Kehien CR smoothbore review

After an update from folk who have fitted these carbs. What do you think? How have the performed compared to premiers? I picked premiers as a baseline as it seemed like a logical starting point.
Am tossing up between cr's and fcr's but would like to have some user feedback first.
I'm running FA head w/beehives on an otherwise stock 850 block and barrels.

Thanks in advance
DKT

just fitting a set (CR33mm) to my current build, engine not started yet but some notes.
sourcing suitable manifolds can be a problem so I made my own. my carbs sit horizontal and am using the standard air box narrowed to use RGM narrow filter element
its likely you will have to change the cable pull setup so it clears the tank. I'm using an alloy tank and dont have to modify fortunately.
the throttle return spring is to strong. I cut about 1/3rd of one coil off.

Thanks madass for the feedback. Am keen to hear your review after a few miles on the board too!!!

I've ran CRs on a 988cc BSA triple and they were great.

The FCR is a far better instrument though. They are one of the best mc carbs available, as demonstrated by many a race team today.

Also important for a Commando is their easy availability, cw with top quality manifolds etc so you can buy them as proper 'out of the box - fit and forget' kit.

I have FCRs on my commando, I have never tried anything else back to back with the bike in the same spec so have nothing to compare, but am very happy with their performance, usability and fabulous quality.

The 33mm CRs on my 920 have only been on for 1500 miles but I like them a lot. The bike starts easily from cold by lifting the choke lever fully & opening the throttle a little. This took a while to figure out, as this type of choke setup doesn't usually require throttle. As soon as the motor fires the throttle can be released & fast idle controlled with the choke lever.
When the bike is warm it always starts first kick with no throttle. The idle is always perfect & after the tweaking session on the dyno. it pulls like a train. I had to make a central throttle drum because the standard setup wouldn't fit with the Interstate tank. I understand Jim is doing this to the CRs he sells.
That said, with the 32mm MK1 Concentrics it was much the same, although I didn't dyno. it when they were fitted. In my humble opinion Concentrics are very good carburetters. Sadly they are (were) made out of the wrong materials, largely down to the accountants at AMC/Triumph-BSA etc. This is now being addressed by Burlen & the latest 600 series bodies are cast in aluminium alloy. I believe the 900s will follow soon.
So, should you buy a set for your pride & joy? Go on, you only live once.
To this I should add, on the advice of Neil Beadling, I am about to fit a set to my 930 O.I.F Trident so you could say I like them a lot.

Martyn.

Thanks martyn and Eddie. Great to hear your views

I am running the Kehien's on my 71 750 the head was done by Jim Comstock and it has a web cycle cam...otherwise a stock motor,manifolds as supplied by Matt @ CNW, I had Barnett build me a set of braided steel cables...these carbs really woke up the performance of my bike,since I first did the install Matt has made available a slick set of manifolds to compliment the already improved performance, only one small install glitch ... the throttle cam is very very close to the petcock,required some shimming of the fuel tank...not a big deal,these carbs with their accelerator pumps really hit hard when I nail the throttle,they are also really well mannered in traffic,cold start ....no problem...holds a consistent idle....and they make a very cool "rattling noise" kind of like a ducati dry clutch but not as loud,I love this modification and am glad I spent the dough to convert my bike to this set up,good to go right out of the box too...once the "pull/pull" cables are asjusted its really a set...and forget deal,the small cone style K&N filters fit nice too.I would definatly do it again.Worth every penny....they aint cheap !!

I just got these photos from someone who installed CRS carbs. I'm posting them because someone asked for photos of mounted CRS carbs in a previous thread. Some special parts and fasteners are required so everything clears OK.

my setup with my one off manifolds cable/linkages clear my alloy tank.

madass140 said:

my setup with my one off manifolds cable/linkages clear my alloy tank.

Click to expand...

Excellent
Please show a photo of the left side - especially clearance at top rear. Dzus fastener location and the 4 bracket bolts near the frame web etc.

