Racing Carbs

[XS11Newbie]

What is the advice from the wise men have about uprgrading my carbs to "racing carbs" for my 78 xs11E????

[DiverRay]

DON'T! You will lose the "driveability" of the bike. Racing carbs are built for wide open, or off. You can tune the carbs you have to let in as much air and fuel as the engine will take.
The only "upgrade" I would try is fuel injection, as it is more precise, and will allow you to get more MPG AND increase throttle response. JMHO, take it with a teaspoon of salt..

[BA80]

What is the advice from the wise men have about uprgrading my carbs to "racing carbs" for my 78 xs11E????

Do some searching on here. There are very few, if any, success stories about this type of "upgrade".

If you want to upgrade buy a newer bike.

[James England]

If you are referring to flatslide carbs, FCR, then it would be a very bad idea indeed and would, as mentioned by others, ruin your ride. Flatslides clack like you wouldn't believe, on tickover. If opened suddenly to WOT, they can cause an engine to stop, apparently.

I looked into these for my XJR and looked at keihin and mikuni. They all clack like castanets at tickover. Have a look on YouTube. A local race tuner who Dyno'd my bike told me that I personally (liking quiet engines) would be driven mad by the carbs. I took his word for it.

[XS11Newbie]

I truly appreciate the advice. I believe it will be in the best interest of the engine and the bike as a whole to not upgrade the carbs. This engine has enough performance and I think the juice isn't worth the squeeze in doing so. Again thank you for the expert advice as always!

[XS1100carbon]

keihin CR 39mm flatslides

Best upgrade to carbon I've done.These things woke the bike up.Lots of ney says on here about these carbs.I have a 1/2 turn throttle on her and when I grab a hand full it don't die that's for sure it flys.About the clacking sound I just don't hear it.Fuel just flows though them wheres the sound come from?How they ride I think is great.They are very expensive though.Throttle to air cleaners installed can run 2500.00.Told my mechanic about the ney says he told me no problem.He was right.They look like machines hooked to the head.I love them.

[TomB]

If you are referring to flatslide carbs, FCR, then it would be a very bad idea indeed and would, as mentioned by others, ruin your ride. Flatslides clack like you wouldn't believe, on tickover. If opened suddenly to WOT, they can cause an engine to stop, apparently.

I looked into these for my XJR and looked at keihin and mikuni. They all clack like castanets at tickover. Have a look on YouTube. A local race tuner who Dyno'd my bike told me that I personally (liking quiet engines) would be driven mad by the carbs. I took his word for it.

It kinda depends on whether they're diaphragm operated slides or cable to linked slides, most bikes engines with cable to slides will cut if the throttle is snapped open, regardless whether they're flat slides or round slides. Its the suddenness at which the slides can be snapped open that baulks the engine and cuts it.

Diaphragm carbs use the engine vacuum to open the slides, round or flat, once the throttle/butterflies are opened the slides open at a speed that the engine can cope with. ......usually

And for this reason a lot of flat slide carbs don't "clack" at tickover, coz they're diaphragm operated, the butterflies are closed at tickover stopping the engine pulses "clacking" the slides.

I have a set of 36mm flat slide diaphragm Keihins stashed away for another project one day.

[James England]

It kinda depends on whether they're diaphragm operated slides or cable to linked slides, most bikes engines with cable to slides will cut if the throttle is snapped open, regardless whether they're flat slides or round slides. Its the suddenness at which the slides can be snapped open that baulks the engine and cuts it.

Diaphragm carbs use the engine vacuum to open the slides, round or flat, once the throttle/butterflies are opened the slides open at a speed that the engine can cope with. ......usually

And for this reason a lot of flat slide carbs don't "clack" at tickover, coz they're diaphragm operated, the butterflies are closed at tickover stopping the engine pulses "clacking" the slides.

I have a set of 36mm flat slide diaphragm Keihins stashed away for another project one day.

Could you point me in the direction of diaphragm operated flatslide carbs please? Yes, I was referring to the cable operated non diaphragm flatslides but, on my quest re the XJR I have missed the diaphragm operated type. I'd like to gen up on them!

[James England]

This is a good example of the clacking from non diaphragm flatslides. It would drive me totally nuts to hear that from underneath me!

http://m.youtube.com/watch?v=tma7Tef...%3Dtma7TefZLlE

[Crusty Snippets]

Carbs

Back in the day when I raced on the paved tracks. About the only thing we cared about was WOT. How much fuel and air would the carbs let in to the engine. The carbs on the 250 Yamaha's did not have idle adjustments. We syncronized the carbs for WOT. For Yami I am only interested in smooth running. The stock carbs do that fine.
When racing there is only two modes. You are on the go pedal or the wo pedal, there is not much in between. If you do not agree with that, you are likely going too slow. Fuel injection has fixed any in between modes. However racing carbs do have a mid range jet, for those that felt the urge to be in that mode.

Lastly, and I have said it forever. " If you want a faster bike, buy a faster bike "
I have a faster bike.
Unkle Crusty

[XS1100carbon]

keihin 39mm flatslides

One way to buy a faster bike without buying a whole different bike is to buy a set of these carbs and get them set up right.Your bike will be faster as in quicker.Mine cruises smooth at all speeds,freeway ,town or wherever.

[James England]

One way to buy a faster bike without buying a whole different bike is to buy a set of these carbs and get them set up right.Your bike will be faster as in quicker.Mine cruises smooth at all speeds,freeway ,town or wherever.

do you have any tips or advice on setting this kind of carb up?

[TomB]

This is a good example of the clacking from non diaphragm flatslides. It would drive me totally nuts to hear that from underneath me!

http://m.youtube.com/watch?v=tma7Tef...%3Dtma7TefZLlE

I'm not convinced, it sounds like just induction noise to me, it sounds identical to one of my XS11's that has open carbs, and a Honda I have, again with open carbs, like the car in the video.

I agree induction is noisy, but I don't think thats the slides clacking, and if it is an airbox will silence it to the point of rendering them quiet enough at the small amount of time you sit with the bike on tickover, with a crash helmet on.

Most later Sports bikes have diaphragm flatslide carbs, mine are from a Kawasaki ZXR 750

[TomB]

The advice I would give is take it to a tuning company with a dyno/gas analyser and let them do it.

Doing your own plug chops and carb changes that involves the carbs in and out lots of times is pretty labour intensive, not so bad with open carbs - no airbox set up that I have.

[James England]

This one is clearer, as the title of the clip says.

http://m.youtube.com/watch?v=X5an2OI...%3DX5an2OI1FKM


Comments here..

http://www.thumpertalk.com/topic/989...b-anyone-else/

And here

http://www.dragbike.com/forum/showth...at-slide-carbs

http://ducatimonsterforum.org/index....=36495.10;wap2


Personally, Couldn't live with it, even with a performance gain....