36mm Mikuni Flatslides vs. Stock CV Carbs

[Mark M]

I know the F.I. bikes have a noticeable time delay from throttle input and when the power pulls through the drive train.

I don't know what EFI bikes you have ridden to get that impression. All the ones I have ridden have been perhaps a touch TOO sensitive to small throttle movements and can be hard to smoothly cruise with at small thottle openings and light loads. The newer bikes are much better at this, the first EFI sport bikes were annoyingly touchy on the throttle.

Mark

 

[TheCafeKid]

I don't know what EFI bikes you have ridden to get that impression. All the ones I have ridden have been perhaps a touch TOO sensitive to small throttle movements and can be hard to smoothly cruise with at small thottle openings and light loads. The newer bikes are much better at this, the first EFI sport bikes were annoyingly touchy on the throttle.

Mark

This is likely helped with the use of modern slipper clutches on todays sportbikes.

Tripp, i think the term "snatchy" they are using is meaning "twitchy" To me anyway. And I understand what they are saying. CVs are very smooth thru the entire powerband, moreso if you have them jetted and the needles shimed perfectly. I played around with simply shimming the needles on my GS1100G, and it made a MASSIVE difference, not only in power (no "flat spots" in transitional stages) but it made the bike respond ALOT quicker than stock when in the needle stages. So much so that i actually had to go back in and add another shim, because the bike was "jumping" at throttle, and i was afraid of tearing up the rear end on it. These were also otherwise stock carbs, stock airbox and stock pipes. I can only imagine what they would have been capable of with a set of pods and a pipe on it.
On my 82 GS11/GSXR/Bandit project, eventually i will attempt using some simple mods, (of course later i plan on having an 1166 in it) but for starters i will use 1150 cams, degreeable sprockets, and BS36SS carbs. I will like to see how that helps out vs stock, as its probably an under $300 set of mods, carbs, cams, and all..

 

[80GS1000]

This is likely helped with the use of modern slipper clutches on todays sportbikes.

Sorry about the thread-jack but on the subject of slipper clutches....

Eh, not so much. The slipper clutch on modern sportbikes only helps prevent wheel hop from engine braking on heavy deceleration. They help match engine speed with wheel speed. They're mostly a track tool, not needed so much on the street.

Imagine this: You're coming into turn 5 at the track on your R6 or GSXR 600, which is a 60 MPH hairpin at the end of a long straight, WOT in 6th at 160+ MPH. On a bike equipped with a slipper at your braking marker you squeeze the front brake, pull in the clutch, bang down 3 gears, and then release the clutch smoothly but quickly and trailbrake to the apex with zero wheel hop and a minimum of rear tire snaking. On a bike without a slipper, you have to downshift at a much lower speed and use a great deal more finesse to prevent wheel hop. Generally speaking, a slipper lets you downshift later and deeper into the corner so lap times are faster.

Example here on my 06 GSXR 750 at about the 2:00 mark, need to drop from about 140 to 85 MPH for turn 1 in a hurry while downshifting a gear. On a bike with no slipper downshifting that fast may have led to some drama.

 

[trippivot]

I have a ultra sensitive throttle hand.

I have a ultra sensitive throttle hand.

snatchy ?? -- from someone who used it as a description??



FYI mark M I am a MMI grad - 95 suzuki yamaha honda water craft snowmobile hi performance dyno room training too. ok I have a solid foundation on the physics.

started at dealership entry level honda moved to kawasaki dealer.\
got picked up by Kawasaki USA. that was after my outstanding tunning /warranty work on the Vulcan 1500 "D" classic introduction(1996). In 1999 the FI models began to hit the sales floors. I - we modified these at the dealership and paved the way for Thunder MFG. products. Mr Dave Rollins is in conjunction with Kawasaki USA producing products that do not void warranties. After that I worked on a factory jet ski team . ever heard of a ultra 150?? 900 pounds of thrust stock. FI integrated in the ignition system.. ok

I am now at a performance shop in the mid west. My fuel injected experience started with the old GPZ 1100 back in the late 80s' and now on the the modern sport bikes.
R1 GSXR 96 and on FI zx12 zx14 goldwing Vulcan CBR VFR

these are just a few examples. I do have extensive hours repairing/riding/tuning modern sport bikes, cruisers , touring, rats. .

how many Different bikes do you ride on a weekly basis? (in season)

ok I know I ride more than normal people not in the motorcycle business.


the slipper clutches are for beginners. preventing compression braking that slides the tire . traction is the objective-not losing it.
down shift and the rear tire is spinning faster than the clutch basket the clutch slips in a reverse fashion.

