GS 1100 cylinder head on GS 1150 cylinder block revamp

[John Kat]

I'm in the process of rebuilding my engine my 1150 engine that came with an 1100 cylinder head.
I believe the previous owner used to drag race the Katana with this engine and I'd like to know if the components are OEM or not.
In attachment you will find a picture of the top of the pistons and the head gasket.
The bike worked fine but consumed a lot of oil.
The bore is the standard 74 mm and the valves are 23 and 27 mm in diameter.
The ports have been polished.
Any idea why the PO went for this setup?

IMG_1908.jpg

[John Kat]

And another picture

[John Kat]

And last

IMG_1907.JPG

[posplayr]

No idea except perhaps PO did not have a 1150 head. On my 1100/1166, I had Terry (Moparsandheads) do a moderate port job with 3 angle valve job and 1150 intake valves in the stock 1100 head.

You can make a 1100 head flow just like an 1150 head even without the larger intakes (28.0 vs 27mm).

I stayed with OE valves rather than go new stainless valves (28.5mm) which are pretty pricey.

https://www.thegsresources.com/_forum/showthread.php?140749-GS-GSXR-16V-Valve-Lift-Diameter&highlight=intake+valves

[John Kat]

That's good news!
Is it normal that the head gasket is not round but has lobes around the combustion chamber???

[John Kat]

Good news today; I found a GS 1100 EFE head in good condition on ebay!
It will nicely complement my GS 1135 engine but I hope that the carbs will still fit in my Katana frame???

[posplayr]

That's good news!
Is it normal that the head gasket is not round but has lobes around the combustion chamber???

I was trying to remember why i did this, but Rapid Ray uses the 1150 Mulit-Layer Steel OEM gaskets on 1100 blocks.
You have to use sharp tin snips to cut something away to fit the 1100 block. IIRC it is the edge of the combustion chamber but can't remember the details now
EDIT: I was doing 1166 so the bore is even bigger than the stock 1135 cc and the edge of the MLS has to be cut back.

Since you have all stock 1150 parts, I would certainly do the OE 1150 head/base gasket with no modifications required.

[John Kat]

I discovered that the GS 1135 engine runs with BS 36 SS carbs versus BS 34 SS on the 1100 engines!
Luckily, I have the larger carbs on my bike.
They are marked OOAOO on the side.
I'm now wondering what pistons I should buy?
Wiseco, JE or MTC?
Should I go for 76 or 77 mm?

[John Kat]

I got a deal on the Wiseco 77 mm K 1299 pistons that I bought today.
The rebore should be done by early next week!
It's far kicker than I thought!

[posplayr]

I got a deal on the Wiseco 77 mm K 1299 pistons that I bought today.
The rebore should be done by early next week!
It's far kicker than I thought!

You might want to drop RapidRay a line if you are going that big. You are going to need a good oil cooler and a series R/R.