Ninja EX500 carbs on an XS650?

[jd750ace]

They made them from 1987-2009, and sold the snot out of them, so there's tons of spares, not to mention most junior level racing organizations had a class for them forever, and lots of people put flat slides on them for racing.

 

[mrriggs]

The photo explanation is wonderful. Thank you!

Now then, if I was to start from scratch, would this be an accurate shopping list:
-Set of Keihin CVK34 carbs from a Kawasaki EX500
-Carb holders for Mikuni BS34 carbs
-Keihin PWK needles (specifically which?)
-Either BS34 needle "doughnuts" or modified CVK "nail head"
-CVK pilot jets (what size range for tuning)?
-CVK main jets (what size range for tuning)?

You will also need air filters. They are the same as the BS34. The carbs are ten or twelve millimeters shorter than the BS34's (don't remember the exact number off hand) so you will need some spacers if using the stock air boxes.

The throttle cable is also different. Others have mentioned modifying the stock cable to work but I'm not sure what that involves. I used a push-pull throttle from a CRF250 which also needs to be modified. It works as is but has excessive freeplay. Most bikes made in the last twenty years have push-pull throttles so there is likely a bolt on solution out there. I do recommend taking advantage of the push-pull capability of these carbs. I've had throttle cables stick preventing the throttle from closing. It's not a fun situation and can be avoided if you have a return cable.

As for jets, it sounds like most guys are using 38 pilot jets and 140-148 mains.

 

[mrriggs]

Believe it or not, I think the little extra preload from the plastic donuts actually made a difference. My mid range throttle response didn't seem as crisp after switching to the nail heads. Raising the needles one step (position #4) brought it back to where it was before swapping spacers.

I ran through my first full tank of gas on these carbs. So far the mileage is the same as the PWK's I took off, 50 mpg. A single tank isn't a very accurate indicator, especially with how much I've been goosing the throttle. A few more tanks should give a better average.

 

[jd750ace]

I'm keeping my popcorn out on this.

 

[56nomad]

Great R&D on this swap, mrriggs. Those PWKs must have really pee'd you off!

 

[Firerunner]

So... WHICH PWK Needle are you using? This chart seems to decode the PWK needles a bit. Any suggestions, since I am going to be ordering them new, instead of pulling them from a set of carbs? EDIT: Never mind. You already answered that. JJH. Thanks! I'm going to leave this up, because the chart seems helpful. -FR

EDIT: made pic link cold. I don't want to confuse anyone and detract from a great thread.
h t tp://i45.photobucket.com/albums/f75/MattR250/Husky/Cafe%20Husky/BasicKehinNeedle.jpg

 

[mrriggs]

That chart is for the bigger PWKs, you want the PWK28 needles. Clicky

 

[wheelhouse8]

Just wanted to say I have had a set of these carbs for a while now and spent a bunch of $$ on jets etc trying to get them going...I had a friend turn me toward this thread. Ordered me up the pieces and installed this am. I could not be happier. You might say I feel like a fat girl in a doughnut shop The bike runs awesome with great pull and no flat spots. I went with mrriggs recs 38 pilot 145 main and the pwk-JJH needles (4th position and nail head off original needles). Don't know if it is exactly dialed in but very happy with the way it runs... THANK YOU for the foot work ippytattoo, mrriggs, and others!

Stats FYI: I live in Nampa ID at 2500 ft; Rephased crank/cam; Pamco ign; PMA swap; 2nd over pistons; open exhaust, headers only...for now

 

[mrriggs]

I've tweaked with mine a bit more and it just keeps getting better.

Currently; 38 pilots, JJJ needles, clip #4, 138 mains.

Running stronger than ever and gas mileage is up to 52 mpg.

 

[ippytattoo]

Just a couple quick questions to put more baseline info together for anyone else doing this conversion. Could the ones that have done the swap post up their jets and clip positions, air filters and exhaust, and altitude.

I will start it out:
40 pilot, mixture screw at 2 turns out, JJH needle clip in middle slot, 140 main, K&N pods, open exhaust, sea level (+30ft). As a side note I haven't actually got to run them with the JJH needles yet and I was probably running a little fat everywhere else when I was trying to compensate for the stock needles. I just got my replacement motor (I hate f-ing thieves) put together and fired up yesterday so I will have more tweaks and numbers to post later. Keep the info coming I think this is going to be something very worthwhile in the long run.

 

[VosaME]

This has been a really helpful guide and I am going to be running a set on my current build. The engine they are going on will be a fresh rebuild (bottom and top end) and so for break in I want to run them just a little rich to aid in cooling. From the testing you guys have done it seems like I should be able to accomplish this via the mixture only, or do you think it would help to have a set of "break in" jets?

The engine is stock with the exception of a very mild head port job and custom airbox with uni filters and a 2-into-1 exhaust. I live at basically sea level, +100ft I think, any suggestions for initial tune?

 

[jd750ace]

Mriggs is right up the road from you in Vancouver WA, so he's at a comparable MSL, although that is not a major consideration with a CV carb. They are self-compensating, as they operate off absolute pressure. I would imagine his numbers should be a solid base line.