Jim there is 1/2" gap between rear of carb top and frame plate gusset.
I didnt have a dzus pin in stock to install and if I did I think it would be hard to turn , the "D" shaped wire handle would likely foul on the carb.
I fitted a fixed bolt and my sidecover bracket without Dzus spring clip just pops over the end of the bolt, not really good setup for production sales.
with shortening the manifolds I could probably get the carbs forward another 1/4".
I'm happy with my one off setup as everything has clearance including the throttle stop and cable, using basically the stock air filter (shortened)

Do the cr's have an accelerator pump?

madass140 said:

Jim there is 1/2" gap between rear of carb top and frame plate gusset.
I didnt have a dzus pin in stock to install and if I did I think it would be hard to turn , the "D" shaped wire handle would likely foul on the carb.
I fitted a fixed bolt and my sidecover bracket without Dzus spring clip just pops over the end of the bolt, not really good setup for production sales.
with shortening the manifolds I could probably get the carbs forward another 1/4".
I'm happy with my one off setup as everything has clearance including the throttle stop and cable, using basically the stock air filter (shortened)

Click to expand...

I seriously doubt that this would work with a dzus. I can barely get at the D with the Amal/K&R 0990 combo.

"I seriously doubt that this would work with a dzus. I can barely get at the D with the Amal/K&R 0990 combo.

I agree, but for my personal bike it dont matter, for those who want to sell the setup as a kit then a modification will probably have to be made.

madass140 said:

"I seriously doubt that this would work with a dzus. I can barely get at the D with the Amal/K&R 0990 combo.

I agree, but for my personal bike it dont matter, for those who want to sell the setup as a kit then a modification will probably have to be made.

Click to expand...

Could the dzus D ring be replaced with a rod or handle that extends to an area that would be accessible, turnable and workable?

"Could the dzus D ring be replaced with a rod or handle that extends to an area that would be accessible"

That was exactly my original thought, I dont think the Dzus needs to turn 90 degrees to function so it may work.
I just checked the Dzus on my stock 750 bike , I reckon it would work on the CR fitted bike but you would not be able to
fold the "D" handle all the way out, probably only 45 degrees .
In a week or two I'll fit the Dzus from my stock bike and see how it goes, I think it should be ok and not much more difficult to use then on a
Amal carb'd bike which is still a pain with the tank on. better order another Dzus.

madass140 said:

"Could the dzus D ring be replaced with a rod or handle that extends to an area that would be accessible"

That was exactly my original thought, I dont think the Dzus needs to turn 90 degrees to function so it may work.
I just checked the Dzus on my stock 750 bike , I reckon it would work on the CR fitted bike but you would not be able to
fold the "D" handle all the way out, probably only 45 degrees .
In a week or two I'll fit the Dzus from my stock bike and see how it goes, I think it should be ok and not much more difficult to use then on a
Amal carb'd bike which is still a pain with the tank on. better order another Dzus.

Click to expand...

Yes - Please keep me updated. I'll be ordering a Dzus as well and looking at swapping out the D ring for another way to grab and turn it.

Here's my idea to replace the left side cover Dzus fastener D ring with a stout wire. The wire inserts into the original hole in the Dzus fastener (try to pry it out the D ring without ruining it so you can re-use it if necessary). Red loctite fixes the 3/32" wire securely in the hole.



For this to work the hole for the wire in the Dzus fastener would have to line up correctly and the wire would need to be able to rotate the Dzus fastener without interference so that it locks in place. It may be necessary to cut off the 2 outer holes of the rear carburetor bracket to get clearance for the 3/32" wire. The other bracket in front is unchanged, it aligns and holds the carbs securely. I noticed that Matchless has done this (see photo below).



I'd appreciate some feedback from anyone who tries this on a Commando.

Jim,

Wrong photo!

Martyn.

Matchless said:

Jim,

Wrong photo!

Martyn.

Click to expand...

This is the correct photo of the CRS carbs on Martyns bike. (I hope that's what you meant Martyn). If you look closely you can see the the rear bracket is cut and the two outer bolts are removed.



Thats where I got the idea and you can see it in the photo above in the previous post. I think the bracket would have to be cut so you could access the Dzus fastener and replace the D ring with a short rod. Matchless has gotten rid of the Dzus fastener all together and uses pins that plug into rubber grommets.