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Richard, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 3020
Experience:  Senior Mechanic & Technician
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Bike..that when you give it full throttle, sputters and loses power

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i have a rm 125- 2 stroke dirt bike, that when you give it full throttle, sputters and loses power. what is causing this


How are you ?


When did this happen, how long ago ? What were the weather conditions ? What were the riding conditions ? Has there been a change in elevation ? Did this happen after the bike had sat for quite a long time without being ridden ?


Lots of directions to go here. I will start with a few and let me know if you have questions, I will list what to check and look for and some tips here.


Clean or replace the air filter. If the bike has sat without being ridden for quite some time or if it has been a while since the last carburetor service, then I would rebuild or clean the carburetor. Check for intake leaks around the intake boot and head gasket, which is located between the engine and carburetor, spray some carburetor cleaner in thee areas and if the rpms change, you have a intake leak, If the boots are cracked or torn replace them. Check your ignition coil wire and spark plug cap for splits or cracks, if there damaged replace them ( I would trim them back about 1/4 of an inch or so and see if it helps, the spark plug cap, can be removed by turning it counter clockwise ) Lastly compression test, vacuum test and crankcase pressure test to verify intake and crank seals and gaskets.


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Thanks. RaceTech ( Suzuki ATV & Motorcycle Expert )


Of you have other thoughts or questions. please post them.


If you do, please reply back by answering my above questions and then your repsonse and your sparkplug colors.

JACUSTOMER-6ohrrx8v- :

Thanks for the advice. My mechanic suggested that i replace the reed valves after doing so, the problem slightly lessened but didn't go away. now when i change my spark plugs, i found alot of oil residue

Richard and other Motorcycle Specialists are ready to help you
Oily residue, could be the coolant or a strong mixture. I would aslo check the exhaust and make sure it is clean and clear, the residue could be fuel mixture build up from a plugged exhaust.
Richard and other Motorcycle Specialists are ready to help you
Customer: replied 6 years ago.
so i changed oil mixture and have same result would anything in the top end need to be cleaned due to the previous high oil to gas mix
Customer: replied 6 years ago.
one more question, engine has close to 40 hours of ride time on it since last rebuild how often do you suggest rebuild
Just the exhaust and make sure your not loosing coolant. Does the choke make a difference at all ? If so, then you could be looking at air and fuel mixture ffrom a dirty caburetor.

20 - 40 hours depending on how hard you ride. You will need to atleast check everything and hone the cylinder to install new rings. I rebuild customers every 15 - 20 hours on the race bikes. So that is about every 2 races or so,depending on the rider.

Non serious riders usually go 40 -60 hours before they will need a rebuild.
Richard and other Motorcycle Specialists are ready to help you
Customer: replied 6 years ago.
thank you so much - i will leave great feedback again - you have been a great help - appreciate it!!!!!!!!!!!

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