Compressing Piston Rings and Putting on Cylinder Barrels

I've recently gotten back home from college this month, and I have been rebuilding a 1980 XJ650; the top end (head and cylinder barrels) was basically crap so I have gone through mostly all of the engine and now I have started to rebuild the top end. I am pretty inexperienced with 4 cylinder motors (I am much more knowledgeable with V-twins lol), so I have been really struggling lowering the cylinder barrels onto the pistons. I have ring compressors and I tried manufacturing some metal props to keep the pistons steady but the rings either keep slipping out or the pistons wiggle around. If anyone has suggestions for putting the pistons into the cylinders, I'd be extremely grateful.

 

Considering that I have never rebuilt a motorcycle engine and have always wondered about getting the pistons back in the cylinders, I wonder if it would be possible to put the cylinder on the floor and lower the bottom end and pistons into place from above using a small chain hoist. (All you guys that now what you are doing can stop laughing now. )

 

It could work, but for all engines, this one included, the piston rods move forward and back and side to side, as well as the piston heads liking to tilt, so lowering it upside down could be just as hard as doing it right side up. I think the main issue I have had is just getting the piston heads to be stable and still enough to slide into the cylinders without tilting.

 

I just thought that upside down at least the pistons would hang uniformly. But it would take a very steady chain hoist--and maybe an extra pair of hands. I assumed that the cylinders were tapered at the bottom making the use of a ring compressor not necessary. Don't think it is a job I want to take on. I'm sure one of the gurus on this forum will chime in with a simple solution.

 

Regardless, I appreciate it my friend.

 

I just did this with my 700X. Raise the center pistons to TDC +/-. Lower the jugs to the pistons and carefully insert the piston tops into the cylinders. Lowering further will allow to top rings into the bottom cylinder taper. Now carefully get your hand on one pistons second ring and align or compress till it slides into the taper slightly, then do the other. Be careful with tilting the jugs which can pop the other pistons ring out. Now, tap the cylinders down carefully with a deadblow. Once down a bit, turn the crankshaft to lower center pistons and jugs and to raise the outside pistons. Repeat the process. Once all compressions are inserted, tap the jugs down to the gasket. Oil control rings are not an issue. I needed my son only to help slide the jugs in and threading the chain and guides up through center and lowering the cylinders down to rest on the center pistons.

 

Thank you! When I have the chance I will give it a try without the compressors; I think I just have been overthinking the whole process. I will post an update after I try it out.

 

Hah, see a typo: "Once all compressions are inserted" should probably be "Once all rings are inserted". BTW, aren't ring compressors meant for inserting a piston down through the top of the cylinder? How would one be used below?

 

They have special smaller ring compressors that are used for motorcycle cylinders. It’s easier to use them on 2 cylinder bikes like V-Twins because it’s one piston and cylinder jug at a time. Basically you screw the compressor tight around the rings, and as you knock down the jug, the compressor slides down until it’s loose (where the piston has gone all the way in). The main issue I had was the compressors kept getting crimped goin slanted into the taper as I knocked them down, so I may just have to compress the rings manually.

 

Our jugs have a taper at the bottom of each sleeve that lets the rings pretty much slide upward and compress themselves. We mainly have to center and guide the rings into the bottom of the taper.

 

Yeah. My XJ also has a taper. I just assumed the compressors would make it easier, but it’s had its own setbacks haha. I’ll try it without the compressors next.

 

Just an FYI but the FSM specifies piston ring compressor and piston base as special tools for the job

 

I feed the piston rings into the bores with flat wooden mixing sticks. I broke a piston ring on my Honda CB750 forty years ago so I am very careful now. Never broke one since.

 

I used to do them with me fingers(and a friend) but a few years ago bought a set of Honda ring compressors and don't need anyone to help. They make different sizes for different engines. This set is for the CB550. Also you can make a set of piston holders out of wood or MDF to set the center pistons on so they will not move. Sometimes the cylinder studs get in the way so you have to make sure you can remove the clamps. In these photos I am replacing the studs so not an issue. The wood blocks are the most important part if you are using just your fingers. Once you get the center rings in rotate the crank to bring the outer pistons up

 

The explanation and photos are much appreciated friend. I have plenty of spare wood and aluminum I can cut to make a piston base like that. I’ll try it out. Thank you again