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Motorcycle Repair/1981 honda nc-50 express


QUESTION: Hi lazaros, want to let you know that i got the honda to run for a few days.It would start easy and ran well both at low and high revs.Tried to start it one day,same old problem,no gas to motor also plug shows signs running lean.Do you think i have a leak in my intake manifold?I thought when i cleaned the reed unit it had solved the issue.Any suggestions? Thanks again!!

ANSWER: Hello Ray,

I'm afraid, you have to give me more info at this point. Go back to my previous answers,
and provide me feedback on the subjects I've pointed (cylinder compression, intake suction,
main switch condition, fuel jets measured size).

I also have some more questions, that are very crucial, in order for me to give you correct
a)Does your bike have electronic ignition or points?
b)Does it have manual choke or controller (a little "box" attached to the cylinder-head with
three hoses connected to the carburettor)?

If your bike is actually an '81 model, it should have CDI (electronic ignition) and automatic choke (controller).
Last but not least, if you could take pictures of the spark plug and the air-filter box, it would be great!

Maybe all of the above seem too much, but bear in mind that, your bike may have a problem
that could drive a Pro crazy even by having it on his work-bench, especially due to long-term immobility. Everything may seem OK and a small crack on a choke hose do the "damage"!

Resuming, since you're a coming-back, loyal "customer", give me the chance to be more effective.
Let's get down to business!!!

Best Regards

P.S.:BEFORE all the above, try setting the air screw to half a turn from fully turned in (feedback on this too).

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

QUESTION: Hi lazzros,Yes the honda has points and a controller.The only way i checked the compression was with my thumb,seemed like it was enough,It ran for those few days.I was running the scooter without the air box on,I'll try to send you a pic .I took the carb and intake off again,i noticed the reed valve seem to stick a little when i depress them might be the issue? Don,t know how to check intake suction.Just seems crazy that it ran well for those few days! Won't be able to try to start again for couple of days,busy with new granddaughter! Thanks again,Ray

Hi Ray,

NEVER and I mean NEVER, run a two-stroke without airbox. Apart from filtering, it controls the intake air flow. Without it the engine runs way too lean, even to the point of piston seizure.

At this point, checking cylinder compression is a must-do. You must get a compression tester,
even a cheap Chinese one, to measure it. If this is out of the question, then check again with your thump, with the carburettor on and wide-open throttle, fast kicks on the starter (you'll probably need someone to assist you) and your thumb should be blown away with loud "pops".

Next, check suction as follows: remove spark plug and plug the carburettor opening with your
palm (put on a single-use rubber or surgical glove) to block incoming air. Hit the kick-starter
swiftly and repeatedly several times. If you feel your palm sucked-in, get wet by fuel and fuel get sprayed out of the spark-plug hole, then you're OK.

Get back to me with results whenever you're ready.
Granddaughter first!!! Congratulations, by the way, enjoy quality time with her...

Best Regards,

Motorcycle Repair

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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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