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DOXFORD

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Has anyone here purchased the JS motorsport dual flat side mikuni carb kit 750/850 and if so what were the results of this conversion pros/cons, good/bad or indifferent? TKS
Doxford.
 
I got a set. With my new cam set up, it's the only set that will run good...er i mean GREAT! They are not as good a quality as the Mikuni but we are not talking a single carb setup. All you need is included. I have add a K&N RU-2850 instead of cheap EMGO air filters provided.
It is a good setup, a little pricey but good.
 
They are not Mikunis, they say PWK on them. I have had my set from Jim since last fall.

They are fabulous. Start second kick with cold motor and chokes on, then first kick when warm with a little extra
throttle to shoot some more gas in the chambers.

WIthin two city blocks from cold it will hold its idle, and thereafter idles strong and steady.

These things flow, period, all through the range, better than any twin Amal or single Mikuni set up I have tried.

I think they are fabulous, and they come with all everything you need. I like mine a lot.
 
Same experience here; in fact yesterday, I attended the SoCal BSA Owners Club meet at Hansen Dam, here in Los Angeles. I rode with a group of 10 or 15 bikes. My Commando appeared to have more power than any of the 7 or 8 Triumphs (none of them a 650) or the 2 other Nortons in the group. Ironically, there weren't any BSAs in the group but there was a Matchless twin and a KTM. A long uphill mountain straight, sorted it out and I was probably the heaviest rider in the group - 275 pounds. Yes, there are other mods to my bike but those guys' bikes aren't stock either.

I can't say how pleased I am to finally have a Norton that idles reliably. The bike has always been a strong runner, even with points and a Lucas auto advance unit and clapped out Amal Concentrics she always made good power. The PWKs and a Tri-Spark are what civilized her.

I too recommend Jim Schmidt's PKW kit; it's all there, done for you, and the customer support is genuine.
 
pvisseriii said:
I got a set. With my new cam set up, it's the only set that will run good...er i mean GREAT! They are not as good a quality as the Mikuni but we are not talking a single carb setup. All you need is included. I have add a K&N RU-2850 instead of cheap EMGO air filters provided.
It is a good setup, a little pricey but good.
Click to expand...

How much did you pay for the K&N RU-2850 & where did you get it? How is the fit and can you post a photo of it installed?
Jim
 
jseng1 said:
pvisseriii said:
I got a set. With my new cam set up, it's the only set that will run good...er i mean GREAT! They are not as good a quality as the Mikuni but we are not talking a single carb setup. All you need is included. I have add a K&N RU-2850 instead of cheap EMGO air filters provided.
It is a good setup, a little pricey but good.
Click to expand...

How much did you pay for the K&N RU-2850 & where did you get it? How is the fit and can you post a photo of it installed?
Jim
Click to expand...

$32.99 w/free delivery right from K&N. This of course will not work with the original backing plate retained.

And Ilet me add this about the PWK Kit, when I say it is a little pricey it doesn't mean it's not worth it. It is!

carbs

carbs
 
swooshdave said:
pvisseriii said:
swooshdave said:
Probably from here: http://www.amazon.com/RU-2850-Universal ... 501&sr=8-1
Click to expand...

No... Here. kn153 oil filter is also here with free shipping. http://store.knfilters.com/search/produ ... od=RU-2850
http://store.knfilters.com/search/produ ... rod=KN-153
Click to expand...

You save $.11 by going through Amazon! :mrgreen:
Click to expand...
Not to beat a dead horse again, but K&N also has an ebay store with that extrodinary $.11 savings.
 
A lot of people want to keep the backing plate, and I think the 850 ignition key is part of it. You can get a bare similar carb cheaper without the necessary manifolds & adapters etc but they don't work satifactorily on Nortons.
 
jseng1 said:
A lot of people want to keep the backing plate, and I think the 850 ignition key is part of it. You can get a bare similar carb cheaper without the necessary manifolds & adapters etc but they don't work satisfactorily on Nortons.
Click to expand...
I hear that, Jim.
I am thoroughly pleased with this Kit and would purchase it again if given the chance, especially now that i am familiar with the details of the setup and the carbs themselves. I want some gold lettering for my side covers the say "Super Combat". My idle is at 1g rpm so much better than expected with your stage 1 cam kit. Also, I need to re-shave my thick RGM pressure plate. I will sacrifice a 1 finger pull clutch for a little more clamping force. By no means do I consider this issue to be negative. I do not know how much HP I've gained. At least 5, maybe 10. Probably more like 6 to 8. On an average with no baseline, what do you think, Jim.
 
