JS Motorsports Carbs

I have been doing a lot of research online and after careful thought, I have decided that the best option for my Combat is the solution from JS Motorsports... I haven't bought them yet but they are on my X-Mas list. How many people here have the JS Motorsports carbs? Has anyone installed them and then gone back to Amals (or another carb)? My goal is reliability, easy maintenance, and better performance over a single carb conversion

I was at my local Motorcycle shop here in St. Louis, Donelson Cycles. (Former Norton Dealer back in the day). I was picking up a few items and mentioned to the owner that I was really tired of messing around with my Amals. They leak, idle all over the place, etc. I told him my plan to convert from the Amals to Flat Slide carbs. The dealer/owner, Carl Donelson who owns several Nortons (Including a really cool/rare rotary engine model), said that I would be crazy to put anything on a Commando other than the Amals or real Keihins. He said that putting Chinese knockoffs on the bike was a really bad idea and that he personally knew people who did that were very unhappy with the change. I do not know what aftermarket carbs he was referring to, so it is not a direct commentary on the JS version. He very well could have been talking about Mikunis or some other type.

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Thanks.

Hi JohnnyMac, I have just received my Keihins from JS and will fit them this weekend.
After some messing around with my Amals, I managed to get them running good and idling at approx 700-750RPM, but it is never totally consistent low down.They do idle though after a hard run and a quick pull up at stops signs or lights. Just that the RPM does differ on some days but never exceeds 1000RPM
Am going to refurb Amals after Keihin fit up in case I become a total purist or or turn the bike into a "show pony"
So will run the Amals on a hill highway before I take them off, fit the Keihins and then run the same piece of hill highway and use that as a comparison and let you all know on this forum.
Regards Mike

I'm a little confused maybe but just going by what I've read here, there are the "real" Keihin FCR flatsides which are very expensive ($1245 at CNW) and are joined together with a common throttle linkage. Then there are the JS Engineering PWK flatsides which are designed by Keihin but built in Taiwan or China for $445 for the setup. Not at all the same thing. Am I right?

Has anybody that can't get their Amals to idle and run correctly tried chrome slides or sleeved carbs and still have the problems? I fitted some older slides to my newer Amals that were not idling at all and ended up with Amals idling pretty well. Since my Amals are reasonably new, I plan to try chrome slides next if what I have deteriorates. New carbs in the price range mentioned have been on my mind so I interested to hear what is brought out in this post. I have another with a single Mikuni and it surely has no headaches.

Hi Batrider, maybe John Schimdt can answer that question as he is often on this forum.
I will email and ask regards Mike

Sorry I mean Jim Schimdt!!!

There is actually a John Schmidt out there with JS flatlsides.

There are JS flatlsides that are tuned/jetted for Nortons that work very well and reliably and there are other cheaper flatslides that are not jetted or set up for Nortons that run like crap and you get no support from the seller. Don't get them confused.

See demo At:
http://youtu.be/6j2nMv9TQb4

I would NOT recommend the chrome slides. I have run them and the chrome comes off and you know where it goes!! I would try the new anodized one's or MAYBE the brass. I also have had the slide break and go through the motor.



I hope the new anodized slides have this problem fixed.

Yellow_Cad said:

I plan to try chrome slides next if what I have deteriorates.

Click to expand...

batrider said:

I'm a little confused maybe but just going by what I've read here, there are the "real" Keihin FCR flatsides which are very expensive ($1245 at CNW) and are joined together with a common throttle linkage. Then there are the JS Engineering PWK flatsides which are designed by Keihin but built in Taiwan or China for $445 for the setup. Not at all the same thing. Am I right?

Click to expand...

Keihin FCR flatslides are race carbs designed for roadrace and high performance street use. They are attached together by brackets and have a common shaft to operate the slides. They are expensive.

They have nothing in common with PWK carbs.

Keihin PWK carbs were designed for dirtbikes and off road bikes. They do not have the provisions for push-pull throttle so cannot be advertised for use on a streetbike. The JS carbs are copies of this carb- Not bad for the price. Jim

Guilty

I am "the" John Schmidt spoken of earlier upthread, NO relation to Jim Schmidt, the carb's creator and seller.