 

[VosaME]

Mriggs is right up the road from you in Vancouver WA, so he's at a comparable MSL, although that is not a major consideration with a CV carb. They are self-compensating, as they operate off absolute pressure. I would imagine his numbers should be a solid base line.

Yea, that is what I was planning on using unless someone had a better suggestion.

Mriggs, is there any place local that you know of that sells jets and the other stuff or are you still using Sudco?

 

[mrriggs]

Mriggs, is there any place local that you know of that sells jets and the other stuff or are you still using Sudco?

Hell, I could barely find an 18" rear tire locally. Pro Caliber has bought out all of the dealers and the small shops are just vanishing. I prefer to support local business but it's getting really hard to do these days.

 

[scabber]

I just bought some off ebay 2009 carbs. They look factory new no dirt or dust or buggered screws. From the performance mrriggs say he is getting sold me. I had to try them on my bike. Hoping to get similar results. I'm running a modified commando 1 1/2" head pipes 36 1/2" long. So with the jetting and needle given by mrriggs and others I should be able to make them work. Thank you all who have contributed to this thread. I will report back with my progress.

 

[scabber]

Progress report. I ordered some jets and needles for the carbs went with the JJJ needles. main jets 138, 140 and 142. 38 pilot. After looking inside 130 main 35 pilots n36 jet needle. No changes for 2009 carbs. I really like these carbs compared to the BS 34 for ease to work on especially the clip that holds the needle drop it in. So far the cost of carbs needles and jets $135 US dollars. Well I'm out to the garage for test fit and throttle cable fitment. Parts should be here in a couple of days.

 

[scabber]

Update the Sudco order came. Installed the 38 pilot and the 138 main. JJJ needles not installed yet. After looking at the throttle cable I ordered one custom made from Motion Pro. Cable shop busy 2 week delay. ipptattoo I want personally want to thank you for starting pioneering the carbs and the information and pictures on your build thread. Nice build by the way.

 

[ippytattoo]

Update the Sudco order came. Installed the 38 pilot and the 138 main. JJJ needles not installed yet. After looking at the throttle cable I ordered one custom made from Motion Pro. Cable shop busy 2 week delay. ipptattoo I want personally want to thank you for starting pioneering the carbs and the information and pictures on your build thread. Nice build by the way.

Thanks for the kind words. I can't take all the credit I actaully was picking up where someone else had left off, but I am glad it has helped others in our little slice of heaven.

 

[Maurice]

I got intrigued and tried this. Got an old-ish set of carbs off e-bay for $35 and set out to rebuild them. They were seized, throttle shaft and slides. It took some patience, pine sol and carb cleaner but finally it's all squeaky clean. Should have taken pics this was epic. Luckily all ended up intact: diaphragms, slides, throttle shaft etc. Cleaned up surprisingly nice and only stripped 2 screw heads (GD JIS screws).

Then I got the recommended 38/138 jets and JJJ needles. Very easy to adapt the needles thanks to mrriggs.

I thought the cleaning was decent enough until I hooked up the carbs and gas poured out the vent tube. Bad float valves. I have spare Hawk GT carbs and they use Keihin carbs with the same valves, problem solved.

The throttle cable setup is a bit ghetto but it works decent enough to test. All I did was clamp a bit of rubber in a shaft collar into the bracket.

Fire up and after adjusting a bit so that it would run on both cylinders, it's quite the shocker how well this works. I still have some off-idle issues and hanging throttle, I suspect pilot jet/screw and needles will need tweaking. It does idle like a swiss watch, and takes off like a raped ape. Also intake noise is different, coming from BS38 and pods (I actually use the same UNI pods, they fit well), hard to describe but it's less of a 'bwoop' and more of a solid 'braap' noise. Better to my ears in other words.

No doubt this is a worthwhile mod., very impressive. The motor gets this modern bike feel when running, just when I thought my BS38s were dialed right. Also as was pointed out they probably weigh half what the BS38 do. I'll weigh them when I get a chance.

Thanks guys, appreciated.

 

[mrriggs]

I still have some off-idle issues and hanging throttle, I suspect pilot jet/screw and needles will need tweaking.

Before you mess with those, make sure the floats are set correctly. It is super simple to check on these carbs. You don't even have to take them off the bike.

Level the bike then find a clear hose that fits the drain on the bottom of the bowl. Stick it on there and open the drain screw. You may need to move it around and tap it to get the bubbles out. Hold the hose up to the side of the carb and wait for the fuel to level off. Now move the hose down a couple millimeters and let it re-level. This will assure a correct reading. Never move the hose up when checking the level since it will dump fuel back into the bowl.

The spec for these carbs is 0.5mm ABOVE the gasket surface, ±1.0mm. The fuel level in the tube will be cup shaped. Measure from the bottom of the cup, not where it is sticking to the side of the tube.

If it is off then stick the tube into a catch can and drain the bowl. You can pull the bowl and adjust the float with the carbs on the bike.

Good luck.