OK any snowmobile guys here ??
I got a question. I bought two TM38 flat slide Mikuni carbs awhile back for $100ca. The guy I bought them from was a snowmobile nut and had some kind of racing machine. Last year I put one of them on my brothers machine. He said it run good except the top end was a bit flat. I attributed it to the altitude we normally run at -- sea level to just over 5000'. Both our machines acted the same and mine had a VM round slide. I have now made and installed my homemade intake, and installed the other TM on my machine. I have looked online at baseline jetting for the TM flat slide. I find two different baseline jetting specs for this carb. On the snowmobile sites they run a 340 main jet and on the other sites it shows a 230 main jet (pilots both about the same). That's a tremendous main jet difference. These are the TM unit and NOT the TMX.
So my question of the day is: What main jet should I really run ?? Anyone got this carb on their machine ??

Be careful with jets in these carbs... I need to find my spec sheet. There are some main jets that are listed as larger numbers but actually flow less. I'm sure if you do I quick google search you'll find what I'm describing. I'm not home at this time so my notes aren't available .
Regards

Thx for the heads up. I didn't know this.

I azzume this is what you are talking about ??
http://www.ozebook.com/compendium/t500_ ... kmnjt3.pdf

I checked the two sources I looked at and they both are quoting the Hex Amal (4/042) style of jet.
One says run the #230 main and the other says #340 main.
Right at the moment both machines have the #340 main installed. That's the one my brother ran last year. It will be awhile before there is any riding around here. Might be June before the low snow melts and probably July before we get at any of the high rides in.
When you get home any info posted would be appreciated.

Here is what I am talking about with regards to opposing info about the same carb:
http://www.nichecycle.com/ncs/mikuni/ca ... obile.html
Note they are talking about the Hex Amal (4/042) style of jet.
Here is the other one:
http://www.nichecycle.com/ncs/mikuni/ca ... -43mm.html
Note they are talking about the same style of jet (Amal 4/042) but this time its a #230
Same site and two different main jets. WTF ??

Oppps never mind.
Just figured it out. It's an issue I got with reading stuff and then not fully understanding what I am reading. Apparently there is more than one kind of TM38 carb. If you look at the two sites I posted just above you will see that one talks about the TM38-102 and the other talks about the TM38-86. This little suffix at the end of the TM38 makes a difference. There appears to be at least two styles of TM38's. The snowmobile guys run the -102 which is what I have. I went out to the shop to look at them and on the outlet side (reed cage end) on the top right side is the number. It's clearly stamped TM38-102.

Update:
It appears they have three different TM38 carbs .
They are TM38-85, TM38-86, TM38-102.
There is a 110 point difference in the main jet. That's huge.
You better know which one you got. Hope this helps in the future.

I'm having a time of it trying to find my notes... time to clean the garage I guess .