Performance Carb Suggestions

xsjohn · Posted: May 22, 2009, 3:43 am Post subject: Re: Performance Carb Suggestions

Well the ole days of 55 to the gallon are gone again....... when the Jews hit Iran and gas quadruples you'll be squeeling again......... Laughing

xsjohn

xs1961 · Posted: May 22, 2009, 3:54 am Post subject: Re: Performance Carb Suggestions

Agreed, thats why Im keen to fit these Kwacker CV carbs, need to save juice on at least one bike!

xsjohn · Posted: May 22, 2009, 4:01 am Post subject: Re: Performance Carb Suggestions

Well since I only have one XS650 and remember last summer and gas prices........have you tried connecting the barbs with 3/16 ID tubing on those VM's to help maintain balance......?

XS919 · Posted: May 22, 2009, 4:58 am Post subject: Re: Performance Carb Suggestions

I see quite a few sets of 34mm Mikuni flat slides from the Yamaha Banshee 350. I wonder how these would go on a 650 or 750 with a bit of work?

The jetting and needle sizes from the round slide would probably be a good start. How much would the slide from a 2 stroke carb vary from one suited to a 4 stroke?

Cheers

ichael

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

I saw something somewhere a while ago about two-stroke carbs on four-stroke engines. It didn't strike me as a particularly happy story.

xs1961 · Posted: May 22, 2009, 6:34 am Post subject: Re: Performance Carb Suggestions

John, you or anyone tried a balance pipe between the two VM's ..Would be intrested in how well it worked..I'll take a look into trying it at the weekend ..

XS919 - Ive only had experience with flatslides on 2-strokes ..Id have thought they delivered a bit too much juice for a low-revving 4-stroke..im sure someone will put me/us right soon... Wink

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

the balance pipe seems like a good idea with vacuum-slide carbs. I'm not sure what it would do with VMs, which have mechanical slides. Do try it and do tell how it turns out, why doncha?

yamaman · Posted: May 22, 2009, 9:30 am Post subject: Re: Performance Carb Suggestions

XS919 wrote:

I see quite a few sets of 34mm Mikuni flat slides from the Yamaha Banshee 350. I wonder how these would go on a 650 or 750 with a bit of work?

The jetting and needle sizes from the round slide would probably be a good start. How much would the slide from a 2 stroke carb vary from one suited to a 4 stroke?

A few things to consider; you would probably need to change all the internals, though the slide is probably ok.

So before you buy, get prices for NJ's, JN's, MJ's, PJ's.

Also need to know if those carbs have a power jets, if they do the jetting process might be a long one, working out all the variables, unless you can find someone with experience........

The slide cut away controls air flow on the first 1/4 throttle, a larger number means a larger cut away, which means a leaner mixture. This should be tuneable with pilot jets, needle jets & jet needles. Or otherwise can be tuned with a heavy right hand, going past 1/4 throttle will take the cut away out of the equation!

yamaman · Posted: May 22, 2009, 1:52 pm Post subject: Re: Performance Carb Suggestions

Just looking at this site:

www.mikunioz.com/throt...slides.htm

Don't know if it's right, or the same as Banchees, but it says the only cut away available for TM 34's is #4, might be a bit to radical, not sure??????

Stoort · New Member Joined: May 17, 2008 Posts: 1

Check out 650performance.com. The manual that is offered has a copy of the Yamaha Race Shop publication from 1976 that includes all the details to tune Mikuni VM34 carbs for flat track use. There's also a dyno comparison of VM36 and 38 carbs with no other changes as well as a bunch of additonal info on carb options for the XS650/750 engine.
Stoort

dwyatt · Posted: July 14, 2009, 7:39 am Post subject: Re: Performance Carb Suggestions

I'm running 36mm flatslides, no problem and started second kick after being down for 2 years. Dyno results via 650 Performance show a significant improvement across the RPM range.

dwyatt · Posted: July 14, 2009, 7:39 am Post subject: Re: Performance Carb Suggestions

I'm running 36mm flatslides, no problem and started second kick after being down for 2 years. Dyno results via 650 Performance show a significant improvement across the RPM range.

What Happened to 650rider.com?

Yamaha xs650