Keihin flatslide PWK carburetor, oppinions, issues?

[grizld1]

Here ya go, Jimmy, Dellorto tuning manual--www.thisoldtractor.com/gtbender/dellorto.htm . I don't know why this isn't coming up as a link, you'll need to type it into your address bar.

Admittedly the Dells are a lot of bang for the buck, but there are a few downsides. With the Dells you can only control AP action by changing slides, which isn't ideal; tuning for low-throttle transitions is best done with the AP disabled. Unlike Mikuni pumpers, Dellortos force you to use two AP's, which makes synch issues associated with split-cable throttle control that much more touchy. In engineering, the Dells are a full decade behind Mikuni and Keihin flat slide pumpers.

It doesn't really matter if those bored out PWK28's are "legit" (produced under license) or not; they're not Japanese quality.

 

[brat]

repositioned the cable wire a couple times its much better.

 

[JonathonD]

I've just got my bike running again, I've done the banshee pm swap, pamco electronic ignition, Xs performance headers w/o mufflers, and the mikes/xsdirect "keihin" carbs. My bike fires up first or second kick every time but when I open the throttle it just stalls. The carbs are still jetted how it came and I've got very minimal experience with most of this any idea what I'm doing wrong or could be doing to fix my problem. Thanks

 

[weekendrider]

Have you messed with the idle stop screws?

 

[mrriggs]

My bike fires up first or second kick every time but when I open the throttle it just stalls.

How does it stall? If it just shuts off instantly then that is typically a sign that it is lean (or the spark is weak). If it stumbles, blubbers, coughs or you see any black smoke from the pipes then it is probably rich.

 

[JonathonD]

It will stumble and fire a couple of times then stall. When I first installed the carbs and fired it up the bike ran and reved up with good throttle response but then the next day when I started it and tried giving some throttle she started to kind of stutter and stalled out

 

[JonathonD]

I put in the next size up jets and the bike doesn't idle as nicely as before and when I crack open the throttle it makes a hissing type sound and backfires out the carb with a puff of white smoke

 

[ukie eagle]

Hi All:

For better or for worse, I've ordered a set of these from MikeXS.
The BS 34s on my '80 SG are shot and I haven't been able to ride yet this year so I figured I'd give these a try.
Having said that, short of printing out the many pages of discussions [on many threads] on this forum, is there some sort of "Standard Operating Procedure" from all of the Forum's experience when it comes to installing these?
My bike is stock, except for a set of MAC 2 into 2 pipes.
What is the best way to install/set these carbs up?
I'm not a perfectionist, but just would like to be able to get the bike running so that I can ride.
I'll be happy to tweak it as I go along, but for now am looking to not have to repeat all the major troubleshooting to get it going: I just want to ride!

Any tips/hints would be greatly appreciated!

Thanks!

 

[JonathonD]

Is there something that I should be looking for that's causing my bike to stall when I open the throttle!? It idles and starts awesome but that's it, once I give it any gas it will make the hissing type of sound and backfire or stall but the engine doesn't rev up at all. I've tried the 3 different sets of jets the carbs came with and notice no change in how the bike was running

 

[visimpact]

Mrriggs a big thanks for all the knowledge u layed out on these carbs. I got a set a month ago. The carbs had several issues. The bike shop I do paint work for helped me out with them because of a few issues and I sent them this thread and he told me everything in this thread was dead on about these carbs. I had a stuck float on my left carb. Turns out the casting was so poor internally it was hanging the float up. There was also a internal pressed in fitting that fell out when carb was taken apart. They were far from synced and the idle was sky high. The needle needed to be moved as well. Other then that hey these carbs were bolt right up and go just as claimed Lol. I will say however Now that all that crap is fixed the bike is a beast compared to the stock carbs. It pulls hard and it runs so nice. Responsive as hell. I haven't even taken it out for a real ride yet and I'm blown away at how responsive it is. Next I have to deal with the two into one cable issue. Not so good either. Add that to the list.

