GS 1000 upgrade to GS 1100 G cylinder block /head

[John Kat]

I read a long time ago on this forum that it was easy to upgrade a GS 1000 with a GS 1100 G cylinder block with it's D shaped cylinder head.
The time has now come to get the project going as I have the components on my bench.
I have a couple of questions.
1) could I use the 1100 cylinder block with the original 1000 cylinder head?
The reason to do that would be to get a higher compression ratio.
2) the 1100 cylinder block has no groove between pistons 2 and 3 to insert a rubber gasket.
Is that an issue as I will use an 1100 gasket?
3) As the deck height appears to be identical between the two blocks, it seems I could use the original 1100 pistons instead of buying a Wiseco or other large piston kit?

Here's a picture of the two blocks:

 

[GSX1000E]

1) Yes, but the combustion chamber volume as well as the valves are identical. No gain in comp. ratio there.
2) No worries there just use a Cometic gasket for the 1100 cylinders.
3) Yes, you can simply use the stock pistons. Or, you could buy an after market big bore kit for the 1100 (thicker sleeves than the 1000 to begin with) and get more cc's and higher compression ratio.

 

[John Kat]

Given the price of 4 new piston rings and a head gasket from Suzuki, it's almost cheaper to buy a Wiseco kit...

 

[GSX1000E]

If the rings on your stock 1100 pistons are still within spec after you hone the 1100 cylinders, you can reuse them.
Both base and head gasket from Cometic cost less than just the stock head gasket from Suzuki.
BTW, ALL Wiseco piston kits come with Cometic gaskets.

 

[GSX1000E]

Here is a '79 1000 bottom end with '81 1100 cylinders bored to 74mm using a '81 GS1000G head and 36mm CV carbs from an '84 1150E.



Here is an '82 1100G bottom end with '79 GS1000 cylinders re-sleeved and bored to 74mm with '79 1000E head and 29mm smooth bore carbs. with cheapo (oiled) air filters that don't work.

 

[John Kat]

The project has moved forward.
As all GS 1100 G pistons were damaged one way or the other, I bought a Wiseco 1085 kit with 72 mm pistons.
I had my GS 1100 G block bored out to accept the new pistons and proceeded to the installation.
Of course, I could have gone with 73.5 mm pistons but they were more expensive and as I'm not out for maximum HP I left it at that.
My concern following "srsupertrapp" excellent thread on the same subject ( http://www.thegsresources.com/_foru...ikuni-RS34/page7&highlight=GS+1100+G+cylinder ) was the piston to head clearance.
In my case I used a Vesrah base gasket that's approximately 1.5 mm thick.
Be aware that the Vesrah gasket kit will not provide you with the correct "egg shaped" rubber O-rings that are used under the cylinder block allthough the base gasket they provide is large enough to take the GS 1000 O-rings...
After tightening the cylinder block down with the help of the handy old piston pins, I measured a clearance of .9 mm (.0035")
Clearly the piston is not flush with the top of the cylinder block but I suppose this is good enough taking into account that the head bolts are tight but nowhere near the recommended torque?

Here's a picture:

 

[John Kat]

I did a quick calculation of the Compression Ratio when the piston drops 1 mm in the cylinder.
The Wiseco pistons are quoted at a 10.25 CR, I suppose this is with the piston beeing flush to the top of the cylinder block?
If the pistons are 1mm lower at TDC the volume of the combustion chamber increases by 4.41 cubic centimeters.
The new volume of the combustion chamber becomes 33,73 cubic cm and the CR drops to 9.04 to 1.
It's the original spec of the GS 1000 but I believe it's a pity to loose that much so I'll have to take some material of off the top of the cylinder block...

 

[BadBillyB]

Hey John Kat,I wanted to reply to this post but I see some of your figures don't seem to be correct. I'm not picking on you but wanted to offer advise. You said 1.5 mm base gasket. Why so thick???....Or was this a typo......1085 kit is 73mm......and .9mm is closer to (.035") of an inch. Another forum member may do this very same upgrade and I wondered if the blocks were the same in height. The stroke is different between the 1000 2V and the 1100 2V.....Can you measure and repost the base gasket thickness please.....Billy

 

[BadBillyB]

Here is a '79 1000 bottom end with '81 1100 cylinders bored to 74mm using a '81 GS1000G head and 36mm CV carbs from an '84 1150E.



Here is an '82 1100G bottom end with '79 GS1000 cylinders re-sleeved and bored to 74mm with '79 1000E head and 29mm smooth bore carbs. with cheapo (oiled) air filters that don't work.

