Alternative carbs

[mro]

How did you handle the throttle cable issue?

I've got dual cables on the hot rod. Think there off an early Kaw...
Last summer I tried to shorten the retun cable
Could not get solder or silver solder to stick to cable end
Even made a mold to form a new end over the cable, mold worked great but when I tested by pulling on it the end came off. Then made a end out of steel with a tappered hole for the cable and welded the cable to it. Worked great for a few hours of riding before it can loose.

Finally went to a local shop, Cycle Salvage. Guys let me sort thru there used cables. Found one that was plug and play for $8.00.

You should be able to find the control/cables same way.


mro

[81xsproject]

The easiest way to solve the push pull issue is to go to a modern push pull throttle assembly. They can be had VERY cheap on ebay and look nice too. I have one from a gixxer, but for you I would match it to the carbs you are running. The only problem after that may be cable length.

[Shuriken]

I have the cables that came with my ZRX carbs, but they are too short. I think I can use the single cable setup if I fabricate a clamp.

[mro]

single cable setup

Could be a reason the manufaturer has a return cable for the carbs


mro

[petejw]

I hadnt read the whole thread,
those carbs look awsome pggg,
nice work,
if you come across any that would fit
the xs could you let me know.

cheers

[Shuriken]

I discovered that the ZRX carbs have the fuel tube on the bottom as well. The XS11 carbs have 2 fuel inlets while the ZRX carbs have one. This is not a problem because it is easy to adapt the hoses using T or Y adapters.

I reinstalled the carbs onto the bike today. I started it using the choke and ran with the choke on for about a minute. Then I disabled the choke and warmed the bike up a bit.

I took it around the block for a ride. It feels like about 25f outside, so one trip was all I made tonight. I noticed that the bike is much smoother. It feels like the carb circuits transition much better. My carbs could be misadjusted compared to stock, so I can't say yet that these carbs are better than an unmolested set of Mikunis. Also, the bike did not pull as strongly. It was also dark outside, so I did not bother to check the plugs. I have not synched the carbs. Idle mix screws are at 1.5 turns each.

So far, all I've done is proved to myself that these carbs can be installed with no serious modifications. But that's about all I can do because of the weather.

I will not mess with float levels on these carbs because they are pristine and I do not question the factory setting. I will probably experiment with the jet needle position if I discover that the main jet is good enough. My bike is stock except for the 4-1 exhaust, and I am at 5700ft elevation. Really, checking plug color is vital, but it's too cold and dark to do much now.

I also have a set of FJR carbs on the way for experimentation as well, although I don't think they are much different than my XS carbs.

Ben

[Shuriken]

After warming up the engine fairly well, I was able to ride the bike today just before the sun went down. I don't have a track for testing, and it's hard to really open it up for testing the main jets, but I did the best I could by killing the engine at WOT in first gear. All of the plugs were soot black. Only at full throttle do the plugs start to clean up.

I believe I could go a step down on the mains and pilots, but I will first see what I can do by adjusting the jet needles.

Ben

[AlanB]

Hi ae,

If it begins to clean up at full throttle, the mains are probably not too rich, so you are probably on the right lines; set up the pilot adjusters, and have a go at dropping the needles a bit. Make one change at a time, keep notes, and beware going too lean; it does a lot more harm than being rich!

Sounds good!

AlanB

[Shuriken]

If I can dial it in with the needles, I will definitely ditch the XS carbs in favor of these.

There is nothing like having carbs that are only 4 years old. Also, they have a remote idle adjuster so you don't have to reach under the carbs. The plastic slides seem more responsive than the XS slides, and the rubber isn't worn out. I also like rubber float bowl gaskets instead of paper. Plus, you can still get parts for the carbs. Just a few of the things I like.

I don't like the black plastic caps, as I think chrome looks much better.

These set me back about $170 shipped, which is a heck of a deal when you consider the price of a new set.

I haven't figured out the vacuum advancer yet. I need to find an inline plug that I can put in the tube to keep the advancer from moving around too much. Does anyone know the orifice size of the XS carb vacuum advance tube on the #2 carb? 1/2mm?

Ben

[AlanB]

Hi ae,

I think it is 0.5mm. The vac advance does not make any difference to power output; when the throttle is wide, there is effectively no vac, so no advance.

It should help with refinement and economy when cruising on part throttle, But makes no difference at all when raggin' it.

XS is almost the only bike with a vac advance; everything else managed without! The only other bike I know of with a vac advance was the RD200.......

AlanB

[Shuriken]

I lowered the needles 1 position, but my hunch is that I will still be rich on the mains and pilots.... Idle mix screws are like 1/4 from seated. I made the changes with the carbs still on the bike.

I expect that I can try out the bike again on Mon or Tues.

Ben

[Shuriken]

I had some time today to do some more testing. I am surprised at the results.

As I mentioned, I lowered the jet needles 1 position. I did this based on sooty black spark plug color from the other day. Well, I took the bike out again today after lowering the needles and checked plug color. They were still black. At this point I figured a spark plug change was in order, so I installed fresh plugs.

The bike was already warmed up, so I ran it on idle for a minute and then checked plug color. The plugs were almost white. I then tested the bike around the block at WOT and checked plug color and they were about the same.

At this point I think I may raise the needles back to the middle/stock position. When I first checked plug color on this set of carbs, the plugs were already black. With new plugs, plug color is off-white.

I think with needles in the middle, I'll be just a tad rich. With the needles where they are now, I think it's just a tad lean. Better to be a bit rich than lean, but I rarely ride the bike at lower elevations than 5,000 feet. So really, I could put the needles back to stock and open up the air box a bit more and I'd probably be spot on.

These carbs have been a joy to work with. There is no such thing as "carb hell" with these carbs. They are new enough that they are not worn out, they don't leak, the screw heads are not buggered up, and you can still get parts for them. The only problem is that they were not easy to find. When I did find them, they didn't cost a lot more than a set of XS carbs. I got these for $170 shipped.

I can't say whether these carbs are better for the XS than a brand new NOS set of OEM Mikuni carbs, but for my own bike, there is no question at all that these are better carbs. At this point, I cannot think of a reason to go back to the original carbs.

Thanks to pggg for discovering this mod.

Ben

[petejw]

Hi Ben,
Nice work, well done.

Heres another quick way of checking the circuits
for correct mixture which i use a lot.

Take the bike out for a ride immediately
after taking the choke off, about a min or so after start up,
check and notice how the bike runsand performes at idle, between 3000 and 6000 rpm and then wot.
Then when the bike is fully warmed up, do the above tests again.

If the bike performs better when the bike isnt warmed up, the bike is running rich, and vica versa if its running better when it is warmed up, the bike should perform well when both cold and warmed up.
Also bear in mind that 1 curcuit can run rich while another can run lean.
Also always clean plugs thoroughly after each throttle chop or replace them, dont expect the engine to 'clean' the plugs as such.

imho id rather the bike run on the leaner side if its not pinging, a richer running engine causes carbon build up.

[Shuriken]

Thanks for the reply, Pete. I will give that a try on the next ride.

Ben

[Shuriken]

I set the jet needles back to the stock position on lunch break today and took the bike out for a spin.

I cannot rave enough about these carbs, so I apologize if it's too much already.... Setting the needles back to the middle position turned the plugs from off white to a nice grey/brown tan. I checked idle, mid, and WOT, and plug color is consistent.

I believe a few other things are in order at this point:
1. come up with permanent cable clamp mod
2. color tune the idle circuit
3. carb synch

I'll post back with results after I perform these steps.

When I am confident the carbs are completely dialed in, I will put the bike on the dyno, since I just found a local dyno shop.

Ben