Reed valve Ass'y

[Clive]

Can any one tell me what syptoms would I have if the reed valves had failed on my Yamaha 20A, She willnot fire up with the chocke out even from dead cold. I have fitted a complete new carb and fuel pump with no change. The plugs ar egetting very black after a short run, I have tired the mixtrue and that does nothing to change the color of the plugs,She is not missing and shuting her slef down as if there is no fuel getting to one of the plugs.

[Hamfisted]

Lots of spitting back out through the carbs, backfiring. Fuel line is in good shape? Coils test good?


Mike

[jb123]

start with the basics...fuel,spark and compression. check compression and ensure your coils will jump at least 1/4 inch and was the carb cleaned or brand new? dont cheat your motor by not cleaning the carb thoroughly.

[Ken]

Clive,
Symptoms of faulty reed valves - spitting of fuel back thru the carb throats, hard starting, and little power, i.e., not reving up to normal max rpm.
With the plugs gettting black, sounds like poor spark, assuming the carbs are doing their job. Or maybe, spark advance not doing it's job.
You need a Yamaha shop manual to help you troubleshoot.
Good luck [img]smile.gif[/img] ,
Ken K

[Clive]

Many thanks all I am going to take it into my local dealer for him to have a look at it for me,its not blowing back through the carb so thats one good thing,it could be one pot is not geting enough spark perhaps the coil is giving up any way I am ver gratfull for the information received. have a good weekend.