VM Carb Slide Shim position

[KEITH KRAUSE]

Thanks. Great explanation Keith. you understand exactly where I'm at with this process. Two more questions. The manual says I have an Air Jet #1.4, where is this jet and how do I get it out? Also where is the Needle Jet on my bike? I have removed the jet holder that has the #80 Main Jet screwed into it and there is no # on the jet holder (this part has a number of cross drilled holes in it). Is the Needle Jet pressed into the venturi, if so how do you get it out. In the parts book it shows the jet holder with the main jet at one end and the needle jet at the other. Can you help me on finding both these jets and how to remove them. Thanks.
Cheers... Don

I haven't tinkered with the VM22's much and certainly not in awhile, so I'll answer as best I can remember.
There are a couple of designs for needle jets and I can't be sure of the parts you have.
You should have two air jets, pilot air jet and a primary (main) air jet. The pilot air jet should be on the same side as the side air screw. At carbs 1/2 (as you sit on the bike), the pilot air jet would be at the lower left section of the filter side. The side screw would regulate it. At carbs 3/4, this jet would be at the lower right.
The main air jet would be accross from the PAJ of course.
You should be able to look inside to see if a jet is removable with a screwdriver or if it's a press fit. Some are removable and others not. I doubt you'd want to change the air jets unless you believe they are corroded or damaged in some way.
As for the needle jet, yours uses the bleed pipe design (with the tiny cross holes). The main jet screws into the bottom. This is what you would replace if you think it's damaged/corroded. If changing for jetting purposes, it's rarely needed with common intake/exhaust mods. More often than not, I haven't seen any sizing stamped into these. There would be a letter, a dash mark and a number to show size, such as "O-2". There is another brass part that is pressed into the carb body and is at the top side of the needle jet. I've never needed or tried to remove this brass part. As far as I remember, this small brass part has a similar if not exact size opening as the needle jet/bleed pipe.
Hope this helps.

 

[KEITH KRAUSE]

Thanks. Great explanation Keith. you understand exactly where I'm at with this process. Two more questions. The manual says I have an Air Jet #1.4, where is this jet and how do I get it out? Also where is the Needle Jet on my bike? I have removed the jet holder that has the #80 Main Jet screwed into it and there is no # on the jet holder (this part has a number of cross drilled holes in it). Is the Needle Jet pressed into the venturi, if so how do you get it out. In the parts book it shows the jet holder with the main jet at one end and the needle jet at the other. Can you help me on finding both these jets and how to remove them. Thanks.
Cheers... Don

Reading your post again, it looks like you think the part that the main jet screws into is a "jet holder" and you think the needle jet is at the opposite end of the holder, mounted in the carb body. Every Mikuni site I've ever visited or catalog I've seen shows what you believe to be a jet holder is actually the needle jet. In your case, the part with the bleed holes.

 

[Suzuki_Don]

Thanks Keith. Your help is greatfully appreciated. I think I have it all in my head now. What was confusing me was that the Suzuki Factory manual for my bike had jets numbered which I could not find. The needle jet was marked as 0-6, and mine being the bleed pipe design as you said has no marking on it. I called it a jet holder as this was the term used in the part book. I have pilot jet #1 = #15, Pilot Jet #2 = #50. So all the jets, needles & slides in the manual correspond to what are in my VM22s (assuming the bleeder needle jet is 0-6 as mine is not stamped with anything). The air jet is #1.4 according to the manual & this is the only one that I cannot find. Do the two pilot jets meter petrol to the pilot circuit and the air jet meter the air to the same circuit? I have just had another look at the carb. Are the air jets the two holes that can be seen when looking into the air cleaner venturi from the rear of the carb or are they jets within the float bowl area? Looking from the air cleaner side of the carb there are three holes, one is oval and the other two are round. The round holes have a brass fitting in one of them on the air screw adjuster side of the carb. On the right hand carbs the fitting is on the right hand side of the venturi. On the left hand side carbs the brass fitting is in the round hole below the oval hole. Is this brass fitting an air jet and if so I guess I don't need to worry about it as nobody could have altered it to something else.
Hope I am making sense with and not rambling.

