Kehien CR smoothbore review

Jim, I fitted the Dzus unmodified and its ok with my carbs horizontal, the head of the Dzus is about 7-8mm away from the carb top.
I cut off the end of the alloy carb bracket also, the standard Dzus works for my setup.
I just gave my new build its first kick (I mean Alton kick) I only ran the engine for 5 min, I want to retension the head.
My carb settings are
30 slides
120 main
68 pilot
main air jet 200
needle yy7 middle notch
motor is:my billet steel rods balanced 65%
Dunstall 810
560-00 cam
stock head with beehive springs
I dont have Dyno access so its gonna be old school tuning which is fine by me.
Have you any advice regarding carb settings for the 33's
my above carb settings are what Martyn advised me to start with.
my biggest problem it takes me about 2-3 months to get the carb parts shipped here and anything else for that matter
so tuning is gonna take some time.
Don

madass140 said:

Jim, I fitted the Dzus unmodified and its ok with my carbs horizontal, the head of the Dzus is about 7-8mm away from the carb top.
I cut off the end of the alloy carb bracket also, the standard Dzus works for my setup.
I just gave my new build its first kick (I mean Alton kick) I only ran the engine for 5 min, I want to retension the head.
My carb settings are
30 slides
120 main
68 pilot
main air jet 200
needle yy7 middle notch
motor is:my billet steel rods balanced 65%
Dunstall 810
560-00 cam
stock head with beehive springs
I dont have Dyno access so its gonna be old school tuning which is fine by me.
Have you any advice regarding carb settings for the 33's
my above carb settings are what Martyn advised me to start with.
my biggest problem it takes me about 2-3 months to get the carb parts shipped here and anything else for that matter
so tuning is gonna take some time.
Don

Click to expand...

Below is what I have so far on the jetting but I don't have a lot of custom feedback yet. I have perfect plug color with the settings below but one of my customers seems to be running lean. Another customer has perfect plug color or richer with the same settings. The variable here is the YY7 needles and the 200 air jets. Both of those settings you are using would make it richer than my settings and my settings originally came from Martyn. My question is why did Martyn recommend the richer 200 air jet and YY7 needles to you? Are the richer jettings an improvement? I'm thinking that they could be richer. I just mounted on another set to test and will be going through needles and air jets the next few days.

JS current CRS 33 settings are:
120 mains
YY8 needles with clip at bottom or 2nd from bottom. I have not tried YY7s yet.
68 pilots (idle jets)
230 slow air jets (main air jet) These could be smaller as suggested by Martyn - I'll be testing them.
Float height 14mm
the throttle slides are 3.0
slide gap approx .020” at bottom
idles screws approx 1 turn
#40 starter jets

My manifolds do not drop down as far as yours so the Dzus clearance is a little different and I think I will be sending out a replacement Dzus handle with the carb kits.

Plug color below is what I'm getting on my test bike with the jetting above.

Any sign of the carb kits yet Jim.
JUG

jug said:

Any sign of the carb kits yet Jim.
JUG

Click to expand...

I'm told the 33s are on their way to the warehouse but I still have to wait. I have the 31s in stock and I'm running them on my test bike now.

Jim , I reset the 33's to what you said only difference is I'm using 200 slow air jet (main air jet), #50 starter jets which I dont think matters a lot, and
1/2 turn out on the air screws, YY8 needle 2nd notch from the bottom.
I could probably lift the needle one notch and or increase the slow jet size.
doesnt seem to be running to bad at this setting, be a while before I can do some serious road testing
Thanks Jim

madass140 said:

Jim , I reset the 33's to what you said only difference is I'm using 200 slow air jet (main air jet), #50 starter jets which I dont think matters a lot, and
1/2 turn out on the air screws, YY8 needle 2nd notch from the bottom.
I could probably lift the needle one notch and or increase the slow jet size.
doesnt seem to be running to bad at this setting, be a while before I can do some serious road testing
Thanks Jim

Click to expand...

EDITED
The #50 starter jets only control the choke which can be over rich. I settled on #40 starter jets because #35 will race the motor to high with the choke on.

YY9 needles can be too lean (smaller number = richer) . I tried the YY7s at the richest setting and they still have good color. You have to change two needle numbers to give you appox one needle notch difference in mixture ratio.

The air jets control 3/4 to wide open - same as the main jet. These are on the bell mouth and you can swap them out without disassembling the carb - very convenient for racers.

I made some tests today. Changing the idle jet and/or the air jet doesn't seem to have any effect on the roll on/mid range. I though it would have some effect on the overall mixture - but very little if any.

The needle position and changing the needle number have the greatest effect on roll on/mid range. YY9 needles set with the clip 1/2 way up can starve for fuel when dumping on the throttle too quick. Going to YY8s and raising the needle fixes that. YY7s are still fine and YY6s should also be good. I'm leaning toward the YY7s. Something nice about these carbs is that you can give it a lot of throttle at low RPM without loading up.

The idle is excellent with these carbs and mid range precision feels like fuel injection.