Keihin CRS smoothbore carbs for Norton

Status
Not open for further replies.
Has anyone tried the JS Motorsport CRS carb kit? Were you able to just install them and go? Or did they require constant adjustment? I have no carb skills at all. Right now I've got the original amals on my Commando 750 and I'd like to swap them out for reliability and some extra power.

Will a single CRS of FCR carb provide more power than the stock twin amals?

jseng1,

Do you have a complete kit for a single keihin carb?
 
I acquired my mk3 with a single mikuni and swapped it out for a pair of CRs from Jim.

It was a tight squeeze installing them, but they did fit without any modification. They came perfectly balanced and due to the way they're connected together, I don't think they'll go out of sync any time soon. Jetting was just about spot on - I think I moved the needle one slot, I don't remember.

I keep meaning to order the modified twist grip that Jim does now - I do find the pull a little on the heavy side.

The difference from the mikuni was night and day, especially mid range roll on and top end.
 
looking at my 2 x CRS carbed Commando, I dont think you will be able to fit a single CRS. the 2-1 manifold will be to long and the carb will foul the frame
at the back, you will probably have the same problem with a FCR, it may be worse for clearance.
Don
 
I have been using a pair of CR 33mm on my 920 for two years now. They are great carbs & the bike goes extremely well. The only problem I still have, is when shutting off for a corner & then opening the throttle there is a very brief dead spot, then the power comes in with a bang. This makes it a bit snatchy. I have not managed to sort this so I have another dyno session booked for January.

Martyn.
 
Sounds like richness to me Martyn, pilot or cut away? Might be difficult to iron out on a dyno too.
 
Matchless said:
I have been using a pair of CR 33mm on my 920 for two years now. They are great carbs & the bike goes extremely well. The only problem I still have, is when shutting off for a corner & then opening the throttle there is a very brief dead spot, then the power comes in with a bang. This makes it a bit snatchy. I have not managed to sort this so I have another dyno session booked for January.

Martyn.
Click to expand...

That's odd and I haven't experienced that problem with all my tests. I could be too rich as Nigel says.

Jetting I use:
120 mains
YY8 or YY7 needles clip usually about 2nd from bottom
68 pilots
230 slow air jets
Float height 14mm as set by factory
3.0 throttle slides
idle screw approx 1 turn

My CRS carb photos got moved and aren't showing in previous posts so here they are.

Keihin CRS smoothbore carbs for Norton


Keihin CRS smoothbore carbs for Norton
 
Nigel & Jim, thanks for the input. I agree that it seems like a richness problem. I have tried YY6, YY7, & YY8 needles in various clip positions all to no avail. The pilot jets seem fine judging by the idle screw position & perfect idle, so I suspect the slides could do with going up to 3.5 from 3.0. The only problem being the price of £60 each. I could of course mill the 3.0 slides to suit, but if that doesn't cure the problem I can't put the material back on. Next step is to borrow some before the dyno session.
Watch this space!
 
Check that the choke lifting arms are in correct alignment with the vertical choke shafts. I had a choke hanging up because of this on one of the sets I tested resulting in a rough idle. If out of line - loosen the pinch screw on the choke arm and move things around.
 
My friend Mic Ofield raced both Seeley and Rickman and he prefered the Rickman.
 
Status
Not open for further replies.

Similar threads

jseng1
Keihin CRS smoothbore compared to Keihin FCR flatslide
2
Replies
22
Views
753
maaseyracer
maaseyracer
jseng1
  • Locked
Best carbs for Nortons
2 3 4 5
Replies
97
Views
12,476
olympus
olympus
Back
Top