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Jetting Keihin FCRs
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Tue Mar 04, 2008 7:00 pm    Post subject: Jetting Keihin FCRs Reply with quote

Anybody running 35mm Keihin flatslides on a Commando?

I have a pair and love them, but they're running a fair bit rich. I want to pull and rejet, but because of their size, getting them in or out requires dissassembling them partially - which means not a quick and easy on/off job, so once I get them off, I'd like to have the right jets on hand.

I'm thinking of just raising the needle clips a position or two to start, but you know how rejetting goes...so if anyone knows what the baseline "as delivered" jetting for these carbs should be - or even better, if anyone's been through this exercise and has suggestions - I'd appreciate it.

I am running them on stock intake runners with K&N pods.

Thanks - Brian
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Jeandr



Joined: 22 Jan 2008
Posts: 86
Location: Canada

PostPosted: Tue Mar 04, 2008 9:12 pm    Post subject: Maybe... Reply with quote

I just bought a new set and it will be some time before the bike is on the road however, I can look at what is inside mine to see if it matches yours. Mine were supposedly jetted for a stock 850 (that's what I asked for).

Jean
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Wed Mar 05, 2008 4:36 am    Post subject: Reply with quote

That'd be great, Jean, that's exactly the sort of baseline I am looking for - many thanks!
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Jeandr



Joined: 22 Jan 2008
Posts: 86
Location: Canada

PostPosted: Wed Mar 05, 2008 8:42 pm    Post subject: Info Reply with quote

http://www.motorcyclecarbs.com/keihin/frames/FCRHframe.htm

for the # refer to the chart or the picture



The main jet on my carb is a 152 (#27)
The main air jet is a 200 (#103)
The air screw is out one turn (#129)
The pilot screw is out one turn (#32)
The slow jet is a 58 (#28)
The needle is a OCEMR and the clip on the third groove from the bottom (#23)

These carbs are really well made, I'm happy with my purchase, I just hope they run well.

Hope this helps.

Jean

PS post your settings, it could help me or someone else.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Thu Mar 06, 2008 4:24 am    Post subject: Reply with quote

Thanks Jean, that's very helpful!

I predict you will love the FCRs. I have them on two bikes. I put them on a Ducati 900SS and they TRANSFORMED the bike. No basis for comparison on the Commando as I put them on before ever getting the bike to run, but I like them a lot.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Sat Mar 08, 2008 11:32 am    Post subject: Reply with quote

Well, I can confirm I have the same needle and clip position. I just raised the clips to the middle position, fourth from the bottom instead of third. Hopefully that will cure my richness problem - 'cause it sure is a PITA getting these carbs on and off, the fit is VERY tight. I find I need disconnect the intake runners from the head and leave attached to the carbs. Still have to do a bit of maneuvering, but it works. Good luck and thanks again. - BrianK
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ntst8



Joined: 14 Feb 2004
Posts: 114
Location: New Zealand

PostPosted: Sun Mar 30, 2008 1:11 am    Post subject: Reply with quote

Brian

i would be interested to know whether changing the clip position did the trick.
I have just fitted a pair of FCR's to my 850 i/state so any feedback on successful set up would be great.

I have only done a couple of short runs so far (todays run would have been much longer if a broken spoke hadn't caused a puncture Crying or Very sad) but very impressed, mind you my old Amals were well knackered.

I have found everything to fit space wise except i had to drill out the rivets on the bracket the throttle cable adjusters mount to and refit it one hole lower on the mount. Otherwise the tank would rest on the bracket.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Sun Mar 30, 2008 6:30 am    Post subject: Reply with quote

I was out yesterday for a good run, although the temperature was in the mid 30s. I don't notice ANY difference in performance. No popping on decel ("the overrun," for you Brits!). But I figure it'll need 4-500 miles before I pull the plugs to check those. I'll report back.

