77 KZ1000 with 75 Z1 engine project

Hey guys, I have a 1977 KZ1000 with a 1975 Z1 engine in it.  It has a lot of problems and I have the motor out and overhauling it.  The head got new valve guides and 2 new exhaust valves, Bill Bune Enterprises did the work.  He also bored it out to a 1015 and I'm using IMD stock compression pistons.  It came with an unknown brand dual exhaust and I already got Delkevic 4 into 1 for it.  The carbs are Mikuni 26mm with the stock cams.

Question:
From what I've read the stock 26mm carbs are going to be restrictive on the top end for the 1015 bore.  The Mikuni 29mm smoothbores seam to the "Holly Grail" for this setup, but they are very expensive and hard to find.  I've been looking at the RS34 flat slides, but have read they can hurt the lower RPM range.  Would getting some different cams, such as the Web Cams #118, work well with the RS 34 carbs, or should I try to find the 29 mm smoothbores?  It's just gonna be ridden on the street, no drag racing, but I do have a lot of back farm roads that we open them up on!

Any advice would be appreciated, thank you.

I have a stock 77' KZ 1000 LTD with RS 34's and a Delkevik exhaust. I have the quieter baffle in and I haven't noticed any issues. It runs real strong even out of a slow corner. I also live out in the country and have a nice 12 mile test loop to play on.

26 mm carbs were standard on the 77 KZ1000.  They should be fine on your bored 900 engine.

VM26's will work fine with the stock compression 1015cc rebore and fitting some later Z1R/MK2 VM28's would bump the horsepower up another 5 to 8 ish HP which would be a much cheaper option than trying to source the 29 smoothies for very little comparative gain over the 28's.
The only major mechanical difference between the low to mid 80s hp of the earlier Z1000's and the later 90hp Z1R was the switch from VM26's to VM28's..
For the stock motor, if you still have the head off the bike i wouldn't bother with big cams ( for which you also need a compression increase over stock ) but go for head work first if anything and make the most of the gas flow potential and $ for $ value power gains.
Without porting the head any significant increased valve lift would be largely wasted and performance could actually suffer with your current stock comp IMD pistons.
Just porting the head alone would perk the bike up no end even with stock cams and no other changes.

 

Welcome to KZR, the most comfy air-cooled interwebs corner for all things Z-bike.

Good Ridin'
slmjim & Z1BEBE

Ditto thoughts on the re-use of your VM26 1200 series 1976-1977 carbs you already have. Depending on what you're going for of course. I've used them plenty of times on 1015/1045 10.25CR Wiseco rebore engines i've done over the years. Actually a better option without the complexity of the "pumper style 28's" would be a set off the 1978 Z1R, also 28mm. Smoothbore 29's are ok but often riddled with problems from previous owners. 

Thanks for the input, I was hoping you'd chime in on this.  This has been a project that was put aside for a while and I'm starting it back up.  There are a lot of options to consider on how to build this!

My experience is similar to zed1015's:
For 20 years, I rode a '75 Z1B bored out to 1015cc and fitted with the original '75-model VM28 carburetors. This 1015cc setup—combined with this light Z1 crankshaft and those 28mm carbs—allowed the bike to rev up beautifully; there was always power in reserve, and by passing, dropping down a gear at around 4,000–5,000 rpm, it delivered brutal acceleration on demand... It had more than enough power for the street, especially on winding country roads
Have fun with you bike!   

Thanks again for the suggestions guys.  I think I'm going to get it back together and see how it does with stock carbs and cams with the 4 into 1 exhaust on it and go from there.  I'll look into those 28s as suggested.  I still have A LOT of other things to fix and a lot of parts to get.  The wiring has been cut and spliced at so many places.....going to get new harness for it.  Going to split the bottom end this week end and send cases and crank to Bill Bune to bead blast and go through.  Going to go with Liska cam parts.  I picked up an 86 454 a while ago and going to be doing that one as well, just got a new garage build!

Chevy to Kawasaki, don't lose your mind ha. As Joe mentioned, earlier Mikuni 217 single spring late 74 and 75 VM28's work just fine too. You've a 75 engine already. Here's a set i'm just finishing-up, wet testing them before i ship them out. These are the earlier 2 spring 417 version but still 28's. Only caveat with this style is they don't hold a sync for too awful long, lots of moving bits in these for slide lifters. Otherwise function great as stated.    I've tupperware containers of these, just ask Ness (ED) ha. 

Yes, Clay, synchronizing those 28mm carburetors was always a headache. Just when you’d managed to get it as good as possible... you’d twist the throttle twenty times, and all that work would be undone. As Clay noted: far too many linkages, pivot levers, ball joints, spring clips, and so on... but I loved those carburetors anyway. I wish I could buy a setup like that cheaply these days—I’d install it again in a heartbeat!

Joe My Friend, how many do You want is the only question. Half a dozen, bakers dozen or just one completed set? I would be more then Happy to send you a set, with my quirky changes that are sensible, proven. Hopefully You're doing Well my Friend!! Don't think i could pull off historic German garb with our climate, i'v become soft and weak ha. Sweated my entire life, air conditioning good.