XS650 Mikuni VM34 Carb Swap & Setup

In this video I replace the stock BS38 carbs with Mikuni VM34 carbs and compare 0-100km/h acceleration times.
Mikuni VM34 Carb jetting and settings:
*Pilot Jet = 25
*Main Jet = 210
*Emulsion Tube = Q-0
*Needle clip = second from top
*Idle air = 1 1/4 - 1 1/2 turns out

[@Quocle603]

Awesome video. I have an XS650 that I put back together with VM34 carbs. I did a lot of research online and found that a lot of people were running roughly this setup: Main Jet - 180 - 190 Pilot Jet - 25 - 30 Needle - clip position - 6F9, position 3 (middle) Needle Jet (emulsion tube) - P-6 (richer) P-5 (leaner) Cut Away slide - 2.5 Air Jet - None Float height - 25​ Air mixture - 1-1/2 turns out. Hopes this helps someone as well. Its not perfect, but its a great baseline to adjust to.

[@CwPlatapuZ]

I just want to say I've been watching all of your videos as I just rebuilt my 73 tx650 and they have all been super useful!!! These videos you are posting are GOLD. Thank you so much!

[@2wheelworkshop]

Glad they are helping mate. Thanks for the feedback.

[@stevehennessey7541]

Amazing. I just put VM34s on my XS650 this morning. For me it was a big improvement but I still need to further tune my carb’s a little bit, but much more responsive than the BS-38s. As always, amazing video and thx for the info!

[@2wheelworkshop]

I am sure I will tweak the tuning over time but where I have it now is a good starting point. We are in lockdown here atm and there is only so many "trips to the shop" I can get away with on the bike.

[@iamezytyga]

Great video. Good content, no waffle. I'm about to rebuild a stock '75 xs650 that needs a lot of love. I have a set of vm34s from another build that I will now use thanks to your video. All the best for your channel. Cheers, mate.

[@2wheelworkshop]

Thanks mate. Good luck with your build.

[@arthurleino]

I have a Mikuni VM 38 on my 83 FXWG. Was lucky my throttle I had for the 38 Deloroto pumper was the same! Had a Mikuni on my 80 Sportster and liked it. Thanks for the post.

[@sandmanGT350]

Great carb info. I cheaped out and replace my originals with Oko's. It ran great for about a day. Went back to originals. I may try again with the keihin knockoffs next summer. Your video may have changed my mind. Thanks

[@2wheelworkshop]

I'm pretty happy with the results. Easy starting, stable idle, better throttle response and more power. Worth every cent.

[@benjaminbeebe9182]

Nice work, been struggling with my stock carbs, now I’m thinking about swapping to these!

[@2wheelworkshop]

I would definitely recommend it. I'm sure you can get the stock carbs to work well but they are all getting pretty old and worn and the VMs were great out of the box

[@GpunktHartman]

The stockcarbs are made for reliable cruising. If you need more accelleration, there is a way for them with "dynojet" ore you do it by just a ~3,2 drill (to open the vacuumhole next to the needlehole in the slide)... bigger mainjet and rise the needle. ☝️🧐You will start to love the originals.😉

[@2wheelworkshop]

I might give that a shot. If nothing else it will make an interesting comparison video.👍

[@jaiclark148]

Keep up the good work mate!

[@2wheelworkshop]

Thanks man. Will do.

[@ArizonaRE]

Nicely done! Enjoying your content B-)

[@2wheelworkshop]

Thanks mate. I really appreciate the feedback.

[@Tater-]

Another awesome video mate

[@2wheelworkshop]

Thanks brother

[@eflanagan1921]

Great video and bike ,hope you made swing out of that back tire!

[@stevesutton6093]

Hey Brodie, nice work and as the owner of a couple of these magnificent machines I really enjoy your content. Try raising the fuel height in the float bowls by adjusting the floats by a poofteenth as that might cure the flat spot.

[@2wheelworkshop]

I'll give it a try. Thanks mate.

[@northvanwan7428]

lol, SAE, then Metric, now i gotta learn a new measure ?!

[@BrentonIsRad]

Legend!

[@2wheelworkshop]

Thanks mate

[@jahnbell8906]

Nice video makes me more interested in XS650 ..i tried to find Xs650 that for sale but no avail,i guess i like more the standard than the special..

[@2wheelworkshop]

Thanks mate. I'm not a fan of the look of the special either.

[@guypigache2105]

I have a set of VM's to fit. This is a helpful video. TBH I dont think you need to do so much speeding up, normal speed would be useful and although the tuning process is slow and boring hearing your analysis after changing each set of settings (idle, main jet, mid range) would have been very interesting.

