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Thinking of rebuilding my BST38SS carburetors myself... HELP PLEASE!


SBK1000

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Posted (edited)

So maybe a bit more information would be helpful.

The motorcycle is an 80/90 GSXR1100. The bike is getting 1216cc high compression JE Pistons. And I am looking into 30/26 valves.

I live in Arizona, USA 1,100' to 1,400' elevation. I venture into 8,000' elevation on mountain rides. Weather is hot 100F to 110F and dry, less than 20% humidity

Carburetors are the 38mm BST38SS  that came of a 91 GSXR750

I was looking into the K&L 18-9311 kit. However, it seems like it does not include main jets or pilot jets, which I was hoping to replace.

Any suggestions of complete rebuilt kits, or a different brand... Suggestions on Jets to run on my set up would be great. 

Edited by SBK1000
Posted

Hi, I'm rebuilding the same 38's right now. Just got a nice rebuild kit from Eblag. Here. The carbs I have found have a crappy Dynojet kit st.1 and I going to replace the tube's and needles with originals. There is not enough info to tell what size jets you should use, but I would start small because of the lack of oxigene in your area. When I was riding a 1216 with large intake valves, the mains were #165 if my memory serves me well... But that works in a country below sea level and a temperature around 60F

A DJ 3135 kit would fit if you want to go from original. 

Keep me informed, good luck.

Posted

You're lucky being in the U.S. - Factorypro  make a jet kit for 38mm carbs being fitted to the 1127 GSXR (the extra capacity doesn't require much of a change in jetting normally) - they cost us Brits and Europeans a lot to bring over here, but they're the best jet kits I've found and they use Mikuni jets. The altitude isn't too much of an issue, but combined with the high temperatures then oxygen will be more scarce, so will need to go down a size or two on the mains and lower the needle a notch and go from there.  If you google it, you can find jetting charts for elevation - don't remember seeing one for temp though.

Best to jet for the altitude you normally ride in - oddly, because you normally have high temps at 1000ft, yes the air will get thinner as you go into the mountains, but the temp will drop by several degrees with every 1000ft of extra altitude which helps a little - atmosphere will still be thinner/cause rich running though !

Changes to air filtration, exhaust, cams and big valves will have pretty individual carb set-up, some time on a dyno really helps here - seems a nasty extra expense, but can save you days of fiddling around with your carbs(and still not being happy).

Good luck with your project.

Posted (edited)

It sounds like the OP is confusing a carb rebuild kit with a jet kit.

A carb rebuild kit comes with some new orings and gaskets and a new float plug and float needle valve. Does not come with jets. you just clean those out with a couple toothbrush bristles. they generally dont "wear out"

A jet kit is a jet kit. Comes with (bigger) jets and does not include orings or wear n tear items..

Edited by boilerdude

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