Performance carbs

Ryan, please be assured that I'm not trying to be snide with the advice I'm about to give you. Be aware that once the intake and exhaust systems have been altered, any set of jetting specs that even the best tuner comes up with at a distance will be an approximation, and fine tuning will be up to you; plug and play is only going to happen if you get very, very lucky. Having a shop jet your carburetors will usually result in frustration and waste of money unless, again, you're very, very lucky. At the bottom line, the only folks who end up with good results from old motorcycles are those who turn their own wrenches, and that's especially true when it comes to old motorcycles that have been modified. Carb tuning isn't that difficult if you start with a good baseline, make small changes one at a time, and listen to what your motor is trying to tell you.

I seldom have a difference of opinion with WR or Skull, and this one is offered with sincere respect: IMO age has made the OE vacuum carburetors touchy for a novice to work on, and I wouldn't recommend them to you. Throttle shaft seals almost always require replacement, and I'm seeing more of these carbs with wear on the throttle shaft seats, so that air leaks occur even after fresh seals are installed. Mine is just one opinion, and like another item, we all have 'em.

That having been said, Oldskool Carbs comes highly recommended.

[QUOTE="grizld1, post: 524205, member: 285" IMO age has made the OE vacuum carburetors touchy for a novice to work on, and I wouldn't recommend them to you. Throttle shaft seals almost always require replacement, and I'm seeing more of these carbs with wear on the throttle shaft seats, so that air leaks occur even after fresh seals are installed. Mine is just one opinion, and like another item, we all have 'em.

That having been said, Oldskool Carbs comes highly recommended.[/QUOTE]

Griz is right. I was trying to keep things simple but there are so many variations with the factory BS38's/BS34's due to age and the variations on bike set up. Griz and 5twins wrote the Holy grail to tuning these CV carbs. If you have read the information in the link Wer posted to the 'carb guide" then as a novice you will be more confused. .............Not because it isn't right but because the information has to be used while adjusting the carbs, and riding, doing plug checks, changing jets, or adjusting the needle, (not necessarily in that order), and redoing the process again and again, (if needed), to get the desired result....................... The understanding of how the carb and its components work at different revs also comes into the learning experience.................

To much to take in........may seem like it, but any carbs used, you will need to learn about them..............knowledge learned will make it easier to understand and apply................no one says it is easy to learn, but how easy do things seem once it is understood.

What ever you decide, (as long as it isn't the performance carbs, all the information is in the link), you will be well supported and will receive good advice, help with any questions, and as long as you help us help you, (with reading the information posted, or linked to), it doesn't matter if you don't get it the 1st or 5th time, support will be there............

Many a person has come on here knowing nothing about rebuilding engines, carbs, re-spoking wheels, and now they are helping others with the knowledge learned from the people here............. Yes they did rebuild that engine, carb, wheel, bike from scratch.

Am I right that Mike's xs don't sell anything but the carb I already have

Even if they did/do I would not recommend them.

So as long as I get any 34 mm carb wether it's for a 500 or 650 it will work
in the matter of getting the right jets

Ryan daberko said:

So as long as I get any 34 mm carb wether it's for a 500 or 650 it will work
in the matter of getting the right jets

Click to expand...

Not necessarily, do a search of ex500 carbs on xs650. That's the hot carb at the moment to be had fairly cheap. Big thread with lots of success.

EX500 carbs.

Follow; ippytattoo, .....Post #63 Link........ mrriggs, ...Post #62 Link, xs1961, and the input of many, with links, and their own observations as input into this great thread.

It may seem a lot of work, CV38s/34/s are way more work.

With luck and they are still had for a reasonable price, could be a couple of hundred. cost of carb and jets, buy enough jets to be able to up and down one size on the recommendations in the links. Seems success can be had with a choice of 2 needles with the jets seeming to be very close and little deviation

Take your carbs off and sell them, (yes there are people who still do),

Carbs can be bought back from the dead, why bother...........Nice ones are out there the carb had a run from 87-2009 before buying have a look around and look around where ever, post a wanted add in the classifieds, go to Kwaka sites.

