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Myles Raymond
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#662111 07/28/16 3:52 pm
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al jam Offline OP
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I'm not sure this is going to work but I'm attempting to fit a Kubota alternator in place of the dynamo on my Viper. I know it's been done before but I've never seen a photo or explanation of the best way to do it.

After raiding the scrap bin at work for some scrap alloy and spending a couple hours at the lathe here's progress so far.

[Linked Image]

Still a little work to do but with any luck it'll fit though I suspect the pulley/belt cover will require a little modification.

Last edited by al jam; 10/23/17 7:44 pm.

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If you have the room OD wise you could make a carrier and drive it off the non pulley end. (Maybe that was the plan anyway)
The shaft is only a light press fit.

[Linked Image]

[Linked Image]

[Linked Image]

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al jam Offline OP
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Aye that's a good idea Les, I'll be able to see what kind of room I've got when I get home tomorrow night and get it offered up on the bike.


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Just as an aside, if you want more than 14A output at some future point I have found a 20A alternative.

http://chinagas.en.alibaba.com/prod...ent_Magnet_Alternator_Kokusan_Denki.html

Model 100 = Universal one wire self turn on unit for conversion or OEM applications.
Model 200 is replacement for Kokusandinki units as found on tractors & refrigeration units.
Model 200 = Kokusandenki OEM unit repl. for GP9905 / GP9906 / GP9907 Lester # 10930
Model 300 = unit without integral regulator. Has long lead wire for external regulator.

I would prefer the Model 300 without the internal regulator but yet to find that version retail, the Model 200 version is available retail.

This is one example

http://www.urqualitysolutions.com/New-Alternator-8970489700-GP9905-Kokusan-Denki-10930-10930.htm



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al jam Offline OP
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It fits!

[Linked Image]

[Linked Image]

[Linked Image]

I'll need to make up a new rear bracket/plate for the belt/pulley cover as the magnet takes up the space where the old one used to attach.

Last edited by al jam; 10/23/17 7:48 pm.

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al jam Offline OP
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Thanks kommando, I'll keep those links for the future. Since I'm not out in the dark that often I was hoping 14A would be enough, we'll see if it is once it's all wired up..


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As long as you don't plan to add electric start 14A will be fine, I was looking for a conversion to add electric start to my Commandos and need a new alternator as the Lucas one is not thin enough.

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al jam Offline OP
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[Linked Image]

Wiring still to tidy up abit but it all works.

Last edited by al jam; 10/23/17 7:52 pm.

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Would this alternator be enough to power electronic ignition, head and tail lights and indicators ?

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14A version would give at 12V 170W, so plenty of juice in comparison to the std Lucas alternators and very close to the high output single phase Lucas versions. The 20A would be 240W and 3 phase so beats the Lucas 3 phase. Only issue is they do not give a rev number for the output, but as they are fitted to diesel generators this should be at a lowish rev number as these are limited to 3 to 4k rpm.

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al jam Offline OP
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Here's the spec/information I have found

Voltage 12V
Normal Output 150W
Max current 14A
Rotation Clockwise
Output rpm 4250rpm
Charge starting 1800rpm
Drive pulley 100mm
Alt pulley 58.5mm
Ratio 1:1.7

I'm assuming that 1800rpm will put the charge light out and anything over 4250rpm is unnecessary but we'll just have to see how it goes in service.

At the moment I think I'm running about an equal ratio but I was planning on making up a toothed belt set-up running the alternator a little faster.


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Ordered toothed belt pinion blanks and a beltfrom belting online and machined them up this afternoon. Just waiting on the correct belt, ordered the wrong width 1st time round!

Last edited by al jam; 10/23/17 7:54 pm.

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[Linked Image]

Belt arrived today, fits great and there's a healthy charge showing on the a ammeter. A little fabrication is required to get the covers fitted but I'm pretty happy it all works. �17 Inc postage and a bit of time on the lathe is pretty good for a belt drive conversion in my eyes, bit of a shame to cover it up.

Now I just need to rebuild the mag. Fitted a brightspark easycap which has helped with cold starting but the last 2 evenings the bike has cut out and refused to restart once hot. Runs great as long as I don't go further than about 15 miles!!


Last edited by al jam; 10/23/17 7:56 pm.

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Nice Job Al Jam!

Questions:
1) What regulator / rectifier is that?
2) Obviously, you went 12v, but did you stay pos (+) earth?
3) No provision for a belt tensioner.....so the tooth belt needs to be spot on..
What is the front and rear pulley full description and belt size?

I'm thinking of doing the exact same thing. Ebay in us has plenty of Kubota alternators for $67 US. Just need to figure the rest of the parts.

Thanks!

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As there is a lit of inertia on the alternator I would use a V belt. Guess how I know

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Could the housing be machined so that the alternator doesn't sit in it concentrically? That would mean the pulley would be off center and belt tension could be adjusted the same way as the stock set up.

Ed from NJ

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al jam Offline OP
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That's what I did, there's not a huge amount of adjustment but there's enough to keep the belt tight

[Linked Image]

[Linked Image]

Just after I bought it in 2013 before mechanical re-commisioning

[Linked Image]

And today after 40 miles in the uncharacteristically sunny Scottish winter...

[Linked Image]


Last edited by al jam; 10/23/17 7:59 pm.

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Thanks for the additional picts you sent and posted. It clears quite a bit up. Mike

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Finished off the last couple jobs today.

Felt a little bad about butchering the inner belt cover but it wasn't in great condition to start with. I turned an extended crankcase stud nut to use as an upper mount having removed the old upper mount that no longer fitted due to the increased diameter alternator compared to the dynamo.

Also had to make a new outer battery strap, the original was a casualty of an early test ride. Unfortunately the flat bar I had was a little thicker than the original but it'll do for now.

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

Last edited by al jam; 10/23/17 8:02 pm.

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Hang on I'm confused Al, earlier you had fitted a tooth belt, -did you later go back to the vee belt?

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al jam Offline OP
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Aye, I decided to go back to the v-belt, I misread the chart when selecting the belt size and the T5 belt is a little on the light side so I've reverted to the V-belt for now until I get time to build up a stronger set up. I'm also curious to see how the alternator performs at the current speed ratio. I'm thinking of speeding it up to increase the current at lower engine rpm but since it was designed for a small diesel engine I'm wary of having it run too fast for fear of overheating it. Don't know if anyone else has an opinion or experience of this?


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Have you measured the output at various revs Al?

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I haven't a rev-counter fitted at the moment but it's on my list of things to have a look at over the winter. I also need to fit a new regulator as the one currently fitted has given up, I think it happened when the live feed to the battery fretted through on a longer ride into the borders. The fuse at the battery blew but I didn't have one at the regulator so I'm guessing that the prolonged short is the cause of the failure. I've bought a cheap Chinese scooter rectifier which seems to work but we'll see how it lasts after a few miles.


1958 Triton
1958 Triumph 650 Speed Twin
1958 Velocette Viper
1959 Norton 650SS bitsa
1961 BSA Bantam D1

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