Mikes keihin carb kit

Starting and idling.

I crossed the two vacuum barbs with a hose and a "T" connected to my vacuum pet cock. What this does is equalize the mixtures in the two cylinders at idle and when starting, meaning that the engine starts up right away by just using one of the two choke controls because enough of the richer mixture is sucked over to the non choked side to allow it to start and run.

The crossed vacuum lines also tends to make the engine idle smoother because it effectively doubles the vacuum pulses to each carb.
 
What if I'm not going to run a petcock that has vacuum? Unless do they make petcocks that have a vacuum side for sporty tanks?
 
So I just got mine and installed them, but when I went to kick it over it fired up but it's revving super high?! Any ideas? I know I need to sync them but how do I begin to approach it when they're doing that?
 
Carb cables got to have some slack by the handlebar grip.High reving at start could be the cables are adjusted too tight or the idle screws on the carbs are set too far in allowing the carb slides to be open too much.Check those two things.
 
Micah,

Yes, Tz is correct. Make sure that there is slack in the cable at the handle bar throttle. Then, back out the big screws on the sides of the carbs to the point where there is no contact with the slides, then turn them back in until they just start to raise the slides.

1. Eye ball the slides and adjust the screws to make them even.
2. Pull the vacuum barb off of one of the carb holder and adjust the opposite carb slide screw for 1,000 RPM.
3. Do the same with the other carb.
4. With the engine off, adjust the cable "elbow" on top of the carbs so that each slide is at the top at the same time.
 
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Hi Pete,I am getting the Keihin carbs kit delivered next week.Have you noticed if the front of the carb spigot sits flush against the rubber intakes or there is an empty space(2-3mm) in front of it?.In short is the Keihn carb spigot shorter then the stock carb?.Thanks
 
Ok...I noticed that some aftermarket carbs have a short spigot then the stock carb and also the carb groove is a bit off allowing some "dead space" usualy 2-3 mm in front of the spigot with the intake booth bolted on.Basicaly when the carb in mounted on the intake it does not seat flush like the stock does.I noticed that problem when I mounted a set of 28mm Tm flatslide on my rd400 racer and also on a friend on mine Xs650 when he got a set of 34mm Tm flats.
 
I finally had some time and got my PWKs installed today. Talk about a complete kit! They come with everything you need including gaskets and extra jets. After a little tinkering with the throttle cable, I'm very happy with them so far.

I wanted to do a back-to-back comparison with the VMs, but they were gunked up and I was impatient so I just installed the PWKs. A comparison will come a later date.

So I got them installed pretty quick since taking the VMs off is easy. It started right up and I had the same problem as Micah where it was reving high. The throttle cable was holding the slides up. I just had to reroute the throttle cable and turn in the adjusters on the tops of the carbs and everything was ok (more on this later). So I played with the idle-adjuster screws (I like to call them slide-stop screws) and air screws a little bit, and was off for a test ride! The motor that is currently in that bike has charging problems so my test ride was fairly short, but all went well. It has been well over a year since I've had that bike on the road. The bike ran great especially considering my half-assed air-screw adjustments.

I'll have to play with the air screws a little more and do some plug chops, but for most the most part, the jetting is damn close on these! I put in new plugs before I started and they looked good at the end of my run..

So to sum it up, the kit is great! You just have to be careful about your cable routing and make sure that the slides are able to fully seat. Just take your time with making sure the cables are right and you shouldn't have any problems. :thumbsup: :bike:
 
More on what I did to set them up and the cable adjustments:

So the first thing you'll want to do (as I quickly found out) is get the cables set up right with enough free play to get you started. I had to turn the angled pieces pretty much all the way into the tops of the carbs (make sure they still point forward) and then turn the cable adjusters themselves all the way in. Ideally, when you're done, you want like 1mm of free play in the cables just as they come out of the carbs, and a few mm of free play at the throttle. The slide should bottom out on the idle-adjuster screws and not bottom out with the cable holding them up (which would be zero free play).

So with enough free play in the cables, start it and set the idle-adjuster screws. I’m not sure if they all come set the same, but I had to turn both screws in a few turns to get it going. I then ran it on one cylinder at a time and got it to the same rpm on each side. Once you have it running on both cylinders again, you'll probably have to turn both idle-adjuster screws out an equal amount to get the rpm down where you want it.

Now turn the bike off and adjust the cable adjusters so the slides open at same time. Adjust only the one side that has more slack and make sure they just start to open at the exact same time (or like Pete mentioned, make sure they reach the top at the same time at WOT). Then check the free play of the cables at the carbs (gently pull the cable housing in and out of the adjuster, it should move just a little bit without lifting the slide). Both carburetors should not have an even amount of free play. If there is more than about 1mm of free play, turn out the cable adjusters on the tops of each carb and equal amount until your free play is where you want it.