[@2wheelworkshop]

I probably could have gone into a bit more detail but I'm juggling a few things atm and I was a bit time poor. If you have any specific questions you can email me. Just put a message on here to let me know because I don't check emails as often as I should.

[@piraltas]

Hi there! How many turns out were you at with the idle screw? Please and thank you

[@ericnelson966]

I have wanted an xs650 and am considering getting one so I am doing a good bit of research on them. I have never had a vertical twin . However I keep noticing the vibration doesn't "look" as bad as some people say. Did you have your crank rephased?? I am a harley person and don't mind a little vibration at all from my sportster at all. In fact I like it but I am curious about the level of vibes on the yamaha. I am 57 years old and when I was young motorcycles still had lots of character which is why I am interested in the yamaha.

[@2wheelworkshop]

The engine is completely stock and it does shake a bit. It doesn't bother me on shorter trips (1-2hrs) but if I were to ride for hours on end I would need to take regular breaks to let the blood return to my fingers. The handlebars (and nearly everything else) have rubber dampers for a reason and I would not like to ride an xs650 with clip ons.

[@1971midget]

Very good video and useful, could you please tell me where I can get the carburetors kit like this? Thanks in advance

[@2wheelworkshop]

Thanks mate. I got mine from here mikunioz.com/shop/yamaha-xs650-dual-mikuni-vm34-complete-carb-conversion-kit/?v=13b249c5dfa9

[@jamilyeo4476]

What happens to the centre breather hose when moving from the oem air box to pods ?

[@2wheelworkshop]

I'm going to make a catch can. Still coming up with a design/location

[@user-rj8oz5cc1o]

Did you do a Dyno run with fuel air ratio check at WOT When I run a 180 jets I’m rich 210 would be extreme

[@1981dasimpson]

i have an en500 cruiser with er5 engine cv carbs giving me real problems thinking of going dual vm34 idle will not stay stable no matter how much i balance tune valves etc

[@2wheelworkshop]

I couldn't really comment on how well that would go but it was a big improvement for the XS

[@brithsb7114]

Hey there, could you tell me the size of the needle please. You said you put the clip on the second slot but not sure what needle it is. Thanks!

[@2wheelworkshop]

Hey mate. I can't remember off the top of my head. I will get them apart later today and get back to you.

[@user-rj8oz5cc1o]

Hi Brody Interesting you can use a 210 mJ What are the other components Needle jet ? Needle ? PJ ? Slide ? Did you check your colour of plugs with 210 MJ you better carry a spare set of plugs.

[@ralphkoch6652]

Put one of these kits on my ‘81 special about 2 months ago. Found adjusting the air mix screw made no difference where I put it Did start to produce smoke out of left cylinder, so have stripped motor and am now rebuilding it , so haven’t had a chance to really try the carbs , only did about 10 is on them it. PS where abouts are you located?

[@2wheelworkshop]

The idle air screw problem could have something to do with your idle speed screw. If your throttle is to far open at idle then you will be feeding fuel from the needle jet instead of the pilot which would negate the idle circuit. Just a guess without having a look at it. I'm in Broadford, Victoria. About an hour north of Melbourne.

[@ralphkoch6652]

@@2wheelworkshop Thanks, Know Broadford, built some dog kennels there a few years ago. I’m down in Cottlesbridge(Hurstbridge way) I sent my head and barrels up to Geoff for an exchange, got the head back but barrels have been sitting with Australia post at Sommerton for over 2 weeks

[@lalnablehector1285]

@@2wheelworkshop I happen to be from Broadford too funnily enough, Wanna come fix the carbs on mine for me? 😆

[@RGV2504]

Hi. I’m just about to fit a friend’s 34’s to my xs650. What idle jet size did you start and or finish with. I’m thinking of starting with 15 and going from there. Thanks.

[@2wheelworkshop]

I stuck with the #25 idle jets that the kit came with.

[@boycottjews]

I have these exact carbs I want to swap on to my Vulcan 500(kawi en500) not sure if y'all got that cruiser. Trying to learn about it so I can finally put them on.

[@2wheelworkshop]

We have the EN500 in Australia but I have never ridden or worked on one. Should be the same procedure to tune but I have no idea on what jet sizes to start with

[@boycottjews]

@@2wheelworkshop they're really fun. Definitely my favorite bike I've personally owned. But yeah the starting point is really tricky, espasically since I don't have much of a clue about this sort of stuff. Found someone selling a kit for the 454ltd, same engine just not bored over. If they email me back that might be a decent starting point.

