Ninja EX500 carbs on an XS650?

[56nomad]

i'm running the 40/140/#4 clip jjj (too rich, getting breakup on the crossover between the pilot and needle transition) but i can tune that out.

Sorry but I probably caused some confusion with that baseline set up. Being too clever, I was thinking about saving you some work by just leaving your main jets at #140 you had fitted. Unfortunately I then instantly forgot that and married the bigger jet up with the JJJ needle in groove #5 that I had with my #138 mains. So yes, I reckon you could experience richness further up the scale with a 140 and JJJ#5 main circuit set up.

This is what I had after I had after I had got rid of the hanging idle:

Float level: 0.5mm - 1.0mm above the gasket line
Pilot: 40
Mixture screws: 2 1/4 turns out initially
Main jet: 138
Needle: JJJ on #5
Sync'd

With the hanging eliminated I was most content over quite a few more happy miles ridden both open road and urban. But once I'd got used to it I then began to detect a small bog at town speeds at the off idle/idle/off idle transition (y'know, throttle on/throttle off/throttle on). Nothing to pee me off big style but there all the same. So I'm currently messing about with needles to improve performance off, above and way beyond idle so I may be able to help you further .......... when you can get out after the snow over there has melted!

 

[jkocr2]

yeah i think i'm good with the 140, i only get that slight breakup on clip 4, i originally had it on 3 and didn't get any breakup through the midrange/upper.

hopefully the new mix screw/washer/o ring will fix my hang, ordered them up today so hopefully i can get some more tuning done this weekend...my neighbors have to hate me by now!

 

[56nomad]

hopefully the new mix screw/washer/o ring will fix my hang

And if it doesn't (but I sincerely hope it does) and there's absolutely nothing wrong with the fuel side maybe it's the ignition. Are you still running contact breakers and an ATU? I'm thinking sticking bob-weights in the ATU here. But if the idle didn't hang when you had the OEM Mikunis fitted that's probably not your problem ...... but worth a check.

 

[jkocr2]

no, when i did my rebuild i swapped out the atu for an e-advance.

 

[Gmorrone1214]

Hey guys, just put the ex500 on the bike. Have a slight problem. The carbs are only starting with the choke at 38 piolts 2 1/2 turns out mixture. I let it start with the coke and when the bike is about to die I turn it off and it just shuts off. It also won't run unless I pull the choke out.

Do I have to go to 40 pilots or is it a dif problem?

Open exhaust and uni pods.

 

[XSLeo]

gmorrone1214, Did you clean the carbs? It sounds like the pilot circuit is dirty.
Removing the carbs, pulling the mix screws, drop the bowls, and spraying carb cleaner in the hole and see if it comes out in all the places it should.
It should come out the pilot jet and the tiny holes by the throttle plates.
56nomad, On the stock carbs I got the same response as you describe, it was caused by the pods I was using. I had K&N tapered oval pleated element pods. These caused to much airflow turbulence through the carb, upsetting the vacuum signal to the diaphragm. This caused the off idle surge/stumble, hesitation. Call it what you will.
I tried the UNI-Filter foam filters. The off idle issues disappeared.
I'm using the same Uni-Filters on the EX500 carbs and run very well.
Leo

 

[Gmorrone1214]

Xsleo, the carbs are cleaned out and spraying through the piolts comes out of all holes. I think it's my inability to bench sync them.

How come when I screw the idle screw in it closes the throttle plates?

When I back the idle screw all the way out and turn the adjustment screw all the way out the right side butterfly valve is open a lot more then the left. This is with the idle and adjustment screw back all the way off. Now if I move the adjustment screw the right side will not close just opens even move.

What should I be doing ? I can easily do it on the bs38

 

[XSLeo]

The idle screw controls how much the throttle plates are open at idle. Backing the idle screw out closes the right side throttle plate.
Now the sync screw adjusts the left throttle plate to match the right.
I bench sync by using a strip of paper cut about 1/4 inch wide and a few inches long. Open the throttle, slip one end in between the throttle plate and the body of the carb, close the throttle. Adjust the idle screw so the throttle plate is just touching the paper, adjust to get an easy slip fit. Now pull out the paper, open throttle, slip the paper in the left side, use the sync screw to adjust for a slip fit of the paper. Adjust the sync screw so both sides have the same slip fit.
Once adjusted install the carbs, start the bike and let it warm up a bit. Shut it down, hook up a manometer, start engine. Adjust the sync screw so both sides of the manometer are even.
Leo

 

[jd750ace]

I do this similarly with #40 drill rod. It gets it close enough to get past starting issues related to synch. Carbs that are massively out of synch can cause you all kinds of problems trying to get a baseline, rideable setup to get you into the realm of hot engine tuning, where the final tuning is done. If your synch is thoroughly jacked up, just getting it started can be a chore.

