Re: 110 thunderbolt pleeeeease need info
hello need some info please i bought a 1978 110 thunderbolt 9.8 hp just had a chance to use it this past weekend and it seems to run very good but some type of problem runs well at high speed but some times i decrease the speed and it starts to buog or back fire and then quits on me and then takes a while to get it started again is it possible that it is the stater or something if anyone can please help me out would be great thank you
Of course, it could be compression fuel or spark. It's always a good idea with an old engine that you don't know the history of is to start off with a compression test. It's easy and takes 10 minutes.
You should also clean/inspect the entire fuel supply from the inside of the tank, including removing and looking at the tank pick up, hose, bulb, etc. to the carb. Also, make sure you have clean, fresh gas in there. This all takes another 10 minutes, and just a few bucks if have to replace the fuel hose.
You might also want to clean/rebuild the fuel pump and carb. This is a little more involved, but pretty darn easy w/ an OEM service manual ... and also do the waterpump maintenance (probably not related to your problem though).
Another very simple, 10 minute job is to check is if it's dropping a cylinder at lower speed. I had that problem, not exactly the symptoms you're describing, but basically intermittent tough starting and rough idle at low rpms but ran fine at higher. I traced it to a coil, replaced it and it worked well for a while. Then I had similar symptoms 1/2 season later. Thought it was the other coil going bad, but turned out to be a switch box. Anyway, here's some basic stuff I did:
First, carefully inspect all wiring and make sure the plugs are good - proper type, gap, not worn out, etc.
You might want to check the spark strength one at a time w/ adjustable spark tester.
If you can get it to idle,
Carefully (insulated pliers), remove one spark plug wire.
- if engine quits, that plug is firing, but the other one is not
- if engine stays the same (rough, but running), that plug is not firing, other one is
- if engine gets worse, but stays running - both plugs are firing and in removing one, you're now only running on one cylinder.
If you've found you're dropping a cylinder at idle, you can switch coils. If the problem follows the coil, replace that coil. If the problem does not follow the coil, it could be a wire issue or a switch box.
I have no idea how to test the stator, but I'd bet an OEM service manual would walk you through that.
This stuff takes a little time, but not a lot of expertise. Sometimes you have to go A-Z on an older engine you get, just to get it up to speed.
