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Plasticpig
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« on: June 29, 2017, 04:21:20 PM » |
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Hi All.
I bought a Kwak GPX 750 which had been standing in a back garden for a long time. I was going to walk away, but the bloke's wife told him let it go, and he dropped the price to a hundred quid. For that money I thought that even if I don't do anything with it, I would at least get my cash back for the bits. Cost me another 25 for the logbook, but it is in my name now.
I am hoping to do a cheap bolt on conversion, but am in a quandry about keeping the 750 lump, and looking for a yam middle box, or similar, or trying to find a Kwak GTR 1000 shaft drive engine, which would save a lot of fabricating. If anybody does have, or know of said lump, could they get in touch.
Otherwise I will be looking for the yam middle box, or perhaps a left hand bevel drive box which can be turned around to provide shaft drive. If I do this I am not sure about the maths involved when working out ratio's and number of teeth required.
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Manky Monkey
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« Reply #1 on: June 29, 2017, 11:35:39 PM » |
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The old Yamaha XS bevel drive units fetch big money these days & I haven't seen one for sale for ages. I think Chris Ireland of Desperate Dan's trike shop was the originator of that idea wasn't he. Must be other bikes fitted with similar systems that might be cheaper to get hold of? Moto Guzzi maybe? If not, it's only 2 cogs running on shafts with bearings, in an oil tight box with a 1:1 ratio -maybe easier to make one? Or look beyond automotive applications & see if they're used for other machinery? (factory equipment, plant machinery like JCBs, dumper trucks etc). There might be a much cheaper, readily available alternative to the Yamaha unit & you could start a whole new trend!  |
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On the last freedom moped out of Nowhere City.
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Plasticpig
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« Reply #2 on: June 30, 2017, 12:04:16 AM » |
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Cheers Andy.
You can also get Honda and Kwak versions, but the Yam middle box is a nice compact unit with it's own oil supply. I am looking at shaft/final drive units to reverse, but if I can find a bigger Kawasaki shaft drive lump to fit it might be easier all round. A mate of mine used an Audi TT transfer box on the back of his 1.9 diesel bike, but it is humongous.
See picture below.
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« Last Edit: June 30, 2017, 12:15:26 AM by Plasticpig »
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minimutly
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« Reply #3 on: June 30, 2017, 09:56:10 AM » |
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I'm not sure what your after here? Is it the bevel box fitted to the kwak gearbox? Mine (gt/z750), has this bolt on I believe. Are these the same? There are a fair few of these engines about for little money, just a matter of waiting for one to come allong. Whether the 750 is enough oomph for you is another matter, the 80 odd from mine feels a little short sometimes - climbing hills 2 up usually.
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Plasticpig
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« Reply #4 on: June 30, 2017, 12:30:42 PM » |
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Huw.
This is where I have opened a can of worms. Different sites put the GPX at about 100 hp. That was when they were new, and mine is around thirty years old and has been standing the rain for god knows how long. Dunno how much it will put out now, and also the power is all at the top end. While surfing the net for info I noticed that ZL and GTr lumps would fit my frame, and would save me farting about with chain drive conversions.
Axle wise I have a shortened Bedford Rascal axle which Morrag very kindly gave me, and another from a mk 3 Cortina which is very wide, and weighs half a ton.
Options are to use one or the other of the live axles with a middle box, or buy a chain drive diff from West Wales trike shack for 290 quid and fabricate an IRS back end. Last night I was looking at BMW 3 series E46 rear subframes and diffs, or one from a Freelander which is much lighter.
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the coppersmith
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« Reply #5 on: June 30, 2017, 02:26:13 PM » |
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Mazda MX5 IRS rear axle, that is the way the kit cars are going. Lighter and strong. Can be cheap too. If your really lucky (like I was) they come with LSD too
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minimutly
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« Reply #6 on: June 30, 2017, 04:18:14 PM » |
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You won't get cheaper than a freelander, provided of course its good, and the right ratio for you. But then, plenty of bimer and a fair few mazda units about.
I still think you need to check if the gt 550/750 bevel will fit your box, but I'm guessing it won't though. You could allways make your own fiesta based chain diff, hung on plummers in an irs frame, better job than a hard tail or swing axle conversion (IMHO)
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« Last Edit: June 30, 2017, 04:34:37 PM by minimutly »
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Plasticpig
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« Reply #7 on: June 30, 2017, 05:37:51 PM » |
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I weighed in a Fiesta gearbox a while back. I will check the GT bits, but I have a feeling the bottom castings are completely different to the watercooled stuff.
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minimutly
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« Reply #8 on: June 30, 2017, 06:28:12 PM » |
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Just zoomed in on that pic of your mates oilburner - lots to comment on there!
Firstly, does he have a left leg? If so I would expect it gets pretty warm.
The drive rearward comes off the diff output (normally the driveshaft on a fwd car), so the ratio is something like a 2.9 to 3.5 allready, so his bevel box is likely to be 1:1 or thereabouts?
Interesting build though - got anymore pics?
I have a desire to build a car engined trike with transverse gearbox, but take the drive off the end of the pinion shaft, cutting off/out the diff. You loose 5th gear but so what, provided the rear diff ratio is high enough you shouldn't miss it.
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Plasticpig
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« Reply #9 on: June 30, 2017, 07:04:49 PM » |
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Huw.
Here is Mouse at this years Rat and Survival show. I think this is the first time he rode it anywhere, as he has a habit of going off somewhere to test his creations, instead of doing it by his house. Last one he built, he went to East Germany on it the next day.
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