Top End

This section will show what needs to be done to be able to get into (and put back together) the top end of your CH80 bicycle engine. Here is where you will find things like the head and base gaskets, piston, piston rings, wrist pin (piston pin) and the upper bearing.

One of the most important things is to make absolutely certain that your mating surfaces are clean and free from any oil residue when you are replacing your gaskets...and this should not be done without replacing the gaskets. It doesn't matter how good your old gaskets may look, if you rip into your engine like this, you replace the gaskets...otherwise, you're just asking for a leak and possible compression issues.

I will try and get the step-by-step part of everything added in with the pictures soon. In the meantime, there is a decent listing of the steps written below, and a small pile of pictures below for you to see. If anyone has any questions...please shoot me an email.

1. Start by making sure that you've got the top of your engine block cleaned up and that there isn't any bits of gasket or oil where the crank meets up with the cylinder.

2. Next, you need to get the piston into the cylinder. You'll want it set so that the piston pin (wrist pin) is sitting crossways so that you will be able to put the pin thru the connecting rod. You can compress the rings with your fingers (finger nails) as you put the piston into the cylinder...just watch for the little pin in the grooves for the rings. You need to make sure that the opening of the ring is where that little pin is when it goes into the cylinder. The side of the piston that has the two little pins for the ring openings should be facing towards to intake manifold…if you have them facing towards the exhaust side there is a possibility of them catching on the port opening and destroying the cylinder. Push the piston in from the bottom of the cylinder. You'll need to start with the upper ring, then do the lower one since you're essentially putting the piston in upside down.

3. Now, you can slip the base gasket all the way down over the studs so that it is on the crankcase of the engine. It's only designed to go on (properly) one way. If you take a look, you'll easily see how the openings are cut for the ports...the angles need to line up.

4. The little black roller bearing sits in the opening on the top of your connecting rod. When you put the cylinder (with piston in it) over the head bolts and start to slide it down, you want to align it so that you can push the piston pin (wrist pin) thru the hole in the piston, thru the connecting rod (and bearing) and out thru the other side of the piston.

5. Swear a couple of times as you put the piston pin clips in place. You need to make sure that they go into the little groves that are in the holes of the piston. I'm sure that you've already noticed them from when you took your engine apart.

6. Push your cylinder all the way down onto the crankcase now that you've got everything attached.

7. Next comes your head gasket...make sure that the top of the cylinder and the matching, mating surface of the cylinder head is clean and free of any oil residue. Make sure that your head gasket is sitting down on the top of the cylinder.

8. Take your cylinder head and put it on top of everything so that the longer and thicker end of the top cooling fins are towards the exhaust side of the engine. The nuts should be hand tightened, then torqued down with a torque wrench in a criss-cross pattern so that they are about 180-200 inch pounds of pressure (CH80 engine). Make sure that you're looking at inch pounds and not foot pounds. I think it works out to be somewhere's around 15 foot pounds if that is all you have to go off of. If you don’t have a torque wrench, you can use a standard ratchet. Make sure that they are good and tight, but don’t over do it and snap them. Only good and tight, not good and super tight, lol.