Blue Needs Help!

[Blue_Runner]

I have a good buddy with an early 90's Yamaha 150. He recently had the same problem and was able to clean the jets and get it back up to par. He lives less than 2 miles from me so I will be calling him soon.

Ferm, explain what you mean by this:

Another thing you can try is to take it out and one at a time pull a plug wire off until you find the cylinder that doesn't change with the plug wire being off.

[willy]

He is talking about listening for the engine rpm change as you remove the plug one at a time. It was an old trick to find out which was the bad cylinder without equipment. Some engines you will hear it better than others, some guys rely on the tach for the detection, the one that is not firing will have no effect on the sound or rpm.
Least that is what I believe he is talking about

[willy]

Just be careful you can zapped by the high voltage and knocked on your keester.

[Mulv80]

I've touched the spark plug boot while the motor was running to make sure I had spark on all cyclinders. You can definetly get a good shock, its not like sticking a fork in the toasted but you can feel it for sure.

Like you said before Blue, if they are all new plugs you should be able to tell if ones not firing just by pulling them and taking a look.

[Blue_Runner]

I'll be sure to pad my keester real good before said test.

Here is the latest question dancing in my head - what if I determine there is one cylinder not firing? What to do at that point?

[Mulv80]

Originally Posted by Blue_Runner

I'll be sure to pad my keester real good before said test.

Here is the latest question dancing in my head - what if I determine there is one cylinder not firing? What to do at that point?

I would check for a bad plug wire first.

[Mulv80]

Blue, i got all kinds of ideas rattlin around in my head about your problem.

Heres one that just came to mind. If the problem started right after you changed the plugs, its possible one plug is defective?

Also, go pick up a cheap spark tester from the auto parts place. You connect it between the wire and the plug and will tell you if you have spark. They are cheap, I bought one at Harbor Freight for like $4.00.