Which new carbs would you fit

[funky]

I have been reading allot of stuff on carbs and jetting and it seems that these carbs or at least the BS34s -38s have issues with most people on the xs650 mods such as pod filters and custom mufflers seem to have a drastic effect on the the carbs in some way shape or form.
I am aware that even new carbs will have to be tuned to these engine but are they more reliable and less prone problems.
If so what carbs would you fit or have fitted to your build .

I have the issue of not wanting to move my battery box to accomadate different carbs is there carbs out there that would fit the area where my old BS34 carbs go.
Thats what im wondering ...
All the best Funky

 

[peanut]

ha ha ...me too

I posted something similar a while back and the general concensus was VM34 .
I think there is some info in the tech section about fitting and tuning them.

The beauty of the VM is that the throttle cables pull directly on the throttle slide of each carb just like a Dellorto so its a fast and direct throttle response and being a simple carb its got no butterfly disks ,a lot less parts and they don't need to be bolted together either.

Hopefully they'll be someone along tomorrow who can explain how easily they can be fitted.
I was looking around yesterday and found some for sale quite cheap but when sold seperately you need to buy a left and a right handed carb
http://www.ebay.co.uk/itm/MIKUNI-CARBURETTOR-VM34-168-RIGHT-TICKOVER-LEFT-AIRSCREW-FACTORY-JETTING-EF-/151781076181?hash=item2356db6cd5

 

[funky]

Hi peanut These are the carbs Howard spoke about I wonder if they would fit in the space my Bs34s are in i also saw some angled inlet manifolds that would allow the the carbs to pass either side of the battery box , that may look real sweet with a couple of velocity stacks pertruding out from my side covers ...found these even cheaper im off to usa soon ,,, What them tubes for there a bit pink if i got some i would change those tubes lol
http://www.ebay.co.uk/itm/Mikuni-VM...8871ae1&pid=100005&rk=2&rkt=4&sd=151781076181
All the best funky

 

[650Skull]

The biggest problem is................if you don't buy the Vm's as a set already used on, or guaranteed, (yea right), set up for an XS650, is the re-jetting and needles for the XS650.

Plenty of info an that, but also lots of variations on peoples set up. Still going to have to start from a base set-up and work from there swapping jets and needles to suit your bike.

MMM at 650 central sells them as a set up kit. Down here, (Oz), the VM's can be bought and then jet. It is hard to get the left and right so 2 rights are often the norm.

Maybe better response but the fuel economy goes down

Here is some good reading on the problems and the set up of the VM's
http://www.xs650.com/forum/showthread.php?t=7060
http://www.xs650.com/forum/showthread.php?t=19322
http://650rider.com/index.php?name=Forums&file=viewtopic&t=6268
http://www.xs650.com/forum/showthread.php?t=562
http://650rider.com/index.php?name=Forums&file=viewtopic&t=8504
http://650rider.com/index.php?name=Forums&file=viewtopic&t=5165&highlight=vm34

 

[weaselbeak]

If you get carbs set up from 650 Central, they will not disappoint. I understand he spent a lot of track time on XS650's and really knows his stuff.

 

[grizld1]

OK, here's the bottom line. VM's aren't the best performance carbs out there, but they're the most bang for the buck, and you'll get the best value for your money from Michael Morse at 650 Central. There are however downsides. Lift synch will have to be tweaked more frequently than on carbs with a single cable and linked throttle shafts, and carbs with mechanically lifted slides will not compensate for altitude as vacuum carbs will.

As far as fuel economy is concerned you can get 48 to 50 mpg out of a hopped up XS650 with VM's without babying the throttle if you take your time and know what you're doing--that means valves and rings that yield a 90% or better seal, proper ignition tuning, etc., in addition to dialing in the carbies right.

I've already written out setup procedures in the VM section of the XS650 Garage USA Carb Guide (click the Tech button and follow headers to the link), so all I'll say here is that no matter how good the baseline jetting is, there's more to the job than "Hang 'em and go."

