mikuni 34mm vm round slide carbs

erkblack · Full Member Joined: May 19, 2008 Posts: 17

i have a 82. with straight pipes and the 34mm mikuni round slide carbs with pod filters. i bought the carbs from sportingforless on ebay. the carbs have 180 main jets, .25secondary and either 12. ro 2.0 air jets(its kind of hard to read the number). since installing the carbs the bike will not run right. i can either get it to idle right but have no top end, or i can the topend right but then it hardley idles and is extremly difficult to start.
if any one has any advice it would be much appreciated.

xsjohn

Think they are taking the air jets out completely.......but honestly I am no expert on the roundslides on the XS........use them on my RT1's though...hang on to the BS34's if you loose the battle........then I can help.......

xsjohn

cdn650er · New Member Joined: Jul 30, 2008 Posts: 4

well this sounds all to much like a bad dream i hade the same problem but my carbs were 36 mm im running a 180 main 25 pilot jet removed the air jet from the carb intake bell my biggest problem was my pipes 2 inch open pipes i ended making exhaust port optimizers and wow what a diffrance it idles pulls like a mule and aint hard on gas im not sure what size needle im running but my first one was way to skinny and went back to the fatter one my carb were off a 700 cc polaris snowmobile got them for 100 buck for the pair at a snowmobile wreckers id check out 650garage.com there is a great carb guide on there

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

The needles and needle jets probably need to be changed as well. Sporting for Less sends out a few sets jetted properly and the rest are not. They don't put in the proper needle jet because it's expensive (about $12). By the time you buy the proper jets, you won't have saved any over buying a properly set up kit from someplace like 650Central. I hear the throttle cable, intake manifolds, and air filters supplied with the SfL kit are crap as well.

erkblack · Full Member Joined: May 19, 2008 Posts: 17

ill give that stuff a try. thanks. and yes the throttle cable is crap, no problem with the other stuff

cpotts454

I just bought these sames carbs. I hope I dont run into the same problem. What is the setup that is supposed to be in these things for an XS? I just need a baseline. I have a 1978 motor.

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

Some notes I took from a thread on this site last year look like this -- For VM34's on the XS650, the jetting is

180 mains
25 pilots
air jets removed
P-6 needle jets
6f9 needles, needles set in center notch

Notes on pilot jets -- air screw best-idle setting above 3 turns, go to next size smaller pilot jet; air screw best-idle setting less than 1 turn, go to next size bigger pilot jet.

If it doesn't run right above 4,000 rpm, it's most likely a main jet problem.
If it doesn't run right below 4,000 rpm, it's most likely a pilot jet problem.

Try that and see what happens.

As I said, those are notes that I've collected from posts by gurus on this site -- Roy Fisk and others such as he. I've never tinkered with them myself, but by the middle of May I plan to be fighting that fight myself. The numbers I've given you are the numbers I intend to start with. If Roy or any of the other gurus here contradict me, I'm pleased to hear what they say about it.

jimmythetrucker

bluebikerblan

Gents......Just a suggestion.....this site/forum has an excellent search feature and it seems to me that using it before buying Mikuni VM 34 carbs from Sporting For Less on ebay might not have seemed like such a good idea if:

A. You'd run a forum search with any of the following keywords
Mikuni, VM 34 carbs, Sporting For Less, SFL ebay

B. You'd sought advice here specifically related to your intentions
before puchasing.

There is a highly recommended source and proper set up for the product you chose with excellent service and results but it's not the route you chose.....Sorry but you've got to give the guru's and prior experiences a chance. Not having a dog in this hunt that's as far as I care to go but there's a number of gents shaking their heads on this one.....again & again.

Best of luck....Blue

cpotts454

Believe me I didnt put the SFL and sporting for less together until after I hit the buy button. We will see how things go when I get them. Before I bought them I asked if there was a return policy and he said yes. The price just seemed so good. I guess it doesnt hurt to give the guy a chance. I hope. Confused

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

I bought mine from 650Central on the say-so of everyone on this list. Everybody said 3M was the go-to guy for VMs. Come warm weather, I will mount these carbs and then I'll know if you guys steered me right.

