The old tang debate

[jon]

It’s been a while since this popular opinion dividing debate was discussed.

Came across these LC cylinders on eBay, which have obviously been running YPVS pistons with the tangs. It’s clear that is what has caused the damage.

C21F0DDB-A065-4A4E-9B43-A0C2E9D7D9CD by Jon Leech, on Flickr

Jon

[JonW]

OMFG!

[jon]

Not that I was in favour of them anyway, but this is proof positive for me.

Jon

[4l04ever]

They look fooked! Relining is probably the only option for those.

[Tobyjugs]

I also believe in removing the tang, but it's more than just the tang that causes the damage.

Wear and high rpm I believe to be the catalyst for this sort of damage, removing the tang will lessen the odds of it happening.

[jessy03]

If you want a quiet engine remove the tang or use LC pistons.
Jess

[jon]

Nov 8, 2020 14:06:19 GMT 1 Tobyjugs said:

I also believe in removing the tang, but it's more than just the tang that causes the damage.

Wear and high rpm I believe to be the catalyst for this sort of damage, removing the tang will lessen the odds of it happening.

I agree 100%, and that is part why I think this debate exists.

On a fresh bore, I’m sure they are fine with the tang, but after wear they cause trouble.

I had a set of 64mm std bore YPVS cylinders with similar wear to the left in the picture. Had to go to +0.75 to get rid, but because the forged pistons I was using went up in 0.5mm had to go to 65mm in one go.

It’s the side thrust on an over square engine with short rods. The long rod (115mm) +4 crank in my 385 should reduce this wear.

Jon

[justyr]

Apologies for the dumb question but can someone clear up what this ypvs piston tang is?

[dusty350]

This is a pair of Ypvs pistons.

20170305_151559 by dusty miller, on Flickr

Piston on the right has the tang in place. Piston on the left has had it removed. The tang is there on Ypvs pistons as the Pv cylinders have a bridged inlet, whereas the Lc cylinders dont. If you use Ypvs pistons in an Lc it's wise to remove the tang as once worn, the piston can rock and the tang can snag the inlet port on it's downward stroke, with devastating results. Not really an issue anymore as firms like Mitaka make a piston for an Lc, without the tang.

Dusty

[lcmarky]

Nov 8, 2020 20:43:02 GMT 1 dusty350 said:

This is a pair of Ypvs pistons.

20170305_151559 by dusty miller, on Flickr

Piston on the right has the tang in place. Piston on the left has had it removed. The tang is there on Ypvs pistons as the Pv cylinders have a bridged inlet, whereas the Lc cylinders dont. If you use Ypvs pistons in an Lc it's wise to remove the tang as once worn, the piston can rock and the tang can snag the inlet port on it's downward stroke, with devastating results. Not really an issue anymore as firms like Mitaka make a piston for an Lc, without the tang.

Dusty

Every day is a school day.  Nicely explained. 

[dusty350]

This is an Lc cylinder, unbridged;

20170304_093054 by dusty miller, on Flickr

And these are Ypvs with the central bridge in the inlet track

20190618_143008 by dusty miller, on Flickr

Hth

Dusty