BMW Airhead Drag Bike

[Dexter]

So far i have spent my time in the Sportster Forum on a build thread and while this has progressed I started looking for some ideads for a new project. You know the one just look won't buy anything just yet need to finish........ sound familiar ?
Anyway you already know what happened but here's the back story.... been looking a old BMW's for a while and looked at the growing scene in Europe for Cafe Racers and the like at the same time going to my local Drag Racing meets and thinking i would like to see if i could combine the 2.
Plenty of time doing homework and picked out a old plunger frame as the bike of choice so a R50 / R69 type, looks like they were going to be hard to come by so hatch a plan to buy just a frame and buy parts as they come up, found a frame in USA but missed it as organising shipping turned into a nighmare. It was all looking a bit of a lost cause when chance phone call which coincided with a planned weekend break just came together - the starts must have been aligned just right.
The bike was a 1959 R69 - roller with reg but no engine / gearbox and 16 size wheels - did'nt tick all the boxes but enough so it came home with us.

So here's a picture of how it looked when we picked it up - san's rear wheel


And after a few hours poking and proding this is how it sits or should that be lays today


So that's about it so far, lots of bits to sell and things to buy just how we like it.

[Dexter]

q

[Supertjeduc]

So dragbike BMW , i think you wil like this one

[farmall]

Cool dustbin fairing.

[Dexter]

So this is part of my inspiration but hopfully my own twist will give it a different slant, if you look at some of the vids from the cafe race meet on Germany this year this also helped to cement the plan.
Should be posting up some more progress from this weekend ........

Thanks for looking

[Dexter]

So all stripped down and looking naked... and the angle grinder seen some action.

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[Dexter]

Lots going on but not updating the thread....

Wheels came in for some treatment.
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[Dexter]

Tank Mounting

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[Dexter]

Started removing the unwanted frame brackets

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And the bits of scrap...

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[555]

Great project, I like custom airheads, but BMW purists all over the world are crying! LOL!

[Dexter]

Hi 555

Yes its never easy messing with a classic bike to know how it will be recived, I also post on an Airhead site and they sort of said do what you want better to be being used than left in a shed.

So its being built for speed in my ownership so i better get a move on....

Thanks for looking

[Dexter]

So no point having a drag bike without a nice engine and Richard Moore was the bulder of choice in the UK. This is a full build with soem of his bespoke parts...

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[Dexter]

18 rims front and back satin powdercoat

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Bit of slick action
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Getting the engine in the frame was not easy so came up with this idea which worked a treat
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And with gearbox loosly in place
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Next up its modify the swingarm

[Dexter]

So that swingarm, to have the later option wheels and more importantly gear ratios in the bevel box we needed a series 5 swingarm, this also has the added advantage of a longer wheel base so double result.
Having bought a series 5 swing arm complete with drive shaft ( this is is also longer ) the fun could begin, now clearly things have advanced since 1959 and one is the swing arm pivot width which has grown by around 25mm. We needed to hatch a plan and this formed in getting the grinder out...

Before
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So it looked something like this we even chopped out the gussets as this would not hinder welding it all back together again.
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To make sure it was all going to line up we also needed to move the swingarm over to the drive shaft side as part of this addaption to get the DS to run through the swingarm tube without rubbing this would mean we had to cut off 10mm from this side and lose the tapered bearing from this side - I will come on this later.

Bit of trial fitting
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With all these mods we couldn't lose sight of the rear to front wheel alignment so some more trail fitting with the hub in place string line ETC - with the drag slick in place we would have very little room for manoeuvre.
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Back to the main plot and having cut everthing off including the middle section we turned up a thick wall tube and pushed this in one side tacked it in place then pushed the other side on then took some more measurements including trying the wheel spindle which slide into place - all good.
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Once we were happy it was seam welded, now we needed to come back to the removal of that tapered pivot bearing, the BMW works by having a threaded hole each side in the frame for the pivot pins to screw into, these are then tightened to a cup which then pushes on the taper and removes any play. We had been able to keep one of the bearings and as this bike will have solid struts to replace the rear shocks this swingarm no longer needs to pivot or allow rotational movement so its more like a locator so our solution was a bush type replacement.

Our cunning plan was a solid steel insert with the piviot pin hole bored through, this was pressed into what was left after we had cut down the drive shaft end..

BMW pivot pin and our solid bush
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Swingarm all ready for some pressing...
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And welded in place
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[Dexter]

Thought it would be a good idea to make up a seat location, wanted something which would keep clear of the tyre and offer some good support for those quick starts

used some thin wall tube and bent this to shape round the trusty welding bottle which looked to be the correct radius also welded on some tags for mount the ali sheet which would form the seat base.

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Then added some support bars

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Offered it up and tacked it in place for a trial sit.

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Then finished off with a seam weld.

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