KZ650 cafe-racer

I like the look of K&N dual pod filters and once I found out that K&N make dual pod filters with flanges center-to-center distance compatible with Kawasaki KZ650 round slide carburetors (75mm it is) I placed the order. filters look great, and of high quality , traditional for KN products.



But anyone who might of check RC-2382 on K&N website find out that inside diameters of its flanges is 54mm (52mm according to measuring made with calipers), while KZ650 Mikuni VM carburetors have 40mm intakes. Difference is huge and quite obvious, that RC-2382 couldn’t be put strait onto carburetors. The solution for this task is applying adapters in form of velocity stacks. I am not inventor of it, however I made drawings of my own version of adapters. I started with measurements and good old pencil and ruler…



I used to make blueprints in different drawing programs (CAD), but this time I had to master a bit new to me 3D drawing program from which drawings could be transferred to CNC lathe. Lucky the task was quite simple…



I modified blueprints for better fitment and ordered parts to be made on CNC lathe. Photos below I shot just after receiving, so to say fresh from under the lathe cutter. At that ерфе I also moved a bit further into 3D modeling program mastering so here are rendered 3D pictures VS reality:

Very cool! are you keeping them shinny?
Those carb kits look top notch, which needle is stock?

Nice. Do stacks hold on to carbs with o-rings only?

Very cool! are you keeping them shinny?
Those carb kits look top notch, which needle is stock?

Yep, I'll polish stacks. I decided to compare these needles and original needle when I'll be assembling carburetors. What I noticed from first glance these sets have no pilot screw for carbs with accelerator pump (it regulated air but has different configuration than pilot screw in carburetors without pump). Also starter plunger from set has no needle on its end.

Nice. Do stacks hold on to carbs with o-rings only?

I'll answer this question in next few posts.

The question of KZ650 carburetors is quite extensive. One may catch a serious case of headache just counting modifications of Mikuni VM24 that were installed on 650 during years of its manufacturing. My knowledge in this is quite superficial, however I counted two modification of VM24 without accelerator pump and three modification of VM24 with accelerator pump. Engine on which I based my project had carburetors without accelerator pump and with late type of pilot screw that adjusts air. However, as soon as I learned about VM24 with accelerator pump, I became curious about it. One may find information that those accelerator pump implicit fuel mix only on idle, so to say produce single jet of fuel in every carburetor when you jerk throttle to start moving. However, only one modification of VM24 with accelerator pump has closing fuel valve (triangle thing on float bowl of second carb), and vacuum actuating circuit that causes valve closing on higher rpm. Second modification of “pumpers” still has valve, but it has no actuating vacuum channel. And the last, third modification has no closing valve at all. Thus, in these two types of VM24 there is no reason for accelerator pump not to work on other than low rpm. However, its only my suggestion and I couldn’t confirm it until I finish with “pumpers” I bought for the project. And even if experiment with accelerator pump will lead me nowhere, I could deactivate all pump system just by replacing float bowls with bowls form carburetors without pump.

So I bought modification of “accelerated” carburetors with closing valve but without actuating channel. They turned out to be in very good condition:







Sure, forty-years-old carburetors need to be completely rebuilt and cleaned through and out. So I put them apart. Counting age, insides also looked rather nice.







Some soot, dirt and depositions in my opinion are manageable.

To my knowledge, there is no vapor blasting here in Ukraine . The closest thing we have is a workshop that specializes on glass beads blasting, which has a range of glass beads of different size and thus coarseness. But even if there was vapor blasting available, I am not sure that I would dare to use it on carburetors, as it is also media blasting. I also don’t like how blasted aluminum looks, so my way is simple: carburetor cleaner, brush and those synthetic detergent I used on crankcases. It works nice and removes all visible depositions, so there is no reason to consider it might leave invisible ones untouched. I like how carburetors look after cleaning:

Thus carburetors’ bodies were cleaned and so were all other components, like heat shield.



Float bowls’ gaskets gave me a bit of work. as they were glued to bowls from factory and after mostly forty years glue and gaskets hardened. To cut them off with a knife might look good idea, but I didn’t wanted to damage float bowls. So instead I put bowls into hot water for an hour, or so, and after some soaking gaskets became softer and thus more removable.



Rough rug and carburetor cleaner helped me to remove last traces of glue. I was glad that I preserved contact surface of float bowls completely undamaged.





I also polished all four top covers.



