Triumphrat

tigercub · 02-03-2010, 10:21 AM

i have a question, when i removed the amal carbs from my 73 bonnie there was a seal and a thick gasket between the carb and manifold. when i look in my parts book it only shows a seal, and i put them back with only the seal. now i read a thread that says you need the gasket to keep the carbs from overheating,my question is which way is correct? also if i need the gaskets where can i get them.

68TR6R · 02-03-2010, 11:42 AM

I'm pretty sure that it goes (from manifold to carb) gasket, insulator, o-ring.

GABMA · 02-24-2010, 01:45 PM

All Triumphs with Concentric type Amal carbs (1968 and later) are mounted the same way.... and there is NO gasket.

If you rebuilt your carbs with the Amal rebuild kit, then you received small cross-section o-rings that are ONLY used on BSA and Norton. If you'll look in the Triumph parts book then you'll see that Triumphs use 3 special o-rings of their own design. THEY DO NOT COME IN THE AMAL KIT!

The manifold to carb mating is closed by a special large-cross section o-ring that is approx 1/8" in dia. That will not only seal the carb much better than any gasket, but stand the carb approx .050" off of the manifold effectively stopping all heat transfer.

Between the carb and the mounting nut, one on each mounting stud, is a smaller o-ring and cup washer. This effectively "rubber mounts" the carb to the engine and makes it impossible to warp the carb body (a VERY common problem on these bikes).

You've got to have all this special Triumph hardware to mount Concentrics correctly.

henryanthony · 02-24-2010, 11:39 PM

Quote:

Originally Posted by GABMA

Triumphs use 3 special o-rings of their own design. THEY DO NOT COME IN THE AMAL KIT!

Can these special o-rings be sourced by most any good spares dealer or are they more difficult to come by?

GABMA · 02-25-2010, 08:23 AM

Quote:

Originally Posted by henryanthony

Can these special o-rings be sourced by most any good spares dealer or are they more difficult to come by?

You're kidding, right?

O-rings, like bearings, wire and fasteners, are standardized across the world. You can simply walk into your local hardware store and buy all the o-rings you want in any size you want for 25 cents each.

The ones a dealer will sell you for $4 each or the official Amal & Triumph ones for $6 each, are simply common, run-of-the-mill, everyday neoprene o-rings.

True, there are some applications where viton is better, but the stock parts have always been common neoprene.

Hope this helps!

henryanthony · 02-25-2010, 11:05 AM

Actually, no, not kidding.

I guess I haven't been to the right hardware store yet. I've found the skinny ones but not the fat ones. I'll keep looking. I was thinking maybe these were Whitworth O-rings.

Thanks!

jimmy bush · 02-25-2010, 11:09 AM

I've been looking unsuccessfully for the O-rings that go inside the fuel petcocks. They aren't listed in the parts books and the ones I've found locally are too thin cross sectionally and let the valve seep. Wound up just replacing the petcocks for a $.25 part.

GABMA · 02-25-2010, 02:01 PM

My local Ace Hardware has an inch-size and metric-size o-ring assortment in a bright yellow plastic case. They typically keep them near those drawer assortments in the hardware section where you can buy single bolts, springs, and etc. I've also seen similar at Lowes and Home Depot. Triumph (being out of England) seems to use a hodge-podge of metric and inch sizes. Try some of both sizes. Thankfully, in the carb mounting situation, sizes that are near-fits can be used. With the big one on the manifold, even the correct part from Triumph is not a "perfect" fit.

Neoprene is "fuel resistant", but not particularly good for constant fuel submersion. Therefore, you may wish to buy viton for use in a petcock... or simply buy a handful and plan on replacing it once a year.

Hope this helps!

JTT · 02-25-2010, 09:47 PM

Quote:

Originally Posted by GABMA

All Triumphs with Concentric type Amal carbs (1968 and later) are mounted the same way.... and there is NO gasket.

My 1970 T100C manual shows an insulator and gasket

I am interested in this oring mounting idea however. So, if I'm understanding correctly, there is the big oring, then smaller ones of similar cross sectional diameter to the big one, on each of the mounting studs, between the carb body and the manifold? You mentioned a cup washer? Where would one get these? ...and they go between the carb and the manifold along with the oring?

GABMA · 02-26-2010, 09:05 AM

Quote:

Originally Posted by JTT

So, if I'm understanding correctly, there is the big o-ring, then smaller ones of similar cross sectional diameter to the big one, on each of the mounting studs, between the carb body and the manifold?

"Between the carb and the mounting nut, one on each mounting stud, is a smaller o-ring and cup washer. This effectively "rubber mounts" the carb to the engine and makes it impossible to warp the carb body."

The cup washers are a Triumph part.