Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Wellworthy Alfin Cylinder.

Does anyone know how far these can be bored oversize ?
Or how thin is to thin as far as the lower part of the sleeves.

As these are quite rare, info on them could be difficult to find.

I would measure the wall thickness of the sleeve and talk to your machinist.

An experienced automotive machinist will have encountered this situation before and likely know what to do.

I've heard stories of these Wellworthy cylinders being provided as original equipment on some bikes.

I have no idea if that is true or not.

Do you know the bore? Is it standard or big bore?

Cheers,
Bill

On the close fin pitch alloy preunit 500 it's not recommended to go beyond .040 OS. If the bike is ridden easy .060 is acceptable. Is it a pressed in liner or cast in?


Bill B...

Alfin liners are corrugated and cast into the barrel.

I have never seen a Triumph one.

Old Mule has it correct regarding ALFIN cylinders.
You CANNOT just press out the original liners.

I have a Triumph one, and I have seen examples that were ruined when a former owner attempted to heat the cylinder and press out the old liner.

I do not know if the old liner can be completely BORED OUT of the cylinder and a new one inserted.
It would take a brave owner, and a master machinist, to attempt it.

Sorry about the delay getting back to the thread, just got in from night shift.

http://www.ebay.com.au/itm/262823813516

The last one of these I saw sold on US eBay for around US$875 the one before (same seller) went for $600 or so.
I doubt the liner could be removed as it is part of the head gasket sealing surface and the big deal with these was the casting was done around that liner for heat transfer.
The auction will end while I am asleep so will take a look this afternoon.
This one is already +0.050" apparently so going to +0.060" may or not be possible or wise.
+0.040" does seem like a sensible limit.
Would be a nice but very expensive addition to the 1957 TR6.

This may be an option if needed. If the bore is far enough out what good is the cylinder afterall. The problems you get into is leaving enough of the alloy for the oversize liner to shrink into without cracking the cylinder. When I was racing my Gold Star I built a cheater engine by overboring a cylinder and putting in a thicker liner so I could run a .120 OS Modial slipper piston. Yes, .120 OS! The Mondial pistons were nicely machined and ran at about 10 to 1 CR. That thing sounded like a grenade going off each time it fired. Unfortunately it didn't fire too many times before it holed the piston. I got about two laps in before it stopped, should have retarded the timing.


Bill B...

I will soon find out one way or the other.
It will be on its way to a new home this week.

Thanks for the replies. :bigt :bigt

I got back from the West coast late Thursday night and there was a pile of packages waiting, one being the Wellworthy Alfin cylinder.

It is in fantastic condition given it age of 50 ++ years ?
The bore looks to be in great condition also and the pistons have the brand Robbins which I am not familiar with.
It looks like a light hone is all that is needed and a set of rings if they are available.

Some pictures to come later.

The cylinder has been soaking overnight in the kerosene tank.
Only thing missing was rings, an email to Dick Symonds last night had not only a reply by this morning but a NOS set of + 0.050' rings available to suit the Robbins pistons.
What a legend.

Photo's have been uploaded to Photobucket.

LINK HERE.

The liners look to have been around 1/8 inch (0.125") thick on the stock bore.
I was told these cylinders can crack from the head bolt holes into the bore and the head bolt holes are much deeper than the stock head bolts so custom longer bolts might be worthwhile.

NOS + 0.050" rings have arrived according to tracking.
I guess the cylinder will need a quick hone with a similar grit to current Hastings rings.

I emailed 'Grants some weeks ago but no reply.

I'd say a TR6 is the right bike for these rare and beautiful ALFIN cylinders.

What a beauty. Don't forget, Alfin liners are corrugated, the idea being maximum heat transfer area as well as mechanical strength.
Keep us informed about your work on that good lookin machine, please.