Ninja EX500 carbs on an XS650?

[Furious D]

My Ex-500 carbs arrived this morning . Still waiting a the throttle cable so I am going to go thru them and give them a quick cleaning before bolting them up.

Whats the float height supposed to be ? They are off an 94 EX-500. Main jets are 132, I am running pods and Sportser mufflers. I think I used 138's on the 34's I had on before it and seemed like it was a little rich. I have not checked the pilot jets yet.

 

[troopthrowback]

You say you got frustrated enough to chuck the carbs after just 6 hours of working with them. Maybe you have the wrong hobby. 6 hours ain't nothing.
It often takes a long time to get carbs right. When I first started with carbs it took removing and cleaning several times, an hour or so each time, just to get them clean, then even more times to adjust jetting and other adjustments.
I'm better at it now, but it still takes time.
Be a bit more patient.
Now that you have them right, was it worth the time?
Leo

I haven't ridden with them yet so the jury's not yet out.

As far as patience, it was 6 hours on float height adjustments alone. That's a lot of time on a single problem. I'm not saying my oversight was silly, it was.

This isn't my first rodeo. I've been rebuilding and maintaining my own Vintage Triumphs for the past 8 years, my father was a factory trained Triumph mechanic with his own shop in Torrance. My base of experience is Amal carbs, so branching out presents new challenges.

I also maintain a small fleet of old honda singles for my youngsters (1974 z50, 1980 xr80, 1981 xl80)

That said, I'm used to spending about equal time riding and on maintenance and repairs. I'm averse to turn key and go!

I appreciate the help and now realize how important adding a single photograph can be.

 

[arcticXS]

So here's what I'm thinking now. Many ex500 owners say that leaks can be a result of the o-rings between the carbs being faulty. that makes sense, but doesn't sound like the cause of my problem since I do get a good, leak-free seal with the blow test. If it were an actual leak I would get air leaks as well. Considering I don't get leaks, jsut floats that don't seat under the pressure of fuel in the lines, this makes sense, see reply #3:

http://www.ex-500.com/index.php/topic,42658.0.html

I'm running a 3/8" diameter fuel line to the "T" connector that feeds the carbs because that's what I had around that fits that monster inlet barb. It turns out the cvk for the ex500 calls for 5/16" fuel line as standard. The increased volume of fuel stacked on top of those very sensitive float needles is enough to unseat them and cause them to leak.

Since I have no other idea what it could be, I'm going with this. Off to pick up some 5/16" fuel line!

The fuel pressure, as seen by the float valves is not inflenced at all by the hose diameter when the engine is not running. Due to flow losses, a bigger hose will give slightly higher pressure when fuel is flowing, i.e when float valves are open. But, again, when float valves are closed, the pressure is the same with any size hose or tube. The only factor influencing the pressure is the specific gravity of the fuel, and the vertical distance from float valve to the fuel level in the tank. So a full tank gives more pressure than a neraly empty tank, not due to volume, but due to the liquid column. (As described by Blaise Pascal and Bernoulli.....)

 

[timbeck]

Ahh, the old Bernoulli's Theorem deal. lol tim

 

[troopthrowback]

The fuel pressure, as seen by the float valves is not inflenced at all by the hose diameter when the engine is not running. Due to flow losses, a bigger hose will give slightly higher pressure when fuel is flowing, i.e when float valves are open. But, again, when float valves are closed, the pressure is the same with any size hose or tube. The only factor influencing the pressure is the specific gravity of the fuel, and the vertical distance from float valve to the fuel level in the tank. So a full tank gives more pressure than a neraly empty tank, not due to volume, but due to the liquid column. (As described by Blaise Pascal and Bernoulli.....)

Exactly. So when I first hooked the fuel line to the carbs the float valves are open, allowing fuel into the float bowl. As the fuel level rises to engage the floats, the floats rise to close the valves. Since the valves were never closing then my supposition that the column of fuel above the float valves could have been preventing it could be a possibility, right? Not due to diameter then, but perhaps too much length since the specific gravity of fuel at the valve is not affected by volume but only height.

