BMW K bikes (Bricks)

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1Back to top Go down   K75 Gas Tank Fixup Empty K75 Gas Tank Fixup on Thu Sep 10, 2020 1:13 am

jjefferies

jjefferies
Silver member
Silver member
Background: My project bike, a '90 K75, is up and running. Minor issues that I'm working on. But the rattle-can spray job that I did on the tank while reasonably decent isn't quite as nice as I wished. So casting around for a solution, a friend showed me a tank he did by simply polishing the tank on a buffer. Now that looked very interesting. Several caveats, first I don't want to sacrifice my current tank in the process. First I thought to find/purchase a new tank. Greg doesn't have a proper one for this '90 bike, but thought that I might locate one for USD$100. So far no luck. Now I do have a tank off the parts bike he sold me but whoever rode it down obviously did a tank slapper. There are serious dings in the right rear of the tank and under the BMW logo on the right front. So my thought is to beat out the dings as best I can and then do the equivalent of "lead (ing)" of  the dings and then grinding/sanding/polishing the filler metal down. And in the process polish out the rest of the tank's upper half. The filler metal I am thinking to use is the Durafix-Aluminium-Welding-Rods-Brazing-Easy-Soldering-Low-Temp things your find on ebay and the internet. The tank itself is sound and doesn't need to be repaired just leaded and polished. For anyone not quite sure what is meant by "leading", you take a torch, heat a piece of metal usually a external car part and apply the metal lead to it. After the lead metal semi-melts onto the car piece rather like bondo you grind and polish off the excess. Way back when, this was the preferred method of fixing dings in cars or bikes.

My question is has anyone else ever tried anything similar and is there a difference in color between aluminium and these brazing/filler rods? Really don't want to do the work only to learn there is no way you can make the different materials blend into one another in terms of color. Appreciate any useful suggestions or experiences.
Thanks
J.

    

2Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 1:22 am

MartinW

MartinW
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I don't know whether it would work on a tank but we have a couple of local shops doing vinyl wraps on motorcycles.
You would have to be extremely careful about not spilling fuel around the filler neck and the area around the neck would have to be painted.
Regards Martin.


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K75s Hybrid
    

3Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 1:41 am

jjefferies

jjefferies
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@MartinW wrote:I don't know whether it would work on a tank but we have a couple of local shops doing vinyl wraps on motorcycles.
You would have to be extremely careful about not spilling fuel around the filler neck and the area around the neck would have to be painted.
Regards Martin.
What do you mean by vinyl wraps?? Applying a vinyl plastic material to the tank? Not heard or seen of it myself. Will ask around. But my preference is for metal. Still might have to clear coat to maintain the polish or polish a lot.

    

4Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 1:57 am

MartinW

MartinW
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This is a  example of a couple of sites (there are lots) that do vinyl wraps on bikes and cars, the advantage is that if you wish to change it at anytime it can be removed with the aid of a heat gun. I bought some bits of a guy who had vinyl wrapped his car and was doing a Brick café racer that I think he was going to wrap. I had a talk about how hard it was to do and he said after watching a few You Tube videos and a few stuff ups he now had the hang of it.   https://secureservercdn.net/198.12.144.78/l2g.63c.myftpupload.com/wp-content/gallery/home/BikeColourchange.png  
https://linehousegraphics.com.au/motorbike-racing-graphics-kallangur-brisbane/
Regards Martin.


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K75s Hybrid
    

5Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 3:38 am

chris846

chris846
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Not sure about the aluminium brazing rod idea. Never done it, but I have used the rods for fabrication and stuff with varying success. The finished braze is usually a dull grey colour (at least with the brand I've used) but then I've never really tried to flat it and polish it as you're thinking. Main issue for me would be the heat you are putting into the tank to achieve a braze. Ally doesn't glow a different colour to let you know it's up to temp - one second its there looking normal and the next - a hole! The lead thing uses the fact that lead flows at a temp where the metal bodywork is still relatively cool so you've a big margin to work in. The ally brazing rods require the base ally to be at quite a high temperature, so you're much closer to catastrophe. Ally expands quite a bit with heat too, so distortion could make things tricky, as could the high thermal conductivity - which tends to mean that you have to keep pumping a lot of heat into to your work area. I'd guess that your idea would be more suited to sharp, smallish nicks and dings - almost like repairing a hole. The lead thing makes me think of large, shallow depressions, and I'm not so sure about that. I'd love to see how you get on, 'cause ideas like this are great.

...Just thinking, what would be wrong with trying plumbers solder? s'basically lead and it would stick to cleaned ally?


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Sometimes I'm not really Suzi Quatro.
    

6Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 7:46 am

Laitch

Laitch
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@chris846 wrote:...what would be wrong with trying plumbers solder? s'basically lead and it would stick to cleaned ally?
Using it would present the same challenge as brazing—developing sufficient heat for it to stick without deforming the tank or burning off the flux first.

Lead is unlikely to polish well or match texture with the tank. Repainting the tank with suitable materials, technique and patience is the most viable alternative.


