, 2010 | Yamaha YZ 250 Motorcycles

1 Answer

My yamaha blaster will not start after my chain came off and over reved it has spark and compression. what should i do?


If this bike is carburettored, not EFI then you have damaged / bent the reed valves in the carby.

Remove carby which has the reed valves on the inlet side and you will see them bent. Replace with brand new, you are wasting your time to try and straighten them!!

Dec 20, 2009 | 2008 Yamaha Yamaha G5

3 Answers

Kx 125 reed valves


The reed valve assembly should hold solvent withot leaking. Remove for test. Disassemble and clean reeds and reed seat. Perfect seal is very important.

Good luck,
Techjoel

May 17, 2009 | 2003 kawasaki KX 125

1 Answer

Carb problem


You have an air leak that is making the fuel mix too lean. Probably intake manifold gaskets. Other sources are reed valves chipped, deformed or broken, cylinder head gasket not fully sealing and crank seals gone bad. Your bike is 20 years old, I don't remember if your bike has reed valves.

The dealer is not going to have new parts. google " suzuki motorcycle parts " and " antique suzuki motorcycle parts "
also google " motorcycle salvage suzuki ". This should give you some sources for parts.

Please rate this solution. Thanks weldin_fool!

Apr 18, 2009 | 2003 Suzuki RM 125

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