TN-27 5 hp motor fluctuation issues

[gmarshall43]

I was given this motor, TN-27 that was not starting. I think it is from 1951. I got it running. It starts up easy and idles nice and will run good at high speed but the one problem I have is that after it has run for a few minutes the motor speed fluctuates on its own. That is the speed of the motor slows down and then speeds up by its self. Sometimes it keep on doing that or just stall out. I tried cleaning out the carb but that didn't help. I like this little motor and would like to get it running correctly. Any one have some suggestions?

Thanks,
Gary

 

[HighTrim]

What is the low speed needle set at? I have found 5/8 about right. High speed? Look for air leaks into system.

Did you go over ignition system? Steady spark on both cylinders?

 

[Rick.]

I had the same symptom with my little 3 HP last week. Turned out to be I had forgotten to open the vent valve on the tank. Never thought I would do that but I did. Certainly sounds fuel related. Best of luck. Rick.

 

[gmarshall43]

I thought that vent valve should be closed when running the motor. Should I run it with it open? My low speed is set about what High Trim suggests and I adjusted the high speed while out on the lake and think both are adjusted correctly. Getting good spark on both plugs. I do have water squirting out by the swivel bracket between the the power head and lower unit. I didn't think much about it since I was getting a good steady stream coming out of the motor. Should I be concerned about it.

Gary

 

[HighTrim]

No that should definately be open! You wont get enough fuel with it closed, if any.