'85 ZN700 carb replacement

Hello,

I'm looking for some opinions on what to replace the original Keihin carbs on my ZN700 with? Not a fan of diaphragm carburetors and would like something that is less
temperamental.

I saw that Mikuni had some beautiful flatslide RS34s, but I'm not sure that'd be such a good idea, even with the better heads that come stock on my ZN700, since 34s would be huge without diaphragms.

Any ideas? I heard VM29s from a KZ650-KZ1000 are pretty good.

Chris

I am not sure why you think constant velocity (cv) carbs are temperamental. I have ridden quite a few miles on bikes with cv carbs and never had a lick if trouble. I checked synchronization after each routine valve adjustment and they will get clogged up if the bike sits too long without being ridden, but those are true of all carbs,

The old 29 smoothbores are a classic choice for a performance build, but they can be a little fiddly to set up and their low speed behavior can be a little erratic. Have you priced a set lately? Some nice sets have sold for nearly twice the cost of brand new RS carbs.

The RS carbs are a nice choice for a performance build, but will need rejetting and tuning to your particular bike,and yes the 34s are more than your engine needs.

Personally, for a stock or nearly stock engine, I think cv carbs are the way to go.

I haven’t had any good experiences with diaphragm (or CV) carbs. The ones on my ZN aren’t bad, but I really don’t trust them. They also come with dealing with the OE airbox. Taking the carbs in and out is a royal PIMA because of that airbox, and knowing CV carbs, I don’t imagine the bike would run right on decent individual filters.

As for VM29s…are they really that tough to setup? And those new Ninja 600 carbs, are they any better than 40yo Keihins?

The Keihin CV34's are very reliable and exhibit excellent driveability.  They are a pain to remove/install, but no more so than any other bike using the stock airbox.  I've rebuilt about a dozen sets, and I sell O-ring kits for them.  They are a little more difficult to rebuild than the Mikuni BS34's, because of the choke system, but they are not difficult per se.  

Changing to something else is going to be way more work than just maintaining what you have.

Okay. I’ll listen and keep them around then.

My experience with CV carbs come from a CB350 with Keihins. Maybe they will be different on my ZN.

Thanks for the input, all
Chris

Oh no! You have broken the unspoken cardinal rule of this place by criticizing CV carbs as infernal, stupid oxy-moronish devices of dubious induction. You now will be selected for group think therapy where every grizzled old mechanic will force you into loving CV carbs and what's more proclaiming your love for CV carbs. Wait for the message from the one "veteran mechanic" who will tell you how well they work on old British cars, that is a clear sign you are now being reprogrammed.

Seriously, if you can afford those beautiful flatslides ...

Quality carburetors...

P1030115 by nessism , on Flickr

P1030119 by nessism , on Flickr

Most critics of CV carbs simply don't understand them

Kind regards

Grizzly veteran mechanic - Lol

I know for a fact that Rob Muzzy hates CV carbs as did the late Mike Velasco. But they're Rob Muzzy and Mike Velasco so they probably just don't understand CV carbs, right?. You're Wookie on every KZ thread, you sell o-rings, right?

Rob and Mike were building race machines so of course use of round or flat would of been the obvious choice. As well as all the other tuners of the era. But that's comparing apples to oranges in the REAL world. Not everybody goes WOT Redlining everywhere they travel looking to flog their engines. Sometimes person's just want a leisurely cruise, CV's fit that bill.  

chopper1963 wrote:

I know for a fact that Rob Muzzy hates CV carbs as did the late Mike Velasco. But they're Rob Muzzy and Mike Velasco so they probably just don't understand CV carbs, right?. You're Wookie on every KZ thread, you sell o-rings, right?

Wrong, that's Nessism. I have no vested interest and you can run what you favour, CV's give excellent drivability in normal road use if set up correctly (there is a reason why just about every manufacturer went that way). I share my opinions when I think I can be of help to people, if you're not interested you can scroll on through. Life is too short to get into bun fights over such things.