Head gasket size

[the108penguins]

so I got in a bunch of the parts I've been waiting for (whew... head gasket was one of them) and I go to put it on the bike and it turns out that th head gasket is about 3 mm larger in diameter than the cylinders. thats 1.5 mm all the way around. is that a problem or will it shrink/flatten when it gets compressed from torquing the head on? it's a cometic graphite head gasket.

cylinder diameter 71 mm
head gasket diameter 74 mm

here's some pics






or here
kodak gallery slide show

[dbeardslee]

You sure you're not looking at the base gasket? Also, make sure you get rid of the big rubber seal (item #4 in the following pic) around the cam chain tunnel - the new gaskets don't use it, and if you put them both in you'll have trouble. The metal ring around the head gasket is basically a crush washer. Maybe they're allowing for a little squish when you torque it down. This show both the head and base gaskets -

[TADracer]

This is not unusual. The stock cylinder bores should be 2.814" +/- and the inside of the head gasket should be around 2.90" +/- after it is compressed. This is to make sure the gasket does not protrude into the cylinder after tightening and the metal ring does two things. 1, makes a seal between the gasket and head/cylinder surfaces and 2, keeps the gasket from being deteriorated by the firing of the fuel/air charge.

Make sure you re-torque your head bolts after a few hours running time.

[nezzer]

Now I am confused. Like TADracer, my cylinders measure 71 mm in diameter. I got a copper head gasket off ebay but it measured 84 mm for the cylinders. This is so far off it can't be right. So now I am looking around for another head gasket. I keep finding gaskets that say they measure 76 mm. That still seems like way too big a gap. From this thread I guess 74 is the right measurement.

Where can I find a head gasket with 74 mm cylinders? All the gaskets that I find that list the bore say 76 mm. Is 2H7-11181-02-00 the right part number for a 74 mm gasket? None of the listings with that part number list the bore size.

I appreciate the help.

[TomB]

Now I am confused. Like TADracer, my cylinders measure 71 mm in diameter. I got a copper head gasket off ebay but it measured 84 mm for the cylinders. This is so far off it can't be right.

We use those on the drag bike, they are 'sposed to be used with compression rings

[nezzer]

Any ideas on where to get those compression rings?

[MPittma100]

Head Gasket Bore

Gasket bore diameters vary a lot for some engines. Builder must choose a gasket with a bore size that is close to, but a little larger, than the cylinder.

[MPittma100]

Bore Size

Any ideas on where to get those compression rings?

Maybe hanging the copper gasket on a nail in your shop and going with OEM style gasket is a better solution.

[nezzer]

Maybe hanging the copper gasket on a nail in your shop and going with OEM style gasket is a better solution.

OEM is fine by me but I want to confirm the size and part number before I order one. Is 2H7-11181-02-00 the right part number for an OEM 74 mm gasket?

[TomB]

I'd try finding out who made your gasket and ask them for Power Rings to suit the gasket.

XS1100 heads were used on Top Fuel racers but very rare now, you may have bought old stock and may struggle to find the rings.

I'd try MTC, give them a call and ask what diameters of ring they stock.

http://mtceng.com/mtcproducts/products/gaskets/power-ring-gaskets

Or make some yourself, I use a complete copper gasket I made


Back to the original question - the original Yamaha gaskets measured 1.2mm when used (compressed) so 1.5mm sounds good for new. The diameters were very loose on the bore size to account for poor fit on the dowels and rebore sizes.

[TopCatGr58]

Hey Nezzer,

There's an explanation to why you're getting confused. I looked on Ebay, and found listings for XS1100 head gaskets, but they were both Wiseco and Cometic brands, which are for BIG BORE KITS...that's why the bores are so much bigger than the stock size.

Here's a listing for a Head/Top End gasket set for a STOCK XS1100 engine.

http://www.ebay.com/itm/Yamaha-XS1100-Top-Bottom-End-Complete-Engine-Gasket-Set-Kit-/151534720993?hash=item23482c57e1

Some of the head gaskets I found were WISECO brand, and descriptions said 1148-1196 which are the sizes of their big bore kits, which were up to 74.5 mm bores....vs. the stock 72mm!!! The other brand was COMETIC, which is also for a big bore kit, not STOCK/OEM sizes.

There are listings for the ATHENA brand, they are from the UK, and are OEM, they have different listings for different years, but they are all the same 78-82 for STOCK Bores.

The Stock # 2H7-11181-02-00 and you'll find ebay listings for Partzilla OEM gaskets for $75.00 JUST for the headgasket, with the kits above, you get ALL of the topend gaskets, exhaust, etc!

T.C.

[TomB]

Nezzer quoted 84mm bore size - 12.5mm difference from 71.5mm (that's 1/2")

That would take the engine out to 1520cc which is what made me think the copper gasket he had was for use with power rings, not a big bore kit gasket.

[MPittma100]

OEM is fine by me but I want to confirm the size and part number before I order one. Is 2H7-11181-02-00 the right part number for an OEM 74 mm gasket?

Yes, that is the correct number.

[nezzer]

Thanks for the help guys! I ordered a new stock sized one.

TomB, I am just curious, is your gasket sitting on some cardboard cut to the exact same shape? Or is the gasket extra thick to lower compression or something like that? How did you go about making your own?

[TomB]

Bolted to plastic sheet for rigidity when cutting.

What I like about the copper head gasket is you can use them many times by annealing, I've forgotten how many times we've re-used the drag bike gaskets.