Pls Help with Carb Jetting

[Jimmy650]

Hi, need suggestions for ballpark jet sizes. 81, BS 34's with xs performance 750 big bore, 277 rephased crank and cam, pamcopete ignition, emgo pod filters, 1 1/2" headers with prforated baffles, no muffler. on inspection my carb jets were not stock,(changed by some previous owner) 140 main, 135 air jet with a stock 42.5 pilot jet. I live pretty much sea level. Anyone out there running a similar setup with their motor? Would love to hear what you guys are running as far as jets.
Otherwise I was going to go back to stock for all sizes and try and figure out where to go from there?

 

[650Skull]

Read Here cover most of your question. People have found the 750 runs as good on standard jetted XS carbs for the 650

 

[Jimmy650]

Cheers mate

 

[650Skull]

You live in Sydney, there is a lot of 650 guys there in the 650 Club who would give a lot of local support and knowledge.

The Oceania XS650, Australia/NZ/Canada have a different needle and needle jet in the BS34's compared to the US models. Same as the Canadian ones Mikes XS sells

Part #48-0663

Part #48-0662

PS. Welcome

 

[5twins]

You're probably going to need to replace those cheap pods with something better like UNIs. Cheap pods do not work on these bikes and cause all sorts of tuning headaches.

 

[Jimmy650]

Thanks Skull, are these 2 part numbers an identical part? Did not realise I could get a needle with adjustable clip position for my carb, thought it was only a feature on the 38's. Will definitely look in to getting one, once mikes has them in stock. I have befriended a 650 club member in my area, who always helps me out with spares and advice, whom builds complete bikes, but unfortunately didn't have a lot of advice about jetting 34's.
5Twins, thanks for the input. I will upgrade my filters soon, before I try and get my bike on a dyno at some stage. I want that air fuel mixture to be as good as it can be.. after all the time and money we have put into the motor. Thanks guys.

 

[5twins]

The general rule of thumb for the 34s is one or two up on the pilots and 2 to 4 up on the mains. Your 140 main is probably as good a place as any to start on the mains. Test with that and go up or down as required. You will want to up the pilots at least one size. Nobody fools with the air jets too much but you can if you need to fine tune the pilot circuit. If, for instance, a 45 is too lean but a 47.5 is too rich, reducing the air jet size with the 45 can give you an idle mix somewhere between those two sizes.