 

[KEITH KRAUSE]

Thanks Keith. Your help is greatfully appreciated. I think I have it all in my head now. What was confusing me was that the Suzuki Factory manual for my bike had jets numbered which I could not find. The needle jet was marked as 0-6, and mine being the bleed pipe design as you said has no marking on it. I called it a jet holder as this was the term used in the part book. I have pilot jet #1 = #15, Pilot Jet #2 = #50. So all the jets, needles & slides in the manual correspond to what are in my VM22s (assuming the bleeder needle jet is 0-6 as mine is not stamped with anything). The air jet is #1.4 according to the manual & this is the only one that I cannot find. Do the two pilot jets meter petrol to the pilot circuit and the air jet meter the air to the same circuit? I have just had another look at the carb. Are the air jets the two holes that can be seen when looking into the air cleaner venturi from the rear of the carb or are they jets within the float bowl area? Looking from the air cleaner side of the carb there are three holes, one is oval and the other two are round. The round holes have a brass fitting in one of them on the air screw adjuster side of the carb. On the right hand carbs the fitting is on the right hand side of the venturi. On the left hand side carbs the brass fitting is in the round hole below the oval hole. Is this brass fitting an air jet and if so I guess I don't need to worry about it as nobody could have altered it to something else.
Hope I am making sense with and not rambling.

You're not rambling any more than me.
I'm not that familiar with the "dual" pilot jet set up you have. I can't give advice that I'm not certain about and I have to work on memory with your carbs. My memory has needed a rebuild for years.
If they are listed as pilot jets in your factory manual, then they would both meter fuel in the pilot circuit. The air jet you describe (mounted with its passage in line with the side air screw) would be a pilot air jet and you could make sense of how it works by blowing air through it and feeling where it exits. Spraying works too but be careful of your eyes. The air screw would regulate it too. This air jet should be on the lower left of the carb throat at carbs 1/2 and lower right on carbs 3/4 when you look into the filter side. It should only effect the pilot circuit.
Since you have a needle jet with bleed holes for better fuel atomization, you should also have an air jet at the opposite side of the PAJ. This air jet allows air into a passage that connect directly to the bleeder pipe. This would effect the jet needle and main jet circuits. As far as I know, any needle jet with bleed holes must also use a main air jet to allow air to enter those holes. A jet listed as a pilot air jet wouldn't have a connecting passage to the bleed pipe. You don't mention having any main air jet or seeing another jet and so I'm not sure what you have there. Main air jets and pilot air jets can both be in the same sizing catagory so "1.4" doesn't help distinguish what jet it may be. From your description though, it sounds like the one you mention is a PAJ. Are you positive there's no jet in the opposite round hole? Do you see threads or a "seating" area or collar built into the passage that suggests a jet was in there? Is the oval hole/passage open? Where does air go if you blow into the oval or other round holes? Do you know any history of these carbs? Without a diagram or something, I can't help much if I'm not sure. Mikuni made several changes, especially in '77/'78.
Hope this helps.

 

[KEITH KRAUSE]

To add, it's possible the air jet you see does double duty and effects the pilot, needle jet and main circuits? If so, this design was inferior and changed I believe in all carbs used on '78 models.
If you have no other air jet and the other holes look like no jet was ever in there, then this should be the case. Still, you could prove the design by spraying/blowing air through each passage and seeing where it exits. When spraying through the PAJ passage, if you observe spray entering both the needle jet/bleed pipe area and pilot jet(s), then it must do double duty. If it only enters into the side of the pilot jet(s) then it feeds only the pilot circuit and then I'm confused as to how all 3 jetting circuits get their air. A simple open air passage to the bleed pipe seems too primitive.

 

[Suzuki_Don]

Thanks again for valuable information. This thread will be of great assistance to others in the future that need to work on VM carbs, even though the 550 and 750 do have some differences.
I have checked out the different air holes on the rear (air intake) side of the carb. I will attach a couple of photos, although in the past the forum would let me insert one only. The bottom right hand side hole has a brass jet in it which I think is pressed in, it cannot be removed. It has no slot like the CV card to screw it out. Also it is way down inside the hole. It allows air to travel to the needle bleeder jet that the main jet screws into.
The hole above that one on the top right feeds air to the starter/choke system.
The top left oval hole is blind. I filled it with WD40 and it stood for an hour or so and was still full to the top when I returned. So I don't know what it does. I did this test on both carbs number 1 and 4.
The carb that I will be showing the picture of is No. 1, so the explanations that I am giving will be reversed for carbs #3 & #4 with air mixture screws on the right instead of the left as in Nos. 1 & 2.
The bottom left hole below the oval one does not appear to have any kind of brass jet in it. When compressed air is forced into this hole it comes out where the air mixture screw would normally be in place. All I can think is that the air jet #1.4 is one of these brass internal fittings that have been pressed into the alloy body of the carb down one of these holes. Again hoping I am making sense.

