correct carburation

[Chooka]

Hello, I have a 1985 GS1100G that has just been fitted with a JE Piston big bore kit, due to an oil ring failure.
Stock engine size was 1074cc but is now 1134cc and 10.25:1 compression. Air box is stock as is exhausts.
Carbies are stock BS34SS Mikunis that did have a standard rebuild kit fitted about 12 months ago.
Do I need to change the jetting of the carbies, (if so what size do you recommend), or do I need to adjust the needle height.
Any information would be much appreciated.
Thanks
Chooka

[duaneage]

You bumped the compression and displacement, did you use different camshafts too? The increase in compression works best with different cam timing , specifically longer durations, and if you degree the cam differently you might eek out a small improvement.
The larger engine will flow slightly more air at a given RPM but without aggressive cam changes you won't see much of a difference.

If your cylinder head is stock it won't require much change, again it's the total package that must be considered.

Do so plug chops and see what you get.

[hampshirehog]

Your carbs probably won't need changing but, bearing in mind the standard setting would have been on the lean side, it's worth doing plug chops as duaneage suggests.

[rapidray]

I would, at the LEAST, remove the mixture screw plugs & adjust the mixture screws using the "fastest idle" method. After that, try doing a few plug chops. You won't know till you start running it. You may or may not need to go up a size or 2 on the main jets. You might also need to shim the needles .040 or so. Welcome to the site! Ray.