Tips on ZRX-1200 carb swap?

[CodyLane]

My carbs have been through a lot. Terrible things like getting a pilot jet stuck, using a screw extractor and having it break, drillpress and retap for new pilot jet sortof terrible things.

I found that all but one of my mixture screws has been broken off and reshaped. They're a mess. When I went to tune them, cylinders 1 + 3 run rich even with the mixture screws all the way in. I had to actually remove the pilot air jets just to get them on the not so rich side.

After looking at the cost of getting carb rebuild kits and possibly having to buy a carb or two, I started looking at options.

The ZRX-1200 carb swap sounds like a superior option to trying to get a bank of Mikunis back in good shape. Also probably in a similar or cheaper price range. I've looked at a lot of info about it and it all seems pretty straight forward but I've still got a couple questions about it.

As far as I understand, they pretty much will slip right on. You have to modify the choke? I've seen some guys use just generic choke cables. Any tips on that? Also, I read a writeup one of the guys did (I apologize for not giving credit where it is due) about drilling a port for the vacuum advance which seems pretty straightforward. Is there any mods you need to make to the fuel lines? How do they hook up to the carbs? What else... oh the throttle cable. I will need to get a new one? Any pointers on that?

I apologize for the barrage of questions. I'm just REALLY interested in doing this. Currently my XS11 is getting a crappy 25 mpg. I'm sure I can fix that with a little more tuning but with jacked up carbs, it's tricky as hell to tune... even with a colortune.

Thanks in advance.

[petejw]

hi CodyLane,

the zrx carbs will slip straight on,
the only problem is ull have to rejet,
the vac advance port was done by Tadracer and works very well,
the way the stock carb vac port does,
the throttle cable i managed to cut sum of the outer sheath off
to make the stock cable fit.
for the choke i just cut a universal choke cable down to size.
for the fuel line the stock carbs have 2 inlets these carbs have 1,
no big deal to alter to suit.
others will chime in soon.

[TADracer]

Pictures are worth thousands of words.

You will have to either change out the throttle cable or modify the OEM cable (which I did). It is a simple removal of about half an inch of the outter sleeve at the carb end and you will need to fab up some sort of receiver to sit in the cable recepticle between the #2 & 3 carbs to hold the cable end. Alot more easy than what it sounds. The carbs will slide right in but they do stretch the two outter boots a bit. I have had absolutely no problems with that.

Here is a shot of my choke setup. Very simple to do.



Here is the way I handled the fuel feed. Single 40 micron flter with a tee to go up to the two fuel petcocks. The line at the bottom is the original fuel line that was on the carbs.



This is what my finished product looks like. Plenty of room behind the carbs making them easy to take in and out.



Try this link for a detail of the vacuum advance modification. http://www.xs11.com/forum/showthread...vacuum+advance

Good luck!

[bcknblkbird]

what about the zrx 1100 carbs? would the jetting be closer?

[CodyLane]

Thanks so much for the tips. Last question I think... Did you have to fab the bracket that holds the choke setup on the left side of the carbs?

[petejw]

Thanks so much for the tips. Last question I think... Did you have to fab the bracket that holds the choke setup on the left side of the carbs?

no if u buy a universal choke kit itll come
with the brackets.

bcknblkbird "what about the zrx 1100 carbs? would the jetting be closer?"
the jets are set up way to lean on the stock carbs,
i think from memory the mains were 95 and pilots were 35.

[TADracer]

what about the zrx 1100 carbs? would the jetting be closer?

The ZRX 1100 carbs had smaller main jets than the 1200s. The 1200 carbs are jetted closer to what our 1100 needs but you will still have to play with jetting anyway to get them dead on. Aside from that the carbs are the same. You have to remember that the ZRX motor is 20 years newer technology and runs alot more efficient than our beloved 1100s.

[CodyLane]

I can't wait until I can scrounge up the money for this swap. I'm more excited than when I installed Dynatek coils.

[Nick7777]

?

what year ZRX-1200 carb was used in the swap? please and thank you.

[Bonz]

I know I'm late to the party on this thread... For the XS11 Special shown in this thread by TADracer, how does the bike run with the pods and ZRX carbs?

My 2001 ZRX 1200 has the full meal deal with jetted carbs, pod filters, full exhaust system, timing advance rotor. The whole system of components and brainwork came from Dale Walker at Holeshot Performance, he knows his schnizzel.

With the ZRX 1200, you won't find a better running or balanced power curve. Easier to ride around town than a moped, incredible roll-on, and a pretty good top end to boot.

