Gs1000 overbore

[R1guy]

Gents, 

Ive done a few hours searching a can’t find a finite answer, so I’ll ask here.

What is considered the maximum overbore on a gs1000 using standard barrels.

Ive read the attached thread but I’m not clear.

Ideally looking to go to 75mm… which I thing give 1145cc ( willing to be corrected) .

Turbo use intended.

 

[Duckndive]

Many moons ago when NCK Coventry bored my GS1000 block Grandad Nash said 1085cc  bigger needs liners or a block son  

[Gixer1460]

6 hours ago, Duckndive said:

Many moons ago when NCK Coventry bored my GS1000 block Grandad Nash said 1085cc  bigger needs liners or a block son  

Confirmed on APE website 73mm (3mm over) = 1085cc biggest - safely - on stock liners. https://gszone.biz/pistons.html

Above thread - 78.5mm is odd size - maybe used GS1100 barrels / liners?

[gs7_11]

There are 73.5mm piston kits available, including Wiseco.

[Markz9]

 if racing and or sustained hi revs dont go over 1085cc ive tried bigger and the liners start to oval as too thin, the yanks sold an 1100 gs 2 valve eng (think that was shaft drive bike but i am guessing) they can be bored out to 1135cc and a modified wiseco piston from a totally different bike is used

this is a mod grumpy does but you will have to get him to buy the pistons and modify them for you, should say this is a successful race mod but will need maintenance new rings etc 

obviously you will have to open the block to take bigger liners but there is enough meat left so they dont distort 

1260cc need a gorilla /ape block avoid this, i know a lot of people that have tried this mod they leak oil constantly, need stripping all the time and the casings will need to welded and widened etc massive ball ache 

[Reinhoud]

73mm anything bigger you need bigger sleeves.

[Reinhoud]

On 8/8/2024 at 5:51 AM, R1guy said:

 

 

That's my engine...

 

Edited August 9 by Reinhoud

[gs7_11]

73.5mm 

[Reinhoud]

On 8/9/2024 at 5:47 PM, Markz9 said:

 1260cc need a gorilla /ape block avoid this, i know a lot of people that have tried this mod they leak oil constantly, need stripping all the time and the casings will need to welded and widened etc massive ball ache 

1238, we're talking about a GS here, not a GSX, needs bigger liners, but the liners go in the stock cylinder block, what obviously need to be machined out. Casings too.

What need to be welded?

And regarding the oil leaks, the stock O-rings around the sleeves can't be used anymore, so a bead of liquid gasket needs to be smeared around the sleeves to prevent leaks.

It's not as exciting as you say

Edited August 10 by Reinhoud

[R1guy]

15 hours ago, Reinhoud said:

1238, we're talking about a GS here, not a GSX, needs bigger liners, but the liners go in the stock cylinder block, what obviously need to be machined out. Casings too.

And regarding the oil leaks, the stock O-rings around the sleeves can't be used anymore, so a bead of liquid gasket needs to be smeared around the sleeves to prevent leaks.

It's not as exciting as you say

What is the donor bike for said liners and pistons?

Edited August 10 by R1guy

[Reinhoud]

6 hours ago, R1guy said:

What is the donor bike for said liners and pistons?

I don't understand the question..

[Gixer1460]

Its quite simple - if you need bigger liners for the size of piston, what engine do the originally come from? IMO swapping liners just to gain an extra mm is a costly exercise - if you have to get barrels and crankcases machined for bigger dia liners you might as well go 'proper' big! Anyway the OP was asking about std. barrels and liners not mix & match!

[Reinhoud]

They don't come from a donor bike, they come from a parts supplier like Dynoman.net