PWK Flat Slide Carbs (2014)

I've been installing a set of PWK flat slide carbs from JSM and noticed the machining in the slide bore of the carb appears very rough.
All the other interior machined surfaces of the carb appear smooth but the slide bore has vertical scoring that I can actually feel.
My thoughts are that the original casting was not thick enough and that the machining process ran out of material leaving unfinished metal.
I'm concerned this is going to quickly wear the surface of the slide. Anyone else running these carbs notice this issue?



I sent a message to Jim at JS Motorsport and he said it was not a concern.

Thanks,
Mark Schmitz
`73 850 Commando
`63 750 Atlas

They look like my amal mk1's after 40years of runnig on open bellmouths! I' not happy with them & I wouldnt be happy with that finish on something new.

After MANY hours and many trips to auto parts and hardware stores - I ALMOST have mine installed.
Other issues with them that makes the install a PITA.
Primary one being the location of the fuel intake fitting. These carbs are only partially 'handed', unlike the Amals.
The left hand carb will have the fuel hose attached between the two carbs and there is virtually no space to do it after installing them.
Tip #1: attach the fuel line to the left one BEFORE installing the right carb. Seems obvious now, but is not mentioned in the instructions and I spaced it out.
And removal / re-installation is not trivial in that tight space.
Also, standard fuel line from auto parts store DOES NOT FIT properly. The wall is too thick and it will not seat on the fitting.
Have to hit a motorcycle shop for new lines today (the old Amal line is too short).
I think this will be third time I had to remove the right side carb and not even fired 'em up yet..


tomas

tomspro said:

After MANY hours and many trips to auto parts and hardware stores - I ALMOST have mine installed.
Other issues with them that makes the install a PITA.
Primary one being the location of the fuel intake fitting. These carbs are only partially 'handed', unlike the Amals.
The left hand carb will have the fuel hose attached between the two carbs and there is virtually no space to do it after installing them.
Tip #1: attach the fuel line to the left one BEFORE installing the right carb. Seems obvious now, but is not mentioned in the instructions and I spaced it out.
And removal / re-installation is not trivial in that tight space.
Also, standard fuel line from auto parts store DOES NOT FIT properly. The wall is too thick and it will not seat on the fitting.
Have to hit a motorcycle shop for new lines today (the old Amal line is too short).
I think this will be third time I had to remove the right side carb and not even fired 'em up yet..


tomas

Click to expand...

Well, Jim does sell pipe that fits, and a specially sourced 2 x in / 2 x out filter to suit his recommended pipework layout. Wudda saved you a few trips to the store !!

Fast Eddie said:

Well, Jim does sell pipe that fits, and a specially sourced 2 x in / 2 x out filter to suit his recommended pipework layout. Wudda saved you a few trips to the store !!

Click to expand...

I did not see that until after I got mine. Jim did not mention it when I ordered.

But $70 for a fuel line setup? :roll:
I'll pass on that "deal"!

Did not mean to hijack Mark's thread.
Back to the SCORING issue please....

tomspro said:

Fast Eddie said:

Well, Jim does sell pipe that fits, and a specially sourced 2 x in / 2 x out filter to suit his recommended pipework layout. Wudda saved you a few trips to the store !!

Click to expand...

I did not see that until after I got mine. Jim did not mention it when I ordered.

But $70 for a fuel line setup? :roll:
I'll pass on that "deal"!

Did not mean to hijack Mark's thread.
Back to the SCORING issue please....

Click to expand...

Indeed, sorry for participating in the hijack Mark... back to scoring... SEVEN :lol: !!!

That does not look good. Not sure how that could be considered okay. This is the riding surface for the slide and will likely induce premature wear on the slide...

Why are those marks there? Assumption would be that this is a die cast part and there is a slide in the mold that forms this area. Worn slides will create this type of marking. Given that the sidewalls likely need to be held close to straight there could be sticking of the slides on retraction (normally side draft is required on slides in order to retract them).

The shape of the opening along with the depth does not lend itself to secondary machining due to aspect ratio (depth and size of opening), so this is a molded in defect that can't be cleaned up.

This is a defect that should be brought to the attention of the manufacturer IMO.

I actually bought the 2in-2out filter kit from Jim. It's a nice idea that eliminates the cross-over fuel line under the tank.
Yeah, you can find the Pingel filter a little cheaper elsewhere but I don't mind spending a little extra if it supports the Norton community.
Pretty sure any auto parts store has black rubber fuel line that will fit. You can get Vinyl or Tygon tubing at most good hardware stores.
It gets hard after a year or two but so what.

Mark Schmitz

What you call scoring is caused by the forming process used in fabricating them - its a hidden cosmetic detail that doesn't show and no one else has ever complained about it. It causes no problem whatsoever even many after years of service. There are no wear or slide sticking problems such a experienced with Amal carbs. Never have been and never will be because I check every carb before I send them out.

The thick walled tygon fuel line I supply is expensive and so is the pingle filter but it makes installation easy. Its a clean a tidy setup and was shown to me by a fellow forum member for which I am very thankfull. The plumbing kit is available at my website along with the carbs. There is also a throttle kit.