 

[bryanjnkns]

I was wondering if going to a dual throttle would solve the 2-1 cable issue? Or would it just complicate things?

 

[Travis]

Dual throttle?

 

[Patches]

Dual throttle?

I believe he means something like the old XS throttle where they had independent cables for each carb like on the XS1 or 2 with solex non linked carbs.

I don't see why it wouldn't work....

 

[bryanjnkns]

yep. thats what I meant. thanks

I'm having to replace my throttle assembly anyway and since the 2-1 cable seems to give people grief, I thought it might be a good idea. I just wasn't sure if it would make syncing the carbs more or less of a pain.

 

[Travis]

Ah yes.. I kept thinking push pull throttle in my head.

I would think it would be the same as far as syncing goes with independent cables to each carb. But then you'll be limited on the throttles you can use and will probably need customs cables anyway. Might as well get a nice 2 into 1 from motion pro to your specs.

 

[mrriggs]

The saga continues...

Yesterday, after some spirited back road riding, the bike was running a bit off. I pulled over and looked for obvious things like tears in the carb boots or missing vacuum caps. Nothing was visually wrong so I kept going. It made it home alright but just didn't sound right.

Today I started with the basic diagnostic checks. Pulled the plugs, both are a perfect light brown. Compression check shows 170 PSI in both holes. Hooked up the mercury sticks, WOW this thing is way off. Tug on the ends of the cable housings to check for free play. What the hell? That doesn't feel right.

One of the cable adjusters that came with the motion pro cable snapped in half! I have never seen that happen before.

Luckily I have a set of genuine Keihin adjusters that I ordered up before I knew that the cable came with some. The threads in the Keihin part taper into the hex portion which I would imagine is much stronger than the sharp shoulder in the Motion Pro part.

 

[backwithabang]

bringing up an old thread. I'm running a 76 stock engine with a pamco, banshee swap, and scrambler style drags. My 38s were running like shit last fall, got them decent right before winter but my wife got me a set of these mikes xs carbs for my birthday. looking for any advice on setting these carbs before I throw my engine back in the bike. I already hate the manifold mounts.

I'm running an odd throttle with the bike. Some motion pro quarter turn moto racing throttle i grabbed on clearance from some local store. After you cut the "j" bend off the stock throttle cable it screws in perfect.

so knowing whats up with my bike with these specs, whats the jetting, needle position advice...
-76 xs650- stock engine, top end rebuilt and adjusted to specs
-
mods..

.pandemonium scrambler drag style exhausts (with home made lollipop baffles)

banshee swap (with a little security system 12volt battery for extra oomph)

pamco ignition with the super coil that shoots an arc like the emperor in star wars shoots lightning bolts out of his hand.

or should i just pawn these things new and grab a set of vm34s

 

[Patches]

All of you answers are in this thread if you go through and read it. Which I highly suggest if you are going to run these carbs. It will also help you in the future when you need to do some trouble shooting.

 

[backwithabang]

I played with my new pwk's a bit today. It was cold out and I didn't want to die of fumes in my basement so it was basically A quick start and a few throttle pulls. A quick sync by sound and feel.

To test out some theories in this thread I hooked up a standard generic throttle (tc bros first) and the carbs were kinda crap. The left side seemed weak on the pull..But it's what I expected from mr. rigg's input and previous issues I had with a set of takeis on my rd200.
(on an aside the rd is running the stock cable from 75 and it's an odd 2-1 cable in 2 pieces and seems a bitch to get an after market new cable from yambits, so I just lubed the shit out of it and routed it off the factory routing so it just hung loose a bit. Fixed all the carb problems with that bike other than a slight hesitation off take off (which I hear is cleared up with a y intake manifold and 1 filter)

anyway back to the xs..... I shut it down and hooked up my motocross turbo throttle... I forgot the model but removal of the "j" end of the standard XS cable lets me connect right into the stock end piece with just enough room for adjustment... Quick start up and quick sloppy sync and it revved well. Returned well, sounded pretty mean.

