Onan CCKB

guyralph · Jun 29, 2009

Hi,
I just purchased a Case 646 that has been repowered with an Onan CCKB.
The engine only runs on one cylinder. If you throttle it up to about 3000rpm the second cylinder will fire intermittantly.
I have done compression tests on both cylinders.
Both show about 110lbs.
I have swapped plugs and wires. No difference.
Any ideas where to go from here?
Thanks
Guy

lucas boy · Jun 29, 2009

ID PUT A SPARK TESTER ON IT TO SEE HOW ITS FIREING ON EACH SIDE WHILE RUNNING.MAYBE NEW PLUGS.TAKE IT FROM THERE. A LEAKING INTAKE COMES TO MIND TO BUT DOESNT HAPPEN OFTEN..

guyralph · Jun 29, 2009

(quoted from post at 15:23:21 06/29/09) ID PUT A SPARK TESTER ON IT TO SEE HOW ITS FIREING ON EACH SIDE WHILE RUNNING.MAYBE NEW PLUGS.TAKE IT FROM THERE. A LEAKING INTAKE COMES TO MIND TO BUT DOESNT HAPPEN OFTEN..

I should have been more specific.
I swapped wires and plugs from cyl 1 to cyl 2.
The plan was to make sure all the componants including the coil were good.

Guy

mowr · Jun 29, 2009

Have you done a thorough tuneup? Does your point box have dual points? Forgive me for asking this but when you swapped the plug wires around, did you make sure the same cylinder was misfiring? If it acted the same but the misfire was now on the other cylinder, that would indicate a bad plug wire. When I had this problem, it turned out that one side of the coil was bad.

guyralph · Jun 29, 2009

Yeah, the problem stayed on the same cyl.
haven't opened the point box. Didn't realize there could be two sets of points.
As an update I purchased new plugs. I put a Champion H10 in that Cyl.
Now it fires when the throttle is opened. Doesn't seem to have any power though on that cyl.
I opened the main jet a half turn and that helped a bit. Another half turn didn't make any difference.
This tractor sat in a damp barn for two years. It might be time to do a rebuild.
Shouldn't be that bad. I had one head off and there is no ring on the cylinder walls.
I think I'll live with it this summer and do that this winter. I only use it for small tasks like rototilling.

Anonymous-0 · Jun 29, 2009

Check for an air leak at the manifold connection. and also, check for a sticky valve. I would spray some carb cleaner around the manifold and carb when it's running. any change in speed/tone would indicate a leak.

A little Seafoam in the gas may free up a sticky intake. Some poured in the carb when running, will create a lot of smoke and may clean both valves.

guyralph · Jul 9, 2009

Update.
Thanks Ken.
You had it right. Replaced the gaskets on the intake and it runs well now.

Onan CCKB

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