Denso Alternator, how to fit mechanically

[RC 166]

Just a short update. I have now designed the plate but have yet to machine it. I changed my mind about the splash shield, I will also weld a rolled sheetmetal shield to the plate. Project will be a bit slower during the summer due to some other tasks around our summer place.

[Jeff Bennetts]

Keep us posted, don’t be a stranger!

[RC 166]

No worries, as soon as I do something I always post the same day.
One more thing about the spacer behind the drive hub: I had to make it longer from L=12.00mm to 14.00mm in order to get some decent thickness of the adapter plate.

[Jeff Bennetts]

Don’t forget to take some pictures !

[RC 166]

Hi all!
Been doing some work on the project.

First I went for the weld-on splash shield solution. I made a groove on the backside of the plate, a bending fixture to bend an aluminum strip with, and then welded it to the plate. It meant that I had to do things I do'nt really like. Fabricating a pre-bent splash shield means sourcing compatible alu sheet stock, make a welding fixture and finally get someone to weld it to the plate. The welds could have been better, but it is a bit tricky to weld a 2mm strip to a 15mm plate. The plate gets very hot to say the least. As you can see there is a lot of trouble to get that shield there with this approach.

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It was just too much hassle to get it done, so I redisigned it to a one-piece solution. It takes 2,4 x as much material and 1,4 x the milling time to produce, but you don't have to do the sheet metal, bending, welding stuff anymore. And you end up with a nice, clean and more presentable product.

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If you want to modify the OEM Denso drive hub you are restricted to a 6mm plate flange and 14mm spacer ring under the hub.
As the CBX OEM square section O-ring is1.4mm up in the flange, this leaves you with max. 4.0mm meat to attach the M8 bolts for the Denso alternator.
Threading this short is out of the question, so I use M8x70 countersunk allen bolts with the heads held in 90 degree angle milled grooves (a wedge groove) in the plate. The bolts will be M8x70 stainless with an added welded spot (see white tape pieces for illustration) on the countersunk side to keep them from rotating once slided into position.

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Here you can see that the splash shield on the adaptor plate is identical to the one on the OEM CBX alternator.

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For any production batch, I will design a one piece drive hub with the correct length, so no spacer needed anymore and with OEM CBX splines of course. This makes it easier for someone that wants a kit as he don't have to send away the Denso hub to be re-splined.
Stay tuned for this.

[RC 166]

Pics of the Denso unit on the CBX

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[Jeff Bennetts]

Thanks for the great write up, beautiful work!

Keep us posted on your progress.

[RC 166]

Thanks Jeff!

Edit: Checked the M8 countersunk bolt length again and found that 65mm is a more suitable length.
I also weighed the total assemblies for comparison, and surprisingly the Denso alternator with adaptor plate is 230g heavier than the CBX OEM unit. Well,I have to chop somewhere else then, because the conversion is deffo worthwhile.

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[Jeff Bennetts]

When the Dutch CBX club first started doing this conversion some 20 years ago, I always imagined trying to fit that ugly Kawasaki alt into the OEM alt cover but that’s for another day.

[CBX-tras]

Nice work.

I see you discovered all the pitfalls and worked around them.

To Jeff: you wouldn't want to enclose the Denso alternator. It makes more heat than the stock one and requires ventilation.
Don't worry about water intrusion either. It's just a smaller version of the one under the hood of your car that gets soaked, driving in the rain. Bearings are sealed, the heat and rotation will remove any water that gets in.

[Jeff Bennetts]

Nice work.

I see you discovered all the pitfalls and worked around them.

To Jeff: you wouldn't want to enclose the Denso alternator. It makes more heat than the stock one and requires ventilation.
Don't worry about water intrusion either. It's just a smaller version of the one under the hood of your car that gets soaked, driving in the rain. Bearings are sealed, the heat and rotation will remove any water that gets in.

It wasn’t going to be completely enclosed, more of a cap for appearance purposes.

[RC 166]

Thanks CBX-tras,

I personally like the Denso design more than OEM. It looks more "high tech" although it could be an inch shorter.
I will make a nicer end cap in alu though. But then my whole bike will be something else with Kawasaki ZX-9R front end, custom top yoke, ZX-9R rear wheel, Yamaha FZR 1000 swing arm, Ohlins twin shocks etc... I will soon start a thread on it under "Project Threads"

[Jeff Bennetts]

Thanks CBX-tras,

I personally like the Denso design more than OEM. It looks more "high tech" although it could be an inch shorter.
I will make a nicer end cap in alu though. But then my whole bike will be something else with Kawasaki ZX-9R front end, custom top yoke, ZX-9R rear wheel, Yamaha FZR 1000 swing arm, Ohlins twin shocks etc... I will soon start a thread on it under "Project Threads"

Looking forward to it!

[Jeff Bennetts]

Peter, like you Stephen Jung liked the look of the denso for some of his highly modified CBX’s! The Euros were way ahead of us here in the states when it came to the amount of modified bikes early on. Stephen was the first that I know of that sold the alt conversion 20 some yrs ago, Tim’s then updated the design and sold them from his store. Others like JR sold them or offered them to their customers as upgrades during servicing their bikes.

Maybe JR or Dave can remember better than I?

[JoeInTUS]

I also weighed the total assemblies for comparison, and surprisingly the Denso alternator with adaptor plate is 230g heavier than the CBX OEM unit. Well,I have to chop somewhere else then, because the conversion is deffo worthwhile.
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You lose the weight of the regulator/rectifier so it is probably close to break even with the weight.