Mikuni VM38
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4th Gear
Joined: May 2009
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Mikuni VM38
Was browsing around this morning, and came across a listing on ebay for new Mikuni VM38s for ~$50. I can't remember what jets etc are required, and I can't make the search here work today for some reason, so I figured I'd ask all of you: Are these what we need? (ebay item #290320080555)
SLIDE - 3.0
JET NEEDLE - 6DH8
MAINSET- 340 HEX
INSET NEEDLE VALVE - 3.0
JET NOZZLE 480/P-2
PILOT JET 40
If I remember right, main was 330, pilot 30 and so probably some other stuff out of whack there. Thoughts?
SLIDE - 3.0
JET NEEDLE - 6DH8
MAINSET- 340 HEX
INSET NEEDLE VALVE - 3.0
JET NOZZLE 480/P-2
PILOT JET 40
If I remember right, main was 330, pilot 30 and so probably some other stuff out of whack there. Thoughts?
Last edited by Wille_D; May 27, 2009 at 11:24 AM.
Tourer
Joined: Dec 2007
Posts: 388
Likes: 0
From: West Tennessee
i like the vm38. its a great carb all around. Heres some info on it for you
https://www.hdforums.com/forum/3153833-post2.html
https://www.hdforums.com/forum/3153833-post2.html
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
The jets and needles are fine, just what you need.
The price for a new carb is an unbelievable good buy if you can get it for $50.
However, there is one thing that bothers me greatly about this carb.....
That is the large piece that sits on top of the slide.
Perhaps this is just a newer model than I am used to seeing, but I would use caution in buying this carb.
The reason for concern is to use a Mikuni VM38 on a Sportster it requires you to have a 90° elbow at the slide. Otherwise, the throttle cable will never be able to be run under the fuel tank.
This is a very important issue with using a Mikuni.
A Mikuni on a Sporty has very little clearance above the slide and between the bottom of the tank.
This carb has that huge 'pot' on top of it and I seriously doubt the carb will fit a Sporty.
Maybe another member is more familiar with this example than I.
It makes me think this fits a Jap bike rather than a Sporty....... pg
The price for a new carb is an unbelievable good buy if you can get it for $50.
However, there is one thing that bothers me greatly about this carb.....
That is the large piece that sits on top of the slide.
Perhaps this is just a newer model than I am used to seeing, but I would use caution in buying this carb.
The reason for concern is to use a Mikuni VM38 on a Sportster it requires you to have a 90° elbow at the slide. Otherwise, the throttle cable will never be able to be run under the fuel tank.
This is a very important issue with using a Mikuni.
A Mikuni on a Sporty has very little clearance above the slide and between the bottom of the tank.
This carb has that huge 'pot' on top of it and I seriously doubt the carb will fit a Sporty.
Maybe another member is more familiar with this example than I.
It makes me think this fits a Jap bike rather than a Sporty....... pg
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,052
Likes: 993
been running a mikuni vm38 since 1975 on a 1974 xlch. they are great carbs and were superior in the old days as i think the newer carbs have some advantages. the vm38 is easy to tune in and parts are still easy to get. what i liked about them in 1975 was one arm choke that only was in service at closed throttle and no accellerator pump which saved leg power when some kid cranked on the throttle when you were in the store.
my set up was a #30 pilot, #Q2 needle jet, #330 main jet, # 6DP1 needle and a #2.5 slide. however, with the advent of alcohol fuel, i had to up the pilot one size. the machine will top out at 133 mph.
if you bought the carb used, be aware that it could be wore out and need overhaul as i had to do to mine , but i have 150k miles on the clock.
my set up was a #30 pilot, #Q2 needle jet, #330 main jet, # 6DP1 needle and a #2.5 slide. however, with the advent of alcohol fuel, i had to up the pilot one size. the machine will top out at 133 mph.
if you bought the carb used, be aware that it could be wore out and need overhaul as i had to do to mine , but i have 150k miles on the clock.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
what i liked about them in 1975 was one arm choke that only was in service at closed throttle and no accellerator pump which saved leg power
That is not a choke on a Mikuni VM38. A choke is a simple butterfly flapper that closes off most of the venturi and does nothing but upset the proper mix of fuel and air. Heavy on the fuel side.
The item is not a choke, but rather an enricher type starter system.