 

[Suzuki_Don]

This photo shows the oval hole or aperture filled with WD40 still full to the brim after an hour or two. Good view of the brass fitting that feeds air to the choke/starter system.

 

[Suzuki_Don]

Which are the passages that get gunked up with crud in these carbs. The reason we soak them in Berryman's. Is it the fuel or the air passages, or both? Thanks.

 

[Nessism]

Fuel passages are more likley to get varnish as a by product of the fuel.

 

[Suzuki_Don]

Thanks Nessism. I thought that was probably the case. Another quick question, do PODS filter the air into the motor as well as the OEM filter.

 

[tkent02]

Thanks Nessism. I thought that was probably the case. Another quick question, do PODS filter the air into the motor as well as the OEM filter.

The best ones, not quite as good. Crappy ones, not even close.

 

[Suzuki_Don]

The best ones, not quite as good. Crappy ones, not even close.

OK thanks Tkent

 

[KEITH KRAUSE]

Thanks again for valuable information. This thread will be of great assistance to others in the future that need to work on VM carbs, even though the 550 and 750 do have some differences.
I have checked out the different air holes on the rear (air intake) side of the carb. I will attach a couple of photos, although in the past the forum would let me insert one only. The bottom right hand side hole has a brass jet in it which I think is pressed in, it cannot be removed. It has no slot like the CV card to screw it out. Also it is way down inside the hole. It allows air to travel to the needle bleeder jet that the main jet screws into.
The hole above that one on the top right feeds air to the starter/choke system.
The top left oval hole is blind. I filled it with WD40 and it stood for an hour or so and was still full to the top when I returned. So I don't know what it does. I did this test on both carbs number 1 and 4.
The carb that I will be showing the picture of is No. 1, so the explanations that I am giving will be reversed for carbs #3 & #4 with air mixture screws on the right instead of the left as in Nos. 1 & 2.
The bottom left hole below the oval one does not appear to have any kind of brass jet in it. When compressed air is forced into this hole it comes out where the air mixture screw would normally be in place. All I can think is that the air jet #1.4 is one of these brass internal fittings that have been pressed into the alloy body of the carb down one of these holes. Again hoping I am making sense.

The pressed in jet on the lower right must be the primary/main air jet. This jet would regulate flow to the needle jet/bleed pipe and effect the jet needle and main circuits.
As for the passage at the lower left, if you can feel air come out of the hole that holds the side air screw, then this passage supplies air to the pilot circuit only and is regulated by the air screw.
Just so you know, I'm on vacation until this weekend and I won't be able to help if you still need it. I'm sure others will help. Have fun.

 

[Suzuki_Don]

Thanks again Keith. You have been a great help.

Have a good vacation.
Cheers
Don

 

[btbarb]

VM slide assembly

VM slide assembly

Yes, dimple down. This is important as it forces the jet needle to go to one side under spring tension. If the needle just stayed straight and under no spring tension, the needle would rattle/vibrate and soon destroy itself.

I'm in the middle of dipping, cleaning, and replacing o-rings on a set of VM carbs and I didn't notice the dimple in that slide assembly plate when I took the slide assembly apart, this old thread answered my question about which way the dimple goes - posting pics of the dimple and slide assembly back to the thread for future reference.

Bryan

 

[KEITH KRAUSE]

Glad it helped. The thicker spacer that goes above the e-clip, actually called a "ring" by Mikuni, sometimes has a small indentation on one side that fits the dimple. I've seen some rings have none at all while others do have the indentation.
Not easy to try mate the rings indentation with the dimple on the plate and keep them from moving while re-assembling everything. I've tried it by using a thin coat of grease to help the parts stick together but once everything is dropped down in you can't see things as you start tightening down the Phillips screws. I'm sure many carbs have had the dimple not go into the indentation and I've never noticed any issues if it did happen. And with all the parts inside possibly being swapped over the years, some rings with indentations got replaced with rings without it and it didn't seem to cause any issues, at least none that anyone was aware of. The jet needle assembly still cocks to one side whatever part you have in there but the tension it's under varies a little.