Now start it up and check to make sure that when you give it a little gas, the slides don’t hang up at all and always come back down and bottom out.

Then put the filters on and either play with the air adjuster screws or if it seems to be running pretty well, go for a test ride. I set both my air screws to 1 turn out and it seemed good enough for a test run.

Well that’s pretty much what I did anyway! :bike:
 
Travis,

I had almost the same experience, except that I pulled the vacuum barb caps off one at a time to do the dead cylinder sync and set the idle for 1,000 RPM on each cylinder that was running, thus I did not have to readjust for the desired idle as it came up to 1200 with both cylinders running when I replaced the vacuum barb cap after the final adjustment. I think that pulling the vacuum cap does not kill that cylinder completely which means that it will idle at 1,000 that way and not require a final adjustment with both caps in place.

Using the vacuum barbs to sync the carbs in the dead cylinder method also means that you are not in danger of frying a coil by removing one spark plug wire at a time.

I also finished by crossing the vacuum barbs together to obtain an even smother idle and to facilitate starting using only one choke.

Now that we have at least one other person on line with these carbs, I can say things and not have people think I am exaggerating!

1. One choke starts are instant if you cross the vacuum barbs to suck some of the richer mixture over to the carb that is not choked.
2. The most noticeable "performance" characteristic is the instant and very strong throttle response. It's like a new bike. You can hear those two carbs sucking in the air!
3. The front of the bike lifts up noticeable when you crank open the throttle. Tons of torque.
4. If you have true dual exhausts (no crossover) you can hear that the exhausts sounds the same from each cylinder.
5. Syncing with the vacuum barb dead cylinder method is easy with expected results.
6. The kit comes with every piece and part that you need for a satisfactory installation.
7. Installation is easy. Just check the free play in the throttle cables, back out the idle screws and push the button. Make sure that the slides start to travel at the same time and reach maximum travel at the same time.
8. Set the idle mixture screws to 1 1/2 turns out and leave them there. Don't screw with them. Just do the dead cylinder sync to get them both running the same.
 
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I have to say that I agree with your list. Performance wise, they feel a lot like the VMs and sound like them too (as they should). A back-to-back comparison would tell me which ones are stronger, assuming both are tuned well.

I also just pulled a vacuum plug and set the idle on each side to 1000 rpm and then used a hose to cross the vacuum lines (thanks for that tip!). I just had to turn both idle screws out maybe 1/8 turn to get the idle where I wanted it.

Starting is easy as shit! If the bike is even a little warm, it'll start with a half-assed kick and no choke. It starts easy even on one cylinder (one dead cylinder for sync) at like 700 rpm. If cold, choke and a normal kick and it starts right up. I think these are a touch better than the VMs in that regard although those aren't bad either.

I also set my air screws to 1 1/2 turns out to start, and turned them in 1/4 turn and out a 1/4 turn and it seemed to like the 1/4 in a little better. Now obviously those are very crude adjustments but that's what I left them at. I'll play with it more later. Pete, what are you running for exhaust? Mine are free flowing and loud.
 
Travis,

I am running EMGO 27" Dunstall replicas. The ones that extend past the rear axle.

The other thing I should add to my list is the fact that I do not like to screw with carbs or points. I took care of the points issue, and now I have these carbs that I do not have to screw with. I have taken a couple of 60 mile trips and they performed flawlessly. Haven't touched them since I installed them.
 
A few good things to note:

JRC Engineering has offered PKW's to the Brit bike community for years now and they have good reviews. This means two things to me. !. The pkw's would be a nice carb for the XS and 2. I'm not so sure the XSPerformance crew had to put forth extraordinary effort to get these carbs right since they were being used on similar 4-stroke twins. I have much confidence these will be super replacement carbs.

If you run a balance tube the initial idle will be much higher because each port/cylinder will be breathing through two carbs. The idle may be stronger without the balance tube because idle and off idle is usually better with a small carb. I'd try it both ways to see what is best. The idle and balance on a twin carb Brit bike is easy to set when one takes the time to play so the XS should be the same.

Please give the cable some free play when you install the carbs. The important adjustment is having enough free play and just tight enough so the slide opens fully without ripping the cable apart.

Tom Graham
 
Tom, thanks for the insight on crossing the vacuum ports. I'll play around with it both ways and see what works best.
 
Tom, the other day I tested the crossing the vacuum ports vs plugging each one. You were right. It ran better with the plugs. :thumbsup:

Bobber Bill, Those choke shafts are probably pretty soft. I bet you could bend it back pretty easily. If not, I would contact them about it. Send the pics in your email.

Use the aluminum spacers and mount the carb holders so that the vacuum barbs point up and out. They say you have to use the spacers for performance reasons. The holders should then point the carbs slightly down and pretty much straight back. Maybe you have the right and left carb holders mixed up?
 

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