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stupid questions about carbs

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WTF does FCR mean?  i've been searching but all i get is flat-cr.  ok...what does CR mean?  is fcr a type of carb, a brand, a model of a certain brand?  does company A, B, and C all make a FCR carbs, or just company A and FCR is just one of the models?  i'm ready to order one for my drz-sm, but i'm having a hard time differentiating them online.  i looked real quick at the TT online store which brings up my questions.

power delivery: i see videos of people pulling awesome wheelies with these carbs.  is power delivery really that snappy?  i saw a few where the guys are rolling on the throttle pretty good and the front wheel keeps coming up.  one of the things i love about this bike is i am able to hammer the throttle thru the turns and not have to worry about being spit off (within reason of course).

 

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first their were CR series carbs ( carb-racing)  , then a flat slide version FCR        my guess anyway? had 29mm CRs on a bike

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FCR is a great upgrade for throttle response. Does not increase horsepower, just intake. Jet it right and you can accelerate faster. No waiting for engine vacuum to lift the slide, and the accelerator pump give a squirt of gas. Cracking the throttle won't buck you off. And wheelies can be done fine with the stock carb. If anything, the FCR is more difficult to wheelie with, due to it being more sensitive.

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FCR is a model series of the Keihin Carburetor Company. The initials FCR seems to mean Flat slide CR racing type.  The Keihin carb company is largely owed by Honda and Honda has long used the initials CR for any special racing hardware, carburetors and other items.

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The bike still needs are few more modifications to run as the Suzuki engineers originally designed. The 39mm Keihin FCR was on the original DRZ.

Yes the power will be much snappier, especially off the bottom end but it's not going to make it unmanageable.

 

The Keihin FCR carburators come in different sizes and multiply different configurations and versions. There are also some companies on the web selling worn out carburetors for around half of what of what you should expect to pay. TT is a good source to buy from. Frank's MX Parts, Sudco, Jets R US are a few others. Any site with Keihin in the name should be avoided. As I mentioned above, these sites put on a facade of being affiliated with the manufacturer but in reality, the carbs are coming from a PO Box in the out skirts of Detroit.

 

 

 

 

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23 hours ago, HansLanda said:

FCR is a great upgrade for throttle response. Does not increase horsepower, just intake. Jet it right and you can accelerate faster. No waiting for engine vacuum to lift the slide, and the accelerator pump give a squirt of gas. Cracking the throttle won't buck you off. And wheelies can be done fine with the stock carb. If anything, the FCR is more difficult to wheelie with, due to it being more sensitive.

When you say sensitive, do you mean more herky jerky on/off the throttle? My buddy has a KTM superduke 990 and I hate that bike. The throttle is not smooth at all.

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When you say sensitive, do you mean more herky jerky on/off the throttle? My buddy has a KTM superduke 990 and I hate that bike. The throttle is not smooth at all.

No the power of the DRZ does not match that of a SuperDuke. The throttle is not going to buck you out of seat, but it will let you accelerate faster than stock CV.

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3 minutes ago, HansLanda said:


No the power of the DRZ does not match that of a SuperDuke. The throttle is not going to buck you out of seat, but it will let you accelerate faster than stock CV.

On the superduke, the bike is manageable, it's just not smooth on the throttle. I feel like a newbie when I ride it cuz it's always lurching. I would say it's very sensitive.

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10 hours ago, ptgarcia said:

Actually, think it means constant velocity.

I've heard both. I like vacuum because it gives a little better picture of how it works.

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Someone correct me if I'm wrong. So carburetors there are basically only 2 types right? Slide Carburetors and CV Carbs. And the Slide Carbs can be further subdivided in to Flat,Round and D Slides?

Just some trivia I've been wanting to know about for a long time.

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CV carbs also have various throttle valve slide shapes.  Although rarely used on motorcycles, butterfly throttle valve carbs were the most common on cars when cars used carbs.  And virtually all fuel injection throttle bodies use butterfly throttle valves.

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Someone correct me if I'm wrong. So carburetors there are basically only 2 types right? Slide Carburetors and CV Carbs. And the Slide Carbs can be further subdivided in to Flat,Round and D Slides?

Just some trivia I've been wanting to know about for a long time.

 

Well then you have the Lectron and Edelbrock carburetors that don't have pilot, or main jet circuits, everything is off the needle or "metering rod". Technically they are "slide" but so unconventional they should be considered their own "type" as well.

 

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You can add Smart Carb brand to the metering rod list.  I really do not see them as very unconventional.  They do have low speed, medium speed, and high sped metering systems, they just do it all with the metering rod.  Lectron has additional low speed adjustment with an air bleed and high speed with a power jet.  Depending on who you talk to, Lectron, Smart Carb and Edelbrock are the best or the worst.  The way I look at it - why would I want a carb with such a limited method of adjustment.

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This is a carb pair out of my Honda Shadow 750 V-twin...it has a butterfly valve and vacuum chamber to lift the slide and needle. Honda manual calls it a CV (constant velocity) carb.

Much different than the round slide carbs in my old 2strokes or the FCRs on my more modern 4strokes. It seems like a more complex, larger and more expensive way to lift the slide and needle...why do it this way?IMG_2438.jpg.1be8b8f86a9efa385cc975ca471aac9a.jpgIMG_2439.jpg.42a3ec24598b914a8375bd73a9b25157.jpgIMG_2440.jpg.26382054f082f007303433cc88e0ddfb.jpg

 

 

 

 

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Why do it?  Because it takes some of the rider control away so the rider can not advance the throttle too quickly and cause a bog.  The rider controls the butterfly throttle valve and the engine responds to what amount of slide height it can use at that moment.  As rpm builds, the vacuum controlled slid raises to meet the demand but no too quickly. If you ever rode a big single with a big slide type carb and no accelerator pump, you know what I'm talking about.  Think Amal GP on a Norton 500 single. Riding required more rider input for throttle control.  It basically makes riding more user friendly.

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Ok...thx...was just wondering...I can feel the delay if I roll on the throttle quickly...but, rolled on slowly, feels fine.
I had been learning to work on dirt bike carbs last several years with the slides attached to the throttle cable...just took this one apart to clean and rejet....CV carb config was new to me.

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