__________________________________________________
1995 K75 77,000 miles
K75 Gas Tank Fixup Usa-lo10
    

7Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 8:19 am

Point-Seven-five

Point-Seven-five
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Lead?  I don't think they even use it in the factory anymore. I had a bike where the previous owner used that aluminum brazing stuff to repair some corrosion holes in the tank.  That stuff is hard, and would be a really hard job to sand smooth.  It's for welding and filling holes where finish isn't important.

You want to get a quart of this stuff:

https://www.bottompaintstore.com/duraglas-fiberglass-filler-24035-1-quart-p-10555.html

Duraglas is better than regular filler because it has glass fibers in it that make it much stronger.  It's also more waterproof than regular fillers because it's made for use on boats.

You can get it at a local West Marine store.

There are people who do paintless dent repair that can pull the dents out without damaging the paint. 

Have you ever painted or done prep work for a paint job before?  Your post doesn't sound like you have.  Post some photos of your tank, and describe what you are trying to accomplish ie. are you doing a custom paint job, or a factory color repaint. 

What is your budget?  A good paint job with a factory color isn't cheap, but it doesn't have to be crazy expensive either.  There are many here who have painted their bikes and can walk you through to good results.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

8Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 8:35 am

tinyspuds

tinyspuds
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@chris846 wrote:Ally doesn't glow a different colour to let you know it's up to temp - one second its there looking normal and the next - a hole!
FWIW, and I wouldn’t risk a tank on it, when bending/annealing ally a few stripes from bar soap around the work area will burn when it’s up to temp.


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106. (Not blind to the irony of an April 1 production date).
1954 Royal Enfield 350 Bullet. Original.
    

9Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 9:13 am

moriarti

moriarti
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A good panel beater will do a top job for not a lot of $$$


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1984 k100 rs red/black VIN  0004449
    

10Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 4:33 pm

jjefferies

jjefferies
Silver member
Silver member
@chris846 wrote:...Just thinking, what would be wrong with trying plumbers solder? s'basically lead and it would stick to cleaned ally?
There was a phrase from the last century "Mad as a Hatter" regarding folks who did leading on the in vogue hats of the time. My understanding is that it didn't take long or much lead fumes to make serious impact on one's intelligence. Back in the sixties, I was shaken loose of the Carny I had started out with and in need of employment for the summer and landed in Chicago in the loop at midnight. Anyway checking in with the local employment folks they tried to send me out to a auto shop to do leading. The boy is dumb but not quite that stupid.  If you don't mind I think I'll pass on anything involving melted lead.

    

11Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 4:41 pm

Laitch

Laitch
Life time member
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@jjefferies wrote:There was a phrase from the last century "Mad as a Hatter" regarding folks who did leading on the in vogue hats of the time. My understanding is that it didn't take long or much lead fumes to make serious impact on one's intelligence.
It wasn't lead causing the damage; it was mercury.


__________________________________________________
1995 K75 77,000 miles
K75 Gas Tank Fixup Usa-lo10
    

12Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 5:52 pm

Point-Seven-five

Point-Seven-five
Life time member
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@Laitch wrote:
@jjefferies wrote:There was a phrase from the last century "Mad as a Hatter" regarding folks who did leading on the in vogue hats of the time. My understanding is that it didn't take long or much lead fumes to make serious impact on one's intelligence.
It wasn't lead causing the damage; it was mercury.
Exactly, there was a factory I called on back in the 80's that made temperature controllers that used mercury in the manufacturing process.  The place was unbelievably creepy.  People who worked there for a long time were almost normal, but would have little nervous things like weird eyes or shaking/twitches.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

13Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Thu Sep 10, 2020 6:45 pm

moriarti

moriarti
Life time member
Life time member
Obviously,K owners then Evil or Very Mad Evil or Very Mad


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1984 k100 rs red/black VIN  0004449
    

14Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Fri Sep 11, 2020 4:44 am

Dai

Dai
Life time member
Life time member
I'm with .75 on using a form of bodyfiller. In either case, it's going to take time and a lot of patience to recreate the tank curves. Been there, done that, succeeded, don't want to do it again.


__________________________________________________
'83 K100 upgraded to K100RS spec, '87 K100RT
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California
    

15Back to top Go down   K75 Gas Tank Fixup Empty Re: K75 Gas Tank Fixup on Fri Sep 11, 2020 10:23 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Post a couple photos of your tank.  What are you trying to accomplish with it?  Is this a custom, or are you doing some repair and a repaint?  What is the present condition? 

There is a booming industry of specialists in dent repair who can pull out dents without having to repaint the repair.  They do most of their work on lease vehicles either for owners who need to turn in an undamaged vehicle, or for dealers who are reselling lease returns.  You might want to have one of them look at your tank.

Some collision shops have someone who can do that work.  Another place to find one is at a place that sells materials to the local collision shops.  The best guy around my part of the world works in a building that is part of the local car wash.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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