KZ750 twin [ 1976 ] 60's style Cafe Racer

I'm already on a couple of KZ750 specific forums [ UK and Germany ] and DTT, but I like to find out what other folks are up to. I started the project 7 years ago with a wreck I rescued from the scrap yard ! Everyone thought I was mad, but it's now turned the corner and I'm in the final stretch after several years of serious health issues [ now under control ].

It started out life as a Flat Tracker project and had a 40DCOE Weber on specially made manifolds, but after I was forced to sell my "swansong" TR1 60's style Cafe Racer - I decided to build the KZ in that style. Fortunately a lot of the parts that didn't go with the TR1 were suitable for the KZ. Like the 4LS Grimeca front hub shod with Borrani rim and a matching rear built on an XS650 hub. I also had Tomaselli clip ons from another project with the correct fork fitting and Tarrozi rear sets. I had a specific style in mind and I ended up with a Manx 5gal tank cover, AJS7R seat and Norvil half fairing.

Somewhere along the way, the Weber gave way to an Eaton M45 supercharger and as long as I can locate parts cheap enough - a whiff of Nitrous. I was tempted to use a Turbo - but they're not in my comfort / knowledge zone, whereas I was brought up with blowers on the road and Drag Strip. Funds are tight on my Old Age [OAP ] pension - but as long as I have bits to sell on E Bay I can get the parts I need.

My shed is very cramped- and without any heat - which has also slowed progress, but a good friend has cleared me a space in his garage and we hope to move the project round there in the next several weeks. Then the rolling chassis can be built up again and my blown engine can be mocked up on my shed bench thanx to a pal who loaned me a wrecked engine to use as a mule [ no innards ]. he's also got a spare frame with no V5 [ log book / title ], so that will also be used to make the brackets, manifolds etc. The engine will be in fairly mild tune [ blower apart ] - using an exhaust CAMSHAFT in the inlet spot - oh yes, and a twin plug head conversion ! A couple of blokes over here have made 865cc conversions, but info is a bit sketchy as to what pistons etc. When I was thinking of going turbo, I designed a stand alone oiling system utilising an external Gixer oil pump. That will probably see use now to feed an oil cooler.

Hopefully there will be some meaningful picture upgrades in the next 4 weeks or so.

What advantage does a smaller intake valve provide?

Apologies - should have read "exhaust CAMSHAFT" - I've corrected the text now/

Just for a laugh - this is what I started out with !! It was 2 days away from the scrap yard. Despite the looks, the engine had been refreshed - rings, bearings, chain etc. and then just left outside in the weather for 3 years !

Cool project. Lots of good work!

Ed_in_Miami wrote: Cool project. Lots of good work!

Thanx Ed - it's been a long and hard [ health wise ] journey to get to this point, but with my pal's offer of workshop space [ and his help ] the project should move on much quicker. I had to sell my TR1 "Vindicator" 60's style Cafe Racer project a couple of years ago when my health issues looked pretty grim [ CKD - Chronic Kidney Disease ], but that has been arrested and I even have a slight improvement from the low point. The KZ is closer to the bikes of my youth - ie parallel twins!!! BSA, Norton, Triumph, Enfield . In fact I've owned virtually every British made post war twin - and all had the Cafe Racer treatment. I'm trying to recreate one last 60's style CR and intend to make it the best I can.

Here's the Weber conversion I designed. I had the two different length manifolds made so that I could play with different airflows. I'm probably going with the shortie version. One will end up as a spare or get sold.

Nice head. Two plugs per cylinder must have taken some precision work since it looks like little room for error there.
It will be interesting to see how the weber works.
I'm thinking you have done this kind of thing before

Thanx for the kind words JR. My pal made a jig for the job and I can't take any credit for the machine work !

Yes, a lifetime of engineering design and manufacture of my own range of replica sports cars - Jag, Cobra, Porsche, ....... and involvement with racing and road conversions has set me up nicely for my "retirement toys". I did a lot of work directly with Carroll Shelby, including building a Caddy Northstar powered Cobra for their evaluation. Our Cobra was the only replica until very recently to carry his personal endorsement.

Ill health has slowed me down for the past 5 years or so, but now out of the woods and back to reasonable health
A few pix along life's way.

The last part for the chassis arrived today - courtesy of Tarozzi. The bike is now stripped to the bare chassis / forks / swingarm and bubble wrapped ready to go round to my pal's garage. I hope to have the rolling chassis mocked up on the ramp before Christmas - then it's making up the spacers / sleeves for the Grimeca spindle and a spacer to centralise the rear and the chassis will be truly rolling !

The bike ramp is now installed round my pal's garage where we will be doing most of the assembly work. We took the frame, forks and wheels round today - along with the top half fairing, Manx tank cover and the AJS7R seat base.

My modified twin plug head will also be here next week and I can begin blueprinting and mods. I'll also be getting a good spare exhaust cam, which I'll modify and use in the intake position.

I've been getting feedback that the stock OEM clutch springs are marginal, so I'm getting my local spring maker to give me a quote for 15% and 20% uprated units.

Dynatec have been very helpful in suggesting an ignition [ DARC-2 ] to suit the supercharged engine.

Over the past week I've been looking into the blower drive take off that I was contemplating - ie from the alternator fixing bolt [ 12mm ]. It's the only logical / practical place, but I was concerned about the torsional shear stress on the fixing. The blower will take around 15 - 20 bhp to drive, but it's the inertia that needs to be overcome that's a concern. Soooooooooo - back to the turbo then !!! What's that about " I used to be indecisive - now I'm not so sure" !!

The blower set up is much more familiar to me, but I do not want to take the risk of a marginal drive output. So I will revert to using he same take off to drive the Gixer oil pump for the oil cooler and turbo feed. The only good news [ ? ] is that I spent some months thinking about the turbo set up and planning the packaging. One of the major benefits is the much lower weight and compactness.

The decision was finally declared a no-brainer when our pal Der-Nanno informed me that he's found a carbon seal turbo for his TR1 project. Thanx mate ! That means I can use the SU carb I have in a draw through set-up and I already bought most of the ancillaries I will need - boost gauge, oil pressure gauge, oil lines and fittings, etc., etc. That makes the whole packaging much simpler - including manifolding, even my 2 > 1 high level exhaust will easily hook up to the turbo flange !

The ramp and all parts are now round at my pal's garage, he's just finishing replacing and moving some of the light fittings and then we're good to go. Bike back on the ramp now and building the mock up. First job is to measure and get wheel spacers made, then it's reinstall the dummy engine to finalise the turbo packaging, exhaust, etc.