This enricher has it's own independent jets (Starter Jets) located inside the base of the float bowl lower chamber.
What the enricher does is provide a proper mix of fuel and air to the emulsion tube.
In the emulsion tube the mixture is broken into tiny particals and then flows to the plunger area.
There it again mixes with air coming in from the intake port for starting and delivers this mixture to the engine in the optimal fuel-air ratio through the fuel discharge passage.
The lever opens and closes the enricher by means of the starter plunger.
Because the enricher system is designed to utilize the vacuum of the inlet passage, it is important to keep the throttle fully closed when starting the engine.
So, that is how the enricher on a Mikuni works. A choke it ain't, by any stretch..........pg
That is not a choke on a Mikuni VM38. A choke is a simple butterfly flapper that closes off most of the venturi and does nothing but upset the proper mix of fuel and air. Heavy on the fuel side.
The item is not a choke, but rather an enricher type starter system.
This enricher has it's own independent jets (Starter Jets) located inside the base of the float bowl lower chamber.
What the enricher does is provide a proper mix of fuel and air to the emulsion tube.
In the emulsion tube the mixture is broken into tiny particals and then flows to the plunger area.
There it again mixes with air coming in from the intake port for starting and delivers this mixture to the engine in the optimal fuel-air ratio through the fuel discharge passage.
The lever opens and closes the enricher by means of the starter plunger.
Because the enricher system is designed to utilize the vacuum of the inlet passage, it is important to keep the throttle fully closed when starting the engine.
So, that is how the enricher on a Mikuni works. A choke it ain't, by any stretch..........pg
Advanced
Joined: Feb 2009
Posts: 84
Likes: 0
From: Siler City,North Carolina
I found this VM 38 kit that looks like a good buy.Looks like everything you need except the 90 degree elbow and you can get that from sudco for $8.24.
http://www.harley-davidsonparts.com/...arts_5_050.htm
http://www.harley-davidsonparts.com/...arts_5_050.htm
Advanced
Joined: Feb 2009
Posts: 84
Likes: 0
From: Siler City,North Carolina
Another thing. If you look at the sudco catalog it will have the specs for the harley carb. Look at the VM38-9 and compare to the carb specs on ebay.
http://www.sudco.com/mikuni2.html
http://www.sudco.com/mikuni2.html
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Stage I
Joined: May 2013
Posts: 1
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I have a VM38 Mikuni on my 1983 FXWG, love this carb! Had one on my 1980 Sportster. My problem is finding a throttle cable. My old Dellorto Pumper cable works, but is old. My bike has the universal throttle that came with the delloroto. Any help please!!
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Order directly from Barnett. Their universal cable is about $20. The cost to modify it for your bike is about $10. Then add a few bucks for shipping.
When i ordered one for my 1978 Sportster i e-mailed ahead of time thru their website then after first contact i sent pics of the throttle end of my stock cable. They sent a perfect cable to run from my throttle control to the VM38.
Lots of info on their website ...
http://www.barnettclutches.com/produ..._misc&model=35
When i ordered one for my 1978 Sportster i e-mailed ahead of time thru their website then after first contact i sent pics of the throttle end of my stock cable. They sent a perfect cable to run from my throttle control to the VM38.
Lots of info on their website ...
http://www.barnettclutches.com/produ..._misc&model=35
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
I am with Mick on that!
Call Barnett and you can tell them over the phone what you want made.
I just received two throttle cables today from Barnett.
Both go on Bultaco bikes I own and am currently restoring.
One is an MX Pursang and the other is an Astro flat track bike.
Both cables needed to be 1 inch and 2 inches longer respectively.
I wanted to add an elbow and an adjuster in the cables.
Barnett did just what I wanted over the phone and the cost was like $25 for each cable.
It took them 4 business days to make up the cables.
Great folks there too!
pg
Call Barnett and you can tell them over the phone what you want made.
I just received two throttle cables today from Barnett.
Both go on Bultaco bikes I own and am currently restoring.
One is an MX Pursang and the other is an Astro flat track bike.
Both cables needed to be 1 inch and 2 inches longer respectively.
I wanted to add an elbow and an adjuster in the cables.
Barnett did just what I wanted over the phone and the cost was like $25 for each cable.
It took them 4 business days to make up the cables.
Great folks there too!
pg
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