Engine Upgrade Advice?

Hey KZr members. Here is my plan and I could use some input.

I am looking to bump my 77KZ650 engine to the KZ750 jugs with the 810 Wiseco pistons. I am probably also going to go with the 750 cams and clean up the ports. What would be the best carbs to put on this combo. I currently have Mikuni 24's on the bike with a 700 Wiseco kit and filters. (fairly well tuned-jet wise.)

I've gone through the archives and learned as much as I can 'bout the swap and it was very helpful in most areas except for the fuel supply side.
So if anyone cam chime in on this upgrade for the carbs let me know. I doubt if the 24's will pump enough to keep up with the extra cc's at full rip.

I am aware that I will have to open up the case bores and maybe the cam chain openings. Hopefully I will still be able to use the stock tach drive off the exhaust cam if I match up the right year of KZ750.
Just looking to give the middleweight a more potent (sleeper) punch.
Anyone got an extra KZ750 top end lying around?
Colin Firth-Ontario Canada

I suspect this is a carburetion related question... moved it...

The VM24 carburetors are not the answer to high performance. The answer to which carburetor to use depends on how much you want to spend. I personally would use some Mikuni BS34 carburetors (cv type). You will need another throttle cable, intake manifolds and pod air filters. Jet them up 3 sizes main jet and one size pilot jet from their stock setting (depends what they came out of) and that will be a good starting point for your new set up which I assume means higher compression as well as the displacement bump and the cams. The reason I would go with the CV carburetors is that they provide the best bang for the buck. I love testing them on my carb test bike as they give it more punch than any other carburetor I currently test through the entire rpm range. You will probably get folks who will tell you otherwise but I tested about 300 sets of carbs in the last year including most of the ones that will be mentioned. I don't test racing type carbs (VM33 or Mikuni flatslides, etc.) and these might work decently but are very expensive. I just test street carbs (VM24/VM26/VM28/VM29/BS32/BS34/CVK34 etc).

I snagged a set of Mikuni BS34s and put them on my bike and never looked back, I love 'em!

Try these:

cgi.ebay.com/ebaymotors/kawasaki-KZ1100-...dZ1QQsspagenameZWDVW

Post edited by: guitargeek, at: 2005/12/13 10:21

Thanks WG-Your opinion on carbs is always welcome. What about 26's or 28's. Shouldn't this increase from my current 24Mikunis cover the extra cc's? Also, are you familiar with which carbs came on the KZ750 four cylinder engine from the factory?

Cheers-Colin Firth-Ontario Canada

The 26s and 28s will definitely be a step in the right direction... I don't see where they will give you a major performance bump but they won't be a limiting factor as much as the 24s. FWIW: The KZ750-4 versions used either the Keihin CVK34 or the Mikuni BS34. The problem is that the Keihins are just plain hard to get parts for. The pilot jets are difficult to remove and most sets I get in my shop are gummed up. You HAVE to clean them as I don't have a source. The mixture screws are nasty to get out as well and if stripped, you can throw the carb away. The BS34s were not only used on SOME KZ750-4 models but also the KZ1000J, the KZ1000 cop bikes after 81, and the KZ1100. The innards vary but essentially it is the same carb. Some have coasting enricheners which work a lot like an accelerator pump. They are located on the BS34 sides and keep the carb from being too lean on decel and the bike backfiring. If you score a set of those, pay attention to the condition of the diaphragms as the cost of the diaphragms may be a bit high, if they need replaced. The main and pilot jets for the BS34 are readily available. The only real negative about the Mikunis is that the choke plungers have lame little rubber shrouds that end up ripping fairly quickly. The older, rubber plunger caps from the VM carbs won't fit. The shrouds (can't recall what they are called) cost $13 a pop from bikebandit.com. Ouch...

Thanks much wiredgeorge. Your wisdom is always appreciated. Guitargeek thanks for the heads up. I think I may wait at this stage to decide exactly what jugs are available. I have a lead on the complete top end for a KZ750 locally and this may include a set of carbs. Cheers-Colin Firth

Post edited by: reborn650, at: 2005/12/13 16:55

I picked up the Mikuni34's on ebay for $46 following guitargeek's heads up. Looks like a decent deal. I am expecting to rebuild the carbs anyway following wiredgeorge's advice for jetting and such. I will need to get some intake manifolds and new filters from Jeff at Z1Enterprises but not until I locate the top end from a Kz750 four, probably an 81 or 82 as they have the tach drive gear on the exhaust cam.

So, does anyone have a decent set of jugs and complete top end from a Kz750/4 lying around that they want to unload? I also am looking for a new 810 Wiseco kit if anyone has one sitting up on the shelf collecting dust? Fire me off an email if you can help. Cheers-

Colin Firth-Ontario Canada
colin@kicks.net

Cylinder blocks can be found on eBay for ~$20 plus shipping, and you can buy a Wiseco 810 kit for ~$355 plus shipping.
I have a couple of extra blocks, but I'm saving them to practice my boring