SuzukiSavage.com - Jetting MIKUNI VM36-4 with UFO at sea level.

uigiroux

Full Member

Offline

SuzukiSavage.com
Rocks!

Posts: 227

Jetting MIKUNI VM36-4 with UFO at sea level.
05/29/14 at 17:49:56

I have an 07 Savage with a Dyna exhaust, just got the Mikuni VM36-4 carb with UFO and am having really hard time properly jetting. What's really unusual about this carb is when the choke is off it acts like it's on, and doesn't seem to be running rich, but as soon as I turn the choke on, it either just shuts off or barely keeps the engine running at far less rpms and then is running rich with black smoke coming out. And just to save some anticipated questions, yes I've thoroughly checked what is the off and on for the choke. I'm currently running a 15 pilot with a 170 main, but don't know if I should reduce the main jet. I also purchased a Dial-a-jet (DAJ) but didn't install it and would prefer to not have to as my altitude doesn't change often. I don't even know how well that would work since it really only engages when running lean, but I'm quite rich. I was also thinking about changing my needle jet to the leaner running 6DH4, rather than the stock 6FJ6. I am trying to think about all points of my throttle range here.

Another thing I'm confused about with the carb is the right side of it has the air idle screw, which you need a screwdriver to turn, but in the other side is the idle screw you can turn with your hand that has the spring, but that doesn't seem to do anything.

Can anyone help me figure this out. Houston is crazy hot and humid so I need to lean this thing out, but really confused how to do that and how the choke seems to work opposite of our stock carb.

Back to top

IP Logged

uigiroux Full Member Offline SuzukiSavage.com Rocks! Posts: 227	Re: Jetting MIKUNI VM36-4 with UFO at sea level. Reply #1 - 05/29/14 at 17:53:03 Also, the tuning manual really doesn't seem to be anything more than a shopping catalog. It gives no advise about how to work the carb, it just says what the parts are. It doesn't even say which position is carb on or off!
Back to top	IP Logged

Dave

YaBB Moderator
ModSquad

Offline

SuzukiSavage.com
Rocks!

Posts: 17825
Camp Springs, Kentucky
Gender: male

Re: Jetting MIKUNI VM36-4 with UFO at sea level.
Reply #2 - 05/30/14 at 08:17:27

I have a VM36 - but I did not use the UFO as I had not seen anyone post results that they were really satisfied with the jetting when using it. Most struggled to get the Pilot jet and idle lean enough to run well. From what I understand you need to solder the pilot jet shut or use a tiny pilot jet, and most of the idle fuel supply come from the needle jet once the UFO is in place.

I have a self made muffler very similar to the DYNA flow I imagine, a large foam air filter, Wiseco piston, Stage 1 cam.

I ended up with a 195 main jet, needle on the second notch from the bottom, and a # 20 pilot on the Mikuni VM36.

It runs great.

If you can't get the idle speed to change with the screw - make sure your throttle cable is not holding the slide up too far. Make sure the throttle grip moves a tiny bit before it starts to pull the slide up.

There is some discussion in this thread about the UFO.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1262724030

Dave

Back to top

Someday I will be old......But not today!

IP Logged

BabyboyKush

YaBB Newbies

Offline

SuzukiSavage.com
Rocks!

Posts: 25

Re: Jetting MIKUNI VM36-4 with UFO at sea level.
Reply #3 - 04/15/21 at 18:21:41

Dave wrote on 05/30/14 at 08:17:27:

I have a VM36 - but I did not use the UFO as I had not seen anyone post results that they were really satisfied with the jetting when using it. Most struggled to get the Pilot jet and idle lean enough to run well. From what I understand you need to solder the pilot jet shut or use a tiny pilot jet, and most of the idle fuel supply come from the needle jet once the UFO is in place.

I have a self made muffler very similar to the DYNA flow I imagine, a large foam air filter, Wiseco piston, Stage 1 cam.

I ended up with a 195 main jet, needle on the second notch from the bottom, and a # 20 pilot on the Mikuni VM36.

It runs great.

If you can't get the idle speed to change with the screw - make sure your throttle cable is not holding the slide up too far. Make sure the throttle grip moves a tiny bit before it starts to pull the slide up.

There is some discussion in this thread about the UFO.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1262724030

Dave

I just wanted to chime in with the following - when I first got the vm36, I was wrong about when the choke was on or off. There are a lot of conflicting pics/info out there. I was having the same problem, thinking that my bike was only running on choke. Turns out it was running perfectly fine with the choke off, but died when I choked it. Duh.

So I figured out how to make it start on choke by going up to a 20 pilot. This also fixed my fouling spark problem, but I noticed after long rides, the spark was getting a light tan - trending - towards - brown color. So I assumed lean when on the throttle. I was on a 195 main. Bumping up to a 200 main has done the trick, the spark plug is a nice light grey/barely tan on the insulator now. I should mention I have the UFO and a screaming eagle side cut exhaust.

It sounds like an old muscle car and pulls like a new one.

Hope this helps anybody that might be struggling? But it seems carbs are like fingerprints... no two are alike.

Back to top

IP Logged

DragBikeMike

Serious Thumper

Offline

SuzukiSavage.com
Rocks!

Posts: 4216
Honolulu

Re: Jetting MIKUNI VM36-4 with UFO at sea level.
Reply #4 - 04/15/21 at 19:32:18

Uigiroux, this post outlines UFO installation & tuning in detail. Its on a VM38 but the process should be the same. Jet sizes will be different but the process should be the same. I personally couldn't get the UFO to work. It was difficult to get it leaned out enough on the idle circuit. IMO, it's hard to beat the stock VM performance. It's a very good carburetor and very easy to tune. The UFO was just too much to wrestle with. Check out the old post. It has lots of pictures and I'm sure you will be able to improve your current UFO installation.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1586597297

Back to top

Knowledge is power.

IP Logged

LANCER

Serious Thumper
Alliance Member

Offline

Savage Beast
Performance Parts

Posts: 10606
Oklahoma
Gender: male

Re: Jetting MIKUNI VM36-4 with UFO at sea level.
Reply #5 - 04/18/21 at 04:30:25

If you got your carb from me this past year then the needle jet should have been changed to a 159 Q-0, vs the stock 159 Q-5. This is needed due to a recent update to the UFO.
The stock jet needle is retained and usually set the clip on the 3rd (middle groove, which is the stock position) while going down to the 4th groove may be needed depending on you location and engine setup..
Main jet at 195 or 200.
With a DIAL-a-jet the main goes down 3 sizes to give the DAJ room to work for you.

The finger screw on the left side of the carb changes rpm only, it does not adjust air/fuel mix.
The screw on the right side adjusts the fuel mixture for the pilot circuit. Turn CW for a RICHER mix and CCW for a LEANER mix. (This is opposite of the stock carb)
If running rich in the lower throttle range then start with a 17.5 pilot jet and tune with the pilot screw, if still rich drop to a 15. BE SURE your engine is well warmed up before tuning the pilot circuit, a 5 mile ride will do it, or letting it idle for 10 minutes SITTING UPRIGHT AND NOT ON THE SIDE STAND...LEST YOU TOAST YOUR CAM WITH LACK OF OIL.

Back to top

IP Logged