Hard Starting 12HP

[Ron7x]

I recently put a 12hp in my 102. The motor runs great once I get it started.

The problem is the starter turns it over but slows way down at the compression point. I took the motor out and checked the compression release spring. It looks fine to me. I also tried jumping it with another battery...same thing. Could it be the timing is off? Could it be the starter? It spins fine with the spark plug out. Could their be another problem?

Any help would be appreciated!

[Rhoderman]

Could be weak cables or connections. Try jumping directly from the battery to the starter gen with a good set of jumper cables. This will help you determine where the problem might be.

If you don't know the history of the engine, you might suspect the decompression is broken or was disabled. You should see the exhaust valve move slightly on a slow compression stroke.

[Yosemite Sam]

Originally Posted by Rhoderman

Could be weak cables or connections. Try jumping directly from the battery to the starter gen with a good set of jumper cables. This will help you determine where the problem might be.

If you don't know the history of the engine, you might suspect the decompression is broken or was disabled. You should see the exhaust valve move slightly on a slow compression stroke.

Above are all good points.

Three things that you need to do, if you ever want your electrical system to work properly.

1.) Check and clean your grounds
2.) Check and clean your grounds
and
3.) Check and clean your grounds
You will never be sorry you did.

Regardless of how the engine seems to start and/or run, your points (the timing) should be set WITH A TIMING LIGHT. I know it's kind of a pain, but this is another thing that you will never be sorry that you did.

These things may or may not fix your problem, but they are a really good start in getting closer to trouble free operation.

[Matt G.]

Or if you don't have a timing light, you can use an ohmmeter to do the same thing with the engine not running. Simply gapping the points to 0.020" is not acceptable.

[ih4ever122]

mine does the same thing. its a 124 rebuilt motor and all new electrical. if u hear anything can u tell them to let me know thanks. keith murphy

[Matt G.]

ih4ever122,

If you rebuilt it and painted it, you probably have a ground problem. Did you set the timing with an ohmmeter or timing light?

These two things are very important; the former because a new engine is usually pretty stiff and needs all the help it can get to crank over. Improper timing results in, among other things, a very hard-starting engine.

[Ron7x]

I checked every electrical connection...all good. Tried jumping directly to starter...no better.

So I pulled the head off to see if the exhaust valve was moving via the compression release...No Movement! ( I checked with a dial indicator)

Being the spring looks good on the Comp release, I think something must be stuck or wore out. I have a good 10HP cam. Will this fit a 12HP?

Thanks for the ideas guys.

I think I can take this motor in and out blindfolded now! I wouldn't take this much grief from my wife of 35 years...LOL
Must be a CUB thing

[Yosemite Sam]

Yes, the cam out of a K-241 engine will fit into a K-301.

[Ron7x]

just to let you know....

The exhaust valve clearance was about .045...now .018

Starts easy now and runs great!