vm carb tunning

royfisk · Posted: February 8, 2009, 1:01 pm Post subject: vm carb tunning

Ok Guys I know we have gone through this before, but here we go again. I would like to get information from experianced tunners who have set up 34,36,and 38mm vm carburators. This is the quest for members whom bought carbs, say off ebay, and are set up for say snowmobiles, which we all know are not set up right. I will list my starting point for setting up these carbs. I would like to get info from others, and knowing this is a starting point not a final tuning point. If you are running vms please list your configuration as well and how it runs.

my config is
piolet jet 22.5
air screw 1.25- 1.75
slide 2.0
p6
needle 6dhs
clip pos #3
main jet 190-200
float height 25mm

this is on a stock 650 with ported head and super trapp exhaust, with 1.75 extended intake manifold and factory air box mild cam. This set up works good.
What is working for you? I also use dual throttle cables versies 2 into one.

Grizz; Your knowledge would be very usefull here,
PLEASE BEWARE THERE IS NO SUREFIRE JETTING EVERY ENGINE IS DIFFERANT, THIS IS JUST TO SET UP A REFFERANCE POINT FOR NEWWBIES TO THE VM, WHOM MAY HAVE THE MISS FORTUNE OF BUYING OR ACCUREING USED CARBURATORS THAT THEY INTEND TO USE.
I will look at all enteries and average out the configurations and see if we can come up with a really usefull starting point. Thanks roy Rolling Eyes

royfisk · Posted: February 8, 2009, 6:28 pm Post subject: Re: vm carb tunning

I plan on hopefully getting to the position of making up kits for the purpose of converting carbs from other then 650 yamaha's for the application. I would like to use a size up on jets and a size down to cover most applications. I also intend to make up kits for my stock torker induction system. this is why i look for info from other users set ups cause there are so many differant engine configs that i cannot do all of them and want to get the kits down to the basic most used configurations.

yamaman · Posted: February 8, 2009, 11:18 pm Post subject: Re: vm carb tunning

Of cousre anyone with VM's would have printed out this book and have it in their workshop:

www.mikuni.com/pdf/vmmanual.pdf

royfisk · Posted: February 9, 2009, 10:34 am Post subject: Re: vm carb tunning

thanks yamaman
good litterture,
How about this
What configuration of vm tunning are you running on your mill. please list any engine and exhaust mods. I am looking for typical patterns between differant configurations. I know 650 centrals carbs are very well tuned for a starting point. They refuse to sell a kit to there jetting specifications, and want to charge you $25.00 for the information. Well that gets expensive, as does experimentation. I doubt even they have as much time experimenting with these mills as the people in these forums. The information is here. Im not looking for tunning info, I can tune them perfectly. I also have a starting point I like for carbs that are way off from being configurated for the 650. But I dont want to offer a conversion kit that will leave the customer way off base tuneing. If I could get 6 complete configurations that work, I could average each item and then come up with a base starting point for the kit.
mayby I am asking what would you put in the kit?
my list includes
all the correct internals+ 1 up and 1 down jets, most common 2 needles
1 pull up enrichner
1 lever actuated enrichner
either 2 into 1 or 2 single pull throttle cables
either pods or extended manifolds and stock air box

You know there is something in a product that works as good out of the box as 650 centrals time proven 34mm vm's do. I want a kit that does the same for a set of carbs that may be lurking on a shelf somewhere that are not at all tunned for the 650. Ive asked 650 central in the past to sell me the recomended internals. They refused unless I pay for the information. Well thats like your car being broke down and the dealer wanting you to pay them a fee to tell you what parts your car needs plus the cost of repair. I will buy from 650 central, just not pay them for information that would generate sales that they would have gotten anyhow. I dont know why they dont just sell conversion kits all made up anyhow. They would sell and they wouldnt even have to change a thing in inventory. So simple for them to do, and profits are built in. But to pay them for information and then pay them for the parts which already have a profit margin is wrong. I can understand them chargeing for the info if one wants it just for the info, but not for someone who only wants to purchase the parts from them. I wouldnt even be writting this if they offered kits to the public.

yamaman · Posted: February 13, 2009, 12:25 pm Post subject: Re: vm carb tunning

Hers some I lifted from the Aussie site:

34mm Round slide Mikuni Jetting.

