On Sun, 07 Apr 2013 23:27:00 +0100, David Billington
wrote:

On 07/04/13 23:12, wrote:
Well, Case backhoe troubles actually. I think it's a CK 74. Anyway,
here are the symptoms: The 1970s engine (gasoline) starts right up,
idles well, and runs OK when it's not too warm. After fifteen or
twenty minutes it starts running poorly. It misses badly. If I let it
die it is very hard to start until the engine has cooled some. What I
have done: replaced the plugs, rotor, cap, coil, and wires. At first I
thought it was the coil. I had another laying around so I swapped
coils. This seemed, at first, to solve the problem. When I replaced
the plugs the only brand available on the island that were the proper
type were Champion plugs. I have been told by several mechanics to
avoid Champion plugs. The old plugs were Champions and they looked
like they were burning correctly when I pulled them. Now maybe the
replacement coil I had kicking around is junk and I need to get
another one, brand new. The ignition system uses a ballast resistor
and the coil is just warm to the touch, not hot like it would be if
the coil was wired wrong and getting the full 12 volts all the time. I
checked that too. The ballast resistor is only bypassed when the
starter motor is energized. The engine is not getting so hot that it
boils over, in fact, sticking my finger in the radiator neck to feel
the coolant temp tells me that the engine really isn't running too
hot. Steam and bubbles don't come out of the open radiator neck when
the engine is running so I don't think I have a bad water pump that is
letting the engine cook while the coolant in the radiator stays only
warm. I do have to run the engine with a little choke for it to run
half way well. I have adjusted the carb, which is a very old design
similar if not exactly the same as the one on my '39 Ford 9N,
according to the directions for this type of carb. That seemed to help
some, but even if I adjust the carb so that it runs rich I still get
the missing problem after the engine has run for 15 or 20 minutes. I
am going to buy a carb rebuild kit but I don't expect it will fix the
problem. So, any ideas? I'm stumped and I know there several folks
here who know about old engines.
Thanks,
Eric
Have you checked the points to make sure they're gapped correctly. I had
an issue years ago on my frogeye where it would misfire and stall when
hot and I discounted the points as a problem because I had only changed
them a few months earlier. Seems the points heal on that set wore more
initially than any other set and the gap closed up. It started fine and
ran well until hot then died, resetting the points gap to the correct
setting cured the problem immediately and it didn't come back.
Greetings David,
I have not checked the points again. That may indeed be the problem.
Thanks for the suggestion. If your suggestion is the solution, and
your going to be travelling to the Seattle area the first week of
August, then you can come to my pig roast and play with the backhoe.
Cheers,
Eric