Cafe Racer Forum banner

1981 Yamaha XV750

10K views 72 replies 14 participants last post by  Coxbow 
#1 ·
Hi Folks,

So I've got this:

105058


And I'm planing to make something Cafe Racer(ish) out of it, it won't be the best handeling nor best stopping XV750 out there, but it will be way better ( not very difficult I have to admit...)

What I already got:

A XJ900 front, not a USD super brake setup, but still, anti-dive system and most important dual disk

105059


I'll have (well a machine shop) bore out the clamps from 36mm to 37mm, that shouldn't be a problem.

The problem is that I don't like the wheel, I already painted it black, it's better but not quite there yet

105060


I also designed and 3D printed a "Boyd inspired" wheel cover just to see if it would be better:

105061



Got a '06 Yamaha R1 rear shock ( that looks like new ! )

105062


I'll have to design an adapter for it to fit, it's a couple of inches shorter than the OEM one.

Got also a Kawasaki KZ650SR fuel tank, it will fit without any modification, I'll just have to make a bracket on the seat side.

105063


It looks like this on the bike.

105064
 
See less See more
7
#48 ·
Hey, you started it with your "worst" rating! :p

I thought about titanium... it's been a lot of years since I worked with it and I never knew a ton anyway, but I'm guessing stamping titanium is a bitch, wears tools quickly, and is a pain to weld in production so not a great choice for tanks.

They made airplanes out of plywood too, doesn't mean it's a great material for a gas tank!
 
#53 ·
I work with carbon for a living and know the stuff inside out, I really wouldn't recommend it for a fuel tank, there are various issues with it, UV degradation being one, more to to with the resins involved.
The resins start to break down over time and turn green / yellow, obviously painting it can protect it to some extent.
And you may need a liner inside, carbon can be porous too as it tends to have tiny pin holes.
It can and has been done though, an autoclave would give the best results but that's mega money!
 
#55 ·
It's a weave yes, but it's filling the weave with the resin that's the problem, I use various silicone bags made to suit the moulds and infuse the resin via a vacuum to pull the resin through the cloth.
This in theory should remove any air from the weave and fill it with resin, I still get some tiny pin holes on occasion, warming the resin with a heat gun as it travels through the mould helps as it thins the resin and expands the air bubbles to get them moving.
 
#57 ·
Thanks for your input, I'll of course put some fuel tank sealer inside, shouldn't this do the trick ?

About the UV degradation, I want a matt finish so I'll clear coat it, and I'm using UV resistant resin as well, that should take care of the outside ?
 
#58 ·
If you use uv resistant resin and laquer it should be fine, but double check the small print for what you use, it may just be 'resistant' but not 'proof'
First sign of degradation would be a slight milky green tint.
But if it's not left outside in blazing sun it should be OK.
A liner would be a good belt and braces practice.
Hope that helps.
Cheers.
 
#65 ·
I was just curious, we use a carbon material that has a PET backing, basically recycled plastic milk cartons, and it's woven in a way that allows it to be moulded in any shape, without stretch or distortion.
Yours looks similar, you did very well with that, getting it over a 3d shape without the weave pulling and tucking into creases.
Is that one half of the tank?
 
#67 ·
Is that one half of the tank?
Yes it's one half, since it doesn't have to be 1/1 size copy of that fuel tank, it comes form another bike, and to avoid making a mold, I did a skinning of the tank, but covered the tank with tape before to ensure release, once the other side done I'll assemble both parts and add layers from the inside.

that's what I came up with, if there's a better way, without making a mold I would gladly here it :D
 
#69 ·
I use both types, infusion is most common and easier for repetitive stuff, I use pre-preg for the tonearm we make as its easier to shape and put it in the oven
We also use a white fabric called PET which is recycled plastic, layers of that over carbon is melted at 220°c, its nice and tough but gives a little flex to the carbon, good for crash protection parts on bikes!

If you go down the infusion and vacuum route, my best advice is control the ambient temperature as much as you can, 20 - 23°c will give you the best results, the resin will flow at a steady rate, and you get a longer pot life, 10 degrees higher will half the pot life, and be wary of thermal runaway of the resin, when it starts to warm its only a few minutes away from going madly hot and smokey, it will set in seconds!
 
#70 ·
I'll also use some white cloth called Silionne in French, I've being advised to use this to provide the fuel tank to explode in a thousand pieces in case of crash, we are maybe talking about the same material but mine is separate to the carbon cloth.

Sorry but I can't follow your second sentence, what pot are you referring to ? Also thermal runaway ? ( thanks for your patience ;-) )
 
#72 ·
No worries mate, the 'pot I'm referring to is your container for the resin, if you infuse the carbon it will need a pot of resin to draw from.
That resin will only last for 25 - 30 mins and will then start to warm up, and when it does it goes quickly! It will basically start to boil, if that happens just get it outside with some thick gloves or tongues. (Thermal runaway)
Anything you need to ask just fire away fella.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top