New keihin flat slide carbs

ashman · Sep 27, 2011

Hi All

Just got my new Keihin Flat Slide carbs from Jim, will be mounting them up this weekend, just want to know from any one who has put these carbies on their Norton, just want to know how you set the fuel lines up from the Tank taps, do you run 1 tap for each carb or do you set them up to run off 1 tap so you can use your nomal tap as well have the reserve tap, thank for any help.

Ashley

kingdaddyo · Sep 27, 2011

I put my new ones on as well. I thought I was going to have to run with both petcocks open. I ended up fitting two Tee fittings and now only need the one open. They sure look good though. Good luck with them.

hudson29 · Sep 27, 2011

Please let us know how you get on with this conversion. This is one of options I'm considering to replace my sweet running but weak on the top end single 34mm Mikuni. I'm interested in hearing how much trouble you run in to and how well the setup works out for you.

Vintage Paul

Carbonfibre · Sep 27, 2011

What model Keihin carbs are you using? The PWK 28's would probably work pretty well for a road bike, and the 34's ideal for anything that was modified to any extent, but body size is bigger than the 28's, and they wouldnt fit quite so neatly.

ashman · Sep 27, 2011

Hi Kingdaddyo
Thanks for your reply I was wondering if you have any pics with the way you set up the fuel lines, I will chase up some tee peices to fit the lines and see how they go, Vintage Paul I will let you know how it goes as it should be straigth forward as Jim has set these carbs up for my motor, all I need to do is set them up, put the cables on and tune it up, these are the 32's and has been set up for the Commando motor.

Ashley

Carbonfibre · Sep 27, 2011

Not heard of Keihin 32mm flatslides before, so anyone have a link with more info as they sound very interesting?

pete.v · Sep 27, 2011

Carbonfibre said:
Not heard of Keihin 32mm flatslides before, so anyone have a link with more info as they sound very interesting?

Please, not again Carbonfibre, spare us of your not so subtle antics, please! I know exactly what you are attempting to do. Now knock it off'.

1up3down · Sep 27, 2011

This has been covered extensively already, but here is the from Jim Schmidt's website, forum member.

Design by Keihin. 32mm flat side PWK Twin Carb Kit, complete with lower cables, airfilters, curved manifolds with rubber mounts and clamps, Customized and tuned for Nortons with our custom needles & jets. No modifications necessary (more info). Customers with 30mm port heads see next item below.

and here is the link, scroll down a little for a picture of the flat slides, I have them and they are magnificent

http://www.jsmotorsport.com/products.asp

I run mine straight from each petcock with nothing in between, and check gas level more often!

xbacksideslider · Sep 27, 2011

I have a set and I'm happy with Jim's carbs too; I installed balance pipes by drilling and pressing a 1/4" hose barb into each of the carb bodies.

At first, not having two tees, I ran two fuel lines, one from the right petcock to right carb and the other from the left petcock to left carb.

Now I have the same setup as kingdaddyo, both petcocks feed a single tee centered and below the carbs; the line then rises to a second tee which then feeds the two carbs. I am a little concerned however about whether my 1/4" fuel line is sufficient to feed two carbs at wide open throttle.

hudson29 · Sep 27, 2011

xbacksideslider said:
I have a set and I'm happy with Jim's carbs too; I installed balance pipes by drilling and pressing a 1/4" hose barb into each of the carb bodies.

What does this balance tube do? Would it have worked as well if connected at the manifolds?

I'm too forgetful these days to want to run without a reserve setting so I would love to see a couple of pictures of your fuel lines. Are the bits easy to get and could it be made just as well one size up to assure good flow at WOT?

I love the easy way my Commando starts & runs with its single Mikuni, how is the JS setup to live with for those of us who are deeply suspicious of carbs in general? Carburetor is a French word that means "leave it alone."

Vintage Paul

1up3down · Sep 27, 2011

Well, after spending 15 years with a single Mikuni and then over a year ago switching to the flat slides:

Starting: Same, one kick, at most two

Idle: Same, like a rock

Performance: Flat slides are much stronger flow, not only from 4500rpm as would expect, but also right off idle

hudson29 · Sep 27, 2011

1up3down said:
Well, after spending 15 years with a single Mikuni and then over a year ago switching to the flat slides:

Starting: Same, one kick, at most two

Idle: Same, like a rock

Performance: Flat slides are much stronger flow, not only from 4500rpm as would expect, but also right off idle

That is just the sort of news I was hoping to hear. The Amals needed balancing once in a while but were not too difficult using the palm of the hand to feel the exhaust pressure method. What is required to setup the flatslides and how often do they need attention?

