Refitting cylinder barrels

T

Tapnell

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Isle of Wight UK
So chaps, when getting the pistons back in the barrels, do you go for middle cylinder first then the outers? Ring compressors or not, if so what type are you using? Finally, where is the best location to earth the negative from the battery? Mine was on the sprocket cover…didn’t look great🤷🏼‍♂️ Cheers!
 
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If the barrel has been bored, it's worth taking the time to check the lead-in tapers. I've been known to hand file better tapers where a reconditioner has left them a tad short. Deburr of course with a piece of fine emery cloth - and clean, clean again.
 
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Going by memory , I think I had all the pistons lined up more or less equally ( 1200 ) ......... As far as compressors are concerned ....... I had a set of coiled expandable ones from Norman Hyde ( Trident Specialist ) ........ USA made ....... Adjusted by a grub screw , in a similar way to a hose / jubilee clip ....... When wound out this screw would separate completely , and of course then fall down into the crankcase mouth , if given the chance ...... Also the compressors would be impossible to remove , once the barrels were lowered down over the pistons , just ending up being stuck between bottom of barrels and crankcase mouth ....... Other compressors may not have offered up these problems .... these particular ones did .......

This was with the engine still in the frame btw , not on a bench .....

Luckily fore saw all this before I tried them ......... Deciding to work with what I had , I just cut back the expandable spring steel of each one so it just covered about 350 degrees of the 360 degree piston circumference , secured with zip ties towards the bottom , below where the rings would be ........... Worked fine ....... zip ties could be just snipped to remove them , and the cut back spring steel could be prised open and removed fairly easily from each piston , before finally lowering the barrels completely .........

( First oversize Asso ? , from Switzerland , I think , originally , now maybe Italy ....... Rings already fitted ..... check gaps are spaced ....... Beautifully finished ..... crown like a CD mirror finish ( flat , not domed obviously ) , and a purple ( Teflon ? ) finish on the sides ........ When I took them to Steve Riley at Piston Broke for measuring up , he said " Ain`t they purr-ty ? " ...... and they were .................... I was thinking of getting a spare one to put on display on a little velvet cushion , with a spotlight trained on it ....... ) .......
 
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I once did it the othe way at a 120 deg. triple. Put the pistons in the barrels and then pushed the piston bolts in and secured- was not that easy but worked.
I dont wanted to damage the rings by handling the weight of the barrels.
 
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andre g said:
I dont wanted to damage the rings by handling the weight of the barrels.
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Try it with an Ariel square four. Best done with the engine on it's side.
FWIW i've got a collection of wooden "forks" cut from MDF which can go under pistons to hold them level. They sit on the case top and you simply rotate the crank till the pistons sit on them. Once in the bores simply pull the forks out from under the pistons.
Plain bearing cranks are easy. Pistons in bores,with rods, barrel upside down on bench. Case top half onto barrel. Lower crank into case and align the rods.
Assemble caps onto rods and torque up.
 
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I've tried a few methods and found the best one to be;
  • Outer pistons somewhere near TDC and supported on slotted wooden blocks to stop them from rocking (as per GregT's comment).
  • 20mm wide strips of 90mm PVC dunny pipe and worm drive band clamps for ring compressors - this works better than any ring compressor I've tried.
  • Get the pistons ready on the blocks and the band clamps snug but not tight, rest the barrel up against the pvc compressors then slam it down in one swift movement. The protruding liners should be stopped by the wooden blocks before coming near the middle piston which is 'down'.
  • Remove the outer ring compressors and then set up the middle piston in the same way, you can only fit something quite thin under the piston, I have a piece of 6mm ally with some layers of tape for this.
  • Repeat for the middle piston.
Stopping the piston from rocking made a big difference for me, this means the piston is fully supported and allows you to slam it on good and hard which allows the rings to enter before they've had time to pop out of the compressor. You do have to hold your breath a bit, but it's worked every time for me since setting it up like that. Obviously that's for a 180, process much the same for others. 120's are a bit more fiddly, haven't tried a 500 or twisted twin.
It's a piece of piss compared with the Porsche I'm trying to rebuild at present. That's one where you have the fit the bank 2 circlips through holes in the bores. Cylinder 6 clip has to be fitted through a 25mm hole which goes all the way from the back of the block and through cylinders 4 and 5. Not looking forward to that bit!
 