FWIW -- I've talked to 3M on the phone at length, and I'm sure he's rather MORE than competent. I don't expect any trouble with my new carbs -- but you never really KNOW until you try.

bluebikerblan

Wish you good fortune and I don't have anything add one way or another...
of my own experience. Hope it goes well and the Mikuni gods smile. Let us know too however it goes. I've been weighing a similar decision on a project my choices being VM's from MMM at 650 Central or del orto's from Mikes. Blue

bluebikerblan

I''ve had a fair amount to do with M cubed myself Jimmy and I've enjoyed almost unheard of consultation, timely service and follow up. Bluntly put,
I'm a lousy tuner myself and having a guy like Mercury standing behind his product and set up (and that's the way he looks at it) is the reason I'd go VM 34's if I do.

We're looking forward to your story on this one too Jimmy. Blue

renegadmonk · New Member Joined: May 08, 2009 Posts: 4 Location: OH

Hey guys i know this is a 650 site but i am really in need of good info and it seems you may have it here. I got a set of VM34's recently but being new to the vintage bike and motorcycles carbs in general i didnt have the knowledge to know what jetting i needed. The VM's that i bought seem to have way more jetting than i need. I mean everything is bigger than the "baseline" number you posted above.
I have VM34 168&275 which are identical just left & right sides. but check out these numbers

ain Jet-260
PJ-#35
NJ-#159 Q-2
Jn-6DH4
T/V-VM32/65 2.5
A/J-BS30/97 2.0

and i am only running 484cc's.....could this be why when i start it the damn thing revs way up? Any help would be appreciated.

xs1961 · Posted: May 9, 2009, 11:00 am Post subject: Re: mikuni 34mm vm round slide carbs

Jeez, even the space shuttle would run rich on that jetting! Surprised

renegadmonk · New Member Joined: May 08, 2009 Posts: 4 Location: OH

indeed it would....i will probably drop down to about a 150 Main Jet. I have to get another cable so i can use my Magura throttle. The CR style one i have on i dont care for.
Also found out my high reving prob. as mentioned above (throttle cable) it seems as though the cables to the carbs are not long enough ....wont let my slides go all the way down so i removed it and will be calling Motion Pro on Monday.

yamaman · Posted: May 11, 2009, 8:57 am Post subject: Re: mikuni 34mm vm round slide carbs

What bike you running them on renegadmonk, those settings you have are the standard issue from the factory (probably a good start for a TZ 350 or similar with a power jet. Standard VM, no power jet, a std TZ 350 takes around a 340 main jet)!

VM's are primarily 2stroke carbs, so come std set up for them!
Here is one guys set up for an XS:

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.

Cheers

renegadmonk · New Member Joined: May 08, 2009 Posts: 4 Location: OH

running them on a CB450. Didnt really want to list what it was since this is a 650 site but i really need some carb info. Those numbers you listed seem like it would be better than the standards that came with it. Also mine is actually a 484 now.
And....what is with removing the air jets i mean should that be done in most cases?

yamaman · Posted: May 12, 2009, 7:33 am Post subject: Re: mikuni 34mm vm round slide carbs

Funny, your in Ohio, I googled CB450-Mikuni and the top of the list was the Ohio Cafe Racers website with recommended jetting for some 450's & 500's..............

www.ohiocaferacers.com...tting.html

No dramas, get back to us with how you get on, cheers!

renegadmonk · New Member Joined: May 08, 2009 Posts: 4 Location: OH

yeah i saw that chart however i am quite certain a 220 MJ which is on that chart for racing is much too big for my bike...i am not racing and VM's came with 260 MJ's. originals were 145 in the Keihins. I am not sure how much bigger than 145's for a starting point but it cant be 220. I got stock cams which may change later but for now they will be there

yamaman · Posted: May 12, 2009, 6:42 pm Post subject: Re: mikuni 34mm vm round slide carbs

Yeah, I thought that too, the 500T I thought seemed closer. Yeah it's a racer as well, might still be a bit hot for you, but close!

Honda 500T Mikuni VM34 190 35 P5 6DH7

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