Either way, those valves couldn't operate in a vacuum! I just didn't realize I was creating one by capping that junction.

Anybody run a filter or anything on that junction? It just seems like a gaping hole asking for gunk and dust to clog up the works. I know the ex500 guys run an internal fuel filter in the fuel inlet "T". Like this:


http://www.ex-500.com/index.php?topic=24823

 

[XSLeo]

Furious D, I went back through this thread and in post 122 they say the float height is 17 mm.
Leo

 

[Furious D]

Furious D, I went back through this thread and in post 122 they say the float height is 17 mm.
Leo

Thanks , I must of missed that. A quick search on the net came back with 3 answers of 17mm and one of 19mm so I will go with 17.

Still waiting on the throttle cable and I need to decide what to do about the choke and I am back in business.

 

[XSLeo]

So far I have been using the enrichener as others have, just push from the right side. It works.
I have thought of a couple ways to hook up a cable. I have a stock 82 left side switches that have the lever and adapting the cable to the carbs, I have an 80 Honda CM400 that uses a pull cable mounted off one of the handle bar risers.
Either of these ways or modding a cable from the parts store. These cables are a bit long but will work.
Leo

 

[Furious D]

Exactly. So when I first hooked the fuel line to the carbs the float valves are open, allowing fuel into the float bowl. As the fuel level rises to engage the floats, the floats rise to close the valves. Since the valves were never closing then my supposition that the column of fuel above the float valves could have been preventing it could be a possibility, right? Not due to diameter then, but perhaps too much length since the specific gravity of fuel at the valve is not affected by volume but only height.

Either way, those valves couldn't operate in a vacuum! I just didn't realize I was creating one by capping that junction.

Anybody run a filter or anything on that junction? It just seems like a gaping hole asking for gunk and dust to clog up the works. I know the ex500 guys run an internal fuel filter in the fuel inlet "T". Like this:


http://www.ex-500.com/index.php?topic=24823

I had not thought about it until your post but since we both tend to ride our XS's off-road its a good point. I think I will run the vent tube up under the tank and use something like this, Its a filter for a fish tank bubbler. I have a few lying around but I would imagine they are cheap to buy:

http://www.bing.com/images/search?q...0FC5689026EA3AFAC207D92ED89C&selectedIndex=15

 

[Furious D]

So far I have been using the enrichener as others have, just push from the right side. It works.
I have thought of a couple ways to hook up a cable. I have a stock 82 left side switches that have the lever and adapting the cable to the carbs, I have an 80 Honda CM400 that uses a pull cable mounted off one of the handle bar risers.
Either of these ways or modding a cable from the parts store. These cables are a bit long but will work.
Leo

For now that's what I will do.It seems to want to slide back to the off position even with the spring removed .A small fiber washer might take care of that.

I have an old choke cable off a an early 60's Chevy pickup that I might modify to work.

 

[scabber]

I bought a throttle cable from Summit RNB-03787. It came with some mounting brackets. cheaply made but it works.

 

[bikefreak69]

You aren't going to make 50 horsepower from a carb switch except in some fantasy land, and the stock carbs are not that hard to dial in.Replace the stock rubber manifolds with billet ones, and start from there.

 

[XSLeo]

I agree, you won't see much change in max power, but the way it is delivered is greatly improved.
These EX500 carbs are a better design. They are lighter, easier to tune and run much better. The transition from one range to the next is seamless. The stock carbs even at there best were not as smooth. The lighter slide improves throttle response. All this makes the bike more drivable.
If you don't believe these improvement are possible, try a set.
Leo

 

[jd750ace]

You aren't going to make 50 horsepower from a carb switch except in some fantasy land, and the stock carbs are not that hard to dial in.Replace the stock rubber manifolds with billet ones, and start from there.

This thread has been going for a long time now, and has always been about ease of tuning and the minimization of some of the little periphrial horseshit that is part of the stock carb mantra. I don't recall too many people thinking there was a tower of power in them, just modern smoothness and reliability.
The stock carbs on an XS are an unparalleled pain in the ass in the Japanese bike world. Never seen such temperamental bitches. This site has more threads on something as simple as CV carbs kicking people's asses than anything I've ever seen.
If I want power, I'll ride my SV 650, not my nearly stock XS.

