Engine Idles Fine, Does'nt Run At High Speed

[pickleme101]

!8hp Fastwinn mod 18002C was running rich replaced float seat and needle stop. It ran fine in the barrel but not on the water, would start to go into high rpm but constantly dropped down to a lower rpm and continously surged up and down. Opened carb and checked HS jet gasket seemed bad tried to seal off with O ring thought fuel might be leaking past threads on jet. Did not fix problem, ran fine in tank in gear, but not on lake in gear. Past experience with a similar problem appreciated.

 

[emdsapmgr]

You may have a weak fuel pump. May not be able to supply enough fuel to run the engine at WOT. Test by constantly priming the fuel hose bulb next time you are o the lake. If the engine runs fine at WOT as long as you constantly prime the fuel hose bulb- you've got a fuel restriction, which could include a weak pump.

 

[racerone]

Check spark---------It is common for these motors to run on one cylinder !

 

[pickleme101]

I will check both this morning on the lake. Thankyou both

 

[pickleme101]

Racerone, Sure enough it is running on the bottom cyl. only. I switched the plug wires top to bottom and it didn't fire. I figured if the top coil was good and the bottom plug was good it would run on bottom cyl. is this correct. Not familiar with timing of these engines.

 

[lindy46]

If it runs with the plug wire pulled off the top plug, but doesn't run with the plug wire pulled off the bottom plug, then it is only firing on the bottom cylinder. That engine will probably idle ok on one cylinder. You may have a coil cutting out once it warms up, resulting of the "surging" you notice at high speed.

 

[oldboat1]

probably a couple of shorting leads going to the magneto -- think I would disconnect those first to rule out potential issues. Can choke to stop. Coils new?

 

[pickleme101]

Yes the plug is good must be a coil I'll take it to some one before I get in over my head. Pulling the fly wheel was straight forward pulling the timing plate looks more serious. Thank you for your time and patience.

 

[racerone]

???----Those magnetos are easy to work on.--No need to pay someone at all.

 

[HighTrim]

Racerone, Sure enough it is running on the bottom cyl. only. I switched the plug wires top to bottom and it didn't fire. I figured if the top coil was good and the bottom plug was good it would run on bottom cyl. is this correct. Not familiar with timing of these engines.

No sorry does not work like that. The plug wires MUST be on the correct cylinder to run.

To test this, get an adjustable spark tester. Set it to 1/4" Spark should jump this with a bright blue ZAP!!. Could also get some neon inline testers, to watch the spark while underway, to see if it cuts out, or timing light.

Flywheel is easy to pop, if you have the correct tools. Take the nut off (air impact gun takes care of that with ease). Then pull with a harmonic balancer puller with grade 8 bolts.

The mag plate is simply 4 screws holding it down. 2 through the coils, 2 just through the plate. Simple and easy. Could be as simple as cleaning and setting the points, but wont know till you open her up.

 

[pickleme101]

https://www.youtube.com/channel/UCQDjj5hcWx-rDbZyyRLb3Wg Here is the link i found to answer all my questions, BUT do you think i can align the coils with a straight edge, or will I need a special tool.

 

[lindy46]

You can align them fairly accurately with a straight-edge, or just use your fingernail. If your nail catches either on the coil or on the mounting boss, just move the coil slightly in or out until your fingernail runs smoothly over the edge of the coil and the mounting boss.

 

[pickleme101]

Ok I removed the wire going to the cut off switch because it was pinched and I couldn't rule it out. I've pulled the flywheel off so many time now I could do it in the dark. I adjusted the coil in and out and still no spark. Before I tried adjusting the "coil gap" I placed one thickness if masking tape over the magnet. I got up to 5 thickneses of tape before the magnet face rubbed the coil. So what is better more or less gap and does any one know what the gap should be. Thankyou one and all for your time and comments

 

[HighTrim]

The closest you can get it to the magnets without touching is best, for best spark.

 

[oldboat1]

plug wires -- need to be solid core, with good connection at the plug and the coil. Spike for the spring connector at the plug has to pushed through, in contact with the core -- likewise the spike at the coil.

 

[pickleme101]

Ok next step will be to try and get coil within 2 thicknesses of masking tape, and trim the plug wire back at the coil. Thank You

 

[Tim Frank]

!8hp Fastwinn mod 18002C was running rich replaced float seat and needle stop. It ran fine in the barrel but not on the water, would start to go into high rpm but constantly dropped down to a lower rpm and continously surged up and down. Opened carb and checked HS jet gasket seemed bad tried to seal off with O ring thought fuel might be leaking past threads on jet. Did not fix problem, ran fine in tank in gear, but not on lake in gear. Past experience with a similar problem appreciated.

Going back to your OP....and usually it's a good idea to review what has changed to cause this problem, when you say "was running rich", what were the symptoms to make you conclude this, and why did you believe that changing the needle and seat was the cure?

Did you actually do HighTrim's test?

To test this, get an adjustable spark tester. Set it to 1/4" Spark should jump this with a bright blue ZAP!!. Could also get some neon inline testers, to watch the spark while underway, to see if it cuts out, or timing light.

If not, you should, and compression as well.

 

[pickleme101]

I have been working on the motor and after replacing the plug wire now have spark to the top plug, but still not firing, plug has fuel on it when removed, first compression test was 90 psi second about 75 psi. Will I get it to run or is this too low to start/run that cylinder.

 

[racerone]

Saying that you have " spark " is not good enuff.----Answer this way, " I have spark that will jump a gap of 1/4" with a snap ".-----That means something here.

 

[pickleme101]

Thanks will try again with a different tester.