Keep in mind a few things.. I didn't ride it yet since it's 12 in buffalo and we have about a foot of snow and I do not run anything by the book or neat on my bike.
I have nothing I do not require on the bike. It's a hardtailed, absolutely no suspension but the fork stripped down bike. It's fun for bar hopping and city cruising.. So I'm not expecting a lot out of these carbs just to run decent and open up quick when I want them too. I just hate vacuum carbs in any capacity because it sucks when they get stuck and often do on one side and you have every person in the world pointing and laughing at you on your bad ass bike puttering on one cylinder maxing out at 45 trying to limp it home. (or worse yet you have the thing wide open and the carb unsticks and you go turbo in traffic)

I don't know my point, just wanted to throw some input based on a bit of trial, error, and a lot of trouble. My major carb problems in "fine tuning" them often resulted more from the cable routing or actual cable or throttle than anything else. If you can stand the hardware on your bars I recommend a motocross throttle with a quick pull and hard return. I also have the ability with the bike style to not route my cables at all. I just let em all hang. Many problems with this.. They sometimes get in the way if you aren't used to it, if you don't run tape on your exhaust they will burn, ect.. but a free hanging cable often leads to less problems for me on throttle and non hydraulic brakes.

older pic, but the only thing I did to this thing in terms of performance was eliminate A LOT of weight (the only thing holding that rear end down is my ass) and throw a brembo caliper upfront which is good for throwing you over the bars or putting 10,000 miles on your rear tire in about 30 seconds.

First impression on the carbs.. They seem to work decent in a casual sense, and are an affordable out of the box alternative then a new set of VMs, dellorto, or lectrons. The overall carb make seems "cheap" and if I ran this bike as a racer I wouldn't get them. They just seem kind of plastic to me. I do look forward to trying the bike out in the spring and will report back when I do. I'm only riding this bike about a month and selling it anyway as I have upgraded my bobber ride with an old shovel and don't have the room

*** oh yea, this was the out of the box settings.. I didn't fiddle with the jetting or needles, I'm kind of confused about the chokes on these things, if they actually work or are just there for show or something, they seemed unresponsive.. All I did was play with the idle screws

 

[mrriggs]

So I'm back to trying to get these carbs working well. I know, a glutton for punishment.

After lapping the slides there was no sticking issues for about a year, then the problem came back. Also, I was never able to eliminate the off idle "blubber", even with the largest jet needles (JJS). I mentioned in another thread that I received a set of new XS Performance carbs and the slides stuck horribly, but the off idle transition was better. Perhaps I could take all the parts from the new carbs and put them in my old carbs and make one good set out of two.

With the new, unmodified, slides the initial test was promising. It had a clean transition but wasn't long before the slides were sticking. I went back to my original slides, after lapping them again, and still had issues. So I replaced the new springs with the ones I had previously stretched out. Better, but still sticking slightly. Finally, out of desperation, I slathered the slides with Mobil Vactra #2 (way oil) and that did the trick. Maybe that was all I needed to do all along? To test that, I put the new slides back in with the stretched springs and way oil. They still stuck, so it was back to the lapped slides.

So long story short, to cure the sticky slides;

1. Stretch the springs about an inch. This will make the pull a little tougher (more hand fatigue) but in my case it was necessary. It's still better than the heavy duty springs which left my wrist aching after a few short miles.

2. Lap the slides. I used a non-embedding garnet lapping compound. Don't try it with the stuff you use on your valves.

3. Lube the slides with way oil. Other oils may work but way oil is specially formulated to prevent "sticktion" of sliding parts. I don't know yet how long the way oil will last. I've burned through a tank of gas and the slides are still oily and working well.

I also want to mention the other annoyance with these carbs, the overflow tube in the float bowl. It comes out at the wrong angle and makes it very difficult to get the bowls on and off (this was the case on three of the four float bowls I have). I was planning to just break it off and fill the hole with epoxy. Before resorting to that, I tried simply bending the tube up so it would clear the float and jet block. Surprisingly, I was able to bent it far enough to clear without it breaking.