Triumphrat

asphyx9 · 04-09-2005

Has anyone installed the Keihin CR-2 Racing Carbs on their Thruxton? And if so, what types of gains did you get? Are there any disadvantages to getting racing carbs?

I am in the process of determining an upgrade path for my '05 Thruxton (Performance-based), and the CR-2 carbs at BellaCorse are not terribly high priced (and they retain the stock airbox, whereas Flatslides will need new manifolds and an airbox kit).

dialysis · 04-09-2005

i'm curious too but i think most here have followed the AI, NARK, pipe route. aurally wonderful and puts a zip to the thrux.

RaceDweeb · 04-12-2005

For the life of me, I can not understand why the people I sell CR-II kits to typically don't participate on discussion forums. Pity too as the feedback I've been getting has been very positive. I think I've got the jetting dialed-in.

Hey L.I. in Chicago... I know you're out there. You've got CRs on your Thruxton. Tell everyone else what you've been telling me.

asphyx9 · 04-12-2005

Quote:

On 2005-04-12 17:57, RaceDweeb wrote:
For the life of me, I can not understand why the people I sell CR-II kits to typically don't participate on discussion forums. Pity too as the feedback I've been getting has been very positive. I think I've got the jetting dialed-in.

Hey L.I. in Chicago... I know you're out there. You've got CRs on your Thruxton. Tell everyone else what you've been telling me.

Thanks for the message. I definitely would like to hear from someone who has these carbs installed. I almost think that I will get a ton more power from these carbs with the stock airbox and pipes than just the pipes and an airbox (NARK) type of kit. And for the low price (Mikunis are $1,395 I believe) they sound like a great upgrade for the price.

A couple of my friends (riding a Duc Monster and an Aprilia Falco) have suggested to me that the race carb route will yield more extraordinary gains (my friend on the Duc is running Mikuni Flatslides - different bike, but has upgraded carbs and stock airbox) than pipes and intake upgrades alone. I am actually planning an retaining the stock airbox, adding aftermarket pipes, and the race carbs.

So are these carbs pretty much a straight bolt on right? Would they work well even if I plan to retain the stock pipe configuration?

[ This message was edited by: asphyx9 on 2005-04-12 20:32 ]

asphyx9 · 04-12-2005

Quote:

On 2005-04-12 17:57, RaceDweeb wrote:
For the life of me, I can not understand why the people I sell CR-II kits to typically don't participate on discussion forums. Pity too as the feedback I've been getting has been very positive. I think I've got the jetting dialed-in.

Hey L.I. in Chicago... I know you're out there. You've got CRs on your Thruxton. Tell everyone else what you've been telling me.

Thanks for the message. I definitely would like to hear from someone who has these carbs installed. I almost think that I will get a ton more power from these carbs with the stock airbox and pipes than just the pipes and an airbox (NARK) type of kit. And for the low price (Mikunis are $1,395 I believe) they sound like a great upgrade for the price.

A couple of my friends (riding a Duc Monster and an Aprilia Falco) have suggested to me that the race carb route will yield more extraordinary gains (my friend on the Duc is running Mikuni Flatslides - different bike, but has upgraded carbs and stock airbox) than pipes and intake upgrades alone. I am actually planning an retaining the stock airbox, adding aftermarket pipes, and the race carbs.

So are these carbs pretty much a straight bolt on right? Would they work well even if I plan to retain the stock pipe configuration?

[ This message was edited by: asphyx9 on 2005-04-12 20:32 ]

04-13-2005

Well, Race Dweeb, thanks for flushing me out of my "lurking mode". I am a recent entry into the Thruxton (more smiles per mile) Club. Details follow:
2005 Thruxton
- immediate removal of A.I. (prior to leaving dealership)
-air box removal kit
-billet intake manifolds
-Predator exhaust
-Mazda fuel cap, etc. for looks
-Hagon shocks for stability and comfort
-British Customs Clip-on replacement kit (I grew to enjoy the original bars solo, however, with a passenger in hard braking & sharp turning,which always seem to go together :wink: , the weight transfer and loading on my arms interfered with safe/stable steering. The new bars allow more comfort and confidence for rider AND passenger!)
-other doo-dads and braces, bar-end mirrors
-and finally...the Cr-II carbs.

