cutting out due to ignition???

[CobyAhh]

1990 Yamaha C85 hp. Ran fine, sat 4 months during transom work. Starts and idles fine. Now cuts out with rhythmic bam-bam-bam when any throttle over 5%. This is with or without load. in or out of gear. Went through all 3 carbs and cleaned. Plenty of fuel visibly spraying in all throttle bodies when i hit throttle. Seemed like starving for fuel until i did all that. Now it seems like an ignition issue, plenty of fuel but not firing to keep up. also put brand new plugs in. Any suggestions?

 

[MikDee]

Re: cutting out due to ignition???

Is your spark advance system working?

 

[CobyAhh]

Re: cutting out due to ignition???

Im not familiar with that...I know about mechanical timing and points, but this is a different system im not familiar with. It ran great prior to sitting, so it must not be that type of timing... any thoughts? Check stator?, coils? Remove flywheel? Thanks

 

[99yam40]

Re: cutting out due to ignition???

timing light will show what the timing is doing

compression, spark, and timing should all be tested, and are easy to do with the proper test equipment

 

[CobyAhh]

Re: cutting out due to ignition???

Very interesting and good news: It was the thermal switch. I just disconnected its lead from the CDI, and motor runs fine! It was a rev limiter in the ignition caused by faulty thermo (anti-overheat) switch. That beat the heck out of testing all the coils, timing, etc.

 

[Capt Ken]

Re: cutting out due to ignition???

I doubt it's a faulty thermo sensor. You probably have a overheating problem and disconnecting the sensor just means you will destroy the engine. Also means your overheat alarm isn't sounding

 

[CobyAhh]

Re: cutting out due to ignition???

I doubt it's a faulty thermo sensor. You probably have a overheating problem and disconnecting the sensor just means you will destroy the engine. Also means your overheat alarm isn't sounding

That couldn't be more wrong! The cutting out happens right after starting a cold engine. This has nothing to do with temperature, but thanks anyway.

 

[Capt Ken]

Re: cutting out due to ignition???

Im not familiar with that...I know about mechanical timing and points, but this is a different system im not familiar with. It ran great prior to sitting, so it must not be that type of timing... any thoughts? Check stator?, coils? Remove flywheel? Thanks

You've already admitted you don't know how the system works. Your alarm system is not working either.

 

[Ldavidgrover]

Re: cutting out due to ignition???

Link and sync you carbs after cleaning?