Fleetwin

I have a 1953 Fleetwin 7.5. Every couple years I get the ambition to work on it again but just can't get it right. I rebuilt the carb and it has new high speed coils, plugs and wires. It's spotless for the most part. The compression is about 70 psi, equal on cylinders. I'm not sure if 70 is good for this engine??? It start easily. The problem is that the RPM's run away (idles then up to about 6,000 RPM I would guess) then it missfires and goes back to idle. It does this over and over and will not maintain consistent RPM. It is worse under load when on a boat pushing the prop. I'm not sure where to go next and hope someone can help me look at some new things... Thanks!

Re: Fleetwin

Well, I've worked on a bajillion motors, but never heard that one. Let us know what you find.

Re: Fleetwin

It sounds like there is still an issue in the carb, because it sounds like it's getting a bowl full of gas and then running it out. Is the carb float adjusted right? Also make sure it isn't upside down.
I think that model has the Tillotson card on it, if so, then your low speed should be about 1/8 to 1/4 turn out, from lightly seated. High speed should be about 1/2 to 3/4.
70psi isn't is fine on those holes. It could be better, but if it starts easy, then that is not the issue.

Re: Fleetwin

I'm thinking carb too :/ search the forums for "runaway carb" and you'll find lots of info too. I know my 33hp has a runaway kill switch on it to prevent just such a problem.

Re: Fleetwin

kfa4303 said:

I know my 33hp has a runaway kill switch on it to prevent just such a problem.

Click to expand...

That is an entirely different situation on the 33, caused by flywheel momentum and high intake manifold vacuum from revving in a no-load situation. This guy claims his motor revs to 6000 RPM for no reason, even in gear. Sounds like a run-away Toyota. Or am I reading the problem wrong?

Re: Fleetwin

The 'high speed coils' are doing their job too well! Just kidding.

I'd scrutinize the carb, sounds like a vacuum leak letting way too much air in with way too much fuel??

Re: Fleetwin

Perhaps F R, but I agree with kbait, if it is reving too high it must be a fuel/air mix issue. there is no such thing as "for no reason". there is a reason and it is a fuel/air issue. I would check the packing on the carb needles. perhpas they are not in correctly, which may be causing improper seating of the needles and thus incorrect fuel/air mix and therefore the highs rpms. I know I just had the bearing and packing installed in the wrong order in my '66 33hp. I could get it to stay running at higher rpm, but not low idle, no mattter how much or how carfully I adjusted the needles. After I removed the lo speed needle, nut, packing and bearing and put them back in correctly, she now idles beautifully. imagine that The good news is that your motor is dead simple, so it can only be a few things. I've never herad of a "high speed coil", so you can eliminate that from the possible list of problems. Obviously she's getting good spark if she's able to runaway on you, which brings us back to the carb. I would re-rebuild the carb with a manual handy just to be safe, if that doesn't do it, then we can take it from there. keep us posted. good luck.

Re: Fleetwin

Thanks much for the replies. I will double check float orientatation and adjustment. I think the possibility of carb air leak or needle/packing problem is good so thanks for the those ideas. I can't get much reaction from either low or high speed needle adjustment as though it's pulling air from some place it shouldn't. I'll take a close look at that for sure. It will be later in spring when I get it back out to work on it so I'll get back on here with some resolution if I get it to work!