1989 force 85 issues

[85mustangman]

3 years ago we spent too much money to have out force tuned up and adjusted and it ended up blowing up. Well we recently picked up a good used power head. it has great compression, and the crank seals dont leak. First our issue was it had a sheared flywheel key so the timing was way off, fixed that. The first issue is at WOT the carbs are not opened WOT they are just shy. Next we set the timing at WOT to 28 degrees as stated in the book. The motor sounds great out of the at home with the muffs or in our large tub but when we launch it it has a stutter under acceleration and a slight stutter WOT. It sounds like an intermitten miss. Could the trigger plate cause this? my brother kept saying it is timing but according to the light and the marks it is dead on.

 

[steveclv]

Re: 1989 force 85 issues

The miss and hesitation sounds much more like a weak mixture - especially given your history of blowing up a motor (melted pistons?)

Rebuild the carbs and ensure that the jets and tubes/holes are spotlessly clean - new gaskets etc and then set the correct idle mixture and see how that helps.

 

[85mustangman]

Re: 1989 force 85 issues

These are a different set of carbs than those from the blown motor. My brother cleaned them but there is no fuel filter so it is likely that it sucked something up

 

[pnwboat]

Re: 1989 force 85 issues

Trigger has a very low failure rate but you can check each trigger winding with an OHM meter. The should be 50 - 55 ohms. Have you replaced the fuel pump diaphragm?

 

[85mustangman]

Re: 1989 force 85 issues

yeah, the fuel pump is all new. It pumps no problem and there are no air bubbles in the line. I just pulled the carbs off and got the bottom one cleaned so far and the pilot circuit was plugged ill get them all clean and try it and post again.

 

[pnwboat]

Re: 1989 force 85 issues

When you get'em back on, make sure the butterfly's in all 3 carbs are in exact sync when you work the throttle. If they aren't, the motor won't run as smooth as it should. Especially at idle, and when you first open the throttle.

 

[Frank Acampora]

Re: 1989 force 85 issues

Carbs don't need to be EXACTLY horizontal at WOT. Look at the difference between the diameter of the inlet and manifold sides to the venturi. As long as they are close to level, and by close, I don't mean 1/4 closed, the engine won't see a difference. But do make the effort to get them as clos as possible and as stated above, as equal as possible.

Some force engines will have a rough spot right around 2000 RPM under slow acceleration. As far as I know, there is nothing to be done for this. However, an intermittent miss or stutter at full throttle should not happen. At this point, I can not hazard a guess at what to correct. It can be fuel or ignition.

However, I strongly recommend putting a cheap filter BETWEEN the fuel pump and carbs. In the long run, it will save you many headaches.