FJ1100 Carbs

[xs11bobber]

So I was doing some "shopping" on the net and was thinking, "hmm, maybe I'll just buy a new set of carbs and use the ones I have for parts or back-up," you know whatever. My first stop was eBay. Then I started thinking BRAND NEW. So then I thought Mikuni. Well, I strolled across a dealer website and found these...



For those wondering the specs are:
MM: 36, (PITCH) SPACING: 77-93-77, SPIGOT OD: 42, MAIN JET: N100/604 120, JET NEEDLE: 9DZH1-3, NEEDLE JET: 568 P-4, PILOT JET: VM28/486 17.5, PILOT SCREW (TURNS): 1/4-1/2

It says they fit FJ1100 and 1200 ALL. Anyone know if these will fit our rides? How about flood our rides? It says they're a high performance racing carb and I'm all about going fast. Fast does have a price of $839. (That's more than my bike!) However, I don't know much when it comes to jet sizes and what works and what doesn't.

[John]

My wife has an FJ11, and a while ago she had the carbs out. I happen to have a spare set of XS carbs, so I compared them. I butted the carbs up to each other, at the engine side, and it was a perfect match. The spacing was exactly the same. There are a few minor differences however. The FJ carbs do not have a vacuum port on the #2 carb body for the vacuum advance, so you would have to use a vacuum port off one of the intake boots, and add a restriction, so the advance mechanism isn't bouncing about wildly, and the FJ carbs use two throttle cables, but a clever man can find a way around this problem. Another issue is the size of the fuel line. The FJ uses 5/16" and the XS uses 1/4'' line.

[Lamric]

There's a guy called Baloo who races an XS1100 fitted with FJ1100 carbs, here's one pic; more pics here

[thewiz]

I'm still learning about ...

smooth bore carbs and the XS11 ... all amounts to breakin' new ground on this great forum. Rarely are they substituted by members here for the factory units, it appears. That looks like a set of flat slides that you're showing there. I have a set of round slides VM33's on my G ... and they are all about the top end ....which I have no idea what that really is cuz I don't ride it that fast ... BUT ... here's a cool link.

http://www.wgcarbs.com/

Even this guy states somewhere that the BS34's are better street performers than the smooth bores. He sells both. There is also a forum connected to this site.

I'm still toying with mine. Put some PODS on there yesterday, didn't even change a jet (currently 127.5s) and it seemed to really unleash even more power and better throttle response in the upper range .... but still not so good right off idle.

Also, even with the two cable, push-pull throttle system I'm using, I'm having trouble shutting down the rpms between shifts in the upper range. This may be due to an advance problem though. I'm workin' on that today.

I also have tried a smaller pilot (because I thought it acted like an over rich condition) with no success, currently I have 17.5s in there, but I now think a larger pilot may be better. I noticed that WG supplies the VM series with a 30 pilot. In my case, I'm now thinking that maybe it's transitioning too quickly to the mains. The flat slides you're lookin' at also have 17.5 pilots.

Another member has reported acceptable results with the Keihin smoothe bores.

Far as the spacing is concerned ... pretty sure they'll fit right on there but you might not like the results ... so prepare for some tinkering if ya' decide to go for it.

[GARTHXS]

I have fj carbs

on my 78 they are awesome fit better than stock , they are jetted like 80 series carbs I think 120 mains with 42.5 pilots, only fabbing I did was mount a handlebar choke lever and I just used the one side of the throttle cable on my stock right hand control.

[thewiz]

Garth, my son ...

The ones he's lookin' at appear in the photo to be smooth bore carbs with flat slides and not FJ CV carbs like the ones you put on your bike. I do agree though that the ones you put on your E worked great.

I would highly recommend he look for some good CVs instead of the smooth bores, (unless he's determined to go racing) I think he would be much happier with them.

[xs11bobber]

I red somwhere in the description that they were in fact smooth bores

[xs11bobber]

the FJ carbs lameric posted are CV's. Correct?

[GARTHXS]

!!!!!!!

I tell you what , every one should have set of these fj carbs they are great!

[Wildkat]

I tell you what , every one should have set of these fj carbs they are great!

I have a set!

