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Motorcycle Repair/81 yamaha sr250 exciter ...


QUESTION: Have a 81 Yamaha sr250 exciter ... It has been sitting for a while ... I can get it started but as soon as I hit the throttle she boggs down and dies ... Any ideas ?

ANSWER: Hello Rob,

Your carburetor needs to be removed and thoroughly cleaned. When the bike sits for a long time, the gasoline in the carburetor evaporates and leaves behind it's solid additives, which clog the jets. If you're lucky, just cleaning the main jet will solve your problem.

The hard part is that, solvents capable of removing the hardened gasoline residue, are only available to professionals and hard to find in retail.
You can soak the main jet in kerosene and then use copper (and ONLY copper) wire to clean it's bore.

If you need further info and/or detailed instructions, let me know.

Best Regards,

---------- FOLLOW-UP ----------

QUESTION: So l cleaned the carb / jets and reinstalled the carb can't get it to fire still any ideas?

ANSWER: Hello Rob,

First of all, do we know if the bike was running O.K. before left unused ?
There is a big difference between, problems due to prolonged parking and problems due to usage.

Anyway, many times we think the jets are clean, but their bore is significantly reduced by gasoline leftovers and no cleaner spray or compressed air can clean it.
Best way to be sure is to find another main jet of the same number, compare the holes and replace to be sure.
Since I don't know what spec is your bike, I'll only refer to the European spec #140 main jet,
which is about 1,3mm in diameter. If you can find a 1,3 drill bit, it should pass through the jet with relative ease.

If none of the above works for you, let me know, when did the problem occurred, what spec is your bike (49-state, Cal, UK, EU or if you don't know, give me the V.I.N. number) and what number is the Main Jet.

All the best,

---------- FOLLOW-UP ----------

QUESTION: OK... Cleaned carb and installed .... Put in ethanol free gas and added sea foam in gas got it to start and run ... I'm still having problems giving it gas it stalls when I pull the throttle , could it be a problem with the battery ? I replaced the battery and charged but the bike keeps dieing like its not charging the battery when its running .... Could that be part of the problem?

Hello Rob,

You haven't answer my question, if the problem occurred before or after left unused.
Also, what number is the main jet.

Insufficient battery charging could mean, malfunctioning generator and therefore weak ignition.
Have you changed the spark plug? If yes, close the gap to 0.5mm and try.
If it gets better, you should check electrical system.


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Lazaros Ampatzidis


I can help you on EVERY issue involving POST-1980 Japanese Motorcycles plus KTM and Husaberg. My field of expertise includes Engine, Transmission, Fuel system (carburation & EFI),Electrics and Electronics. Maintenance, repair and tuning. Road and off-road suspension tuning. Please don't ask me about non-Japanese Motorcycle, especially American built on which I have low to zero experience.


I'm a rider and hobbyist since childhood. 25 years motorcycle workshop mechanic.15 years motorcycle racing mechanic. In order of experience high to low:Kawasaki,Suzuki,Honda,Yamaha,KTM,Husaberg.

Hellenic (Greek) Technical School.Internal Combustion Engines Engineer. Automotive Electronics.

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