Heck, the ZRX is pulling 75 ft/lbs from 3500 rpm with a peak of 85 ft/lbs at 7000 rpm, then back to 75 ft/lbs at just over 9000 rpm, so the carbs definitely flow on that bike with more to go. The ZRX carbs are good for about 150 hp, then you need to start looking at bigger carbs.

Question, thought...

I'm wondering if the issues running pods on the stock Mikuni XS carbs is because of the carbs themselves, or the engine? Meaning, after a certain amount of jetting up to go with the increased airflow of the pods, the carbs don't do it well simply because of their inherent design.

Anyway, could the XS run better with pods on the ZRX carbs because the carbs are a better match to the job at hand compared to the stock Mikuni's? The stock carbs don't seem to run too well with pods on the whole as I seem to read.

Correct me, guide me, enlighten me?

I have a set of ZZR 1200 cams to go into the ZRX, and am probably going to put a set of ZZR1200 carbs on the ZRX, so will have a set of ZRX carbs that could find a home on an XS... Thus my inquiry.

[CaptonZap]

I will profess as much ignorance as you when it comes to carb theory, but this I know.
The stock air box has, as a built in part of the flow path, four velocity stacks, which extend the flow path in back of the carbs about 4 inches. Velocity stacks do a good job of straightening the airflow to the carb, and when "tuned" to a desired RPM range, do increase the HP output of the engine while in that range. The longer the stack, the lower the range. Sort of like organ pipes.
A pod does not extend the air stream, and therefore would only be of any use at the upper limit of the RPM range, and you know what percentage of your operating hours you spend at those RPMs.
Hang them on the end of some stacks, and they might be of more use.
But that is just my take on the subject. And I'll let someone with more curiosity try long stacks with pods.
CZ

[petejw]

I will profess as much ignorance as you when it comes to carb theory, but this I know.
The stock air box has, as a built in part of the flow path, four velocity stacks, which extend the flow path in back of the carbs about 4 inches. Velocity stacks do a good job of straightening the airflow to the carb, and when "tuned" to a desired RPM range, do increase the HP output of the engine while in that range. The longer the stack, the lower the range. Sort of like organ pipes.
A pod does not extend the air stream, and therefore would only be of any use at the upper limit of the RPM range, and you know what percentage of your operating hours you spend at those RPMs.
Hang them on the end of some stacks, and they might be of more use.
But that is just my take on the subject. And I'll let someone with more curiosity try long stacks with pods.
CZ

i did just that, i used the rubber v stax but had uni foam filters, the v stax fitted inside the pods and for me i liked the way they worked especially the low and mid range.

[TADracer]

I know I'm late to the party on this thread... For the XS11 Special shown in this thread by TADracer, how does the bike run with the pods and ZRX carbs?

I had the pods on long before the ZRX, Keihin carb mod and had tuned the flat spot out with jetting the Mikunis, cam timing and spark plug heat range (with the Mikunis the bike always seemed to like a plug range hotter). When I installed the ZRX carbs I left the cam timing as it was but went back to the stock plug heat range as the Keihins have a better fuel delivery or something because the bike likes the stock BP-6ES plugs better than the hotter BP-5ES plug.

All I can say is after the mod the idle is smooth, the power band is strong all the way up past redline, at idle you can just easily let the clutch out to get on the move without a stumble and once the motor gets up on the cams, it is a rocket.

I naver had a problem with the length of the runners with the pods because I always used a band of 24-gauge stainless steel that is 1 1/2" long mounted to the carb air bell. In the picture below you can see them on my old Mikunis. I did not install these bands with the intent of replacing the velocity stacks but instead for a better fastening mount for air filters. Mounting the pods onto these bands makes for a much stronger surface to which to fasten the filter (don't you hate when pods fall off into the street?).

[conquest87tsi]

Thats a very nice set up TADracer. Was the function of the aluminum plate behind the filter just for mounting? Or for a kind of ram air?

[Bonz]

TADracer, that's a sweet pod set up! How are the stainless bands sealed to the carb bells?

Between what you did with the stainless bands, and what CaptonZap shared, I think this is what many have missed when doing pods. Petejw seems to be onto it as well.

TADracer, when you say... "after the mod the idle is smooth, the power band is strong all the way up past redline, at idle you can just easily let the clutch out to get on the move without a stumble and once the motor gets up on the cams, it is a rocket." ... Is that to mean after the ZRX (Keihin) carbs were on the bike with the mentioned mods, or with the mentioned mods and Mikuni's?

I'd almost like to try some stainless bands and pods on the Mikuni's I just rebuilt on my project 80G. I'm comfortable with pods, been tuning them and running them on the ZRX for years, so this could be fun!

TADracer, what jetting do you use with the pods?