I keep forgetting you are in Sweden; my bad.

11:1 is not the critical measurement; you should be making decisions on CCP and corrected compression. IIRC, you are running a programmable ignition? If not, you will definitely need one. The tuner would should be skilled in the practice of tuning a carbed bike; a handful of needles and jets will be required. Dyno tuning a carbed bike can be time consuming.

 

I believe Don at HDSP has mentioned that he likes to cut down 124 cylinders to stock length for his 117 builds. Randy at hyperformance would be a good one to check with.

 

Don's the guy that put me in touch with advanced sleeve. He was planning on doing cylinders but unless he's got some advanced equipment, I don't see it being cost effective. Trimming cylinder seems like a plan.. SnS may make cylinders the correct length on request. Typically 117 cylinders are the same length as stock 88/96/103 but SnS ones are shorter.. Go figure. I believe 117 FM cylinders are the right length but don't know if they are specifically for 110s with thin spigots.

 

Yes I know it's the corrected compression that matters, and that is dictated by compression ratio and intake valve closing.

In this particular case the 79 cc combustion chambers will render a high compression ratio even with flat top pistons, which in turn will require a cam with a bit later closing intake.

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Or, a thicker head gasket and/or a dished piston and/or sinking the valves a bit to increase chamber volume.

I forget what lift your valve springs will accommodate but many cams with a 50*, or later, intake close wil have lifts exceeding .600" lift. Also, TDC lift of the selected cam should be compared to the TDC lift of the current cam to see if piston to valve clearance should be checked.

 

If you can find a good tuner it's not necessary to go with a 50° plus camshaft at 11:1..
When I increased my 103 to a 110 I went with 3 cc domes that put my static at 11.26:1 and I went with a 43° IVC cam, Woods 888's.. My dynamic comp is at 10.2:1 with 217 ccp.. no issues and real good usable power at all rpm's

 

Agree the tuner better know what he is doing; the OP's bike is carbed and CCP being that high will be a challenge IMHO. I run similar compression on my 98" but it's EFI tuned by one of the best in Texas.

 

Maybe he’d like peak torque to be closer to 5000, a 43 degree close isn’t everyone’s cup of tea but nothing wrong with it if it makes you happy. I normally don’t even go WOT till 4000rpm and like the torque curve of later closing cams a lot better.

 

A small update, I have been discussing this with the workshop that would do the case boring, and I was right, they said using 124" cylinders cut down to correct height is the way to go.

I have also found a source for 4.125" pistons with a slight dish that will keep compression down to around 10.3:1, this would actually work nice with my current Andrews 55 cams.