1986 50 ETLK Yamaha- Stutters past 4500 RPM

[w2much]

Can't figure it out. Thought it was a fuel issue. Replaced the fuel pump, tried other fuel line, rebuilt the carbs(they appeared fine but purchased the OEM kit anyway), bypassed the fuel water seperater. Fuel does not seem to be the issue.Idles perfectly. When I slowly increase the throttle I can get to 5000 RPM. If I open her up quickly from slow speed she will go to about 5000 RPM the start to stutter and slow down to 4500 RPM. Motor has run perfect in the past at 5600 RPM which is all she would do. Can not figure out why I can not get her to open up and stay at WOT. It was mentioned that intermittent spark on the 3cyl CDI's is problematic? I checked for spark in all cylinders which seemed OK as idle is not the problem. What I did notice was that when at idle I pull the plug wires the #2 cylinder spark does not jump as far as the other two. I then swithed the wires from the CDI to each of the other coils. Each time I switched the #2 CDI wire to the other coils the same thing happend( the spark did not jump as far). I am fairly convinced this is not a fuel issue. Might this be CDI, coil, or what the heck? If you need more info ask. As always your replies are appreciated.

 

[w2much]

Re: 1986 50 ETLK Yamaha- Stutters past 4500 RPM

Pulsar coils, stator, charge coils, CDI?

 

[JUSTINTIME]

Re: 1986 50 ETLK Yamaha- Stutters past 4500 RPM

you need a manual and a meter with a dva

 

[rodbolt]

Re: 1986 50 ETLK Yamaha- Stutters past 4500 RPM

a K model is beyond my poor memory.
does your engine have a CDI with a link rod attached to the carbs or 3 pulser coils?
what your describing is a fuel issue unless your CDI uses the link rod. then it could be a rod adjustment.
in anycase,like justintime says, a quick spin with a DVA attached to the coil primaries will tell the tale.

 

[w2much]

Re: 1986 50 ETLK Yamaha- Stutters past 4500 RPM

Once again, Thanks Rodbolt and Justintime. The CDI does not have a rod attached. The engine has 3 pulsar coils. I have a manual and have been going over it in my spare time. I have a multi meter. Will that work? I just need the time and quiet to do the testing. It has taken a bit of learning just to know how to go about the testing. Any suggestions are appreciated. By the way, when the symptoms occur I can sqeeze the fuel bulb but the symptoms persist. What do ya think?

 

[w2much]

Re: 1986 50 ETLK Yamaha- Stutters past 4500 RPM

OK. Had time to study the manual. Did the test on the pulsar, charge and ignition coils. They all checked out to spec. Finally I used a new fuel tank and fuel line with a new Yamaha fuel connector. I noticed a hairline crack in the line to motor connector. Problem solved. The simplest of all repairs after fuel pump, carb rebuild and many weeks of frustration.