If it wasn't such a PITA, I'd drop the needles another notch right away and see how that works. But it's enough work to not want to do it more times than I need to (although generally I believe in going to the "just a tad too lean" stage and then backing off one setting).
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ntst8



Joined: 14 Feb 2004
Posts: 114
Location: New Zealand

PostPosted: Sat May 10, 2008 7:08 pm    Post subject: Reply with quote

After my broken spoke i decided to get the wheels relaced with stainless spokes, hubs polished, very nice now that all is back together. So finally back on the road today and wonderful autumn day on nice twisty roads - until i ran out of petrol about 10 miles from home.
I have the large Interstate tank and ran out at 180 miles which means under 35 (UK)mpg!!!
I haven't played with the Carb set up yet, and have a couple of other issues to deal with which may be affecting things, but if that is anywhere near typical these sure are thirsty little suckers.
Would be interested to know what mileage others are getting.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Sun May 11, 2008 1:50 pm    Post subject: Reply with quote

I had been getting about 35 MPG with the FCRs. They were waayyy rich. I have now raised the needle clips THREE positions, to slot 2 (they were in slot 5 when I got them). Haven't been far, but they still don't "feel" too lean. I will check plugs in a few hundred miles and report back.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Wed May 21, 2008 2:36 pm    Post subject: Reply with quote

Progress report:

As mentioned, I've raised the needle clips (lowered the needles) THREE slots. Just pulled the plugs - maybe a slight improvement, MAYBE. But still sooty black.

This is just riding normally, coming home, letting it cool, and pulling the plugs. Not plug chops.

I'm at slot one - no more needle adjustments left. So I think I will get some 145 mains and try those next. Once you get past that, I've got tons of Keihin jets so I'm on easy street.... yeah, right! But for labor and hair-pulling.

To be continued.

Jean, how you doing with yours?

Thanks - Brian

PS, wonder if I should play with the pilot screws a bit too? Is that a gas screw, meaning screwing it IN makes it leaner? Still, one turn out seems "in the range" - maybe I have to go with smaller slow jets?

Comments from the peanut gallery and beyond are welcome. - B
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Wed May 21, 2008 2:37 pm    Post subject: Reply with quote

Oh, and PPS - I'm getting 34-36 MPG around town - and I'm talking 40 MPH roads for the most part; yes, occasional stop signs and lights, but not Manhattan traffic fer cryin' out loud....
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Thu May 22, 2008 6:49 am    Post subject: Reply with quote

Got me wondering. The FCRs really like the idle turned up to start. Once it catches, you can just about immediately turn it down a bit, then more once it warms.

I wonder if this may indicate that I need a bit more air (via slow air screw) or less fuel (via slow jet or slow air screw)? I'd like to do something about my sooty plugs!
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Ron L



Joined: 27 Feb 2004
Posts: 1030
Location: Ohio

PostPosted: Thu May 22, 2008 9:20 am    Post subject: Reply with quote

Quote:
The FCRs really like the idle turned up to start. Once it catches, you can just about immediately turn it down a bit


I think it has more to do with the lack of choke or enrichener circuits.

Since the FCR's are pumpers, what starting procedure are you using? On my 900SS bevel (kickstart) with 40mm Dellorto pumpers, it likes a couple twists of the grip to shoot some raw fuel to start. The 900SS SP (electric with fuel pump) with the 41mm FCR's prefers I don't touch the grip when it is cold. It will fire and idle and once it has begun to warm (1-2 minutes) I can blip the throttle. If I twist it before starting, it will wet foul one or both plugs.
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BrianK



Joined: 14 Jun 2007
Posts: 314
Location: Boston, MA USA

PostPosted: Thu May 22, 2008 9:28 am    Post subject: Reply with quote

Hi Ron. I have FCRs on both a 900SS CR and my Norton. On both bikes, I use the accel pumps for cold starts and crack the throttle a bit, no accel pump, for warm starts. But both like the idle turned up a bit first. The Norton seems especially sensitive to this.
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The Unapproachable Norton Commando

At the end of 1967 the Norton Commando was announced.

The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.

It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.

Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.

It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.

The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.