I recently bought a set of NOS EX500 carbs off eBay from England, for 70 English Pound. That is good for Australia. $180 Aus to the door

PDF Needle chart..........mrriggs link lost in post #108. http://www.xs650.com/threads/ninja-ex500-carbs-on-an-xs650.13070/page-4



XS650 carbs will have to be learned as well with the same problems when coming to buy and identifying the right carb you want. 2 different systems to learn, as they both have there merits, throttle shaft seals seem to be problematic on older 38's.

All i'm doing is giving all the information i have gathered with charts for jets and needles and semantic of the EX500 carb, Use this information for a comparison with Factory 38's/34's.

If fact here is a link to theXScafe.com All things XS650 and good value. And the manual link, has all manuals from 70-83 has a set "parts manuals" ..........as with a lot of the XS650 manuals, and part manuals, there is some discrepancy here and there. Just a caution to x check at times.

Go to the Tech menu here and have a look at the carb link by inxs http://www.xs650.com/threads/carbs-carburetors.43/
Lots of good stuff have a look around

Condensed a lot of information, some files have been Taken from threads on here and other internet sources.

No claim or affiliated with the wousers who are disputing the famous Samon/Kiwis, defense of his WBO heavyweight champion Crown.

More EX500 Information in PDF form. Tuning, Jett and Needle charts. Different to the JPEG files

"money is not an issue" A chill went though me when I read that.
With the greatest of respect to you, and with much kindness, throwing money at these bikes without taking the time to learn and understand them is an exercise in futility.

Yeah im kinda overwhelmed with what everyone has been saying and I've already learned alot , it's just hard to understand while not working on it like someone had mentioned , I just dont wanna be working on something "a carb" that in the end is never gonna be a right , which is why I wanted a good baseline . And now I know is the ex500 carbs . And it's not that I have all the money in the world I just feel I got it for a steal so I dont feel bad puting a little money into it . But thanks everyone ! Greatly appreciated

Ryan.....................you're afraid that you may be working on a carb, that will never be right. Well, I have to tell you, that carbs are a crude mechanical device, with multiple overlapping circuits to mix fuel and air,and carb tuning is never going to be "right"! That is why automotive manufacturers changed over to computer controlled fuel injection. Using oxygen sensors and mass air flow measurements, etc. the computer can have combustion "right".

My Mikuni BS38 carb will never be 100% right, but for a 1970's design, it works amazingly well. I'm happy that it always starts the bike, gives good acceleration, very good gas consumption and my spark plugs are tan colour. That's all a carb needs to do.

Carburetor synonyms:

Comprimiser.

Carbon maker.

Yep, carburetors have to adjust the fuel mixture to respond to a complex set of conditions using simple vacuum and fuel control devices, and that involves compromise. That having been established, some carburetor designs are capable of reasonably close approximations to the ideal A/F ratio across a wide range of conditions, and others are not. But EFI systems also compromise, which why more advanced fuel systems (as on the FZ09, for example) have a switch that lets the rider choose from 3 or 4 different fuel maps, depending on what he needs to do at any given time.

I know that and understand it , I was just told by a few people on here that the carbs I have now are not worth my time dealing with or money

retiredgentleman said:

Ryan.....................you're afraid that you may be working on a carb, that will never be right. Well, I have to tell you, that carbs are a crude mechanical device, with multiple overlapping circuits to mix fuel and air,and carb tuning is never going to be "right"! That is why automotive manufacturers changed over to computer controlled fuel injection. Using oxygen sensors and mass air flow measurements, etc. the computer can have combustion "right".

My Mikuni BS38 carb will never be 100% right, but for a 1970's design, it works amazingly well. I'm happy that it always starts the bike, gives good acceleration, very good gas consumption and my spark plugs are tan colour. That's all a carb needs to do.

