1997 30 hp misfire

[rdm924]

I have a 1997 2 stroke Yamaha tiller, it has started to misfire, mostly at wide open but at times lower speeds too, I think it is intermittently dropping a cyl. I have changed the plugs and run some sea foam through it. I was wondering if there were any common problems with these motors.

Thanks for any help

 

[Kamdyn]

Re: 1997 30 hp misfire

What kind of plugs and whats the heat range are you using?

 

[rdm924]

Re: 1997 30 hp misfire

I'm using Champion L77JC4, I just went by what was in it from the factory. Are you able to tell the heat range from the part #?

 

[Kamdyn]

Re: 1997 30 hp misfire

I'm using Champion L77JC4, I just went by what was in it from the factory. Are you able to tell the heat range from the part #?

Yep the first number tells me you are using a 7 heat range, try a hotter plug like a 6 and see if that solves your problem, I think you are fouling your plugs. I was told by my mechanic that there was a misfire and that I might have electrical problems. Another mechanic told me to use a hotter plug, Now my motor runs like a champ. It warms up fast and I havnt fouled any plugs since.

 

[rdm924]

Re: 1997 30 hp misfire

Thanks Kamdyn, I'll give it a try, yesterday it did run better after using it for about half an hour. so I get plugs that have the same part # except for the first #?

 

[rodbolt]

Re: 1997 30 hp misfire

why not simply fix the motor, your heat range plugs are not the problem.
the fact it has champions may be as ALL yamaha 30 motors came from the factory with NGK plugs.
heat range on plugs has absolutly NOTHING to do with how fast the engine warms up.
its funny how even most techs have no clue about what heat range means.

 

[rdm924]

Re: 1997 30 hp misfire

why not simply fix the motor, your heat range plugs are not the problem.
the fact it has champions may be as ALL yamaha 30 motors came from the factory with NGK plugs.
heat range on plugs has absolutly NOTHING to do with how fast the engine warms up.
its funny how even most techs have no clue about what heat range means.

OK Rodbolt, how do I start to figure out this misfire? Its only intermittent and hard to narrow down to a particular cyl