Performance carbs

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Ryan daberko

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Hey im new here I just bought a 78 xs650 and it's been made to a bobber and it has performance carbs , I was told that at an idle it won't run good with those , and he was right so I tried turning them up and then down and then it got so bad it wouldn't start then I would imagine flooded , is all this true and if so how do you start over with getting the carbs adjusted. Thank you any advice would help
 
Ryan, WR has read your post to mean that by "performance carbs," you mean the XS Performance Chiwanese clone of the Keihin PWK sold originally by JRC Engineering for Brit twins, then me-too'd by Mike's XS and Heiden Tuning for the XS650. If that is in fact what you have, the best advice I can give you is to remove them, put them in your recycle bin, and buy some decent carburetors. The PWK is a dedicated 2-stroke carburetor, and the clones add to that inherent problem with cheap, substandard components and manufacturing defects. If you jump through enough hoops and spend enough money you can make those carbs work on your XS650, but they'll never be right.
 
Ryan daberko said:
Hey im new here I just bought a 78 xs650 and it's been made to a bobber and it has performance carbs , I was told that at an idle it won't run good with those , and he was right so I tried turning them up and then down and then it got so bad it wouldn't start then I would imagine flooded , is all this true and if so how do you start over with getting the carbs adjusted. Thank you any advice would help
Click to expand...

welcome to the forum Ryan.. My 78/79 special was imported from Ohio so I always feel a kinda affinity with the place
If you could post a picture of your carbs or at least tell us what make and model they are it would help us a lot to offer some useful advice.

there is a very long thread on here somewhere about fitting a pair of Keihin carbs from a Kawa GPZ500 or E500 I think is the equiv model in the US.
Ah here ya go http://www.xs650.com/threads/ninja-ex500-carbs-on-an-xs650.13070/
They are a much more modern carb with excellent spares and parts availability. it would be worth your while reading through a few pages .
I have standard BS38 Mikuni carbs on my 79 which is the what your bike would have had stock.

There should be no reason why you cannot achieve a stable idle with your carbs if they are set up and jetted correctly. Chances are you have straighthru exhausts and pod filters and they are not correctly jetted and set up.
 
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What to believe.......posted thread about he problems associated with some carbs............confirmation the carbs linked to are shit...........another post stating those carbs in the link should be ok if done properly..........

My question is.......... what are these so called "Performance Carbs" that are on the bike............lets identify these carbs, post some pics
 
That's my question too, Skull. All that I can conclude from the original post is that the carbs in question are not OE, and that if they bear "XS Performance" markings, they are not worth fooling with. I've given the reasons for that assertion many times. They still hold.
 
Not having a go griz. Followed that thread as it was being posted, and if mrriggs cant do it I'm bloody sure I'm not going to even entertain the thought to try.......

Sorry Ryan, welcome, post some pics of the bike, carbs and tell us a little about your sefe so we have an idea of your capabilities. helps when helping
 
Didn't think for a minute that you were, Skull! The whole experience with those PWK knockoffs still sticks in my craw. I called them for what they were from the start, and got jumped on by a high profile shill who called me an anti-Chinese racist and a bald-faced liar motivated by unreasoning hate for Mike Lalonde, and claimed that I knew nothing about the Pukes because I hadn't bought them (examining a pair removed from a Triumph at a local shop was more than enough for me). It's worth noting that said shill dismissed sticking slides as a "minor issue." The shit storm didn't abate until mrriggs bit the bullet and documented the grief, and I owe him for that.

The Pukes were originally sold as Keihins with Keihin markings by both Mike's XS and Heiden Tuning, and were not produced with XS Performance markings until I and others pointed out that they were pirated copies.
 
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Sorry I was late .. but yes they are the "xs performance" carbs .. I got it to idle fine but as soon as I crack the throttle they won't come down from there rpms ..and I am new to the whole motorcycle thing how ever I am not mechanically a dumbass lol .
 
Sounds like the slides are sticking, which isn't surprising with these carbs. They are very poorly made. The parts inside don't fit together properly. Slides stick, floats hang up, etc. You can't tune carbs like that by changing jets and turning adjustment screws. But have at it if you like. I just hope you have a full head of hair because you will be pulling lots of it out, lol.
 
Yea probably........did you read the link weekendrider posted.