[quote="mschmitz57
I sent a message to Jim at JS Motorsport and he said it was not a concern. Tomas recently bought a set and his look the same as mine.
Is this really an acceptable surface for the slide?
[/quote]

Well obviously these Taiwanese OKO replica Keihin carbs share the same machining quality :shock: Would like to see a picture of that machining surface of a genuine Keihin flatslide :?:

Well I have been running my flatslide carbies from Jim for over 4 years now and haven't had a problem with them yet, they take the same time to fit as the Amals, easyer to tune and once set will stay set, I made my own fuel lines that run straight from the taps to the carbies from the top so the fuel has a down slope run, it would be good if they were left and right carbie.

Ashley

I have a Keihin flat slide on my KTM and it finished like jewelry inside. Beautiful stuff.

I realize the knock-off carbs are made to a price and I will say that the pictures look worse than reality due to the reflective nature of the carb surface.
The slides seem to slide nicely. I'm willing to give them the benefit of the doubt because of all the positive reports I've read. However I'll be keeping a close eye on the slides for abnormal wear. I'll report back on these in the summer after 500 miles or so.

I do have a fully rebuilt set of Concentrics on the shelf that made the trip to Lund for sleeving, but I'm really reluctant to bolt them on after going through the same issues with my `71 Commando several years ago. Even after thorough cleaning and re-sleeving they constantly required fiddling from day to day. They were great for the first day, then got progressively worse at idling, presumably from the problematic pilot circuits clogging with fairy dust.

Mark

nortonspeed said:

Would like to see a picture of that machining surface of a genuine Keihin flatslide :?:

Click to expand...

Pretty sure these are die cast parts. Don't think that surface could be machined but I may be wrong. This looks like the area is formed by a slide in the die casting mold and it is dragging when it retracts to eject the part from the mold.

The slides are chrome plated, they are not going to wear. Those striations are the high spots in the body being worn down by the chrome of the slide.

This might be of concern in an Amal since the Amal's problem was air leaking around the sides of the slide and the curve of the slide makes a lousy bearing surface - two round areas on the two sides of the slide.

In the PWK design, the bearing surface AND the sealing area at the sides of the slide is the slot in the body of the carb and the wing on the slide.

I have been running my flatslide carbies from Jim for over 4 years now and haven't had a problem with them yet, they take the same time to fit as the Amals, easyer to tune and once set will stay set,

Click to expand...

exactly my experience with Jim's carbs too

I was one of the very first purchasers, very happy with them

These carbs are brand new, never been used, so the slides have not been moving in them to cause the marking.
I believe the idea about removing the casting insert is partially correct, but the slide bore still has to be machined afterwards
for a precise fit of the slide. I believe the rough casting does not have enough material in the bore for a smooth uniform surface
after machining, and what's left behind are the low spots that are untouched by the grinding process.
I'd be curious to see if the slide bore on your older PWK carbs have the same casting marks as mine.


Mark

Mark, How do you suppose you would machine a shape like that?, Can't get a milling cutter or grinding wheel in there, (Grinding aluminium/zinc alloy is a specialised process anyway) I'm guessing they were broached, difficult at the best of times. What you should be interested in is how much air they leak when in use. There are a good few users on this site that have had good wear out of these carbs. I've got some and they improve the usability of a Commando by about 75% IMHO, yeah they do look a bit rough but they work well.

I was one of the original five who bought Jim Schmidt's flat slides four years ago

like any dual carb set up there was a little initial fiddling around to get both plugs the same color

I leave them alone, put them on and see what they do after you have dialed them in, then learn how to start your bike with these carbies, my bike starts on the second kick in the morning, first kick to suck the fuel in then one big kick to fire it up, but once started for the day it will start first kick every time, but when I first put them on the bike it started first kick even before I set the mixture screws, I can take my hand off the throttle when stopped at lights.

One thing you got to make sure about when fitting for the first time is to make sure the springs on the idle screws have enough tension on them to hold the srews in place, when I put mine on the first ride I lost a idle screw and spring and had to get another one sent over from Jim, I haven't had any more problems with the springs once you put more tension for them to hold better.

Jim is good to deal with and if you have any problems he will help you out, my 850 is a bit of a hotrod and these carbies with the other work that has been done to my motor and with the Joe Hunt maggie work so well together, put the old Amals to shame.

Ashley

OK, time for an update (finally) on my new PWK carbs.
I finally got the bike out of the basement and into the garage for gas and oil, and the first startup after the rebuild.
Amazingly the bike started on the first kick and and ran really well on my initial (careful) carb adjustments.
I did have to increase the idle speed a tad but that was it.
Before I starting it I did have some overflowing problems with both carbs, and after removing one carb and dropping the float bowl
for inspection, the overflowing mysteriously stopped on both. Hmmm.
Since this was the first start since the top-end rebuild, I wanted to run it hard to seat the new rings, I didn't care too much about the idle settings, etc. I also had Fred at Old Britt's update my Power Arc ignition which cured my kickback problem. Many Thanks to Fred and Ella.
I stopped a couple times during the first ride and the bike always restarted easily with 1 kick when hot. Looking forward to a long ride tomorrow. I need to set the idle circuits a little more carefully but it runs strong and idles well.
I have a little bit of pippity-pop when cold on deceleration but nothing objectionable. Maybe fatter idle jets in my future.
Also running new exhaust pipes so I may be leaking air.

I am running the Oval air filter pods from Mikes XS. They're quite a bit larger and look better.
I do not have the rear air filter plate so these filters fit easily.
So far so good.

Mark