 

[pamcopete]

The carb guide for the VM34 - 36 is also available on www.amckayltd.com/vm34-36.pdf

The original carb guide for the BS34 and BS38 is also available on www.amckayltd.com/carbguide.pdf

 

[TwoManyXS1Bs]

Ohboy, I get to do a 'rant'!

As oldschool, archaic, obsolete, primitive as they are, carburetors are still delicate/precision instruments, trying to function in a harsh/demanding environment, and should be treated as such.

They come from a time when folks were more tweaky and fiddly with their gizmos, like fixing wristwatches, shoes, darning socks, fixing vacuum-tube radios, hot-breath warping wings on balsa gliders, adjusting circuits and yoke coils on vacuum-tube TVs, setting ignition points, hand-winding and tweaking rf coils on ham radios, ...etc.

You MUST master the understanding of the carb internals, what each part does, and when, and why, in order to successfully tune the things. Of course, the carb comes fully engineered to perform its function, years of development have taken care of that, but the tuning variables can create a humongous variety of combinations. So, a methodology must be used to isolate and target specific areas of adjustment.

If you find yourself thinking less about the tuning chores and more about the 'bling' and 'intense', like velocity stacks, polishing/painting, custom spigots, etc., there'll likely be problems ahead.

A $5000 paint job on an old, used Yugo won't help its performance.

It'll still slow down when you use the cigar lighter...


(*Rant* off. That was fun.)

 

[Stoop22kid]

Joe from wiseguy customs recommends vm36's for his intakes.....$687 for 2 carbs prejetted and the intake. Good? Bad? I've never ran the Vm's before.

 

[hooser]

We use vm34 for most apps from my stock 1973 650 our 70hp 750. Gary
all available from hoosracing

 

[peanut]

this might be a useful link
http://www.allensperformance.co.uk/float%20valves.html

 

[figure8]

We use vm34 for most apps from my stock 1973 650 our 70hp 750. Gary
all available from hoosracing

Quoting for good guy, nothing against 650 central at all but Gary doesn't get enough shouts outs here. As I said, easy to work with and a stand up guy.

 

[hooser]

Thanks for the shout out! Are coming to Davenport the 4th, big swap meet and Friday night racing. I will be around we have a area just east of the pavilion.

 

[grizld1]

+1, figure8. Didn't mean to ignore you, Gary; we've spoken only a couple of times, but that was enough to get my recommendation as one of the good guys--ethical, experienced, and skilled.

 

[hooser]

No problem, I don't feel slighted.. just put in my 2 bit where I can.

 

[Stoop22kid]

What's the difference is the vm34 and vm36? Just the size or is the performance better?

 

[figure8]

It's size first, but most go with the VM34 for the 650. Well done right these bikes run well with them. I cant speak from experience on the 36's, but the 34's are commonly used on race bikes in the 650 community.

 

[funky]

Well if you click on peanuts link you will see the company that i spoke to today I told them what my bike is and what the problem was and where i live in the UK.
The chap was very helpfull and explained that they have jetted VM34s for numerous owners of XS650s.
I was quoted for two one left one right with filters pancake type jetted for my 707cc engine with reverse cone muffles or as we call them Exhaust ....he assured me that they would fit the space vacated by my old BS34s with manifolds and cables all under a sesamee seed bum for ............................... DRUM ROLE £490 delivered ..... I got up off the floor..... and thanked the gentalman for his time and wondered what size yatch he had and how many houses.
you can get a pair for about £100 each and all the other stuff you need for a further £130 total £330 give or take a few quid Im sold

 

[hooser]

I just calculated my carbs. 344.00 eruo and shipping would be around 87 EURO. , . Just for comparison. Gary

 

[grizld1]

Re. venturi size, 2 mm. either side of 34 won't make a big difference on a street bike. A dyno will show very small gains near redline and very small losses at low rpm for the bigger carbies, but you won't feel much difference in the seat of the pants.