Triumph Rat Motorcycle Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter #1
Recently spent the weekend upgrading my 2005 Thruxton with the CR 35's. After reading up on them and discussing this upgrade with a couple of vendors without a clue, I finally contacted Mike from Bella Corse (http://bellacorse.com). He was knowledgeable and said he would guide me through the upgrade and infamous tuning. And so he did. Got the carbs and was soon on the phone with Mike with one question after another. Even on a Sunday he picked up... gave me valuable pointers on fitment and tuning, and offered some free jets as well!
Bike runs and sounds fantastic, and I'm very pleased.
Shocks are next.
Here's short clip

https://www.dropbox.com/s/2dwjio3fduybe1p/New Carbs e.mov?dl=0

http://https://www.dropbox.com/s/2dwjio3fduybe1p/New%20Carbs%20e.mov?dl=0


Carpalmer
 

·
Registered
Joined
·
1,541 Posts
After a few days riding it would be great to have a report. Pros and cons, performance, fuel mileage, etc. It's good to hear everything is going good so far. Everybody likes a positive report.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #3
Keihin CR 35 Carburetor set up and tuning

Hi rweb.
Here's some tech data: Keihins CR 35's were set up with #58 pilot (slow) jet, #125 main jet with #2 needle clip position. After tweaking the air screw to get good response revving up and down, settled on just a 1/2 a turn out. Ideally should be at 1-1.5 turns out (according to Mike and others), so I got the next size up pilot jet #60. With this change air screw is set at 3/4 turns out. The bigger the pilot jet (more fuel) the more the air screw (oxygen) needs to be open to maintain the right lean / rich mixture.
As far as performance, the bike certainly pulls more. I have had 2 instances where it's bogged down on me as I was taking off aggressively from a standing start. Has not happened again. Not sure if the bigger pilot helped, or I've toned down my throttling... will explore this further in the next weeks.
Does anyone have any advise / comments on this?

Fitment was straight forward once Mike advised me to keep the spacers on the original carbs. I purchased the billet manifolds from Bella Corse, but without the original spacers there was some rubbing / locking issues with the throttle mechanism. By using the spacers the carbs were pushed further back, and fit was PERFECT.

BTW, starting not a problem, but pls note I live in south Florida.

cheers!

Carpalmer
 

·
Registered
Joined
·
607 Posts
The stock Keihins have vacuum controlled slides that prevent the rider from “loading up” the engine at lower RPMs with too much throttle.
CR’s and FCR’s do not have this feature. With them, your throttle movement translates directly to rising of the slides.
You grab a fist full of WOT at low RPM and the CR’s will open up and dump too much mixture into the engine and cause it to bog down.
CR’s require throttle discipline on the part of the rider. Normally no WOT below 2500 RPM or so to prevent bogging.
 

·
Registered
Joined
·
473 Posts
Do you have the airbox still fitted ?
 

·
Registered
Joined
·
203 Posts
Carpalmer,

I've had the CR's on my 01 Bonnie for two years now. Set up is 60 pilots, 1 turn out, #2 needle clip position and 130 mains. Air box removed (DIY), Procom igniter, Norman Hyde pipes. Like you, I have had this bogging down on aggressive pull away from a stop. This has also hampered me a bit on getting an accurate dyno run, because the bike chokes. But it is much more responsive is most every other way (except of course fuel economy, which is typically around 34 mpg) and with the NH pipes and airbox removal, Bonnie makes her presence known!

George in VA
 

·
Registered
Joined
·
473 Posts
I have 120 mains but still with airbox (gutted) (60 pilots needle on 4th, airscrew 1 1/2 turns out)
I can't say I get the lean bog
Mine were second hand and the previous owner did warn me about the lean bog but he had pod filters too

Maybe an airbox helps out or I'm pretty limp wristed LOL
 

·
Registered
Joined
·
1,363 Posts
Correct, CR-II's do not have accelerator pumps, so you need to 'roll-on' the throttle. You can still get a hard launch, you just need to work on throttle control.

Thanks for the shout-out CP.

/M
 
1 - 12 of 12 Posts
Top