30mm PWK carbs?

ScottaKR · Post by **ScottaKR** » Tue Jan 01, 2008 7:04 am

Just found a guy on Ebay selling OKO (keihin PWK replica) 30mm carbs for $80au each.
Just wondering if you guys think they would be much of an improvement over the 28mm PWK's on a KR1 with 1-S barrells and the usual case matching and minor porting (or even a stock KR1). I realise that it's only another 2mm diameter, but maybe enough to get to the low/mid 60hp range? Besides, I only got 2 set's of carbs, and plan to build 3 bikes.
Not sure if they'd go into the stock rubbers, but if they did, it would make for an easy upgrade. Will ask him about the dimentions so i can compare it to the stock Keihins.
Any thoughts?

PS. apparently they are exactly the same as the genuine Keihins, so needles and jets etc should swap over.

the-elf · Post by **the-elf** » Tue Jan 01, 2008 12:18 pm

I bored out a set of standard carbs to about that size and they worked really well, but not as good as a standard set of 35mm. Jetting wasn't that far of standard neither.

corky · Post by **corky** » Tue Jan 01, 2008 2:58 pm

I bored out a set to 30mm and ended up with a gap either side of the slide

ScottaKR · Post by **ScottaKR** » Wed Jan 02, 2008 9:36 am

Just got a reply from the guy about the dimensions

Hi Scott
They will work very well and only half of the price.
Inlet 50mm
outlet 35mm
overall length 84mm.
I have sold lots of thease carbs and never 1 problem.
Kind Regards
PC

went out and measured up a carb....
sure enough, it'll go straight in.

Although, to get the true performance increase from these carbs, you will need to open up the throats of the manifolds and the stuffers. Dremel can be a bit tricky with rubber, but can be done. Still not as difficult as the 35mm conversion though, and quite a bit cheaper me thinks.

Besides, unless your after the really big HP, I wouldn't think youd need to go as big as 35mm, so these may be ideal for a mild street bike.

mgtkr1 · Post by **mgtkr1** » Wed Jan 02, 2008 10:38 pm

your way of thinking is logical in that a 30mm carb should offer a better compromise on a mild tune/std bike rather than the much larger 35mm carbs which common sense would tell you the 35mm carbs will sacrifice midrange in turn for a bit of top end while 30mm carbs give gains at the top while still been good for midrange thanks to the faster flow speed. however, the 35mm carbs have proven to give a healthy increase throughout the range(which suprised me) and thus indicates the std are restrictive to a point?? this was pointed out yrs ago in early 90's pb but they decided it wasnt the carbs but a combination of various things. however the std carbs are good for 64hp so dont go throwing them out just yet!! also the ypvs apparently responds beautifully to kr1s carbs in various guises inc 70hp plus rocketships!! 30mm carbs should certainly be a step in the right direction though as long as the reed stuffer is modified to match. those thinking that 35mm carbs are overkill on a std machine could well be suprised though i cant back this up personally, sure someone will know for sure??

the-elf · Post by **the-elf** » Thu Jan 03, 2008 1:31 am

The 35mm carbs give a minimum of 2 BHP everywhere. IIRC they gave a tad more in the mid range, which surprised me and that was on a pretty mildly tuned engine, and running standard KR1S exhausts. I'm unsure just how much the 30mm carbs would boost things [-o< compared to the 35's

but i'll be interested to know.

Changing to Lomas pipes gave a lot more, about 5bhp, mid range and a tad more, around 2bhp, on the top as well. The nikkons gave the same mid range as the Lomus pipes but lost loads at the top as they stopped the engine reving lossing about 1500RMP in total. Wrapping them gave back about 500 of those revs. I've not tried wrapped lomas pipes yet, but I'll give it a go on my next trip to the dyno.

So, the best combination found so far are the 35mm carbs with the lomas pipes which give about a 7-8 BHP boost in the mid range and an extra 4 BHP at the top. Next is the 35's with standard pipes. I'll love to see some before and after dyno runs with the 30mm carbs.

NOS EXUP · Post by **NOS EXUP** » Thu Jan 03, 2008 9:23 am

Elf

if i get hold of a set of 35mm carbs - where would you suggest starting at with needles / jets ? and settings ?

It looks like new 35mm carbs are available on ebay from USA -How easy is it to get a throttle cable to fit to kr1s throttle ?
Do you fit choke cabe with the 35s ?

look forward to your response

the-elf · Post by **the-elf** » Thu Jan 03, 2008 2:00 pm

These are my settings Pilot jet is 40, for main I've found something around 155 is very good at 1000 Mbar 20^C and 50% humidity but I would start at a 160 or bigger on the road unless you plan on changing it often. air screw is 1/2 a turn out. Needle is DEL, in middle clip IIRC.

The throttle cable fits OK it just needs extending to allow the carbs to open fully. The plastic tube where the cable splits needs extending so the throttle opens more. Your need to make sure that the oil pump cable is still working as well if your running the pump and not premix. Its an easy job which took me about half an hour.

Standard choke cable fits without any problems.

ScottaKR · Post by **ScottaKR** » Fri Jan 04, 2008 12:38 am

Keihin 35mm PWK on Ebay USA
These are the cheapest new 35mm PWK carbs I've seen, and even come with 3 different pairs of main jets.
Not sure what the difference is with them being the "Air Striker" carbs though

Any ideas?

KR-1R · Post by **KR-1R** » Tue Oct 14, 2008 4:05 am

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found these Excel spreadsheets for tuning PWK's

JET NEEDLE: Kawasaki/OEM conversion to Keihin part no.'s...KDXNeedles.xls
http://ourworld.compuserve.com/homepages/rushbe/kdx.htm

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also this
Relative carb tuning...try possible mains, needle, pilot combinations against your current setup...
http://home.att.net/~wbarrow/jd/download_jet.html

for comparing theoretical tuning options against each other /Relative tuning selection (may only be fitting a spline to different opening ranges)

SO from graph above you might see...

in the 0 to 1/8th throttle openings a R1472J is up to 10% richer over standard R1372J. Going up 5cc per minute on MAINS, richens up to 10%% from 3/8th throttle to WOT

good for seeing how dropping clip position might show you where you should expect a difference in throttle response

the spreadsheets have multiple sheets with other info thats covered in other available on-line literature and data.

anyone keen on attempting a FCR flatslide setup?

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the-elf · Post by **the-elf** » Tue Oct 14, 2008 4:19 pm

Great bit of info there. Helps you work out how to get the carbs working well. I've got a big flat spot low down where its running rich and this really helps you work out what needle and clip postion should help sort it.

KR-1S.co.uk Forum

30mm PWK carbs?

30mm PWK carbs?

Pilot, Needle, Mains selection for PWK