No more gearbox questions. Now it's the engine...!

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BrianK

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Next project is rings. And God knows what else, once I get in there. Please God, not the valves!

First question: I like the install method of putting the pistons into the block, then putting the block into an elevated position on the crankcase and fitting the wrist pins. I've seen U-shaped wooden contraptions for holding the cylinder block up, but it's not clear to me that's what I need - or how to make one.

Any other ways to do this? and/or dimensions for the wood "tool"?

Yes, it's the beginning of four solid months of "god help me, what have I done now" questions about top end renewal....sorry! :oops:
 
Hi Brian,

My preferred method is to use large hose clamps around the rings, put wood blocks under the piston skirts to keep the crank from turning then lower the cylinders over the pistons. The hose clamps (loosely fitted) will be driven downward as the rings seat into the cylinders, then un screw the clamps and remove. Finally pull out the wood blocks and allow the cylinders to align on the crankcase, place the base nuts and tighten. Just did my BSA A50 engine last week this way - always works great for me.
 
Thanks Dave. I've never had good luck with that method - even with single cylinders like v- and l-twins. So I'll probably try to put the pistons in the block first, but hopefully won't struggle TOO much with the wrist pins.

I've gotten smarter though - I have SIX new wrist pin circlips in the parts box!
 
one easy way to do it your way with the pistons in the block. put the pistons in with the inner circlip in place, I use 4 of the long head nuts (the ones under the exhaust port) on the 4 outer most base studs to hold the block up till I get the pins and outer circlips in. another tip is to stuff a rag in the crank case to hopfully catch a flying circlip.
 
I've never found the clamp or ring compressor method very helpful either. If it weren't for the taper at the bottom of the cylinder it would probably work, but they do work great to put the pistons in from the top. The trick is you need a helper that understands how important it is to hold the cylinder still and even when you install the pins and clips. It makes the job a snap. BTW, the clips are punched, so they go in sharp edge outward.
 
Why is it so complicated??

Put a pair of pushrods or similar across the top of the cases, turn the crank so the pistons rest on them. Arrange the rings so the gap in the top ones faces forward, and the second ring has the gap to the rear.

Gently rock the barrel into place, starting at the rear, so that as you straighten it, the ring closes in and the barrel is horizontal, then tilt gently forward so the you do the same with the second compression ring. The oil rings normally slide in easily just by pushing down gently once the two compression rings are in.

It will take you longer to read that than to actually do it....no need for clamps etc. Thats how it was done in the factory, and how I've ben doing it for 25 years....and believe me, when you're racing, it's not a once every couple of years job!! Never broken a ring yet either!

Try it on the bench with the barrel upside down and a loose piston if you want to practice!!
 
If only I had the facilities to do it!! I have done it for other people who have come round looking for help though!!
 
I have been using seeley's method for years as well, mainly on BSA twins. Sometimes they go in easier than other times.
Tend to sqeeze the rings with my fingers, or a screwdriver if necessary, & my extra aid is to press on the barrels with my chin.
 
I'd always used Seeley920's method too. Real men don't need ring compressors ! :)

...at least it always worked with Hepolites and their three-piece oil control rings. I came unstuck with the cast oil scrapers on GPMs 750 pistons. The first time that I'd broken a ring on assembly since my Fantic GT50 (and that was the start of a very steep learning curve !)

The Commando cylinder is quite heavy to hold in one hand if the rings need any help and if they don't go quickly then it's not too pleasant. Having borrowed ring compressors for the first time ever, I must say that I found them a doddle to use. They rather made me wonder why I hadn't always used them.
 
I've used hose clamps for ring compressors on the Norton for years. One of these days maybe I'll buy real ones, I'm sure they'd make the job simple.

I think I have the dimensions for the plywood "tool" somewhere.. I'll post them if anybody wants it. A bit softer on the pistons than pushrods etc.
 
maylar said:
I've used hose clamps for ring compressors on the Norton for years. One of these days maybe I'll buy real ones, I'm sure they'd make the job simple.

I think I have the dimensions for the plywood "tool" somewhere.. I'll post them if anybody wants it. A bit softer on the pistons than pushrods etc.
Click to expand...

Hi Dave,

The problem with "real ring clamps" is they are too tall to fit under the cylinders when lowering. Hose clamps are just enough height to capture only the rings. Believe ring clamps are intended for installing pistons from the top of the cylinders.

If real men don't need ring clamps, real men risk breaking rings. :D
 
Dave, I could use the dimensions for the plywood tool if you have them....thanks
 
I have a pair of British made ring clamps that I got from Domi 35 years ago. They are about 5/8" wide. I've never had a problem using them while lowering the barrel from above and using the proverbial plywood U piece that used to be shown in the older manuals. These ring clamps are nice because you don't have to completely unscrew them like a hose clamp. They are like the old fork boot clamps that come apart when loosened.
 
Since I only had ring clamps for my 650 cc bikes that were too small for my 850cc Commando pistons, I made myself a set from plastic plumbing strapping tightened down with a 1/4 inch bolt and nut. The strapping is gray, about 1 inch wide with holes in it. Bought it at Ace hardware. I believe it's used to hold plumbing pipes against floor joists. The stuff is pretty strong and because it was plastic, there was no risk of scraping up the pistons as the barrel went down over the rings. I just sprayed a little silicon on the clamps before tightening down over the rings and they worked quite well.
 
I have used sections of plastic oil bottle (round gear box oil bottles) and a pair of "jubilee" clips (screw type hose clamps for those of us on this side of the pond). The plastic slides much easier than the clamps alone. However, a proper set of piston ring clamps are better.

The putting the piston in the block first is tougher for me as it is tough to balance the heavy cylinder and insert the clips without dropping them down the crankcases. I also find that the wrist pins can sometimes be a little tough to push in. I won't use any kind of hammer here. Mounting the pistons to the rod first lets me use a wrist pin tool.
 
I use another variation of the hose clamp.

I use strips of aluminum, about 1" wide and long enough to wrap around the pistons with a bit of overlap, and compress the rings by wrapping the strips around the rings and tightening the hose clamps over the aluminum. The pistons are held up by a pair of wood dowels. Once the pistons are in the bores, I remove the clamps, aluminum strips and dowels.

Nice thing about this is you can adapt it to fit any size piston.
 
Here's the recommended plywood "tool" for supporting pistons during engine assembly. Installed with open end on the timing side, wide support up front. Works a treat.

No more gearbox questions. Now it's the engine...!
 
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