Hercules Misfiring When Hot

[Jim N]

OK. Here Goes. They are numbered

4 3 2 1 from left to right.

[Edited on 8-27-2002 by Jim N]

[thecatskinner]

Jim, I jump in the bucket and see who kicks me out here;)

The center two plugs could be the immediate cause of your missing--but you have another problem:(

I would suggest you do a compression test.  When you do the test have all the plugs out and do them in sequence writing down the readings from each.
Then repeat the test but first shot a couple of good shoots of oil in the cylinder and record those readings.
I suspect on 2 & 3 you are going to have low readings (ie: less than 70 psi).
If your second set of readings on 2 & 3 are higher it is an indication that the rings are bad--if not valve guides.  I have to emphasize indication.

You may also want to try putting new plugs in when it is hot and see if the miss goes away--that would be a pretty good indication that it is not the mag.

[Blake Malkamaki]

I agree that it may be a problem in #2 & 3 cylinders. See what it does with new plugs and if it fouls out these two again you definately have a problem. Besides fixing the problem - new rings, pistons, or boring - you might get by by running hotter plugs in these two.

I'm glad you're not running Champions. They are not what they used to be. I've had all kinds of problems with them fouling out, even with just gasoline.

Blake

[Jim N]

Well here goes. I will try to explain everything that happened.

The root cause was taking a shortcut and not replacing the manifold gaskets.

This made the outside two cylinders(#1 and #4) suck extra air on the intake stroke.
In order to get the thing to run at all, I had to adjust the needles in the carb out way farther than normal, hence the two inside cylinders (#2 and #3) were getting way too much fuel and building up alot of carbon. So much, in fact, enough to keep the exhaust valves from seating.(when I sprayed a water mist into the air intake in the carb, the valves would seat better.)

Once I cleaned out the carbon the best I could and installed new manifold gaskets, the engine started right up and sounded completly different. Certainly all the ignition parts that were replaced helped out too. Lots more power and I  don't have to run a whole lot of throttle to do meaningful work with it.

To everyone that had suggestions and offered help, a heartfelt  'THANK YOU'
Maybe this time I'll learn my lesson and not to cut corners on a rebuild and do the job right the first time.

[John]

check timing...the mag will jump time at the govenor....on my HG,there is no timing marks...try advancing the mag one tooth

[John]

I'm still trying to understand this fomat,please disregard previous message...sounds like youve got her cured,good luck,john

[John]

By the way,nice shirt Blake....

[Harvey Havens]

Nice hat and truck too Blake

[Blake Malkamaki]

Well thanks guys for the compliments!:D

I got to meet Jim Novoty again at our fall show on Saturday and got to see his OC-4. A nice tractor! Time did not permit me to hear it run, but I'm sure I'll get to see it again next year at the show. I think it's the only first generation OC-4 I've seen in person.

Blake

[tim forry]

Hey John, the reason that the mag jumps time on these engines is because in the impulse housing on the front of the motor is a blind bushing which limits the travel of the impulse coupling. It is common for the end of this brass bushing to be busted out allowing for the coupling to jump out of time. Landis helped me here. Just fixed mine. Tim:)

[Blake Malkamaki]

Originally posted by Jim N
OK. Here Goes. They are numbered

4 3 2 1 from left to right.

[Edited on 8-27-2002 by Jim N]

I replace Jim's picture as it was over 100 kb. Please keep pictures under 600 pixels wide at 72 dpi.