Where did you source these 74mm pistons or are they custom made ??????......Billy

 

[BadBillyB]

John, this is how I always checked deck height. Place it anywhere on block to read zero, then lift plunger and rotate over piston.......Billy

 

[John Kat]

Hey John Kat,I wanted to reply to this post but I see some of your figures don't seem to be correct. I'm not picking on you but wanted to offer advise. You said 1.5 mm base gasket. Why so thick???....Or was this a typo......1085 kit is 73mm......and .9mm is closer to (.035") of an inch. Another forum member may do this very same upgrade and I wondered if the blocks were the same in height. The stroke is different between the 1000 2V and the 1100 2V.....Can you measure and repost the base gasket thickness please.....Billy

I remeasured the base gasket and it came out at 1 mm.
I must have made a mistake the first time...
As the piston crowns appear to be at the same height between the GS 1000 and the GS 1100 G, I suppose the cylinder block is a little taller to take the longer stroke into account?
In fact as the difference in stroke is 66-64.8=1.2 mm, it would be normal to have the deck at 1.2/2=.6 mm higher.
If you add the .2 mm clearance it seems normal to see the piston .8 mm down in the cylinder.
In fact my measurements at .9 mm are in line with those of "srsupertrapp" who shortened his block by 1 mm.

 

[BadBillyB]

Hey great John, I have 5 or 6 Vesrah base gaskets for the GS1000. All of them measure around .021" . There is one oddball one that measures .051" but I don't know where it came from. I would be willing to bet a factory Suzuki base gasket will measure out around .020" .....Since your block appears to have been surfaced already. Why not just use a thinner base gasket. That should put you around .011" "in the hole" , leaving you room to resurface in the future if needed. I can mail you one if needed, how much is postage to France????

 

[John Kat]

Hey great John, I have 5 or 6 Vesrah base gaskets for the GS1000. All of them measure around .021" . There is one oddball one that measures .051" but I don't know where it came from. I would be willing to bet a factory Suzuki base gasket will measure out around .020" .....Since your block appears to have been surfaced already. Why not just use a thinner base gasket. That should put you around .011" "in the hole" , leaving you room to resurface in the future if needed. I can mail you one if needed, how much is postage to France????

That's very kind of you Billy!
In fact I believe the GS 1100 G base gaskets are thicker than the GS 1000's.
I still have some GS 1000 gaskets and they measure .6mm.
I decided to shave the cylinder block in any case as I prefer to use the thicker base gasket to keep the oil inside the engine and to get my CR as high as possible...

 

[Frankenzuki]

Billy, not to jump the thread but I have a couple sets of 74mm pistons for two valve motors I bought from MTC. Got a set of Turbo pistons for my 78 1000 and a set of big dome pistons for my sons old race bike. I use the 1100G/GK cylinders, the sleeves are thicker than the 1000 sleeves and can go 74mm without a problem. Check with Cliff at MTC, they may still have some available.

 

[Steve]

Where did you source these 74mm pistons or are they custom made ??????......Billy

The person that posted that comment (GSX1000E) is no longer a member of this forum. :dancing:

Thankfully, Frankenzuki has offered a possible source.

.

 

[BadBillyB]

That's very kind of you Billy!
In fact I believe the GS 1100 G base gaskets are thicker than the GS 1000's.
I still have some GS 1000 gaskets and they measure .6mm.
I decided to shave the cylinder block in any case as I prefer to use the thicker base gasket to keep the oil inside the engine and to get my CR as high as possible...

OK John, sounds like a good plan. It's very simple to make a deck checker like the one I posted and it's very accurate. I usually was looking for .038" to .040" piston to head clearance .......Billy

 

[BadBillyB]

Billy, not to jump the thread but I have a couple sets of 74mm pistons for two valve motors I bought from MTC. Got a set of Turbo pistons for my 78 1000 and a set of big dome pistons for my sons old race bike. I use the 1100G/GK cylinders, the sleeves are thicker than the 1000 sleeves and can go 74mm without a problem. Check with Cliff at MTC, they may still have some available.

I don't think we got too far off topic. The MTC pistons (in their 1982?) catalog shows turbo pistons with 7.8:1 CR.....Too low.....And the high domes with 13.5:1 CR....Too high for street application. I ran a MTC 1175cc piston kit in my street bike (back in the 80's) , and it was rated at 10.5:1 but it was IMHO totally underrated. Looks more like 11.5:1 using the eyeball. I ran a mix of Avgas and premium in it but couldn't really go too far from home on a tank. They were also very heavy compared to Wiseco's....Heres a pic of MTC 10.5:1(on left) and Wiseco 13.5:1(on right) If you look at the top ring placement you can see where I machined the Wiseco piston to push it even deeper into the combustion chamber........Billy

 

[John Kat]

I finally got my cylinder block back from the machinist...
It's now back on the engine and it looks OK to me with respect to the deck height?
In retrospect, I believe it's not a good idea to use a GS 1100 block ( unless you want to go beyond a 73 mm bore) as you must shave it to get the correct deck height.
I took .9mm off but 1 mm would have been OK.
Here's what it looks like: