34mm TMX Carbs

[Suzukidave]

I picked up some 34mm TMX carbs off ebay to put on the yellow custom GT750 to replace the modded stock 32's .

[tz375]

Dave,

Do those have the cast in place Q-8 needle jets and -61 needles by any chance? You will probably find it very rich on the needle.

[Suzukidave]

Richard , i opened one up and it has a 6FM4-60 needle , a 300 main jet , a 3.5 cutaway slide , i tried to get the needle jet out to check it but it does seem to be peened in in the bottom . It should come out the top of the carb right ? These came from a Arctic Cat 440 twin .

[Suzukidave]

And the second newer looking set TMX34-26 Arctic Cat Sno Pro 440 had 230 main jets , 3.5 cutaway slides , 6FM6-61 needles and i also couldnt get the needle jet out to check them .

[Suzukidave]

Your right again Richard , it doesnt look like the needle jet comes out

[tz375]

Those carbs all had fixed (cast in place) needle jets. That means that teh needle has to be swapped out instead. Mikuni carbs usually have teh same root diameter on the needles and different pares and different places that the taper starts.

To get the lower mid range right you change needle jets. On these you swap out the needle for one with a thicker root diameter to change the size of the jet orifice. On Polaris needles, the last two digits typically determine the size and higher numbers are a larger diameter needle. On Arctic Ctas it seems to be the middle number. there are 6FM2 and 6FM5 both dash 60 but IO can't say which is leaner. My guess would be the 2.

And of course OEM needles are all model specific and that doesn't help at all. Measure your needles at 10mm gaps and determine the taper and root diameter and call Olav Aaen in Racine WI for a thicker needle. When you tell me the root diameter of the needles and teh size of the needle jet I may be able to work out a starting point on which needles to use.

And check teh float valve assemblies - they are probably 1.5 or 1.8 for snowmobiles with fuel pumps. You need 3.3 or 3.5 - whichever is available.

[Suzukidave]

Thanx Richard , i will measure up the more stock looking set with the 230 main jets and the 6FM6-61 needles . There will be no problems with the float valve as i use a snowmobile fuel pump on it Alpha Sports.... where i picked up the diagram , showed a good range of the needles listed .

[merckid]

will these carbs fit on a T500 as well?

[tz375]

Physically yes, but jetting and cables might be a challenge

[merckid]

would there be any advantage to having these carbs on a T500?

[tz375]

The advantages of flat slide carbs relative to round slides is that they flow slightly more air, make more power and most importantly are more responsive to throttle input.

On a tuned bike that needs bigger carbs, they are a great upgrade but they are not easy to set up and so far we have three people who we know have tried them. The first gave up and changed to Keihins, and the other two are working out what's available that might work in the real world. So you could say the jury is still out.