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Similar to Rocketonarail, my compressors would fall to bits when undone but also didn’t pinch round but pear shaped using the screws provided. I used the clamping strips but used my fingers to pinch the clamps so I could feel the piston rock in. I was going to make plastic clamps from plumbing pipe but decided not to - the sharp edges of the rings could shave plastic into the ring grooves, which you wouldn’t event see.
Old guy I worked with told me if your easing rings with a screwdriver, hold blade vertical not horizontal- then it doesn’t get dragged in and break the rings, sounds obvious . Only ever pat barrels with palm of your hand.
 
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Tippie said:
Using screwdriver method will almost undoubtably one day break a ring.
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I've done it many times without breakage - always with support under the piston - but as you say, the inevitable day arrives and for me that was doing a friend's SF. I had to donate a new ring from a pair of full sets - bummer. I bought some fancy looking compressors but they couldn't be used as was with an SF so I cut the spring steel down and used large hose clamps. I do have one I made from a used car oil filter canister that worked a treat but it was too short in circumference to use on the SFQ's 88mm pistones.
 
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I always go for the centre piston first (180 degree engines) and then the outers next, the important thing to remember is that the ring compressors must only be just slightly wider than the width of all three rings, I use steel strips (not alloy as it binds) well oiled and jubillee clips. Geralds note about Ross pistons is highly valid and is even more essential if you are using Omega pistons, I have only (tried) to fit one set of those and I bust a ring, I think because of its mega thin size and it "catching" on the taper as it leads into the bore from the ring compressor, remeber that they are "compressed" and when entering the taper, then "de-compress" only to be squeezed in again by the closing taper, it might also be possibble to get the rings in unbroken, but with edge damage, causing oil burning later on. Fortunately my current engine build is using NOS pistons from Toddy (decades ago) which are MK11 Acrollite, so no very thin top rings to deal with, but the next time I build an engine with Omega's, I am considering inserting them into the top of the bores which is square edged, much the same as I have done many times with big diesels, this means sliding the pistons down until the gudgeon pin (wrist pin for the yanks) is just visible and then inserting the pins, whilst still keeping the rings up in the bores, might be fiddly, but might be safer.
CLEM
 
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I'taken the steel plate out of some ring compressors cut it down in height so it just covers the rings and I use worm drive clamps. Pistons with a piece of wood underneath.
Paul
 
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CLEMTOG said:
I am considering inserting them into the top of the bores which is square edged, much the same as I have done many times with big diesels, this means sliding the pistons down until the gudgeon pin (wrist pin for the yanks) is just visible and then inserting the pins, whilst still keeping the rings up in the bores, might be fiddly, but might be safer.
CLEM
Click to expand...
Most pistons I fit seem to need to be heated to just able to handle to fit the gudgeons easily, and getting the clips in can be challenging enough without the cylinders sitting there.
 
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I used pvc strips and jubilee clips..pvc never goingto scratch the bore, oil up, didnt use force or bang anything!.If I can do it, anyone can😉 done other bikes, though just singles, in my time. I think you have to be pretty ham fisted to break a ring..
 
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I found using bits of wood really useful. Here is a pic of one I made and another pic of how it looked after fitting the two outside pistons. two down one to go. I recall that a lovely thing happened at the time. I did not succeed in my first attempt and broke a ring. So I rang up Omega and a very nice guy said he would send me a new ring set for one piston free of charge. ‘These things can happen” he said. Wasn’t that great ?
 

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I also found this video very helpful. I enjoy the narrators bone dry delivery, and appreciate the absence of horrible musical accompaniment.
www.bikerstoolbox.co.uk

Install Motorcycle Pistons Like a Pro: Step-by-Step Guide

In this video we show you how to fit piston rings and then the easy way to install the barrels. Sadly in this litigious age we live in, we have to state that the contents of this video are given freely to help you our customers service your bikes for your safety and enjoyment, but we will not be...
www.bikerstoolbox.co.uk www.bikerstoolbox.co.uk
 
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