I have an NH carb which usually performs very well. It still starts OK, and idles. It balks when accelerating, but gets somewhat better if I make the mixture adjustment richer. Even with the richer setting, it is missing a lot of power, and just doesn't feel right. I took it off, cleaned it, reset the float height, but it didn't help. Any ideas?
Maybe it is not carburetor trouble? Is there any other carburetor that you know is good that can be swapped on to make sure you actually are fixing what is broken?
Are you using a timer and have you checked it out lately? Also, may be restricted fuel supply getting to the carburetor.
It's not the carburetor. First I shorted out the plugs one at a time. #3 didn't change anything. Did a compression test. #3 had no compression. The others had between 25 and 27 lbs. This was with hand cranking, so not sure if results would be better with a starter. Looks like a valve job is on my schedule.
John, you should try doing a wet compression test first. Squirt some oil into the cylinders and redo the compression test. If the oil improves the compression reading, you need new rings. If the oil doesn't help, you need new valves.
Have you opened the valve cover to see what is going on? Often if the cheesey reproduction valve pins or spring retainers are used one of them wears thru or falls apart, yielding no compression. Or it might just be a head gasket burned through between cylinders.
Please check the sediment bulb screen.... crud slows the rate of flow.
One valve is either not opening or sticking open. You might loosen it without a valve job, but you might need to remove the head. This can be caused by a weak spring or as suggested above a keeper missing or worn through. It can also be caused by carbon build up or rust caused by water seepage. Good luck.
This morning, John & I removed his head and found that the exhaust valve in #3 was bad. We could easily slide a 0.003" feeler between the valve and seat. His engine is rather interesting. The intake valves have a larger head than the exhaust. I was told that these could be Fordson tracker valves and may be an early attempt at improving horse power. Mike
Royce has recommended using Fordson tractor vales in the past.
Here's a picture of the worst exhaust valve.
It almost looks like the edge of the valve melted some. We installed all new exhaust valves and cleaned up the intakes and the engine is running fine.
I would check the fuel bulb filter and the timer if it were me. Tim
Are you on battery or mag?
I think there are people posting here that have not read this whole thread very carefully! On JUNE 6TH, John determined that three cylinders had very, very poor compression, and #3 cylinder had no compression at all!
So, while folks are still recommending checking for fuel flow and ignition problems, always a good idea, however, Royce and Norm knew right away, where to check to determine reason for lack of compression, and John and Mike Zahorik are addressing the main problems!
No use for the doctors to keep checking for bad circulation and poor reflexes when cardiologists can go right to "the heart" of the problem, right?
Sheeesh! Prioritize and diagnose guys,.....( ;^),.....harold
Sorry Harold, you are correct. I'll try not to wake you again!
How is your tire pressure?
An old man once said,"90% of carburetor trouble isn't "
Hey Steve, How's your garden? Couldn't resist!!