Triumph T100 rebuild - Bores glazed...

[rustybill]

My 71 T100 has about 300 miles on a complete rebuild. The rings never seated, and I am getting some blow-by...

I have done a heap of research on bore preparation and am going to try honing the cylinders with 150grit stones. Do I need to purchase new rings or can I run the originals (Tri-Cor)?

Anyone who's had a similar experience, I'd love to hear how you resolved it.

Thanks in advance.

[need louvers ?]

You will probably be best off to go with new rings. Get something quality like Hastings and follow their dirrections on surface prep to the letter and things will go fine for you.

[Daddy Boy]

I dont have a speedo but I reckon my 68 T120 has done same miles and still getting blowby. One cyl has less comp but I aint gonna go pulling it down just because of that, I'm gonna just ride it and wait. Seems to have good power but likely not max power, spose I've got too much happening to bother about it really and a fella called Mr Pete on here set me straight about rocker clearances, anyway, when I used to be on britbike forum I recall that rings are being made (dunno which) with a pre gap of .020" which John Healy from memory says thats ok but ring gap is such an important issue concerning blowby to engine builders they never use pre gapped rings. Mine weren't and I had to file to .014" yet blowby occurs still.
Did I crosshatch properly? I used the standard 3 pronged sprung tool with 170 (I think) but they were used but I cleaned them with kero and used kero when honing. Perhaps I shouldve used proper honing oil with new stones.
I have norton barrels here that have been honed by a well known norton race bike builder (RIP) and I reckon mine looked as good as his job.
I blew a base gasket after full rebuild and this is a rehone, new ring job, the pistons were scuffed a little so I cleaned them up and used them, did I clean them 100%? it's hard to get all that shit from previous blowby out of ring seats without doing micro damage, I'm not positively sure whether thats my problem but I hope I've helped with your Q.

[Daddy Boy]

Ah, first thing to do is measure bores with the head off and inspect the bores before you remove the barrels.
How did you run the motor in? Pussyfooting around is no good, ya gotta give it a few berries for the rings to bite. No idling for 10 mins while trying to get the carb PERFECT.
A quick strobe a poofteenth retarded for safety and well your carb is already tuned, again richer is better than leaner for run in, hope I'm not mothering you here, youve been studying obviously, all the best mate.

[rustybill]

The pistons and head are full of carbon which leads me to believe there is way too much oil gettin past. Maybe I'm just paranoid...

[Daddy Boy]

Have you taken the head off or are you reading the plugs? Is there smoke comin out your breather ? Could just be runnin rich.

[mblab]

If you use Hastings rings, give them a good looking over. I had 2 sets that had defective oil rings.
Mike

[Tony the torch]

with the soft cast iron rings and today's oil with anti friction additives it is important to never oil the rings when you install them, just wipe the skirt of the piston with a little oil and put them in there dry.
We use Hastings rings .014 gap, 150 hone, and clean the cylinders in soap and water.

[Goldy]

Daddy Boy is 'bang on'...pussyfooting around is no good for break-in...you have to load it up every now and then to get the rings to seat, but you should also avoid lugging or over-reving the engine. Oil is a critical consideration too...a monograde oil of the proper viscosity is your beat bet and be patient, the first 100 miles or so is critical, but a proper break in can take over 500 miles.
I would replace the rings, hone the jugs and start over.

[Daddy Boy]

Well said Torch, for sure about the smear on skirt, and use oil for motorcycles only, the oils they make today people think they'll make better in their old bike but it isn't the case, oils for todays cars and old bikes are chalk and cheese.

[not45blesk]

If the oil gettin past the bores, the rings are in a correct gap ?

[Tony the torch]

Originally Posted by not45blesk

If the oil gettin past the bores, the rings are in a correct gap ?

The oil getting up there is not normally a gap issue, it's a ring seating issue

[rustybill]

All back together now. Any recommendation on what oil to use at break in?

[Glider]

non-detergent — a.k.a. break-in oil