Thread: Oil Pump

I am working on my second CT70 KO engine and have run into the same problem on both. I have done a complete tear down of the engines and when I put the oil pump gears cover on, the pump will not turn. I fiddled with the first engine long enough that it finally started turning freely, I am not sure what I did to make it work. It seems to be very straight forward as to how it is installed, but obviously I am doing something wrong.

Well, once again I fiddled with it long enough that I was able get it to spin freely. I would still love to know what I might being doing wrong. Only thing I can figure is something as small as a hair can lock this thing up, because I cleaned it everytime before installing it and it would still be stuck and then out of no where it just starts working. I am going to master these little engines if it kills me!

You've gotta get the drive shaft indexed correctly with the input tang on the pump itself. It's an easy thing to get wrong. BTW...you should always check the old drive sprocket & pump action. The oil pump should spin freely with two fingers. Examples that are binding internally are far from rare. That's where the drive sprocket inspection becomes important. A binding oil pump will almost always manifest as worn sprocket teeth. If you find either, then both the pump & drive sprocket should be replaced...very cheap insurance once you've already put $250 - $400 worth of parts & machining into a rebuild.

Thanks for the input RACERX. Everything spins freely upto the point when I put the cover

on. It was also spinning freely when I removed it.

I'm having this exact problem. Smooth as butter until the screws are tight, more specifically the shared screw that holds the cover and the body.
The 3 smaller 5mm screws that hold on the cover can be tight, and the pump is ok, but when i tighten the one 6mm screw, it binds. Anyone have any ideas?

Edit to add:

I took the inner and outer rotor out and lapped them on a fine abrasive stone, cleaned and reassembled. Seems to be better, but not like i would prefer.

My guess would be that the aftermarket gasket is just too thin. There isn't much room for error on the gasket thickness, and maybe the A.M. gasket makers don't realize this...

Have run across the exact same thing. The problem was I was not using Honda gaskets! They are the correct thickness!!

So you got the honda gasket and it worked ok? might have to order one

Yes it worked fine with the Honda gaskets!

I have wondered if this was the problem. It sure makes since. I even thought about doubling the aftermarket gaskets.

Thats what i think i'm gonna do. I would be surprised if they were .002" thick to start with. I thought about even making one out of notebook paper which i'm almost sure would be thicker than the aftermarket gasket (though i'd have to mic them).