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76degree-triumph, Gordon Gray, HughdeMann, JubeePrince
Total Likes: 5
Original Post (Thread Starter)
by JubeePrince
Perhaps my question got lost in all the drivel I posted earlier in the “Royal: Repair and Recommission” thread.

I gave the barrels the thumbnail test. A very slight catching of the nail in one or two striations in both cylinders, but not enough to catch the nail and stop the finger. I had to do it a few times just to be sure, that’s how slight it was. I’m trying to discern is I can get away with new rings and hone, or just bite the bullet and rebore? (Currently .020” over)

I know many of y’all have seen many more cylinders than I have, so any advice is appreciated. Any other ways to tell besides the fingernail test? Was last rebuilt in about 10 years ago, ridden infrequently. Last ridden in April and was started and ran in July.

PO says he changed oil regularly/frequently, but based on the things I found due to lack of regular maintenance, I’m not sure what to believe.

Here are pics of the cylinders:


Attached Images
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by Mike Baker
Mike Baker
Just had a set of .020 pistons done at Line to line. It was $75 for the pair. Jake honed the cylinders and I believe the pistons were coated .0025" for an assembly clearance of .002". What happens is the coating will wear off as required for a proper running fit. Jake and Rob Hall have done this to a number of motors successfully. Talking to the guy who owns the business, he coats for race teams all over the world. Had a set of pistons there that he was getting ready to ship to Australia for a big block Chevy race boat.
The bike is ready to start, I'm waiting on an oil filter. Will report back....
2 members like this
by Mike Baker
Mike Baker
There's another option if the bores are getting marginal size-wise. A good hone and have the pistons coated to take up clearance. There is a shop near me that has coated pistons that are in 2 of my bikes. He can do any thickness (up to a point). Save the overbore for next time and save the cost of new pistons.
Line2Line Coatings SE
1 member likes this
by Ginge
I’d just hone and re-ring it. I’ve seen worse.

I agree that chasing out the metal flakes would be worth the time. To me that bore looks like a rebuild that was not done with care or engine hygiene. Nothing looks blue so there is no over heating.
1 member likes this
by TR7RVMan
Hi Steve, The honing on your cylinders doesn't look right. I don't see the 45 degree cross hatch. Looks more like 5 degrees, but maybe just the photos.

After honing it's very important to clean cylinders well. I have old school garage sink with hot/cold water. I use water hot as I can stand. Put water in bucket with lots of dish washing soap. I specifically recommend Dawn ultra platinum 4x. Sold at most grocery stores.

I start with wiping really well with solvent, compressed air if you have it. I can't recommend it, but gasoline is very effective. Use safely if you choose that. Then soap & water.

I put plastic pad in bottom of sink. Old school cement garage sink which is pretty large. I put plastic bucket of hot water next to cyl in sink or near by. Use stiff plastic scrub brush like for cleaning bottles or glasses. An old wash cloth is good to use along with brush. Brush is a must. Again lots of soap in the hot water. Scrub both bores very well with the soapy water. Dawn is indeed special in that it lifts oil & abrasive out of cyl wall very effectively. Much better than Ivory liquid. Just saying my experience.

Work as quickly as you can. The bores will want to rust instantly. Rinse well quickly as possible. Scrub again both bores. Rinse. Dry quick as possible with white paper towel. Not really even fully dry really, but get all the excess off. I mean like 15 seconds or less. Paper towel should not have even a trace of grey on it from bores. If it does, you still have abrasives left. Scrub more.

If towels are clean, they will be if you scrubbed well. Then be ready with WD 40 in spray can. Spray bores well soaking them well. Then wipe with paper towels to really well to get any moisture out. Then spray with WD40 again. Wipe again, then coat with motor oil thickly.

Before installing cyl. Use clean new solvent or gas to remove the oil & any WD40. Then wipe well with break in oil. Wipe excess break in oil off. Just leaving a wet film. Not dripping oil but wet. Oil pistons, pins (best you can) rings well. Line up rings & install cylinders.
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