Replace Keihin CV34s on KZ750E with better carbs?

Hello KZ Rider members.I recently removed my Keihin CV 34s from my Red Rat bike(1980 KZ750E),a mechanic acquaintance of mine said he thought I was having trouble with the pilot circuit,so I figured it was time to clean the carbs.I last did this in 07 when I bought the bike.At that time I cleaned them in the Yamaha stuff for about a week(w/all of the needles,jets,floats,seats,diaphragms,springs,etc.---removed). At that time I rebuilt them with KEESTER rebuild kits(bowl gaskets,needle valve and seats,pilot air screws-springs-washers,and o-rings for the bowl drain screws and the plastic covers-that go up by the main jets),blew out all of the passage-ways,put them together and synched them.The carbs worked decent for the last couple of years.I stabilized the fuel the last couple of winters and everything was OK. Anyway-I get them off and found the casting on 1+4 carbs was cracked below the air bleed hole-so I figured they were no good.I know i can find some CV34s out ther,but I have heard that Mikuni Flat Slides were better carbs,or the other one I heard about about was Keihin CRs(?).Does anyone have info about these and/or the proper sizing/model of either of these to get/use? Also how much changing would be necessary for either,and which would be the better choice and for what reasons,etc?THANX TO ALL that respond) !!!

The 34mm cv (BS34s)carbs a great on a stock bike and have nice drivability.
I would stick with them unless you plan on performance upgrades.I'm running them.

i'd be looking for a set mikuni bs 34's if you don't have any major engine mods the flat slides and the cr's will be to much for your engine and by major engine work i'm talking about cams ported head and bigger bore with more compression you could probably get them to work eventually but it would take a ton of time and parts plus a E.G.A and maybe a dyno.

TJMD, I see you have stock airbox & pipes. Carbs alone give slight improvements and usually require lots of fiddling. IMHOP, The time & cash involved to change out-weigh gains. My 2 cents, luck G

A set of Mikuni BS34s can be built to have better performance than 31mm Smooth bores. My stock KZ1000 with BS34s on it will pick up the front wheel going from first to second gear.

OK Dude_I will probably try to hook those up.I know where there are several sets of CV 34s(KEIHINs),but I will look for the Mikuni BS 34's.I got a dude local that specializes in Vintage KAWAS.You should see his collection!He might have a set though.THANX MAN!!! Only mods are: DYNA-TEC 3.0 ohm ignition coils,and PROGRESSIVE SUSPENSION front and rear. I might try this set-up(MIKUNI BS 34's) and put the K&N drop in air-box air-filter replacement I bought,along with a used KERKER 4-1 used pipe and muffler set-up I got on ebay and see what happens!!!

I'm glad I did a search, I was going to post the same thread. I have an KZ750E too, but it's an 82 with pod air filters, rebuilt factory carbs with a jet kit and a V&H 4-1 exhaust. My next mod was going to be sending the head out to be gas-flowed and bump up the compression a little and maybe a larger cam. Should I stick with the factory carbs or Mikuni 34mm carbs?

I actually like the Keihin CV34 carbs on my 750/4 and feel they work well. I have K&N pod filters and a 4-> exhaust. Carbs have 140 seconday mains and 70 primary mains jets and I'm happy as a pig in **** with performance.

If you guys go with the Mikuni BS34s (which are also CV carbs) please come back and let us know what difference you find.

My brother did the swap on his ZR750 and the Mikuni are MUCH more friendly, and much smoother. The Mikunis do not have any kind of hesitation.

Why, what's wrong with the keihin cv34s? I have these carbs, are the mikunis that much better?

Nothing at all really.I never swapped mine out,because I was chomping at the bit to have a running 2-wheeler;) .I took my carbs to a retired metric mechanic and he found about 4 things wrong with them(KEIHIN CV34s).Some of these things I should have known(one plugged pilot jet,and three collapsed diaphragms[when I put the Tin Tops back on-after the cleanse]),but others I could not have-because of my experience level:the #125 Mains were drilled out-never a good way to get more gas in I guess,and two questionable needle valves(I thought they looked OK).Also-he set the fuel level in one of the carbs.Something that when I redoe some other carbs I will definitely check!(I never use to check this because I assumed it was OK-just too many times of being lucky I guess!)Also-the carb pilot jets were clean when I put them in:silly: .Guys:I would suggest rinsing out your gas tank when you do a carb clean/rebuild.I will always rinse my gas tank out when I rebuild carbs again.I had changed out the fuel filter and both gas and vacuum lines,but had not done the tank clean(I did the Yamaha Tank Cleaning/Prep Solution-which here in Ohio is no longer available because of EPA Regs---maybe 2-3 years ago and the tank is still clean looking).It was incredible what crap came out of there though:blush: .Also.I took the petcock and gas cap apart and cleaned them with brake cleaner-and they had some groady in there! Then the dude hit the carbs with his Merc Stick and it was incredible.Now I am riding every day(ambient temp above 40 degree F).I am going to drain the carb bowls soon though:( We are starting to have 30degree days here in Ohio(I am glad and thankful that I have been able to ride my 80 KZ750E this late in the year thoughB)