Vintage Paul

pete.v · Sep 27, 2011

1up3down said:
Well, after spending 15 years with a single Mikuni and then over a year ago switching to the flat slides:

Starting: Same, one kick, at most two

Idle: Same, like a rock

Performance: Flat slides are much stronger flow, not only from 4500rpm as would expect, but also right off idle

I am in agreement here. I will add that with cold starts, I only have to pull the left choke (the right is a bit of a bear to find).
Fuel line, I have a tee in the middle running line off right angle fittings to the center of the tank line, Then a 5/16 line straight down between the maniflods to another tee. From there I loop under and over the right carb to connect the left and under and over the left to connect to the right. I pulled a WOT to the ton mark with only one pedcock open.

I tried the short route with the gas lines and found that it is just too easy to kink and suffered starvation for it. The big loop may seem strange at first but works well.

It is said by Jim that the balance tube is not needed. I found the idle easilier attainable and steadier down to 500rpm. I keep it at 900rpm. It stays that way all the time.

1up3down · Sep 27, 2011

Paul, why don't you contact Jim Schmidt at JS Motorsport with your questions, his support has been terrific.

Carbonfibre · Sep 28, 2011

Why such a big problem with brand names in the US? Chinese/Taiwanese copies of Keihin carbs, seem to work pretty well and only cost approx 25% of the price of the genuine article, so why call them Keihins?

ashman · Sep 28, 2011

Hi All

Thanks for the replies, I won't get into any aguments about weather they are Keihin made or weather they are designed by Keihin, I have been hearing good report about Jims carbies and have studied Jims set ups and videos, my 850 motor isn't standard and has a bit of work with SS cam as well a Featherbed frame, I have never had any troubles with my Amal carbies, yes they do wear as I am on my 2nd pair of Amals in 35 years of owning my Norton, I have had some money to spare and throught I give these carbies a go, if they work as good as everone that has used them say I will be very happy and will make my own opinon on the performance they make to my Norton.

I would still like to see some pics of the fuel line set up that some are using, I use to run one tap for each carbie, but after running my tank dry a few times and in some out of the way places, the hassels that it corses if I am on my own, so thanks for everones help as this is a good forum and there are so many loyal Norton owners here, as well Norton owners are such friendly poeple.

Ashley

cjandme · Sep 28, 2011

I seem to remember a slogan ...."you meet the nicest people on a Honda".....but that was years ago. +1 for a lot of friendly Norton owners. Cj

Carbonfibre · Sep 28, 2011

Those carbs are not designed by Keihin..........they appear to be copies of the PWK 28mm, which have had the brand name (which is generally to be seen just above the letters "PWK" removed. Nothing at all wrong in that though, as the Chinese/Taiwanese Keihin copies seem to work very well indeed, but in terms of quality the Taiwanese OKO carbs are better than those made in China.

Keihin PWK series carbs are made in 28mm, and 34mm sizes, but the 34mm ones are noticeably different to the 28's as they have a round screw on carb top, and the body is a little bigger than the 28mm ones.

1up3down · Sep 28, 2011

My set of flat slides from Jim Schmidt do not have any name removed, they clearly say PWK on them.

Personally, I don't see why any reasonable person would care at all what the name is or is not on the body.

All I care about is performance: starting, idle, and flow, and these carbs do it all.

Although I have had them only a year and a half, I have not experienced any "build" issues, such as fit or reliability issues. These carbs have been dead on bullet proof, and Jim sells them with all jetting sorted out.

72westie · Sep 28, 2011

This is how I routed my dual Mikuni lines. T fittings off of the petcocks, line looping around towards front of bike connects both petcocks, line running towards back of bike runs to each carb. I can cruise 70 plus MPH and no fuel starvation issue's. I like running it this way so I still have a reserve if I need it.

New keihin flat slide carbs

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