Some of the members have asked recently where to start with Mikuni jetting and I contacted the vertical twin discussion group for some input on this subject. Here are some of the responses:-

VM34:
ains: 180 to 190 is most probable.
Pilots: 20 to 25.
Needle jets: P5 or P6 both work well.
Needles: 6F9; start tuning
in the middle notch.
Slides: the generic 2.5 works fine.
Air jets: remove.
Richard

VM34
ain: 180
Pilot: 25
Needle Jet: P6
Jet Needle: 6F9
2.5 slide
That is at 1000 ft elev. depending on your exhaust should be very close.
Dwayne

VM34:
2.5 slides, 27.5 to 32.5
pilots, P-5 or P-6 needle jets, 6F9 needles, 180 mains, air correction jets
removed (standards are 2.0). Usual disclaimers "Works great on mine, but no
guarantees for OZ" - doesn't the air spin counter clockwise in the carb
throats down under? Finally got the high ratio primary gears completed, but
have not got the engine back together and in the project bike yet.
Bob Hart

royfisk · Posted: February 13, 2009, 10:07 pm Post subject: Re: vm carb tunning

Nice that is what I am after. the more configurations the better.

xsjohn · Posted: February 13, 2009, 10:14 pm Post subject: Re: vm carb tunning

Welcome back roy............xsjohn

royfisk · Posted: February 14, 2009, 9:57 pm Post subject: Re: vm carb tunning

John how you doing?

xsjohn · Posted: February 15, 2009, 12:38 am Post subject: Re: vm carb tunning

Doing good roy.....just watching the mayhem here and enjoying my ride......running better than I ever thought possible...site has gone to wacking and hacking.....live and learn.....spring is about to begin.........hope everything is well there.....

xsjohn

sinister_customs · Posted: February 27, 2009, 9:30 pm Post subject: Re: vm carb tunning

i am buying carbs and can't decide dellorto's from mikes or vm34's from thomasracing? vm's are half the cost but i realy like the idea of having accelorator pump dellorto's any sugestions? this will be fitted to the 750 big bore, and #1 shell cam, stock tci ignition

yamaman · Posted: February 28, 2009, 12:35 am Post subject: Re: vm carb tunning

If you are buying VM's, consider 650central, as they are set up with a good base line setting for our bikes (let them know what air filters/exhaust/cc's/hp your running) As you can see above there's many configurations and the above listed is only scratching the surface! On some VM's yiu could end up changing ALL the internals. So just be careful what you buy!

I've never run the Dellorto's so I can't speak for them, though I've only ever heard good reports!
VM's are a delicious carb (mines 750cc with 34mm VM's), simple, precise & parts available everywhere!
Nobody grizzles about well tuned carbs, weather they be CV's, VM's or any other carb. So it's not what you've got, it's how you use it! Laughing

sinister_customs · Posted: February 28, 2009, 10:46 am Post subject: Re: vm carb tunning

i hear you there, well tuned carbs of any nature are nice, although my big concern is weather or not there is a substantial gain using accelorator pumps vs. round slide no pump? any one hear run the dellortos?

yamaman · Posted: March 1, 2009, 9:23 am Post subject: Re: vm carb tunning

check this out sinister:

650rider.com/index.php...ght=tuning

yamaman · Posted: March 26, 2009, 5:23 pm Post subject: Re: vm carb tunning

HALCO (UK)
Carb: VM36
ain jet: 220
Pilot jet: 25
Spray tube(needle jet) 159-Q-2
Needle type: 6DH3
Slide: 2.5
Air jet: 2.00

BOB BERTAUT (VM36 CARB KIT)
Carb: VM36
ain jet: 190
Pilot jet: 22.5
Spray tube(needle jet) 159-P6
Needle type: 6DP1
Slide: 2.5
Air jet: None, removed.

yamaman · Posted: April 2, 2009, 3:22 pm Post subject: Re: vm carb tunning

I stole XS1961's settings off another thread, shh don't tell him!

ine. 34mmm with Ramair pods, Triumph silencers ,Halco 1 1/2" pipes.
Pilot jet 25
Slide 2.0
Needle jet P6
Needle 6DH4
clip pos 3
ain jet 185 (190 some days)

yamaman · Posted: April 21, 2009, 12:08 am Post subject: Re: vm carb tunning

Here is a basic set up difference between snowmobile & bike carbs.
Snowmobiles are obviously set up for high altitude!

www.motorcyclecarbs.co...43C146.cfm

yamaman · Posted: May 12, 2009, 7:35 am Post subject: Re: vm carb tunning

No XS 650's listed, but plenty of VM tunings here:

www.ohiocaferacers.com...tting.html

What Happened to 650rider.com?

Yamaha xs650