I prepared and gave most of steel components in workshop that specializes on zinc plating. Refreshed parts look very nice.

Sure, it wasn’t hard to notice that I grinded outer parts of carburetors’ intakes.



I made six cuts in every velocity stack to fix them on carburetors with help of clamps.





These works I made to warrant the tight fit of velocity stack to carburetor. And as you may see from photos below inner transition from velocity stack to carburetor is also very smooth. Thus, there is no need in any sealing gaskets or O-rings.





Carburetors with velocity stacks look great.

Wow! and I mean WOW!

I am used to buy OEM parts for our projects from USA, thus when I decided to order new carburetors’ manifolds I found that only right carb holders are currently available. After some thinking I decided to try aftermarket manifolds, a set made by TourMax (company that states Japan as a country of origin on packaging of its products). Earlier in my repair practice I have positive experience with their products. Their set of manifolds for KZ650 with VM24 carburetors has code CHK-2. I ordered this set of manifolds on German ebay and was quite accurate to chose seller who not only hase a lot of positive feedback, but who also clearly stated in item description TourMax as manufacturer and CHK-2. Parcel arrived and at first glance its content looked good. However, as I wrote I used TourMax products earlier, so I know how their packaging looks like and their logo as well. The box I received was made in TourMax style but has no Tourmax logo nor “Made in Japan” statement on it.



Manifolds were quite soft and looked good until I take a closer look on vacuum gauge attachments.



That was clearly a moment for “Holy Moly” exclamation. Just take a look at this picture:




Only one attachment looked as it should look like. Three other were different from it and from each other, and seemed to be made by drunken turner in tenth shift. Sure, one may say: “what a problem, just round the edges and let it be”. My answer will be “Nay”. It’s clear that these parts never seen Japan even in their deepest dreams. And if manufacturer, whoever he was, managed to make such simple work so poor, guess what he could use instead of proper rubber compound.

So we wrote email to seller and in result got complete refund, apologies and some explanation:

“Our wholesaler told us that these parts have been sold out at Tourmax for 5 years. We did not notice that because we order parts from our wholesaler with the same article number. But at a lower price.”

I’ve made some additional search and it might be true that TourMax does not manufacture manifold any more. So as it’s said on the only one page of TourMax website dated by year 2016: “beware of imitations”.

After such experience I wanted no more experiments, so I looked for OEM manifolds again. Turned out. that left manifolds (part number 16065-046) still available in Europe. So I ordered two of them from European source of OEM parts and two right manifolds (part number 16065-047) from USA. Thus in result I’ve got right set of carburetor manifolds, even if it turned a bit pricey.



OEM parts are OEM parts, what else could be said? In case of manifolds, however, I could say that OEM are softer than those of “pseudo TourMax”.



o those of you who traced new manifolds on ebay here is my advice: take a closer look at manifold mounts on a lot photos. If strips of white metal around the holes are wider than traces of factory countersink you may see on photo below…



… it’s likely that manifold was installed before. I saw a couple of such manifolds on Ebay. However it’s up to you to decide, if they are still may be counted for new…

To finish work on carburetors I ordered some set of parts form Z-fever. Between them were five rubber cups for vacuum gauge attachments.



Why five if there are only four manifolds? I am about to use manual fuel petcock, so I need fifth cap to cover vacuum port on second carburetor.

Most of modern carburetors have fuel tees and fittings of similar design: they could be made of plastic or aluminum but they have a couple of O-rings on legs that fit into carburetor body. Situation with old Mikuni is different: its tee and two fittings that connect carburetors 1-2 and 3-4 covered in solid rubber. I saw the same design of tees on later Mikunies, and they all have same flaw: in time rubber dries and cracks. This issue could be fixed only by parts’ replacement. Tee and fittings of my VM24 carburetors still look good and seem tight, but I won’t take a chance of fuel leakage. so I decided to replace them.



No wonder that original parts are not available for a long time. Fortunately, the tee and fittings used in KZ650 carburetors (part numbers 92005-1010 for tee and 92005-1009 for fittings) were also used in Z1R and KZ1000. thus there are a choice of decent aftermarket products. Sure, as soon as I detected that PMC makes tees and fittings, I ordered them.





They are made of stainless steel.



Here are some close photos to give you an idea about quality. They are very accurately machined and tee neatly welded from two parts:









Dimensions completely correspond those of OEM parts. I shot some photos to demonstrate this: