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Old 08-18-2009, 02:19 PM   #1
AKjeff OP
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My Airhead Project

I've wanted to build a bike for years. First it was a Harley, then a Triumph (both would have been bobbers) finally I wanted to build an Airhead dirtbike.

Most of my incentive is from the airhead dirtbikes thread: http://www.advrider.com/forums/showthread.php?t=56044

So this is what I started:



Parts so far:
'77 R75/7 frame - from E-Bay
'83 R80RT subframe and rear fender - E-Bay
'86 R80G/S tank - from my G/S - the tank is only for moral support and encouragement, it will go back on the G/S and the R100GS tank that's on the G/S will go in this.

The rear fender will be bobbed, the subframe will be modified, the frame will be modified. It was the permanent mods that I want to do that helped me decide to build this, rather than make permanent changes to my G/S.

I have a '83 R100 swing arm coming that will probably be modified too. Unless I go back to my original plan of using a single sided swing arm. Soon I'll be shopping for a complete airhead for the drive train and various little pieces. I'd like to find a wrecked bike, so I don't take a runner off the road.

Forks? KTM, DR, Yamaha YZ... I'm pretty open right now, whatever shows up first will get put on.

I have no time frame in mind for completion, it all depends on finding the parts. It won't be pretty, though I hope it's not too unsightly. I want it to run good and function. I imagine it will be a work in progress for years as I try new things, tweaks, mods and different parts. I'm envisioning this as a dual sport for local use, maybe short trips. I've got my 1200 for freeways and long trips.
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Old 08-18-2009, 02:29 PM   #2
Airhead Wrangler
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Quote:
Originally Posted by AKjeff
I have a '83 R100 swing arm coming that will probably be modified too. Unless I go back to my original plan of using a single sided swing arm.
I'd go the double sided swingarm route. It allows you to use BIG FAT tires without them rubbing. A monolever is limited to 120s and a paralever is limited to 130s (which still rub in some cases).
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Old 08-18-2009, 05:48 PM   #3
L.A. Woman
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Hi Jeff

This ought to be interesting. I will be watching (and hopefully learning) with baited breath.
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Old 08-18-2009, 06:11 PM   #4
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forks? I learned my new favorite spanish word while talking about forks with some Costa Ricans: invertido!
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Old 08-18-2009, 07:32 PM   #5
AKjeff OP
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Quote:
Originally Posted by Airhead Wrangler
I'd go the double sided swingarm route. It allows you to use BIG FAT tires without them rubbing. A monolever is limited to 120s and a paralever is limited to 130s (which still rub in some cases).
Thanks for this info. I knew there was an issue running fat tires on the monolevers, I didn't know the double sided swingarms didn't have the same issue. I will plan on using the double sided swingarm then.
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Old 08-19-2009, 11:49 AM   #6
wolfy317
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Like what you're working with. I'm gonna be starting an r75/5 GS build soon. Thought you might like to see this bike. It's not an offroader obviously, but it's a cool build. Might give you an idea or 2.

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Old 08-19-2009, 11:57 AM   #7
Caddy82rats
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Nice project
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Old 08-19-2009, 12:07 PM   #8
AKjeff OP
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wolfy, I've seen that bike before, is it yours? I love it, I really like the rear suspension. I'm thinking of doing something different for the rear suspension on my project. That one gives me some ideas, if I can make it fit.
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Old 08-19-2009, 03:04 PM   #9
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Just to get the juices a-flowin'.......................






















And, in the interests of full disclosure: no, those are not my bikes, and no, I have no idea who took them.... I just liked 'em and stole 'em and put 'em in my pornobox.....




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Old 08-19-2009, 04:15 PM   #10
AKjeff OP
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Thanks, I have that orange framed on saved too.

Does anyone have any input on rear suspension? Looking at the pics that bpeckm posted, I'm thinking that the suspension would work better on the blue framed bike than the orange framed bike. I think if the compression is more in line with the axle it will be easier on the frame and swing arm, I guess it seems the energy would be transmitted better.
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Old 08-20-2009, 05:44 AM   #11
wolfy317
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Quote:
Originally Posted by AKjeff
wolfy, I've seen that bike before, is it yours? I love it, I really like the rear suspension. I'm thinking of doing something different for the rear suspension on my project. That one gives me some ideas, if I can make it fit.
I wish it was mine. Just a good looking ride. I love that gs'd R100s too. I'm gonna be GSing an 75/5, but I really don't even know where to start.

Good luck on the project. Looking forward to seeing more.
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Old 08-20-2009, 06:10 AM   #12
bpeckm
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From my studies of mechanical loads ( long time ago....) it seems to me that the blue bike has built a triangle, which would transmit suspension loads the swingarm at the ends, making it stronger (same principle as gusseting or reinforcing the swingarm to limit deflection)

The orange bike is using the same shock point on the swingarm as used by a monolever G/S, but he has a double-sided swingarm, so he is theoretically halving the load for each arm/shock, as compared to the 80G/S mono f'rinstance....

In both cases, the aim is to get longer suspension travel: this is achieved by having a longer shock, which is accomplished by having the longer shock laid on an angle rather than more up and down. In the end analysis, the loads imposed by a human riding a 400# bike, even with shock/impact loads, is pretty small and easily accomplished with metallurgy. Yes, ideally it is nice to make a fairly straight load (look again at wolfy's black and orange beauty and see how that shock is compressed pretty much straight in, but the "bridge" that holds the aft end of the shock probably has some interesting loading......).

The typical airhead of the /70's has a very straightforward and conservative load, but suspension travel is low due to the short-and-vertical shock mounting.
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Old 08-21-2009, 05:11 AM   #13
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Baby GS

Kind of like this?
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Udo screwed with this post 05-21-2011 at 10:59 AM
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Old 08-21-2009, 05:24 AM   #14
wolfy317
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Quote:
Originally Posted by Udo
Kind of like this?
R65?

Seeing these pictures really makes me wanna get started on mine.....guess it's time to pull out that frame and get to blastin.


What kind of seat and subframe is that on the orange bike? Anyone know?
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Old 08-21-2009, 10:31 AM   #15
AKjeff OP
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Like that Udo, very nice.

wolfy, that might be a modified G/S subframe. The upper rear bend looks right. The left leg has been bowed to go around the shock. I want to do some similer mods to my RT subframe. It's 18mm tubing, which I found online at McMaster-Carr. I haven't found a metric tuding bender yet.

What are you waiting for, get started. Share some pics, here or in another thread.
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