Cub only runs on Cylinders 1and 2

[yellowcub]

My cousin's Cub had a bearing knock so we put new bearings in. While we were there, we put new rings in (standard) and lapped the valves. He has owned the Cub since 1965 and this was the first time the engine was taken apart. There was very little cylinder wear ( didn't need a ridge reamer to get the pistons out). We put it back together and now it runs only on cylinders 1 and 2. There is spark at all 4 plugs. We checked each valve by putting brake cleaner on them and none leaked. Any ideas? Thanks!!

[Bob McCarty]

Yellowcub, Welcome to the Forum. I just found your post from yesterday. First thing I would check is that you have the spark plug wires in the right order coming out of the cap to cylinders 3 and 4.

Bob

[Boss Hog]

firing order 1342

[thiggy]

How does brake cleaner help test valves for leakage?

[ricky racer]

A compression test will be helpful here. But then again, my John Deere B runs on 2 cylinders, but you know, after a while you get use to it.

[Boss Hog]

A compression test will be helpful here. But then again, my John Deere B runs on 2 cylinders, but you know, after a while you get use to it.

Pull off one wire and see how she does

[yellowcub]

The firing order is ok. Tried new cap and rotor. We took the head off again and sprayed brake cleaner around each closed valve (Ponded) and none seeped down. We did a compression test a while back before we took the head off again . I forget the psi but 3 and 4 were low until we sprayed oil in those cylinders. I am thinking the new rings in cylinders 3 and 4 didn't seat. We pulled the pistons again and I checked the ring gap and it was within spec.

[Eugene]

Timing light. Cylinders 1 and 4 fire at the pulley and pointer indicators. Cylinders 2 and 3 fire 180 degrees off the pulley and pointer.

[ricky racer]

Champion spark plugs by chance????

viewtopic.php?f=1&t=83131

[yellowcub]

We put a timing light on each plug wire. 1 and 4 fired at the timing mark and 2 and 3 fired 180 degrees from the timing mark. ( made another white mark)

[ricky racer]

Have you taken a compression test? What kind of readings did you get? Check it first dry then wet and record your readings and report back. Until then, we're only guessing.

[64/67lo-boy]

like Ricky said do a compression test. Also is the spark occuring on comp stroke or exhaust stroke? Just because the spark occured at the mark on the crankshaft pully doesnt mean it was on the compressin stroke. You may need to move your spark plug wires on your distributor.