mikuni bst40ss or keihin 40mm?

[manden]

what is best?

 

i have the mikuni but the upgrades will cost the same as buying the keihin carbs. what will be the best solution on my gsxr 1100 fry with some extra ponies? mande 112kw at the wheel with bst36ss carbs

[Gixer1460]

That translates to about 152hp - which is pretty high reading for a stock bore with CV 36mm carbs. It's even exceptional for an 1100M with 40's.

40's are a pain to set up with anything but std. - suzuki did a good tune with them and don't know of anyone who's used 40mm cv Keihins - so set up advice is gonna be really scarce!

All depends on what you want - good top end with excellent mid range or exceptional top end (that you'll mostly never use) and a mediocre mid range (which is were most peeps spend their time?) Lots try 40's and then revert to 36's or 38's which is sort of best of both tunes.

[Oilyspanner]

Good info by G1460 - my 1100N came with 40mm cv Mikuni carbs, being stubborn I've stuck with them as the bike evolved. They can work well, but in my experience only with an airbox, I had to give up when I dabbled without an airbox - lost loads of bottom-end and mid-range, even the top-end wasn't that good. With big bore kit fitted, some flow work and the Akrapovic system/Pipercross filter already fitted the carbs are working very well - I've got good bottom-end power , with a  lift as 4k approaches, from there it's very quick and has winch like torque, top-end is very strong.

If you want to use dual filters it's best not to use the 40's, if you don't like working with carbs - don't use 40's - I've got a couple of journals listing the various projects I've carried out on my bike, there's a lot in there about me fiddling with the carbs trying to get a factory type delivery  - the bottom-end and early mid-range is the difficult bit - easier with a bigger engine though, but it still likes the airbox.

If you're bike is putting out 112kw at the rear wheel I think someone has worked on the engine - the only time I've seen big hp from a std bike was when Superbike magazine tested an 1100K in 1989, it put out 143hp (about 107kw) - but according to the dyno it was revving to nearly 12000 revs, which the don't, but the tacho does show - so they'd got the rev signal feed wrong(this would muck up the hp calculation).  If your dyno printout is to about 10800 revs and makes 112kw, you're a lucky man with a tuned bike !

[manden]

112kw at 10300. dynos can vary but an k4 gsxr with an commander and an eshaust made 113kw and was on just before mine. it has a chims head that is ported and has altered combustion chambers, modern 78mm pistons and 11.7 compression, busa rods, balanced 58mm crank. i havent tried the 40´s cuz i dont have inlet rubbers for them. but they are with 42.5 pilots and 160 jets. inlet rubbers cost the same as the keihin carbs and they are already set up for a 165hp engine and will need to have made some inlet manifols and put on conecting rubbers. all can be done fairly cheap. the keihins also have dual throttle cables. i would like that too

[manden]

i have been playing with the thought of an fi engine. but its complicated to get the cam sensor in place. the sensor for the oil cooling and recalibrated for the oil temperatures and general mapping can also be a problem

[Oilyspanner]

There's a few on here who've converted to efi - there's a member called Artu, who's done a fair few - if you look in the projects section you should see some conversions - I like the idea of efi too, could get some good gains I think.  G1460 has done this too, with turbo just to speed things along ! There's definitely plenty of knowledge on here to help you.

That's a decent tune you've done - 58mm stroke will give 1109cc with 78mm bore.

[Gixer1460]

If you haven't got the 40mm inlet rubbers - your going to need them whichever type of carb so can't see how the Keihins will be a cheaper solution?

Yes I have used EFI - you do not NEED a cam sensor for EFI only if you want to run fully sequential. You don't NEED an engine temp sender - I didn't use one........ it's only really of use during warm up! EFI only REQUIRES a good crank pick up, a multi tooth trigger wheel, an intake air temp sensor, a throttle position sensor and/ or a MAP sensor (to assess engine load) and that's it!

[manden]

On 9/15/2018 at 10:21 AM, Gixer1460 said:

If you haven't got the 40mm inlet rubbers - your going to need them whichever type of carb so can't see how the Keihins will be a cheaper solution?

Yes I have used EFI - you do not NEED a cam sensor for EFI only if you want to run fully sequential. You don't NEED an engine temp sender - I didn't use one........ it's only really of use during warm up! EFI only REQUIRES a good crank pick up, a multi tooth trigger wheel, an intake air temp sensor, a throttle position sensor and/ or a MAP sensor (to assess engine load) and that's it!

i wanted to use a kawa system, so it would go straight to limp home when missing 6 sensor signals uless i could make in run closed loop