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Extending Service Life of Post-war Cylinder Barrels

Started by aggettd, 22 Jun 2009 at 20:33

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I am, slowly but surely, gathering the components to build a spare motor for my T35. I have most parts I need but the cylinder barrels I bought are so badly scored that even boring them out to take Suzuki GSX650 pistons (62mm) has left both bores with two longitudinal score marks and some deep wear marks up near the ridge. I didn't get ripped off. I knew they were badly worn when I bought them. Machinists around here are reticent to bore them out enough to install liners as there isn't a lot of meat left between the fins.

Has anyone any experience laying down a thin bead of weld to fill imperfections in cylinder bores? Should they be cast iron rods or ductile iron rods? Once filled I can bore them back down to size and hone them into service, but I'm not sure if a welded fix is at all feasible. I realize this is not standard practice, but the cylinders are junk right now so if I ruin them in an experiment, not much is lost but if I can salvage them, I will have learned something and still have the parts.

Any thoughts?


Not sure if this is standard - or even recommended - practice, but many years ago my dad had the misfortune of cirlips coming out of all the pistons on his Indian 4, putting very deep tram rails in the cylinders - from memory some were up to 3mm deep! This he had fixed by getting the grooves filled with braze, or perhaps bronze weld, I can't remember and we wouldn't have known the difference back then in any case! The barrels are still in service, with no problems since the repair. Well no problems in the barrels in any case, the machine has had lots of other problems, but don't let me go there!
What do the engineers here think?

ian scott

Kevin Cass (ex GP racer, motorcycle engineer of note, rode a 2 3/4 around Australia etc) showed me a repair he had done to a 2 3/4 barrel many years ago.

He had filled a deep groove, made by a stray gudgeon pin, with brass.
The barrel had seen service since the repair and seemed fine.

Kevin said this was a satisfactory way to fix this problem. I'm not sure this would work so well if you required the brass to fill the full circumference of the barrel.


A guy here repaired deep grooves in his TS barrels with hard solder - with no further problems. Not sure of the exact details - can find out.


Cast Iron welding will almost certainly distort the barrels and render them useless as they have already been bored out to the maximum. It may have been possible to repair them by this method if the welding had been done prior to the boring. If the scoring is the result of circlips coming adrift, then the damage will be restricted to the non-thrust sides of the bore and a brazed repair should be OK as it only has to work with the piston rings to provide a gas seal.


I hadn't thought of brazing them. I suppose if I had, I'd also have thought that it would be too soft, but these posts have given me heart. I'll give it a try and let you know how it turns out.

Thanks again for all your help.

David Aggett
Nova Scotia, Canada


Hi all
If you are doing all this welding in the cylinders, you will have to make sure it has joined to the casting and no chance of fragments comming away to cause damage else where in the cylinder plus no distortion to the barrel, surly you will have to machine it back to size.
Would it not be easier to sleeve the barrel and bring it back to "standard" in size. Although this is probably not the cheepest route to take.
Regards     Martin


I agree that distortion will be an issue even if the barrels are preheated and I use braze instead of weld. I also intend to machine it back to shape to guarantee concentricity. As for adhesion, I'll just have to be meticulous in preparation as penetration is not possible with braze.

As for resleeving the barrels, I've talked to two highly-regarded machine shops here and they both are not keen to try that route, as the barrels are perilously close to being too thin now. To bore them out enough to fit a sleeve, in their opinion, would risk the entire piece collapsing.

As a last resort I can use the barrels to make up a mold and have new ones cast from aluminum. There is a foundry about 10 km from my shop that has that type of experience. They've been in buisness since the late 1800s and produced all the fittings for the sailing vessels Bluenose and Bluenose II, plus for the HMS Bounty, used in the film starring Marlon Brando. It should be a museum!! But they do good work.


I recently had a similar problem with my D23 600, I limped back after a run with a very sick motor.  On inspection I found that all 4 gudgeon circlips had done there bit and escaped leaving very deep tram lines in each cylinder, there was virtually no compression in either cylinder.   I had the cylinders machined and new sleeves inserted ( believe they were Mercedes wet liners) after reboring they were brought back to the original size of 75mm.  I then got JP Pistons in SA to make new pistons.  The liners were machined with a lip at the top with a corresponding recess machined into the top of the barrel thus allowing the head to keep them in place. Hopefully this is a good fix and will last, all the best with it.