Questioni have a pw50 that has been rebuilt,went well but it lacks power now and has slowly got worse. the rebuild was neccassary as the bore was worn out and piston. now i have been thru the carburator and thats all right. our next possibility is the ignition system. spark plug makes no difference but we need a second opinion. If the coil or cdi are dying, will this cause the bike to lack power as time goes on or will it just stop all together. it is our last possibility but after all the things i have tried, i need someone that knows these bikes to give me there own opinion...thanks.
AnswerHi Kathy,
Check cylinder compression and verify the condition of the engine. This will test the integrity of the new cylinder and piston.
With digital ignition, the system will work or it won't.
Spark plug does matter. The plug should have a blue arc at the electrode gap. The plug must be clean and in good condition. An oily or otherwise dirty plug or plug wire may result with flash-over; a condition where electrical current passes over the wire and exterior plug body, to engine ground. When flash-over occurs, there is no arc at the plug electrode.
If the spark plug is loading up (fouling either sooty or wet) engine performance will be affected. Several reasons could cause the plug to foul or load up.
De-carbonize the exhaust pipe. The pipe may load up with oil and carbon, by-products of combustion. The pipe should be inspected and de-carbonized according to Yamaha's perodic table of maintenance or as necessary.
Check reed valves for wear and defects.
Inspect fuel system for evidence of varnished fuel and other contaminants.
It's crital to thoroughly clean the carburetor. Every pinhole in the carb body has an important function.
I return tech information files by email. There was no email address with your question as requested and explained in my instructions.
Respectfully,
Mark Shively