 

[troopthrowback]

Ride report:

138 main jets
38. Pilot jets
GJH needles on bottom slot with shim
Mixture screw at 1.5 turns from stop
MAC 2 into 1 with MAC muffler
5" Uni foam filters

I replaced Mikuni bs38 with 130 mains and pods with CVK off a 1999 ex500.

Motor is stock bore, stock charging system.

Starts first kick, immediately with choke on and cold motor

Choke off after 20-30 seconds

Pulls nicely with broad torque across low and midrange. Zero hesitation, hiccup, or burble.

Sensation of increased torque at low and mid range.

No change at wide open throttle (but I honestly don't spend much time there with any carb set)

Seamless power and very crisp throttle response. I experienced a loss of power I attribute to float height set too low. After WOT takeoff the motor would die. Pull to shoulder, watch through inline fuel filter as fuel refilled bowls for 15 seconds. Start back up first kick an go.

I'll reset float heights and try again next weekend. I also experienced a difficulty getting idle to stay consistent. I need to dial in my mixture control a little more but believe I'm in the ballpark.

These carbs work. Even a total idiot can do this swap (as long as he posts photos when he's got problems!)

I got readings of 500 horsepower from my seat of the pants dyno.

 

[Furious D]

The stock carbs on an XS are an unparalleled pain in the ass in the Japanese bike world. Never seen such temperamental bitches. QUOTE]

Couldn't agree with you more. If I wanted horsepower I would go out and buy a V-Max. I am looking for as much reliability as you can get out of a 30+ year old bike.

I have owned 4 XS's over the years and every one of them has had either carb or charging issues or usually both. Once you get these challenges resolved its really a pretty good motorcycle.

 

[Maurice]

jd ace nails it eloquently, thanks man.

It's never been about power, these bikes feel like they're going to fall apart beyond 5k rpm anyway. Yet we love to ride them. Windy back roads is where it's at.

These carbs also bring an important aspect IMO which is availabiliy of parts. I do no like the idea of gorilla-gluing a diaphragm to an old slide, not to mention the butterfly shaft bushings/seals issues...

 

[ippytattoo]

Troop, what I have done recently with the vent was to make sure it was pointed down and ran a long tube down the backbone exiting by the starter location. It will keep dust and crap from getting into the vent but will keep it open to the atmosphere allowing proper operation of the float valves.

 

[WTX_XS650]

For reference sake - here is a photo of my swap (close up) and the bike in general.

The motor is a stock XS650 with TCI ignition and Mike's Commando style exhaust. The carbs are off of a low mileage 2005 salvage. They were very clean inside when I received them. I put in 38 pilots, 140 mains, and JJJ needles (middle slot). I am running UNI foam filters. I adapted the XS650 cable and brackets to work with the EX500 carbs. After some slight tuning and syncing the carbs, the bike start up on the first kick and runs great from idle on up. In the future, I may try a set of 138 mains as it may still be running a little rich.

Thanks again to everyone for their pioneering work on this mod. It is a great upgrade!

 

[troopthrowback]

Troop, what I have done recently with the vent was to make sure it was pointed down and ran a long tube down the backbone exiting by the starter location. It will keep dust and crap from getting into the vent but will keep it open to the atmosphere allowing proper operation of the float valves.

Hey thanks for the tip! That makes sense since it just needs access to air to prevent vacuum in the bowls. Seems like the volume capable by that huge I radicle is a little excessive for the purpose, like they just had that size fuel barb around.

I'm having fun now that I don't have mysterious, mind stumping issues. It's always the simplest things, right? Keeps us feeling humanly fallible. That and falling down!

I'll post up my final setup specs this weekend when I've got a chance to ride it again and tune. I'm feeling confident that my 38/138 jet setup is right for my Sierra Nevada foothills altitude (1200-3000 feet ASL). Hoping to get some good miles in and extend that altitude range a bit. Well see how it performs then!