[@STARCROSSEDMOTO]

Which tubes/hoses are for the fuel?

[@2wheelworkshop]

Ask your local automotive shop for fuel hose or you can get it on ebay. It is sold by length and comes in a variety of diameters.

[@patrickroberts7847]

if you could tell me the throttl ecables and throttle ass. you used that woul dbe great!!!1 i cant seem to find the right ones

[@2wheelworkshop]

Im using the stock throttle and the cable came with the kit. The link below is to a throttle and cable kit from the same place that I bought the kit from. mikunioz.com/shop/2-universal-throttle-with-2-into-1-cable-mikuni-vm-tm/?v=13b249c5dfa9

[@patrickroberts7847]

@@2wheelworkshop what throttle sleeve and assembly are you using? The stock Xs650 one? Or did you get a separate one and use it with the cable that came with the kit?

[@2wheelworkshop]

Stock xs650

[@patrickroberts7847]

@@2wheelworkshop did you have to modify the cable at all that came with the kit?

[@2wheelworkshop]

No mate. The kit is straight bolt on

[@robbenalfans5501]

I adjusted the carbs, but if I want to turn the bike with chocke, dont function I need to oppen the screw, after the Idle will go 4000 rpm,, next I turn down the screw,bike run normaly, what can cause this problem

[@2wheelworkshop]

Not 100% sure what you are saying. Are you turning the idle speed screw or the idle/air mix screw?

[@robbenalfans5501]

@@2wheelworkshop I mean the Idee speed screw, if I want tu turn my bike, dont function I need to turn the Idee speed screw, next the bike will turn on, in 4000 rpm, next I turn down the Idle speed screw to 1100 rpm , sory my englisch is not the best 😁 In the morning is the same thing

[@2wheelworkshop]

It could be air leaks between the carbs and the head, idle circuit mixture, ignition problems or a combination of all plus more. Kinda hard to say without having a look in person. I would check your timing, make sure you have a good strong spark then start looking at the carbs.

[@KT-fi7tm]

So you left the carbs the way you got it and it worked fine?

[@2wheelworkshop]

It's been a while, but I'm pretty sure I went with the emulsion tube that came with the carbs. I give a run down of exactly what's in them at 6:35 in the video.

[@eljaibas16]

Hello, I have a vm34 but it leaks, it's not the float level, maybe the needle seat it's worn out, does someone know how to fix it?

[@2wheelworkshop]

I have never seen a needle and seat wear out. I would say everything needs a really thorough clean.

[@eljaibas16]

@@2wheelworkshop I've seen a few videos and they fix it either by using metal polishing compound with a q tip, or by putting a 2mm ball bearing inside the seat and punching it with a small hammer. I'll try with the metal polishing compound and I'll share the results.

[@2wheelworkshop]

I look forward to hearing your results. Good luck.

[@willcollins4243]

I have a question how do you setup two single carbs to work for the one bike I am confused how to bridge them together to work simultaneously

[@2wheelworkshop]

This kit has a 1 into 2 cable and to balance them you just use the adjusters on the top of each carb. The stock carbs are linked at the shaft. I have a video on balancing carbs that shows the stock setup.

[@willcollins4243]

@@2wheelworkshop so the cable doesn’t confuse how do you get the fuel to get to both carbs?

[@2wheelworkshop]

There are 2 fuel taps lines. One for each carb.

[@willcollins4243]

@@2wheelworkshop so you’re running a split to the petcock right like a y tube

[@2wheelworkshop]

No. The stock tank has a tap on either side. One for each carb.

[@mulletjocks]

My 74/75 idles a heap lower. Not that its an ideal setting for good power pull

[@mulletjocks]

Sorry. High comp rebuild, boyer ignition. Fast bike but.....

[@mulletjocks]

I have 2 of 2010 spec VM34 from "SUDCO?" in a drawer, should i use them?

[@2wheelworkshop]

Couldn't hurt to give them a try

[@morteneide3857]

Extent,...

[@dmuise]

Those air filters are garbage, mate. The UNI pods will give you far better throttle response (especially when you give it a fist full).

[@2wheelworkshop]

I'll give the a try when I get the other bike built. They aren't on there any more. I just wanted them tuned for when I run the new engine in and thought I would make a video out of it.

[@garylynch5263]

Hi mate what is wrong with 38s why change to 34s please

[@2wheelworkshop]

The old 38 CVs off the engine I was tuning these for are very tired and I wasn't willing to put the time, effort and unknown amount of money into them to get them to a usable condition.