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Motorcycle Repair/1981 honda nc-50 express


QUESTION: why will the motor run for only a few seconds when i spray starting fluid into carb? The carb was cleaned, jet blown clean,float working freely gas in float bowl but not getting gas to the motor. Gets good gas flow from fuel shut-off,tank was cleaned out completely. carb cleaned number of times to check for plugged jet.Sure could use your advice!!!

Drill bit kit
Drill bit kit  
Jet Cleaning
Jet Cleaning  
ANSWER: Hello Ray,

In most cases, the residue clogging the Jets is too hard to remove with cleaners and/or compressed air.
The way to go is, get a Jet cleaning needle kit or drill bits (pictures) according to the size
of your jets ( i.e.: size 80 jet requires 0,80mm drill bit).

Visit this page:, to learn more about jet needle-cleaning.

Get back any time, if you need more info...

Best Regards,

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

QUESTION: Hi again lazaros,my manual states that loss of crankcase compression could be part of the problem,if thats true,do i use a compression gauge like u would use in a car?If that is the problem,how do i correct it?Thanks again for your help!Rayuqxo

Hello Ray,

I don't know why, but I thought that the bike worked well before, left unused and the carb is the only problem... Sorry about that, seems I messed up questions!!!

First thing, yes, the reed valve affects a great deal the fuel mixture delivery, but also the crankcase compression.
If this is the case though, I find it difficult that the bike would start even with starting spray, because the mixture is blown back through the carburettor.

Cylinder compression on the other hand, could be responsible and it makes sense with the starting fluid, which helps combustion when we have low mixture flammability due to lack of compression.

You can check cylinder compression, the same way as you would in a car.
Normal pressure is 10bar, but it should be able to start with as low as 5,5 to 6bar .
Crankcase compression can not be measured with conventional tools, but if the crankshaft seals
and the reed valve are in good condition, it shouldn't be a problem.

Start by measuring cylinder compression and if you find it low, you should remove the cylinder,
check it for scars, and also piston and piston rings.

Another common issue is the main (key) switch. Disconnect it and try to start the engine.
If it runs OK , the switch has a leak and "steals" current from the ignition.

Get back to me with results...

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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