Ninja EX500 carbs on an XS650?

mrriggs, wow that is nice to know. I set the floats on the bench and it's not easy since you have to tilt them just so so the valve springs don't compress. I also could only find the specs for bench float height (17mm IIRC).

I've replaced all the screws with hex heads, should make it even easier.

Thanks for these detailed instructions!
 
Stock exhaust.

Last things I did: checked fuel level in bowls using the tube method and it was spot on. Took the pilot jets out there was dirt in there. Sync'ed them. Now they're running fantastic but I need to ride more. Seems to pull stronger than my re-jetted BS38s (1 up pilot/main, thought it was pulling better than stock already...) throughout the whole throttle range.

I'm making a bracket to hold a generic choke pull knob. This thing seems like a keeper to me.
 
The slightly smaller carb throats generally fill the cylinder more efficiently at our mid-range RPM, or on any engine with a relatively mild cam and low compression. The venturi effect in these carbs and their length may be highly complimentary to the natural resonance of the intake system. Sync helps more than people think too. Glad it's working well for you.
 
Hey all, quick question. I am assembling my set here and am going with 138 main, 38 pilot, JJH needle. I was going to do 140/38/JJJ but for some reason sudco was out of the 140s and JJJ needles... I suspect this little thread might have something to do with that.

My question is with the 138/38/JJH combo, what clip position would you recommend? I am using the head off the originals and last I saw it was #4 position was best? Also, that is #4 from the bottom... right?
 
That guide assumes you don't have a wide variety of available jet needles. The PWK needles are available in just about any diameter, length and taper you could possibly need.

Set the main jet for best WOT performance, set the pilot for the best idle, then ALL the other tuning can be done with the needles. Off idle and low speed is tuned by changing needle diameters. Half throttle is tuned with the length (clip position). Three-quarter throttle is tuned with the taper.

Of course with CV carbs it's hard to pinpoint what is half and three-quarter since you will experience them all while holding the throttle wide open. I wish I could tell you some magic secret to make the whole process simple but I'm still fumbling through it myself.

I already had a pile of JJ(x) needles from my PWK debacle so I was able to try several different diameters to find the best off idle performance. The clip position was selected to give the best pull immediately after cracking the throttle. When I would whack open the throttle at a low RPM it would pull well, then pull slightly less well, then pull well again. I figured the clip position was good and I've already dialed in the main jet so that just left the taper to experiment with. On a hunch, I tried a leaner taper. I'm happy with the straight diameter (last letter 'J') and the length (middle letter 'J') so I just needed to change the first letter. 'H' is one step leaner than 'J' but there are no 'HJJ' needles. There is, however, an 'HKJ' needle. 'K' is half a step leaner than 'J' which means that adding a single shim to a 'K' length needle makes it the same length as a 'J' length needle.

I put it in with the clip in the #4 slot but I didn't add a shim (I know, I know, you should only change one thing at a time). The leaner taper did what I was hoping it would do, give it a consistent pull throughout the range. The length may still need a little fine tuning.

So I'm still running 38 pilots, 138 mains, clip #4, but needles are now HKJ. Not sure I mentioned it before but I have big UNI filters (3" dia x 5" length), stock pipes with dipstick baffles and turn-downs in place of the mufflers, and a 256 cam. Otherwise, the motor is bone stock.

I'm still messing with the tuning because I can be a bit nit-picky, not because there are any serious issues. Each and ever setup with the PWK needles has worked well. The changes I've made have been very small. Just kind of massaging them to get the best sound, feel, and mileage.
 
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Thanks mrriggs and Maurice for the additional information on the exhaust. Since the cable motionpro sent me was shorter than what I wanted I had to remove my beloved buckhorn bars. I now have the eurobars. 5twins says they are the best choice. The carb install went well other than a minor setback. The right carb slide was not lifting so off with the tank for a look. The diaphragm Fits in an o-ring type grove. A small amount of grease to hold it in place problem solved. The bike started right up and idled perfectly and revs good. I need to finish a few things and out for a road test. :D Hope to have it ready later today. Another pleasant surprise is the Quick turn throttle. The carbs and the Yamaha throttle fully open 1/4 turn. The stock Yamaha air box will work with some minor modifications. The carbs are shorter but the stock air box moved forward will fit behind the side covers no problem. Or some short tubes should fit the bill. Stay tuned for more up dates. :thumbsup:
 