They sound like the ticket to me and I think they're a STEAL at that price. Of
course I'm used to a grand for a set of FCR's for a Ducati :(
 
pvisseriii said:
jseng1 said:
A lot of people want to keep the backing plate, and I think the 850 ignition key is part of it. You can get a bare similar carb cheaper without the necessary manifolds & adapters etc but they don't work satisfactorily on Nortons.
Click to expand...
I hear that, Jim.
I am thoroughly pleased with this Kit and would purchase it again if given the chance, especially now that i am familiar with the details of the setup and the carbs themselves. I want some gold lettering for my side covers the say "Super Combat". My idle is at 1g rpm so much better than expected with your stage 1 cam kit. Also, I need to re-shave my thick RGM pressure plate. I will sacrifice a 1 finger pull clutch for a little more clamping force. By no means do I consider this issue to be negative. I do not know how much HP I've gained. At least 5, maybe 10. Probably more like 6 to 8. On an average with no baseline, what do you think, Jim.
Click to expand...

I'd got with 50hp more just to make hobot's eye's bulge with jealously. :mrgreen:
 
You need a dyno to determine the HP gain. But with those carbs and the JS stage 1 cam I can imagine how well your bike runs. I run a similar setup (JS stage 0 cam but with raised ports) and it makes me smile every time I roll it on or settle down to a 75 mph freeway cruize). I haven't adjusted them in 6 months and it idles at 800-900 RPM and hits every beat.

For the dry clutch I just use a stock back plate with an added steel disc.

carbs


Jim S
 
Jim, in the above pic, do those intake manifolds accomodate a raised port? My experience with Amal Concentrics was that the racing style of velocity stacks, which stay at the 32mm + or - inside diameter and are affixed with set screws, worked far better than the alternate - more common threaded "screw on" style of stacks that had an far larger inside diameter.
 
The manifolds started out by cutting the flange off stock 28 or 30mm Commando manifolds, boring the hole offset in an upwards direction with a porting tool and welding on a tube matched up with the hole in the flange so the port is raised/offset and then cleaning up the distortion made by welding. These are actually my very first manifolds from my 1st race bike from way back and I lately added a another sleeve to adapt the PWK carbs with a step in the ID so the bore is consistant. The port is offset to the bolt holes and stays high all the way into the bowl. You have to go wider around the guide and not weaken the roof directly in front of the guide as explained and illustrated in the JS race manual. Nothing is taken off the port floor. Making the fuel charge turn down so it flows completely around the valve (not across)is more important than anything. This is all difficult hand crafted work usually invested on race engines.

The small diameter velo stacks you mention work much better because you are extending the length of the intake tract and keeping it closer to the same diameter as the carb throat & intake manifolds. Most tuners & racers miss this. Its the cheapest HP gain and can make a tremendous difference. The full length needs to be at least 9-1/2" from the head (not the valve). But this is with regular large velo stacks. More researh & dyno testing needs to be done on this subject.
 
Jim -

Thanks for your independent confirmation. If I recollect correctly, C.R. Axtell told me that the distance from carb bell to valve should be no less than 14" and as long as 17" depending on application and other factors; that tracks with your finding of a 9 1/2" head to bell distance.

Now I'm wondering if my bike would benefit if I fabricated more intake length for my JSMotorsports PWKs. I'm wondering if the added length should take the easy form of a velocity stack (of an inside diameter greater than 32mm), or the form of a 32mm ID extension of the existing intake manifold.

Placing the extension between the valve and the slide lengthens (and increases the volume of) the intake tract for all engine speeds and throttle positions while placing the extension on the other side of the slide, by way of a conventional velocity stack, really only affects WOT, particularly so since its ID is so much large than the throttle ID. Trade offs . . . .
 
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