 

[BlackStar]

The "Snatchy" that I'm familiar with is abruptness from closed throttle (in fuel cut mode) back to any throttle opening. Seems to be worse at lower speeds. Many FI bikes cut fuel completely when the throttle is cosed on decell. When the fuel is re-introduced sudenly you get the snatch. People have problems with this during low speed turns, like when they downshift and re-apply throttle while they are turning. The fuel is cut to reduce emissions. My FZ1 has this as does my Roadstar Warrior. There are companies out there that make FCE boxes (fuel cut eliminator) for some FI bikes.
Iv'e gotten used to it, so it doesn't bother me anymore.
My Yamaha Grizzly quad is carburated and has a fuel cut circuit. The decell can take you by surprise when you let off the throttle at speed.

 

[trippivot]

ok, well enough. I get the description as you have described it-- cause and effect.

thank you .

 

[Mark M]

I am now at a performance shop in the mid west. My fuel injected experience started with the old GPZ 1100 back in the late 80s' and now on the the modern sport bikes.

<snip>

the slipper clutches are for beginners.

So you have lots of experience with EFI sport bikes, and you feel like there is a lag from rolling on and the power hitting the wheel? I have never felt a carb work as immediately and smoothly as EFI when it is working well. I guess we just have different impressions of the same things.

I wouldn't say slipper clutches are for beginners. They are really just a way to reduce rider workload under pressure. Which could be a beginner or a factory pro running at lap record speeds. It just takes away one more thing for the rider to deal with when he is overloaded and trying to cope with multiple problems at the same time.

Mark

 

[trippivot]

Can you tell if it is intake or another engine control effecting the power feel during specific throttle open and closing.


the ignition control does a few things -depending on specific system- open loop, closed loop. ignition integrated 2 channel 3 etc.

now what you are feeling is not exactly fuel and air charge "snatching" on-off-on again like a fuel cut on decel into a partial open throttle jab.

that is ignition hitting at a different time. most of us are used to a centrifugal mechanical advance. some of us have digital ignition advance pre set and pre programed non curve alterable.

these newer systems move it all over the place at weird times. I think that creates a "feel" that is unnatural to some and/or they just get used to it like black star had described.

knowing what you are feeling is good, knowing the how and the why takes research.

Now most of all= being able to separate what is going on between your legs and between your ears is not an easy task.


flat slides are BOSS .

 

[Mark M]

Now most of all= being able to separate what is going on between your legs and between your ears is not an easy task.

So true! And it can be really hard to keep the biases between the ears from affecting everything else.

I never did use the term "snatching", that was someone else.

Whether it is the ignition or EFI, I would just say that many EFI bikes seem extremely sensitive to small throttle changes when running on light loads and small throttle openings. They have gotten much better in recent years. A buddy had an F4i that was very touchy while my 06 GSXR1K is very nice and not at all touchy. My 08 RMZ450 is superb coming off idle and puts any FCR carb I have tried to shame. Of course, that is a race bike only, so the light load touchiness is not at all relevant because it never sees that condition.

Mark

 

[trippivot]

I am just trying to help...guess I deserve to get bit....

Mark M it appears to me you know enough to answer your own questions.

so lead on wise master, enlighten us here.

 

[Mark M]

I am just trying to help...guess I deserve to get bit....

Not biting, I was just wanting to know why you felt there was a time lag between rolling on and getting power on EFI bikes. You have a lot of varied experience working on bikes and riding a lot of different models and I wondered which ones were like that. My experience has been different and I wanted to know what I was missing.

Mark

 

[RobGS850L]

I've been using RS38's on my red bike and other than the lag in response at off idle in gear at too low an rpm (lugging the engine) I feel pretty pleased with them. I've got a set of .355" lift cams and a Star Stage 1 ported head which ain't all that great and 3mm overbore. I'm not sure if this helps in this case but I'd think the RS36's may work well. Actually I'm a bit curious if they'd work better on my bike than the RS38's.

 

[rapidray]

Hey Rob, I've got a good set of 36s I will swap you for your 38s. I GUARANTEE you the 36s will work better for driveability on your CURRENT combination than the 38s. You will have more port velocity with the smaller carbs & NOTICABLY better throttle response. Two mm may not seem like much but in your case it is. Let me know if you are interested. Ray.

 

[RobGS850L]

I've got a set of 40's I'll get rid of but the 38's I'll hang on to. Great acceleration at 5k rpm. Almost pulls you off the set. Before I let these guys go I'd like to see some real numbers on the performance differences. Dude I've had a few instances with 3rd gear pulling the front wheel up. My 900 can't compete with the 1100. Drag racing that is.

 

[rapidray]

I've already got 40s but I'll kick it around if you are serious. I just don't have a need for anything smaller than 38s. Ray.