BMW K bikes (Bricks)

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1Back to top Go down   TANK SWAP Empty TANK SWAP on Wed Sep 30, 2020 7:34 am

moriarti

moriarti
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Life time member
Hi ALL Your thoughts ideas and suggestions on fitting early single bolt tank to replace later 2 legs/pin fittings.A weld fittings onto frame to accommodate single bolt position cross rail.B make 2 legs/pins and fix to tank to utilize original tank fixing.  Chatter


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1984 k100 rs red/black VIN  0004449
    

2Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 8:05 am

chris846

chris846
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Life time member
I've done the swaps in both directions. AFAIK the change from the single bolt type was because of a problem with the mounting - the 'tongue' on the tank - not being strong enough. That said, I've been running a single bolt mounting tank for over thirty years without an issue.
That 'problem' aside, I think the later type of mounting is pants - the clips are really fiddly, the rubbers keep coming out, and I don't think they'd stand much chance of holding a full tank in place in a collision. So...I'd junk those clips and pins and weld 2 captive nuts to the frame to replicate the earlier type mounting. 
Not that I'm biased.... Laughing


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Sometimes I'm not really Suzi Quatro.
    

3Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 8:55 am

moriarti

moriarti
Life time member
Life time member
Cheers,chris, welding the captive nuts on was my first choice too but its a mates bike so thought best to ask on the ORICAL. Very Happy Very Happy


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1984 k100 rs red/black VIN  0004449
    

4Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 11:06 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Chris, with regard to your comment about holding the tank in a collision I have heard people worry about it not only coming away from the bike, but also having the pegs tearing holes in the tank or some such.

A couple years ago I had the unenviable opportunity to test the performance of the bike in a crash caused by being rear ended by a car going 75mph while I was doing about 40mph.

The results were that the bike was thrown over 100 feet, and tumbling, as witnessed by the debris field and the damage. The severity of the impact was witnessed by the 2 foot deep indent in the front of the KIA that hit me.

At the time of the assault, the tank had approximately 4 gallons of fuel in it. At some point in the tumbling, the tank separated from the bike along with the seat, and the bodywork. Both of the pegs that hold the rear of the tank had their welds fail allowing the tank to leave the bike. The fuel lines failed at the hose clamps, one at the rail, and the other just below where it enters the tank. The electrical connections broke where they entered the tank.

Despite being pretty beat up, the tank held all it's fuel and did not leak. The welded pegs appeared to be designed to breakaway without tearing the surrounding sheet metal of the tank. They stayed in the rubber grommets in the frame where they were held by the C-clips.


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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
    

5Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 11:50 am

chris846

chris846
Life time member
Life time member
"the tank held all it's fuel and did not leak. The welded pegs appeared to be designed to breakaway without tearing the surrounding sheet metal of the tank"


I get that completely, I'm sure you're right about the design and I'm amazed to learn that the welds gave way before those clips. I know that Buell had to design their fuel in frame bikes so's the headstock would break off without compromising the integrity of the tank. Me? if we're at the point where I'm sat on a bike that's just hit something so hard that it's headstock has snapped off/tank has launched itself, well, I don't think that I'd be thinking "golly, hope no fuel got spilt" at any point soon. I'd guess you maybe felt the same as you were sailing through the air?
Glad you're still (able to be) on a bike  Smile


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Sometimes I'm not really Suzi Quatro.
    

6Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 12:18 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Chris, actually, I don't recall much beyond the impression of alternating light/dark while I assume I was tumbling along in the median.

When I regained consciousness a while later all I was thinking about was being able to stand up and wondering how the hell I was going to get the bike back together as I looked at bits of it spreading out to the horizon.


__________________________________________________
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
    

7Back to top Go down   TANK SWAP Empty Re: TANK SWAP on Wed Sep 30, 2020 5:49 pm

MartinW

MartinW
Life time member
Life time member
Some of the Bricks side covers are held on by the edge of the tank. If the "C" clips aren't in place hitting a reasonable size bump or speed hump can allow the tank to jump up freeing the side covers allowing them to make a bid for freedom. A mate who lost a few side covers took a lot of convincing before he reinstalled the clips. I got him riding around a super market carpark hitting speed bumps. Eventually one came loose. The excuse for not fitting them is that they are too hard  to fit and remove. This can be remedied a few ways make a hook with a finger loop (velcroed under the seat ). Fit a cable tie to the "C" clip and trim it to a suitable length. Or make really long "C" clips out of thin sheet metal.
Regards Martin.


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K75s Hybrid
    

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