Click to expand...

you've had some excellent advice here Ryan ...probably the best to be found anywhere on the net but....

To someone not used to fettling carbs its just going to seem more and more confusing with all the different options and opinions.

What you really need is a bolt on solution but I'm afraid nothing like that exists especially for a bike that has been modified like yours.
Even if your bike was stock and you bought a brand new pair of original stock carbs they would still need installing setting up and adjusting.

I could be unkind and suggest still further options like a pair of simple Amal Mk2 flat side carbs which are about as simple as it gets or maybe converting to a single carb which although easier to tune and maintain involves a lot of work for the uninitiated.

I think most would agree that the best advice you have had is from Weekendrider to buy a set of reconditioned stock carbs that have been rejetted for pod filters and straight thru pipes and then find another xs650 member local to you to help you install and tune them . There is a member on the forum that reconditions carbs but I cannot recall who it is .

hey nice bike by the way

Ryan, I don't envy the situation you are in. if you had original carbs for your XS650 then all the help need to get you running would be available to you now. Having to buy, a new to you set of carbs, when carbs are completely foreign to you is a dilemma. This is why i gave you information to read up on and not a, do this, or do that, or listen to this or that person in particular.

VM series Round Slide carbs

There are other carbs that are commonly bought for the XS650, one of these is the VM 34's or VM 36's, these are considered a performance carb as in they will deliver more fuel but also are not as economical.

A downside, (but avoidable), to these carbs is the jetting, because they weren't designed for the XS650 there are sellers who will sell them and state they are jetted for the XS650 when they don't really know about the XS650.

These are not cheap as persay and if you want information regarding these carbs ask as there is a lot of information on them and there jetting requirements from members who are running the VM series carbs...........Grizd1 and 5twins also have written a carb guide about the VM carbs. This is also in the link weekendrider posted.

Micheal Mercury Morse, (MMM), has a web site dedicated to selling good products for the XS650. Can't buy through the internet but he will talk to you on the phone and his policy is talking to people, he is of the old school in this respect. MMM sells the full VM series carb kits. Carb page; http://www.650central.com/carb.htm Talking to him personally will mean he will be able to advise you, on you telling him what you are running............Again like all carbs there may be some adjustments or changes needed to fully gell with your bike.

Here is MMM's site's home page www.650central.com

Also check out the left side of the page down lower, lots of good tips and articles.
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Some more information on the Yamaha BS series carbs and one of the best descriptions, (thanks 2M), regarding the thought process on all mechanical carbs.

Um, I don't mean to be a fussbudget, Skull, but the VM section of the Carb Guide was my solo work. As far as fuel economy goes, it's not unreasonable to expect 48 to 50 mpg from a well tuned pair of VM34s on a stock XS650 motor in good condition. Ryan, I don't mean to patronize or insult you, but you might ask yourself if a more current and less "needy" motorcycle might serve you better.

Apologies Griz. My mistake for assuming 5 twins was involved as well. .............And yes i think you have a right to be a fussbudget, credit where credits due

Not a problem, my friend. Your manual is on the way; if you see anything that could use revision, let me know!

Yes, the VM guide was Griz's doing alone. I only helped with the stock CV carb guide because that's what I have, use, and know most about. The stock carbs have served me well over the years so I doubt I'll even change to something else. I've also acquired a few spare sets as back-ups should mine ever wear beyond repair. They've been cleaned, jetted, and tested on my bike so I'm good to go for many years to come.

"Helped?!" 5twins, you did all the heavy lifting in the OE Guide! I just "helped" by doing the easy stuff.

Confusion over authorship occurs because attribution got deleted when Pete offered to set the Guide up in PDF on his site and eliminated the forum posts format. It looked like a generous gesture at the time. Result: diversion of traffic from XS650 Garage USA and ultimate collapse of the site. We never saw it coming.