My first build - Z50


Mar 25, 2008
Hi peoples,

After joining a while ago and reading, reading, reading thought I'd show the progress of my first build and hopefully seek a bit of advice.

Got myself a Zbox Z50 and found a Kona Lanaii on Ebay for the right price. Didn't like the colour so I resprayed and thought a two-tone tank would be the go. A couple of photos of the transformation attached.

Also a couple of pics of progress to date. Engine installed OK after fabricating a mount from some plate steel and exhaust clamps. Replaced / loctite every bolt I could find and filed the intake & exhaust manifolds to match. Sealed the magneto cover, o-ringed the carby etc.......

Then (and this is where any advice would be good), I ran into some issues with chain clearance on the reay stays. From the photo (Stay1) you'll see the stays of the Kona bend in quite a bit. You will also see how this deflects the chain.

Effective chain saw - probably. Effective motored bike - probably not.

So I fiddled with axle position, shimming the wheel in the frame with washers etc but nothing would resolve the chain / frame rub.

I have one idea to solve (which involves one of Ghost0's jackshaft kits) but I was hoping for a more immediate solution - I Wanna Ride This Thing!

Anyway thanks for looking,




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Here are a few things to try. One of them may be irrelevant. Most rear sprockets are dished so my first thing to say would be try your sprocket mounted the other way but it doesn't appear that yours is dished, hence my irrelevant comment. The second thing to try is remove the rubber ring in between the sprocket and your spokes and just use the one on the inside of the spokes. You may hear lots of differing opinions on this but I have built 5 different kits and a friend has built at least 10 others and we have never used the outside rubber. We also have never broken a spoke. I think it helps align the sprocket and keeps it true. It is also easier to tell when your bolts are getting tight since you only have one rubber washer to squish. But make sure you tighten it well. It appears from your picture that yours are not tightened enough. Don't be afraid of it. I don't really think you can over tighten those bolts but you will break spokes if you don't tighten it enough.

Another thing I notice is that because of your engine mounts, the motor is sitting higher in the frame than stock which is also making your chain alignment problem worse. Because of your frame I think you are stuck using your front mount but if you use the stock rear mount set up you may be able to lower your engine a little.

Hope this helps.
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Mar 25, 2008
Thanks Ghost,
The rear mount is basically stock just replaced the part that goes behind the seat tube with have an exhaust mount. Then using 80mm high tensile bolts to bolt through into the engine block. Therefore no room to be gained there.

I think you may be right about the rubber washer not squishing enough and I think I may no why. Going out the shed to check but I think I may not have enlarged the centre hole in the sprocket enough and its now binding on the hub. So rubber not being squished and sprocked being held out from the frame hence the clearance.

Anyway after thinking about this at work all day I hope its that! If not, I'll lose the washer and run it with one.