Carburetor seems to have many places for air leaks

This carburetor is off my 74 TC185. there are no O-rings or gaskets in places I'm used to seeing them on other carbs I have worked on.
1. Choke assembly has no seal on brass threads that screw into carburetor body.
2. there is no gasket where the carburetor top screws on to the carburetor. Even if there was, there is a cutout notch on the top of the carburetor that would prevent a seal.
3. the idle speed screw has no O-ring to prevent air getting past the threads.
4. Same with the mixture screw, no O-ring.
Maybe I'm over thinking this and the Mikuni engineers knew these areas   didn't need to be sealed. The parts break down shows no O-rings or gaskets in these areas.

   

Have a box full of similar Mikuni single carbs Ckahleer. They didn't but..sometimes did, use an oring under choke plunger cap. More so didn't though. Again, normally didn't use any oring on air screw or idle adjust. But there IS a flat rubber gasket underneath the cast bit that is sandwiched casting and knurled cap, it's glued to the bottom of this piece and has a cut-out for cast locating tab. Your diagram shows a different style of Mikuni, Not the Suzuki you're working/wondering about/on. It doesn't show a rubber gasket because it's glued to underneath of knurled cap and came with cap and not offered separately. Cap/gasket came with carb when purchased as an assembly.   

asphalt900 wrote:

Have a box full of similar Mikuni single carbs Ckahleer. They didn't but..sometimes did, use an oring under choke plunger cap. More so didn't though. Again, normally didn't use any oring on air screw or idle adjust. But there IS a flat rubber gasket underneath the cast bit that is sandwiched casting and knurled cap, it's glued to the bottom of this piece and has a cut-out for cast locating tab. Your diagram shows a different style of Mikuni, Not the Suzuki you're working/wondering about/on. It doesn't show a rubber gasket because it's glued to underneath of knurled cap and came with cap and not offered separately. Cap/gasket came with carb when purchased as an assembly.   

You can't buy this level of knowledge, Clay please out live me

asphalt900 wrote:

Your diagram shows a different style of Mikuni, Not the Suzuki you're working/wondering about/on. 

The carburetor diagram is a screen shot from Partzilla. A PO may have replaced the carburetor, but I'm not seeing the difference between the diagram and what I have.
My problem is the engine breaksup/sputters at full throttle, with the stock 130 main jet. As I gradually go down in jet size, things get better until this problem goes away at a main jet size of 105.
Compression is 120 psi. Crankcase leak down test pressure drops from 7 to 6 psi in 43 minutes. There are no problems with starting, idle, or below 2/3 throttle.
I'm afraid of damaging the engine running a main jet this far undersized.

Info I can find indicates that model and year came stock with a Mikuni VM26. To see if a smaller one has been installed in the past, measure the carb throat at the slide.There may also be markings on the carb which may help determine what carb you are working with.

Some photos of the two types of knurled slide caps. And an assortment of TS125 (2 but different years) and RV125 similar carbs. Just like gd4now mentioned, check the numbers stamped on the intake flange! One side will have a series of 5 numbers other will have 2 numbers often occupied with random alpha/numerical sometimes Japanese fonts. Side with 5 numbers will be arranged with 3 numbers over 2. This is the carb identification for machine it was intended for. Your Partzilla  schematic states Carb Assy 29110 so you should see 291 over 10. Date coded otherside will "sorta" correspond with your machine year +/- DOM. Showed a picture of the two types of caps but note the two piece design was generally reserved for Rotary valve (side mount) carbs or the early multi cylinder two-strokes that used a rod to pull-up the slide for idle. The Main Jets on all the 125's i have are in the 85-92.5 range so Your use of a 105 would be in the ballpark. Note when cleaning!! The Air Correction for Pilot system is hidden underneath that little brass ball bearing you will note looking down the intake port of carb. The Air Screw gets it's air from the Main (Center Bigger) galley. I often drill out the brass ball to really get in there and clean crap correctly then replace with a grub screw but that's just me.     Wookie, I'll try to outlast You but no Guarantees, Ha.    

The slide opening is 27.5mm. The intake manifold opening is 24.5mm.
The markings on the carburetor left side are: MIKUNI JAPAN ISO and on top of the manifold area are: 45 and 291 10. Hard to see in pics.

   
 

Ha hit the send button right when You did!! Yes that's the correct one then, just follow jetting from schematic. Build date May of 1974

Thanks for all your help Asphalt 900.
The bike is 100% stock. New air cleaner foam. Shop vac/blower blows and sucks through muffler fine. Good compression. No crankcase leaks.but I need to drop from 130 to 105 main jet to run at full throttle. What am I missing?