EX500 carbs are a straight bolt on with some jet and needle change. These carbs are reported to run smoother and easier to tune, compared to the original bs34's/bs38's. Here is a link to a thread on the EX500 carbs. Most of the relevant information with the jet sizes and needles are in the first 10 pages, well worth the read.
http://www.xs650.com/threads/ninja-ex500-carbs-on-an-xs650.13070/

Looks like your engine may be an 82/83 going off the cam covers. Bike looks quite tidy.
 
OK, one more time. Poor production quality is only part of the problem with the PWK knockoffs. Those are actually knockoffs of the 28 mm. PWK with venturis bored out to 32 mm. The reason that's done is that the PWK was designed as a dedicated 2-stroke carburetor, and one needle jet (AKA "atomizer," AKA "emulsion tube") was offered for each size in the PWK range; the NJ's do not interchange. But 4-stroke motors require leaner NJ's than 2-strokes. It was evidently cheaper and easier to punch out the venturi on the 28 than to produce a suitable NJ for the PWK33.

And that NJ is still too rich for our application. The NJ is the main mixture control in the cruising range of the throttle where most street riding is done, and a fat NJ means high fuel consumption and excessive carbon buildup. Sure, you can try to get things under control with fatter needles and leaner main jets; but then you'll wind up with problems in other parts of the throttle range. Why did Keihin continue to produce the CR round slide carburetor after the PWK was developed? Because the CR is a 4-stroke carburetor and the PWK is not.

+1 re. Keihin vacuum carbs from the EX500 Kawi, if you want to take a chance on used carburetors that's a great design with a deep knowledge pool to dip into. If you want new carburetors, the biggest bang for the buck is the venerable Mikuni VM34. Just be careful where you buy; cleaning up after a lowball vendor will cost you time and money. I can recommend 650 Central and Hoos Racing. Buy elsewhere at your own risk.
 
650Skull said:
.......did you read the link weekendrider posted.

EX500 carbs are a straight bolt on with some jet and needle change. .
Click to expand...

thats rich :doh:

DID YOU read my earlier post #4 ? where I requested more information about the carbs and I also suggested using Kehin GPZ500 carbs and I provided a link to the NINJA thread.

I sometimes wonder if you and Griz actually read the thread properly before steaming in with criticism of every new members posts and turning every thread into a battleground.
 
Ryan it will/would depend on your abilities?
I would say yes it will be easier with a different carb set. You can purchase by price point or need. If you are handy and have an understanding of carbs you may want to try an alternative. If you are not familiar with tuning you may want to stick with something more reliable with a HUGE knowledge base like the OEM's. You could purchase from eBay or Craigslist and work through any bumps your purchase may have or you could pay more for a set that has been given the OK by someone who is familiar. For the latter I would suggest contacting gggGary. You could try other members. In the shop section is a thread for rebuilds by a reputable member where you get not only reliable but a butt load of pretty for your money.
One thing is for certain no amount of messing is going to get you satisfaction from those carbs.
 
Money is not an issue I just want to get it running good so I can do some other things this winter to it .. and both of those threads had me confused on all the different needles people were talking about .. my càpabilities go as far as the fuel to air screw and the idle screw anything above that I would have to have someone else do , which isn't a huge problem .. but if I were to buy a mikuno or however you spell , could someone tell me the jet sizes needed for my specs or no ? Or any higher end carb for that matter , it seems like the 500 carbs will work but also require alot of tuning , again money not being a deal at all what's the best carb out there to plug and play with ?
 
if your not a carb guy then any carbs are going to be confusing............With your set up, (straight pipes), using non original mufflers and/or non original air-boxes, any carbs you buy will need to be adjusted to the set up on the bike........This will involve changing jets and needles.

Here is a simplified explanation on the carbs. not trying to confuse you it is just what is

There is a lot to learn about these bikes and the interchangeability of components between models. Just as an example.......the carbs changed every 2 years..........
From 70-79 the carbs are BS38's........

Every 2 years the jets and needles changed.........Carb bodies are essentially the same but the bowls changed .

In 1980-84 they changed the carbs to BS34's, the needles were fixed in position for epa restrictions....Because they are fixed tuning is very limited

There is nothing wrong with any of the factory carbs.

Weekend rider mentioned oldskool carbs. This guy rebuild and jets his carbs based on the set up the owners tell him. His reputation is second to none.
http://www.xs650.com/threads/carburetor-rebuilding-oldskoolcarbs.5882/page-10 A link to his thread on here in the shops section.
 

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