Tips on ZRX-1200 carb swap?

[TopCatGr58]

Hey Bonser,

I've run the Pods since 2000 when I did my topend rebuild and Tranny Fix.
The lower portion of this tech tip shows the modest velocity stacks I mounted my pods onto. I feel that my carbs and bike have behaved quite well with these and haven't had the headaches in tuning like others have reported with Pods, and I have 4-1 pipes as well!

http://www.xs11.com/forum/showthread.php?t=8269

I cut the PVC sections in half, but there was/is plenty of room to make them longer, but then the PVC would be showing, would need to either be painted or otherwise covered for a nicer look. I thought I had posted and addendum to that tip about finding some thicker black pipe/rubber tape in the plumbing dept that would work better than the Duct Tape.

T.C.

[TADracer]

Conquest, the function of the aluminum plate was merely to close the front of the battery compartment off when the side covers are installed.

Howard, I see no need to seal the bands at the carb bell since the most common types of stainless are relatively soft metals. The band clamps cause a very tight connection there.

And yes, my comment about "after the mod the idle is smooth, .......once the motor gets up on the cams, it is a rocket." is after the ZRX mods.

Right now jetting is 138 mains and 45 pilots but remember, that is what my machine likes and yours might be different.

[Bonz]

Thanks, great info!

[Bonz]

TADracer,

So you are basically saying the ZRX Keihin carbs made the XS into a much better performer than the stock Mikuni's with the same mods, correct?

[TADracer]

TADracer,

So you are basically saying the ZRX Keihin carbs made the XS into a much better performer than the stock Mikuni's with the same mods, correct?

Yes. Now do not get me wrong, by making this switch you will not cut a second off of the elapsed time in the quarter nor will you get your bike to have a higher top speed but you will notice a much more crisp throttle response, a smoother off-idle transition (in that at low speeds they do not 'hunt and peck' looking for a good mixture), a more accurate transition from midrange to full mains at a hard throttle, a tune-up that is easier to obtain and maintain and an overall easier to ride machine. At least, that is the result I have obtained over the best tune-up I could get out of my 30+ year old Mikunis. The Keihins are newer technology and the resulting accuracy of the fuel mixture just seems hands down better.

Like I said every machine is different but I simply have not seen a down side to this mod and I have had them on over two years now.

[Bonz]

TADracer,

What is your gas mileage with the Keihin's vs. the Mikuni's, as you seem to have as much run time with this mod as anyone.

[TADracer]

TADracer,

What is your gas mileage with the Keihin's vs. the Mikuni's, as you seem to have as much run time with this mod as anyone.

In mixed riding I have been averaging 38-41 mpg depending on how hard I twist the throttle. But I will say that there is a ride around here that I like alot that just begs for some heavy throttle twisting. On that one I only get around 30-32 mpg.

[Bonz]

Thanks TADracer...

[Bonz]

You guys had any experience with keeping the stock airbox with the ZRX carbs?

I have a set of ZX11 carbs coming for my ZRX, and that frees up the ZRX carbs that could be used on one of my XS's. (80G, 80SG)

I'm intrigued by the idea of ZRX carbs on an XS, if for nothing more than to try it because I can. And because I have a ZRX that will benefit from the ZX11 carbs in a similar way to how the XS benefits from the ZRX carbs.

Win-Win...

Anyhow, anyone tried the stock airbox with ZRX carbs?

[hobbsy84]

I can probably chime in on that one. I've done the ZRX carb change-over to my XS, and I've retained the original airbox. Mainly because I prefer the look of the airbox over pods, but I guess thats just a personal preference thing. As for whether there was performance benefits vs pods, I'm not really sure. I do know the bike rode a hell of a lot smoother after the install.



Still haven't hooked up a choke cable yet, but I tend to just push the linkage until its started.




Installing the carbs into the airbox was a bit fiddly, since the ZRX carb spacings are just that little bit different to the XS OEM carbs. Also had to leave the top airbox mounting bolt out so it would slide in further, since the ZRX carbs are a bit 'thinner' than the OEMs (the airbox slides closer to the motor, but only slightly). Once they're in though, its fine. And the vacuum advance mod wasn't too tricky, just had to be careful. Managed to get it right the first time, thankfully.

So yep, airbox retention is definitely possible.

[Bonz]

Awesome info, hobsy84. Thanks a lot! I'll update this thread when I've pulled the trigger and done it. I'm putting together the parts and bits to get the ZX11 carbs onto the ZRX as we speak so I hope it's in the next month or so.

What size main jets are you running in the ZRX carbs and the XS airbox?

[hobbsy84]

If I remember rightly (and its been quite a while), I think it was running 135 Mikuni mains (they screw into the Keihin emulsion tubes with a 'slight' bit of effort and oil, and they're a lot cheaper), but I cant remember for the life of me what the pilots were. Admittedly, its running a tad lean I believe, which is something I've been meaning to fix, but am yet to get around to. The stock air filter was replaced with a UNI foam filter, which probably increased the airflow a bit, but not dramatically.

Done plenty of km's on those settings though, so its hardly hurting it. I think I have a set of 137.5 and 140 mains to try out when I get some quality shed time. There's a good chance I'll be doing some work on the bike in the next couple of weeks, so if that happens, I'll get the jet numbers.

[Bonz]

Thanks, let me know what you find when you get in there.

[Bonz]

hobbsy, what is the throttle cable arrangement you are using?

[hobbsy84]

I just used the stock cable, with a bit of fiddling, it'll work. By the time I'd tried the ZRX carbs, I'd also tried a different set from a different bike (which failed miserably), and I'd had to lengthen the cable for them. So while I had to shorten my cable, you shouldn't. The setup I used was always going to be temporary, but its working fine, so I guess if its not broken, don't fix it.

Also, I found the thread that I'd written a while back for this mod, I thought I remembered doing that.

http://www.xs11.com/forum/showthread.php?t=36885

That should have most of the answers to what you need, it turns out I've been meaning to up my pilot jets for longer than I thought. The general consensus is pilots that are about 45, and ballpark figured for mains from 135s to 140s. I guess this will change from bike to bike. Mind the pun, but your mileage may vary... Let us all know how it goes though.