29's vs 34's

Been wanting to ask about this. I have the 1980 B4 with the 28mm carbs with the "ugly squirter" on the bottom. I've toyed with the idea of spending the bucks on some 29 smoothbores, but I'm having a hard time convincing myself that an extra 1mm diameter bore will give me that much more performance. Especially considering that I have no immediate plans to upsize the cylinder bores or change the cams.
So with that in mind, would there be any performance to be gained by going to BS34's with my stock motor, again with no plans to hop it up?

And Sax, I happen to enjoy my ugly squirter. My ugly squirter has kept me very happy for a long long time. Could it be you're just jealous? :woohoo:

I think everyone's missing the point Larry has been trying to make with his quiz posts. It's more about the combination than about the carb itself. You can't possibly predict the outcome of a carb on an engine unless you know the entire story.

At least I think thats what he's getting at. correct me if I'm wrong.

Larry should know all! He is the professional with the flow bench and the experiance!

Have you all seen the Kaw LTD on youtube on the dyno????

What a sound! Makes for great veiwing.

4th gear twisted all the way.

I came across it just surfing Kaw dragbikes on youtube.

A must see. Don't have it saved right now, easy to find on youtube.

What's with all this engineering stuff anyway? Are you looking for hundred of thousanths of a second on a race track? Oval or dragstrip?
Put it together and go out and beat er up! Loud and fun?
Then you did it! Too rich you foul a plug. Too lean then you learn, when you burn a piston or valve. I always ran stuff fat, nice and rich!

Man, don't make it so complicated!

My old man opinion!

yes I have lusted for the 29mm snmoothies, I tossed my rebuilt 28mm pumpers, for the BS34's, I then tossed the BS34's for RS34 Flatslide smoothbores, the 29 smoothies are just too rich (reads expensive) for my blood, the RS34's are newer technology, but then again is newer better? I will stay with the 34's.....

Fair enough muddy1, can you give real world performance gains/losses between these setups. Your one of the few that have run them all, so your input would be great. I'm assuming this was on your 80 KZ1000.

But then again I think RS34's are too large for a street riden 650/750/810 so it really wont apply directly to us little fellows LOL.

hardr0ck68 wrote:

PLUMMEN wrote:

i can see the call from the customer now:Weve got a problem with low water pressure,somebody told us we needed a bigger water service.
so they call a plumber from down south way who has a stack of 6" iron water main and some fittings really cheap,problem is he leaves the old 5/8" meter and lines inside the house.
so now they have lots of pressure at 1/8th turn of faucet but when they open it all the way the pipes hammer and they dont get any more water! :woohoo:

Are you making a velocity vs flow argument, saying 34mm is to big for a stock carb?

im making the argument of mismatched combination of parts! :woohoo:
the small line is going to reach maximum velocity and volume long before the supply ever does ,causing lots of tuning issues or pressure issues along the way in this case

M357.5 wrote:

But then again I think RS34's are too large for a street riden 650/750/810 so it really wont apply directly to us little fellows LOL.

Not really... I had a set of bored GXSR750R Flat slides on my 831cc KZ650 motor back in 1986... I believe they were taken out to 33.5mm - that was a street bike for one summer... not a daily commuter but I rode it quite a bit.

I just broke down and sold those carbs in the spring... they are very similar to the RS34's that my buddy has on his 900.

There was not issues with drive-ability on those carbs... not flat spots, hesitation or anything like that, but again my head was flowing at least 80CFM or more... no clacking either like I have heard stories of - mine were off a brand new bike.

Hey Injected, are the GSXR carbs 31mm stock ? And what all is needed to fit them to a KZ. Can the stock carb boots be used, carb spacing close etc.

The setup described sounds rather stout, which cams were you using ( GPz ? ) At some point I'll be buggin you through PM's to pick your brain, if ya dont mind.

Yes I believe those are 31mm stock... the spacing is different (Suki) so there are some upper and lower L angle rods to re-fabricate which is very easy.

They are big so you need to run a 1/4" thick adaptor plates between the rubbers (J series) and the head... clock the mounting bolts and port match the plates to the head.

They are a very rare carb because they were for Japan and Canada only (the US never got them) so if you find some you are in luck.

Yes GPZ750 cams...

Thank you for the info, very informative. I'm a Canadian boy so I may luck out and find a set. There was an 85 GSXR I found a while back that could be picked up for a decent $, part out the rest and the carbs might be a cheap alternative to 29's or 34RS's

Yeah, I am pretty sure I met you at Paris Swap Meet this past June... you were camped out across from us... my red 650 drag bike?

BTW - I sold those carbs to a member here... Timebomb in Alberta... they went on a small cc KZ drag bike, he seemed pretty happy with the throttle response over a set of 29 smoothies... they also don't weigh anything compared to the round slide stuff - I think they take off a few lbs.

I was talking with you at Paris I believe, or your friend, I was looking at the Z1 calipers for a friend of mine. I was down by the consesion stands at the other end of the bleachers. There was a guy accross from you with a 750 parts motor though.

I had a GPz550 for sale there, a T500 Suzuki and a bunch of KZ stuff, some Cafe seats and Tracker tails etc. I dragged home my current 750L4 that weekend....not a bad score.