Of course... they're still on the FJ... but dang it, I have 'em

[thewiz]

That's right, Bobber ..

the pic that Lamric posted ARE CV carbs ... you can see the diaphram on the top. The ones you posted are flat slide smooth bores, designed primarily for racing ... a WHOLE different animal than CV carbs.

Again, the FJ carbs that Garth used on his E are CV's and work wonderfully and I can attest to that.

[xs11bobber]

So what would be the set backs to the flat side smooth bores(FSSB)?

Am I going to run rich a lower speeds (regardless of how much tuning I do)or anything?

[thewiz]

Ok, Bobber ... this is a bit windy BUT ..

Here's my experience ... again remember that I have a set of Mikuni round slide smooth bores called VM33 ... now out of production .... but pretty sure you'll find most of the same issues with a flat slide set.

Very hard to R&R with the air box and the two cables. Even though the throttle shaft has a VERY strong return spring on it; you still NEED to use a two cable throttle because there is no 'butterfly' throttle valve ... only the slide is there to shut down the fuel. The push-pull cable system is basically a safety feature. These two cables are a real PITA to work on, I kid you not, which is most of the reason why I've let it go so long without fixing it. I have other bikes to ride and fix too ... but anyway ...you will need to find at least the bottom half of the right hand control that has provisions for two cables that will also match up to the top side with your kill switch and starter button on it, and a throttle grip for a two cable system and of course, the cables themselves. I think my right hand control is from a Slowzuki but not sure. Sudco shows a kit that includes the cables, hdwe and grip .. PN 005-230.

Once you've got that stuff, I recommend PODS instead of an air box and you should have a header. Fuel inlets on the carbs are 5/16 instead of the 1/4 that the 11 uses but most single wall fuel line (Mikes XS) will make the stretch

The problems were ... my G has had various driveability issues that I have just learned to manage and live with over the last couple of years ... most annoying: a slow return to idle speed, rich idle and bad off idle performance. When I got the bike from the original owner, it had two primary problems, PU coil wires and carbs. I fixed the wires and cleaned the carbs but didn't know enough to tune them at the time ..... Sooooo....with two OTHER project 11s already in process occupying my time, I paid a shop .. actually two shops!! Screwed again, right?. I had a job then and money to spare .... big mistake ... without getting into all the stuff they jacked up ... at least it was driveable.

Fast forward to last week ... I resolved to solve the problems and tame this beast down once and for all; OR dump these carbs and go back to BS34s, so, first I began with running it a while without the bottom of the air box as a lead up to maybe getting some PODS .... ran better .. so I bought a set of PODS. Better yet but still problems. Spent a day fiddling with adjustments and timing components .... no better.

Finally determined that I had to pull the carbs and check float levels (which was s'posed to have been done by the shop) and synch. Best way I know to synch these kind of smooth bores is on the bench, since the lock nut and slide adjuster is in the venturi and causes a huge vacuum leak when you access it with the engine running.

The short of it, my float levels were all over the place .. every bit of 5mm of variance from the highest to the lowest... WTF? ... any amatuer should have noticed that much difference without even measuring .... I even remember one particular shop owner telling me that float levels couldn't cause my driveablity issues ... what an idiot !! ... anyway ...yesterday .... set the floats correctly, re synched and set the air screws .... back together ...geez, what a PITA ... but what a huge difference !! ... runs and behaves like a different bike ... NO more driveability problems ....LOVE it now ... makes my perfectly tuned stock F feel like a slug in comparison ... maybe it's just the sound of the intake noise made by PODS, I don't know .... lol.... but ..

Bottom line: If you're willing to tackle the job of putting the smooth bores on there, you may find that results will be worth it, JMHO.

[thewiz]

one more thing, Bobber ..

the good news about my smooth bore carbs is that you can change out a main jet with out pulling the carbs off .... handy ... but I don't think I'll need to. 128 is what it says on my main jet and it pulls till I don't want to hang on any longer ... up past 90 mph indicated ... roll on response from 60mph without downshifting is excellent too ... go figure.

[GARTHXS]

bit the bullet

so you finally got the pods Steve , i guess with no vacuum slides you wouldn't need all the back pressure of the air box , sounds like you got it running right congrats