 

[pekka]

Does anybody use a fuel pump with the CVK's? I'm thinking about an aux or "under the seat" fuel tank...

How much pressure can the float valves take? 4psi? A Mikuni vacuum pump would probably be OK but how about a low pressure electronic pump? Maybe a Facet Pump Part No. 40104 / ss500 or similar?

Thanks,

Pekka

 

[ippytattoo]

I know that the zx-7r uses 4 cvk carbs and a small fuel pump so it should work. You may take a look at zxforums.com. I read on there at one time that the fuel pump is usually about 2 psi (just enough to mimic gravity feed since about 70% of the tank is below the carbs) but there was one guy who said his was at 6 psi. This idea could open up the possibilities to a fuel cell way down low and the appearance of a tankless bike.

 

[jd750ace]

The pump pressure, float inlet, and float level all have to be balanced out so the pump maintains the proper fuel level in the carb. On my Road Star, I removed the pump and you have to go from a 1.2 float valve to a 2.7 to flow enough by gravity to keep from starving it at WOT. Most go to a 3.0 from the 660 Grizzly ATV. This setup works with the pump float level, but going the other way, you would have to find the "dry" float level that results in the correct level wet, with the pump forcing fuel into the carb.

 

[pekka]

Thanks for the info. I've also read somewhere about having to use smaller float needle to handle the pump pressure. Or would an overflow line back to the tank from the pump drop the pressure enough? Will need to do some experimenting.

pekka

 

[XSLeo]

I think if I was going to use a fuel pump I would at least set it up with a return line. this way very little pressure would be applied to the float valves. Maybe even build a small inline tank of some sort just above the carbs. This will allow a bit of reserve for extended WOT.
I would still use the return line.
Leo

 

[ippytattoo]

A quick check on partzilla.com shows that the 93 zx-7r (which is what my son has) uses the same float valves in their carbs as the ex500 and uses a diaphragm type pump which only flows when the pressure drops, in other words when then float valve opens, with no return line. Since the fuel pump is a diaphragm type pump the return line is not needed. If you used this pump I think it would just be a matter of verification of the fuel level with the float valve under pressure to make sure it is in the recommended range for these carbs.

My curiosity is now peaked since if I am not mistaken the wiring harness I am using, from an ex500, uses the same fuse box as the zx-7r. Hell I may already have all of the wiring already in place for a fuel pump to test the idea.

 

[yamahammer]

I scored a cheap, very dirty set from eBay and I'm finishing them up now. This is what they looked like when I got em, I'll post some afters on the bike and a butt dyno report. BTW pine sol in an ultrasonic cleaner is the shit, never seen anything clean like that, even diluted.

Thanks to all the pioneers!

 

[gggGary]

Pinesol works well. A few heads up; it works better diluted than full strength. DO NOT leave parts sit in Pinesol! About 15-20 minutes, no more. Soak, rinse off, dry. Carbs or aluminum left in pine sol turn an ugly mottled black that takes forever to buff out.

 

[JAGspeed]

Decided to go with this Ninja 500 carb swap. I had a set of Mikes XS PWK carbs on my bike but was never really happy with how they performed. I set the new carbs up with 138 Mains 40 pilots and jjj needles clip in 3rd position mixture screw 2 turns out. Started up and idled better than ever. Did a short test ride in the rain and it seemed to run good. I will get it back out when the weather clears and let you guy know how it performs.

 

[yamahammer]

It barks with the cvks, even sounds different out the muffler. Be careful if you install the cm400 throttle cable in the xs housing, the aluminum gets very thin. Worth the time/money, pulls better than ever.

 

[wannabridin]

Decided to go with this Ninja 500 carb swap. I had a set of Mikes XS PWK carbs on my bike but was never really happy with how they performed. I set the new carbs up with 138 Mains 40 pilots and jjj needles clip in 3rd position mixture screw 2 turns out. Started up and idled better than ever. Did a short test ride in the rain and it seemed to run good. I will get it back out when the weather clears and let you guy know how it performs.

What work did you do on the PWK to get them to run? I'm toying with the idea of getting some ninja carbs as backups to the PWK's that I bought used, just don't know what exactly to do...