TM125 carburator air jet

[brent j]

Can anyone tell me the air jet size for a 74 TM125?

I've checked manuals, parts books and Alpha-Sport. None of these even show an air jet.

I'm setting up a new carb and would like to get the jet right. I'm not sure how much effect they but the bike won't quite run right and I'd like to eliminate this as a possiblilty.

Any help appreciated

Brent

[oldyzman]

I would start with a 0.5mm. Have you got one? I think this mainly effects top end air correction at full noise....
Brett

[brent j]

Thanks Brett.

There's a 0.5 in there now. The carb is new and has the specified needle, needle jet, slide, pilot and main.

The problem is at high revs coming into the power band. I ran out of time on Sunday to try a few other things so it will have to wait till friday (gotta love RDO's)

i found the bike as a non running wreck at the local dump shop. The carb that was fitted to the bike when I got it was of unknown origin but had the correct slide, needle and needle jet. It's long gone now so I can't check the air jet. I have a TM125 carb from a wrecker which has all the correct parts apart from a bigger pilot and main but it has no air jet

[oldyzman]

Check the size of the needle and seat as some of the new mikuni's are made for Snow mobiles which run a fuel pump....

[oldyzman]

By the way, so many of the suzukis and yammys i have seen have no jet especially 250 and up...

[brent j]

Check the size of the needle and seat as some of the new mikuni's are made for Snow mobiles which run a fuel pump....

I forgot to mention I changed the needle and seat as well, thanks for the reminder.

I'm starting to wonder if the TM didn't have an air jet fitted as you say. Mainly since four different sources so far make no mention of it

[Lozza]

Air corrector is there to stop the ever richening of the fuel curve with rpm. They are a size jet so you can drill out and solder up to you hearts content. But I  think your looking at the needle more.

Only old sleds run VM style mikunis new sleds run CV type carbs.

http://www.ebay.com.au/itm/Set-of-20-MICRO-JOBBER-DRILL-BITS-0-3-to-1-6mm-Polished-High-Speed-Steel-AUS-/320762778731?pt=AU_HardwareParts&hash=item4aaef3946b

[ninjamk]

Air corrector is there to stop the ever richening of the fuel curve with rpm. They are a size jet so you can drill out and solder up to you hearts content. But I  think your looking at the needle more.

Only old sleds run VM style mikunis new sleds run CV type carbs.

http://www.ebay.com.au/itm/Set-of-20-MICRO-JOBBER-DRILL-BITS-0-3-to-1-6mm-Polished-High-Speed-Steel-AUS-/320762778731?pt=AU_HardwareParts&hash=item4aaef3946b

I have never seen a sled that runs a CV carb.  They ran VM's, and to a lesser extent TMs, right up to fuel injection.  I dont think CV carbs lend themselves to 2-strokes very well.

[Lozza]

Air corrector is there to stop the ever richening of the fuel curve with rpm. They are a size jet so you can drill out and solder up to you hearts content. But I  think your looking at the needle more.

Only old sleds run VM style mikunis new sleds run CV type carbs.

http://www.ebay.com.au/itm/Set-of-20-MICRO-JOBBER-DRILL-BITS-0-3-to-1-6mm-Polished-High-Speed-Steel-AUS-/320762778731?pt=AU_HardwareParts&hash=item4aaef3946b

I have never seen a sled that runs a CV carb.  They ran VM's, and to a lesser extent TMs, right up to fuel injection.  I dont think CV carbs lend themselves to 2-strokes very well.

Yeah your correct silly me for some reason I was thinking of the jet ski type BN/SBN

[brent j]

Just returned from a test session.

Tried slightly advanced and retarded ingition settings then back to std. No improvement

Removed the air jet and lo and behold we have a motor that runs pretty much like it should!.
I raised the needle one notch which fixed a slight hesitation then ran out of fuel!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If it's not one thing it's aother.

I may get a run on Sunday arvo, I'd like to try a size larger on the main.


Now it looks like I've got this sorted I'll try the ZY80J ignition again then Lozza's barrell.

Lozza, your comment about "Air corrector is there to stop the ever richening of the fuel curve with rpm" pointed me in the right direction

Cheers

Brent

[Lozza]

Why take the yz ignition off ? The new cylinder will be much better than the TM cylinder

[brent j]

Why take the yz ignition off ? The new cylinder will be much better than the TM cylinder

I couldn't get the thing to run properly and I couldn't work out why. I put everything back to standard and started to work through it that way, process of elimination I supose

The air jet was the only thing that seemed out of place.

I'm going to change the ignition and cylinder back but I'll do one thing at a time.

We have three natural terrain meetings up here to get things sorted then roll on the Nats!

[Lozza]

That would have never been an ignition/cylinder problem was always going to be fueling.

[brent j]

I've built up a second, completely standard, motor Lozza and the one with the YZ ignition and your cylinder is on the floor waiting waiting to go back in.

I used this motor to find the problem as I wanted to remove all the variables I could. I also had a second motor that I always intended to rebuild anyway.
I didn't know if my jetting with the mods was too far off the mark or it was something else.

Now I've found the problem I'll switch motors and try again. The symtoms were the same put more pronounced with the modded motor

[Lozza]

What pipe are you using the standard TM one?