The first ride was way to short around the block. Did a couple throttle chops low speed the bike accelerated well . Just enough to tell the carbs work. I need to ride it hard to redline to tell how well at all RPMS. If it will pull 7000 RPM top gear or better. The bs34 could do that and have been trouble free still working great. Some people here are not as lucky. Backyard beauties Leakey barn finds with crapped up carbs. I looked at the thread with great interest. Comparing the two. So far the EX500 carbs are winning. They look better my opinion. Sound good the exhaust sounds better. I may need to make some changes but off to a good start. Like mrriggs said all three needles worked for him. Some are using the nail heads with success. The carbs appear to be very versatile lots of needles work. So add that to the + column. Will report back once I ride it more for an up date. :thumbsup:
 
I've put more miles now and this is what I noticed:

- off idle is excellent, very quick, return to idle is same. I can take off from a red light or a stop with just a crack of the throttle and take it from there.
- I don't always ride at highway speeds, but when I do, I notice that 3/4 to WOT pull could be better. I will probably try raising the needle, one whole slot could be too much and I'm not sure I have shims around. That is not a priority, all of my riding is back roads.
- They do look nice, what with the cables/hoses tucked between them, leaving the sides "bare". Now I have the choke button sticking out on the side but I could have easily routed that elsewhere.

I think I will sell my BS38s. They are in good shape and someone could benefit...
 
Thanks for the update on the carbs Maurice let me know how the clip change works. My initial thought about the stock box working by moving foreword wont work. The side cover fit the top but would not fit at the bottom. It will work with spacers. I might go with the unifilters. It is experimental to find the best combination at this point. Will get to ride today and find out top end power. I haven't changed the pilot screw adjustment from the stock ninga settings. I did notice some hanging throttle after the bike warmed up.
 
Hanging throttle might just be where you want to set idle at when warm, but likely needs some mix screws adjusting.

I didn't even bother with the stock airbox, I had UNI pods already and they fit fine. I know these carbs prefer an actual airbox but work amazingly well with pods so... They might tell you when it's time to oil them I guess.

I get roughly similar mileage (to stock carbs) but I need to go through a tank to find out for sure, last tank I was making adjustments/sync'ing/dealing with some crap in the pilot circuit etc.
 
After a longer ride the carbs working out really good. Nice low-end throttle response gas and go. needs some fine tuning but pretty close now.
 
Maurice said:
Hanging throttle might just be where you want to set idle at when warm, but likely needs some mix screws adjusting.

I didn't even bother with the stock airbox, I had UNI pods already and they fit fine. I know these carbs prefer an actual airbox but work amazingly well with pods so... They might tell you when it's time to oil them I guess.

I get roughly similar mileage (to stock carbs) but I need to go through a tank to find out for sure, last tank I was making adjustments/sync'ing/dealing with some crap in the pilot circuit etc.
Click to expand...

THOSE carbs run exceptionally well without an airbox. 20 years of club racing pretty much seals it. Less than half put flat slides on EX500's for racing. They just did not need that level of response. If you have ridden one you know why. Impressive little motor.
The oddity of the stock carbs on these bikes (34 and 38 alike) not enjoying pleated filters is something I've never encountered on any other bike. Twins as a breed seem to fare better with individual filters than fours in my experience, but no matter at all about that if these are getting the job done for you. :thumbsup:
 
They don't look too much out of place once on the bike:

DSC01566.jpg


This is the bracket for the choke, it needs a bit of trimming:

DSC01570.jpg


Another angle:

DSC01568.jpg


Overall:

DSC01569.jpg
 
Nice bike Maurice. I gave up on the air box. Ordered some 4229 Uni. Where did you get the seat I want one looks great. The carbs look like they came on bike.
 
Thanks, it's a motolanna SR500 seat. You have to grind the tabs off or otherwise just make sure the seat rails are bare tubes and the seat just plonks down and sort of interference-fits. Front has two tabs that go underneath the tank tongue. I just put some velcro for added grip but it's as simple as it gets.

Let me add that vibration-wise this is quite good too. I don't know if it's the sync'ing or I'm just getting used to it but now I can redline it and not feel tickling in my feet. I just noticed it today, or rather noticed what I was not feeling anymore.
 

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