1989 Pro50LF doesn't idle well and bogs

[tal]

I own a 1989 Pro50LF. I rebuilt it about 3 years ago and the cylinders compressions (from 1-3) are 125, 110, 116. I removed the oil injection and mix in the gas manually.

One symptom is a hard miss at idle. Somtimes it runs fine then all of the sudden the miss starts. Occasionally, the miss will cause the engine to die. Everyone I talk to tells me carbs/fuel. It has a new fuel pump, yamaha bubble, gasline, and I redid the carbs last weekend for the 3rd time. They sat in a dip overnight and everything looked clean upon assembly.

My other symptoms are bogging down when trying to get on plane and sometimes while on plane it will surge and hesitate at anything below 5000rpms. Another thing to add in the mix is it will get on plane fine from time to time, just like it will idle fine occasionally.

If I try to isolate it down to a cylinder it will only start and run on #1. #2 it starts then dies off after a bit and #3 it won't start on at all (even if I give it gas through the carb manually).

Before I rebuilt the engine it ran fine except for shutting off for oil starved cylinder #3. It continued to run fine for a while after as well. Are electronics my issue? I don't know what else to do at this point except take it to a mechanic.

 

[tal]

Re: 1989 Pro50LF doesn't idle well and bogs

Well, I think I figured out part of my problem. After I resynchronized my timing and carbs and reset the idle adjustments the powerhead operates much more smoothly at idle. The timing was advanced 2 degrees too far and the retard stop was cranked up, letting it retard way too low at idle. Spark looks good visually on all cylinders but still doesn't run that well on #3 by itself, #2 is better but still not as good as #`. I'm thinking some intermittent electronics. It only spat and died 2x in the time period and rpm it would normally have died probably 10 times. One of those I blame on the head not being fully warmed up. I think I'm getting closer.

 

[Yamajoe]

Re: 1989 Pro50LF doesn't idle well and bogs

Just checking, did you adjust the airfuel mixture screws (1-1/2 turns out from close) and do your final adjustments from this point? connect a timing light to each HT lead in turn and observe consistency of fire. if you notice intermitent fire, then further checks of your electrics will be requried.

 

[tal]

Re: 1989 Pro50LF doesn't idle well and bogs

The Seloc I have says 1-7/8 so that's where I started. They're maybe 2 rounds out all across the board. I've pulled plugs one by one and briefly let the engine run to observe spark and they all look fairly consistent. I accidentally shocked myself and it was a good spark, made me jump in the air. I will try the timing light too, didn't think about that.