The carbs are a relatively simple installation with minor clearance issues relative to the fuel petcock. After various permutations I finally just inserted some spacers on the rear tank mountings and used some longer tank mounting bolts.
These are very direct effect carbs....mechanical linkage to slides means you roll on throttle = you GO, roll off throttle = engine braking/deceleration. You have more precise control, but it requires some adjustment from the more forgiving stock carbs. I tried these with the stock intake manifolds AND the billet intake manifolds. After various permutations (+/- spacer,+/- polishing stock manifolds,etc ) the bottom line is that the billet manifolds are superior if you jet accordingly (they flow more air, thus require more fuel). The Cr-II carbs start flawlessly, require very little warm up time, and rarely the choke (40 degree riding days). With proper jetting, needle, and air screw adjustment (60 low speed jet, 120 main, 1-1/2 turns out air screw, 2nd slot from top on needle-Many thanks Mike!) this Thruxton makes me SMILE! I get respectable pull from low range, a very sweet, but sane, rush through the entire mid range, and a nice top end to boot. I weigh 270 lbs (123 kgs) and can top 110 mph indicated (~100 mph actual) without pushing the motor beyond a roar and into a scream. On a run through the gears with full throttle acceleration (never exceeding 6500-7000 rpm) on my favorite countryside acceleration/exhiliration stretch, slightly uphill with a knoll at the crest, I pulled the front wheel off of the ground at 110 indicated at the crest with enough top end pull left over to make this old man plenty happy with the entire package! The SOUND is a wonderful sensation which takes me back to 1960's growing up around flat track racing with Bonnevilles and BSA's. By analogy this sounds like a Big Block Chevy with dual exhaust in comparison to a high revving modern sports car (think crotch- rockets) or a diesel ( think Harley). My wife and daughters are so thrilled with the bike that I rarely take the time to put on the plastic rear seat section cover. :wink:
Well, this is getting long. In summary, I am very pleased with the CR-II carbs IN COMBINATION with the rest of the performance package. You have to let them breathe! (reduce intake/exhaust restrictions).
Mike at BellaCorse has been very helpful (as are most of the vendors associated with this Forum) and has handled all transactions professionally. Thanks for your patience. I hope my response is helpful to those who are considering upgrading their Triumph.

[ This message was edited by: Allthumbs on 2005-04-13 08:48 ]

04-13-2005

Well, Race Dweeb, thanks for flushing me out of my "lurking mode". I am a recent entry into the Thruxton (more smiles per mile) Club. Details follow:
2005 Thruxton
- immediate removal of A.I. (prior to leaving dealership)
-air box removal kit
-billet intake manifolds
-Predator exhaust
-Mazda fuel cap, etc. for looks
-Hagon shocks for stability and comfort
-British Customs Clip-on replacement kit (I grew to enjoy the original bars solo, however, with a passenger in hard braking & sharp turning,which always seem to go together :wink: , the weight transfer and loading on my arms interfered with safe/stable steering. The new bars allow more comfort and confidence for rider AND passenger!)
-other doo-dads and braces, bar-end mirrors
-and finally...the Cr-II carbs.

