1989 Yamaha V4 115

[goffball56]

Have a 1989 yamaha 115 freshly rebuilt and idles perfect. when put on the water idles around perfect and take off it will shoot out of the hole and run couple 100 yards and drop #3 cylinder but idle around all 4 fire great. Switched coils and still same #3 cylinder. Anyone have an idea what might cause this. Thanks Justin

 

[99yam40]

Re: 1989 Yamaha V4 115

need to find out if it is dropping the spark or if it is fuel related.
Timing light should indicate if spark is going away.

Not sure if fuel pump is getting its pulse from #3, but if so check to see if it has hole in diaphragm

 

[goffball56]

Re: 1989 Yamaha V4 115

Done checked the spark and its fine. it did how ever have an orange looking spark and as for the fuel pump we have put 3 different fuel pumps on this motor. were thinking it could be either the Stator or trigger. Is either one of these a possibility?

 

[99yam40]

Re: 1989 Yamaha V4 115

How did you test the spark at the problem RPM?
If you want to see if charge coils and pulsar coils are good then you need to test them with the proper equipment like the service manual states.
Did you test the fuel pressure and vacuum to see if they are a problem at the RPM you are having problems?

Testing things is a lot better than throwing parts at it and hoping that was the problem

 

[goffball56]

Re: 1989 Yamaha V4 115

Checked the spark idleing on water hose and buddy had timing light on the #3 cylinder on the water as we ran it and still getting spark but the spark would have a consistant pause in it flash, flash, flash, pause, flash. All fuel pressure is good cause we tried squeezing the bulb when it does it and also spraying mix gas in carbs still nothing. i hear its rare for a stator to go out on a yamaha but im no motor mechanic. My buddy is and he can't figure it out either. We have done resistant test on the CDI but none of the numbers come out right.

 

[99yam40]

Re: 1989 Yamaha V4 115

peak voltage readings are best of inputs and outputs of cdi..
Pause on timing light sounds like it is dropping spark
without testing pressure and vacuum you are guessing
CDI does not have resistance tests that I know of, just the coils for input and out put of CDI have resistance /ohm tests

 

[goffball56]

Re: 1989 Yamaha V4 115

What exactly do you mean by testing pressure and vaccum? we have pretty much done everything we could do instead of throwing parts to it. if it was a trigger then wouldn't 2 cylinders go down instead of 1. is this something caused by a bad stator?

 

[multimech]

Re: 1989 Yamaha V4 115

You are on the right track...keep the timing light on #3 while you hit the speed it causes a problem at. If the light "blinks" then that cylinder is missing. Compare it to the other cylinders. Check the stator and trigger with an ohms check and an output check. If they both pass, then the problem is most likely a pack that is heating up and failing.

 

[goffball56]

Re: 1989 Yamaha V4 115

checked all these things and all seem to be fine.

 

[goffball56]

Re: 1989 Yamaha V4 115

Im beginnig to lean towards more on a bad CDI rather than a Stator. What do you guys think?

 

[99yam40]

Re: 1989 Yamaha V4 115

If you would give us the results of your testing ( not just they are fine)and what equipment you used to test these things with, we might be able to answer with some kind of accuracy