125 Mikuni jetting

[vntg136]

I'm looking for help finding out if the jetting of the Mikuni on my '72 Sachs engined 125 ISDT is in the ball park. I would appreciate any list of recommended jet sizes for not much above sea level. I'm having hard-starting and loading-up problems. Thanks, Bob.

 

[skipperclyde]

I'm running a 28mm Mikuni on a "B" motor.  I'll pull it off and post the numbers in the next two days.

 

[skipperclyde]

I purchased a 28 mm carburetor from my local dealer.  He ordered it from Marshall, got it for about $85.00.  Carburetor number is VM28SC-E0865.

The only changes I made were to change the pilot jet to 40, main jet to 160 and the needle to a 5F3.  Needle is set at the first notch, or the richest position, (all the way UP).  I'm sure there are a better needle and needle jet set ups, but this works great.  The needle jet is a 169 N-8, which is standard on this carburetor. The air screw is out 1¼ turns.

To mount it on a SixDay I did the following:

Cut the air boot on the air box side one ring making sure the diameter is the same.  The boot is now shorter.

The diameter of the boot side of the carburetor is similar to that on a JackPiner with a Bing.  Use the same rubber sleeve, clamp it together and the air box side is done.

On the engine side of the carburetor I shortened the spigot by sanding it on my stationary belt sander.  Remove enough metal that the spigot on the carburetor fits close to the spigot on the intake of the cylinder.  They are of similar diameter on most cylinders so a hose and clamps will take care of the engine side of the carburetor.

Now you will notice the carburetor has to lean about 15 degrees to clear the pipe.  I ran mine like this for a year with no problems.  Recently I did some "fine tuning" on the pipe to make room for the carburetor to stand straight up.  This took no more than a torch and a hammer.

That's about it.  Hope it works for you as well as it has for me.

SkipperClyde




Edited by - skipperclyde on 05/08/2002  1:28:51 PM

Edited by - skipperclyde on 05/08/2002  1:33:43 PM