The carbs are a relatively simple installation with minor clearance issues relative to the fuel petcock. After various permutations I finally just inserted some spacers on the rear tank mountings and used some longer tank mounting bolts.
These are very direct effect carbs....mechanical linkage to slides means you roll on throttle = you GO, roll off throttle = engine braking/deceleration. You have more precise control, but it requires some adjustment from the more forgiving stock carbs. I tried these with the stock intake manifolds AND the billet intake manifolds. After various permutations (+/- spacer,+/- polishing stock manifolds,etc ) the bottom line is that the billet manifolds are superior if you jet accordingly (they flow more air, thus require more fuel). The Cr-II carbs start flawlessly, require very little warm up time, and rarely the choke (40 degree riding days). With proper jetting, needle, and air screw adjustment (60 low speed jet, 120 main, 1-1/2 turns out air screw, 2nd slot from top on needle-Many thanks Mike!) this Thruxton makes me SMILE! I get respectable pull from low range, a very sweet, but sane, rush through the entire mid range, and a nice top end to boot. I weigh 270 lbs (123 kgs) and can top 110 mph indicated (~100 mph actual) without pushing the motor beyond a roar and into a scream. On a run through the gears with full throttle acceleration (never exceeding 6500-7000 rpm) on my favorite countryside acceleration/exhiliration stretch, slightly uphill with a knoll at the crest, I pulled the front wheel off of the ground at 110 indicated at the crest with enough top end pull left over to make this old man plenty happy with the entire package! The SOUND is a wonderful sensation which takes me back to 1960's growing up around flat track racing with Bonnevilles and BSA's. By analogy this sounds like a Big Block Chevy with dual exhaust in comparison to a high revving modern sports car (think crotch- rockets) or a diesel ( think Harley). My wife and daughters are so thrilled with the bike that I rarely take the time to put on the plastic rear seat section cover. :wink:
Well, this is getting long. In summary, I am very pleased with the CR-II carbs IN COMBINATION with the rest of the performance package. You have to let them breathe! (reduce intake/exhaust restrictions).
Mike at BellaCorse has been very helpful (as are most of the vendors associated with this Forum) and has handled all transactions professionally. Thanks for your patience. I hope my response is helpful to those who are considering upgrading their Triumph.

[ This message was edited by: Allthumbs on 2005-04-13 08:48 ]

asphyx9 · 04-13-2005

Wow, pulling the front tire off the ground? That is the type of high end power that I am definitely looking for.

Thanks for the detailed input about your set-up. Have you dyno'ed your set-up yet?

I do still plan on putting just the racing carbs in with my stock airbox and pipes, then I will work up from their (pipes, possibly airbox kit, billet manifolds, etc).

Mike at Bellacorse:

Can these carbs be sent to me jetted for stock airbox and pipes, or do you just jet them for non-stock pipes?

Thanks!

[ This message was edited by: asphyx9 on 2005-04-13 09:16 ]

asphyx9 · 04-13-2005

Wow, pulling the front tire off the ground? That is the type of high end power that I am definitely looking for.

Thanks for the detailed input about your set-up. Have you dyno'ed your set-up yet?

I do still plan on putting just the racing carbs in with my stock airbox and pipes, then I will work up from their (pipes, possibly airbox kit, billet manifolds, etc).

Mike at Bellacorse:

Can these carbs be sent to me jetted for stock airbox and pipes, or do you just jet them for non-stock pipes?

Thanks!

[ This message was edited by: asphyx9 on 2005-04-13 09:16 ]

04-13-2005

As a qualifier..I was coming over the crest of a small knoll when the wheel lofted...but it was still pulling hard and this would NOT have happened with stock performance. I have also experienced a bit of clutch slippage (time for stronger springs-thanks Mike) from the higher power output and it will pull the front end up (but not like a modern powerbike) if you snap it from a slow rolling start. I have not dyno tested, but repeated runs through familiar roads comparing performance with the upgrades definitely supports my conclusion that you get a favorable return on your performance investment.

If I were to take the upgrades one step at a time I would start with an aftermarket exhaust (Predators work for me) combined with stock airbox modification (snorkel removal, drilling, upgraded filter, etc. as covered by other posts) and appropriate jetting changes of stock carbs. I would next budget for the airbox removal kit and carbs/manifolds and install them all at the same time. None of these modifications are really that difficult mechanically, yet provide a lot of bang for your buck!

As an aside: I have had the bike for 1-1/2 months and have about 700 miles on it while battling the cold upper midwest weather. I ride for fun...I do not commute with a motorcycle. The concept of "gently breaking in" your motorcycle has never been valid in my personal experience. All of the motorcycles I grew up racing were immediately put on the race track (sometimes the day I got them

) and all of my "Adult" motorcycles were broken in with plenty of rev time up to the point just below where the engine starts to scream and flatten out. No long constant RPM stretches, and definitely no lugging the engine. In all that time I have never had disproportionately high mechanical problems, and have always ended up with motorcycles that others seem to think perform like they were built on an especially good day at the factory. I don't know if it has been luck/fate or there is something else to it. All I know is that my Dad was a great mechanic and race engine builder and this is what I was taught worked for him.