cv34 carb jetting

[jabberjoe87]

I tried to do a search and couldn't get the results I wanted. Buddy and I got a super awesome deal on a kz750 that we are gonna use for a drag bike. I know this isn't a zooky but the bike has cv34's on a 16valve motor so other people could benefit from this info. The bike will be for drag racing only and there will be no airbox, which for the street is not a good idea. Anybody have these carbs on their second gen gs 650 and jetted it with pods and a 4-1? Any help would be great thanx.

[almarconi]

I know this isn't a zooky but the bike has cv34's on a 16valve motor so other people could benefit from this info.

You sure its a 16 valve Kawasaki motor? My KZ 750 only has 2 valves per cylinder. The KZ750 had either mikuni or Keihin CV34 carbs.

[Nessism]

You sure its a 16 valve Kawasaki motor? My KZ 750 only has 2 valves per cylinder. The KZ750 had either mikuni or Keihin CV34 carbs.

I was thinking the same thing about the number of valves although Kawasaki did make a number of different engines over the years. As to the carbs, 34's are pretty big for a 750. No wonder those engines made such good power.

[almarconi]

My KZ750 has 34mm Keihins. I looked up specs for a few different years of the KZ750 & GPZ750 and they all had 2 valves per cylinder.

[woodman]

GPZ's have Mikuni CV's, reg 750s dont at least up to 84. GPZ motor is black, 8 valve

[jabberjoe87]

The carbs on this is a Kehinin, i've never had the valve cover off, but it has to be a 16valve, the sounds between the 8 and 16valvers is so distinct its a 82 kz 750 ltd, it has an electronic ignition on it from the factory and the valve covers look so similar to the 16 vlavers on the gs's ?

[Nessism]

The carbs on this is a Kehinin, i've never had the valve cover off, but it has to be a 16valve, the sounds between the 8 and 16valvers is so distinct its a 82 kz 750 ltd, it has an electronic ignition on it from the factory and the valve covers look so similar to the 16 vlavers on the gs's ?

82 KZ750 is definitely 8V. That same basic 8V engine was (is?) in production well into this decade and as far as I know, Kawasaki never made a 16V air cooled equivalent.

[jabberjoe87]

okie doke on the motor, now any idea what sized jets i should slap in there if I am taking all the emissions tubing and airbox off? right now there is 125 mains and 63 secondary. I'm gonna assume 15% bigger ont he mains and 2 sizes bigger on the secondary. If I can find some bs 34's for it i would look into that but the basic question is jet size for now any ideas?

[almarconi]

The problem you are going to have is the stubby keihin needles. My KZ 750 has a V&H 4-1 pipe and stock airbox with K&N filter. Initial jetting is 110 secondary main, 68 primary main, 35 pilot and shimmed needles. I have not tried to run it yet cause the bike is still being put back together. The PO installed the pipe with stock jetting (90 sec main, 65 primary) and it was way too lean. I am going to try my initial jetting settings and see how it runs. I still may end up getting a jet kit.


In your case, since you are proposing some radical mods, I would highly recommend a dynojet kit if you are going to run the keihin carbs. Shimming the needles on these carbs is not like on the mikuni's since the the needle has to be able to float. Basically you need to install one washer, under the head of the needle and then another washer on top and lock it down with the set screw.

I would also recommend searching these two forums

http://www.wgcarbs.com/forum

http://www.kzrider.com

I have not been able to find out much information on rejetting these carbs, but wiredgeorge (www.wgcarbs.com) has been able to provide some help.

You may also want to PM Rapidray, a member on this forum. He is into drag racing and could probably give you some insight. There might be a better carb choice for your setup but I know nothing about drag racing.

[jabberjoe87]

Thanks for your help, i'm gonna do a plug chop tonight to see if the main is too small, its a 125 so i think it should be ok

[jabberjoe87]

made some runs at the track last weekend, with 150 mains and 75 secondary, the clutch was slipping real bad so we are workin on that now, but the jets still need to be bigger i'm thinkin 160 and some 165's ? there was alot of poping after the 1/4 mark when the throttle was let off. There is no air box and the vacuum holes have been bored out. The throttle response is way better then with the airbox, but still needa figure out what main's and secondaries shoudl be, any ideas?

[almarconi]

How about getting rid of those carbs and getting some carbs suitable for drag racing like some lectrons.

http://cgi.ebay.com/ebaymotors/40MM-LECTRON-CARB-DRAGBIKE-DRAG-BIKE-LECTRONS_W0QQcmdZViewItemQQhashZitem230358d85aQQitemZ150380009562QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_976

[jabberjoe87]

Thats too much money for this build right now, we are more worries bout a shifter and clutch, these carbs are workin fine for now and should work better when the jets get figured out.

[Steve]

I tried to do a search and couldn't get the results I wanted. Buddy and I got a super awesome deal on a kz750 that we are gonna use for a drag bike. I know this isn't a zooky but the bike has cv34's on a 16valve motor so other people could benefit from this info. The bike will be for drag racing only and there will be no airbox, which for the street is not a good idea. Anybody have these carbs on their second gen gs 650 and jetted it with pods and a 4-1? Any help would be great thanx.

I know that many on this board have other bikes and other interests, but specialized questions like this might be better answered on a KZ forum.
As far as I know, the only GSs with 34mm carbs were 1000s, so any jetting suggestions would be WAAYYY off.
Second gen 650? I thought the 650 was only made for three years. When did the "Second gen" happen?

... but still needa figure out what main's and secondaries shoudl be, any ideas?

I understand "mains", but "secondaries"? Maybe something on the Kehins that is not on the Mikunis?

Have you checked with the guys that almarconi suggested?

http://www.wgcarbs.com/forum

http://www.kzrider.com

.

[almarconi]

You see Steve..he has his terminology mixed up. On the keihin carbs, the primary main (small number 65..etc) controls the midrange and the secondary main(big number 110,120..etc) controls the wide open throttle jetting. He has his numbers backwards. But then again he has the only 16 valve KZ750 on the planet. Some people will do what they want no matter what you suggest. I am not an expert on jetting the Keihin carbs but as I mentioned there are some knowledgeable folks out there. I have gotten some helpful advice from the KZrider forum, which I needed when resurrecting both my KZ bikes. That is why I suggested he check out wired georges forum. There are many thread dedicated to carb tuning. If the OP insists on looking for KZ information on a GS forum, what can you do.