I have had Jim Schmidt's (JSmotorsport.com) 32mm PWK flat slides for about 18 months now.

Prior to these I had twin Amals and a single Mikuni 34.

I will never go back to either. These flat slides are fantastic.

They start like any other well set up carb(s), first or second kick from cold to get fuel drawing.

They idle perfectly like a rock.

They FLOW, from right off idle all through mid range and to red line, no hesitation, just keep delivering

perfectly jetted fuel/power to my motor.

For the price of some $450 they come with everything, even including air filters, manifolds, and lower cables!

All set to bolt on.

Everything already figured out, pilot jets, needles and needle positions, and main jets.

Honestly, this is a no brainer. Just get them if you are looking for a fabulous set of twin carbs for your Commando.

Hi John, thanks for the enlightenment, am in the process of fitting the JS carbs, and will be all done by the weekend. Just doing checks getting ready for a ride, found my rear oilt tank mount broken off!!!
Once I put the carbs on i will give some feed back and pics
Regards Mike

Hey Johnnymac,
I recently had a pair of Amals sleeved, and it is a big improvement. Still not perfect though.
I don't believe the unadjustable idle, or, design is quite good enough to suit every engine.
However, they are working, hopefully I can find the cash for a pair of Jims carbs before I wear them out again.
Then I'll have a pair of Amals in the cupboard for later.
AC.

comnoz said:

Keihin FCR flatslides are race carbs designed for roadrace and high performance street use. They are attached together by brackets and have a common shaft to operate the slides. They are expensive.

They have nothing in common with PWK carbs.

Keihin PWK carbs were designed for dirtbikes and off road bikes. They do not have the provisions for push-pull throttle so cannot be advertised for use on a streetbike. The JS carbs are copies of this carb- Not bad for the price. Jim

Click to expand...

My Friend has a totally tricked out late model large bore Triumph Thruxton street tracker with the Keihin 35mm flatslides. They are great carbs and his bike flies. He had me test ride it because he thought it was pinging but it turned out to be a faint rattle with the slides and nothing to worry about.

I'm going to get these carbs for my Xmas present.
I had my Amals sleeved but the bodies just wore out and I barely put any miles on them.
It's time to get out of the past and embrace what technology can offer.
If you want to restore your bike and put in on a pedistal for all to see as a show case bike then yes, Amals are the way to go.
I will miss the look of the stock air filter though.

Guido said:

I will miss the look of the stock air filter though.

Click to expand...

You might still be able to keep it. I've been running a single Mikuni with a shortened airfilter element from K&N. I cut down the perforated surround and got a single hole front cover for the aircleaner. Just from looking at the pictures on Jim's site, it looks like they might fit by going back to the original two hole cover.

Reading about all the trouble people have with Amal carbs even after they have messed around getting them sleeved in the hope they will work better, makes me wonder why anyone would bother when there are far better alternatives such as twin flatslides or single Mikuni, both of which seem to be far superior.

Uh, like say?- $money $ -or some actually like authenticity. Norton airbox sweet lookin'too. I can tickle flood my resleeved brassslide Amals in freezing temps. like this morning and get a reliable first kick start to work. Shell V - Power drippin' , no choke startup ice cold frosty. Light brown plugs last pull 4 days ago. Yes when these wear out and my ship comes in for myself and others here and elsewhere.

My PWK's from JS have been great. I have tried so many combinations (not the FCR's though, I maybe a little extravagant, but not crazy), and these have offered the best performance and stability. Like all systems of this nature, some fiddling is needed.

My only issue now may be that they are a little cable sensitive where a slightly beefier slide spring could correct.

I think you got yours about the same time as when I received my flat slides.

What color are your springs?

If they are silver, call Jim Schmidt and ask him for the newer gold springs, they are stronger, will return slides better

Oh, oh! I feel $445 slipping away. Based upon what you guys report, it will be well worth it. I don't seem to get more than 10-12,000 out of Amals.

Now, back to basting the turkey. I'm the cook today.