Airhead frame rake difference between G/S or GS and R100/7. R100/7 into a HPN

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bartek_ns

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Hi Everyone
I was wondering if any one knows a definite answer to this question:
Is there any difference in rake between airhead GS and other frames from that years ?
Also any objections in using the twin shock mono lever in HPN like application?

Above question regards my new project /idea with is converting my 1978 R100/7 into a HPN like motorcycle.
Since I cannot justify spending five grand on the motorcycle that i will be chopping and fiddling with to the point where
there isn't much left of a stock GS I am considering converting my 100/7 into HPN like machine .
I am familiar with the subject I know it involves a lot of work done to the chassis (reinforcement of the frame relocating the shock mounts ,swingarm extension ,front fork swap ) and i still would like to give it a go. I do know a really talented engineer with a lot of welding and fabricating time under his belt who does work on the vintage motorcycles ,so I am sure we can pull it off and will try to do it on a "budget"

If i can also ask you guys for any suggestions on a front end setup (WP from 640 or maybe a better option ),general suspension geometry setup,correct frame brace placing , rear shock mounts location on the arm and the frame rear shock setup.Any input will be much appreciated

I will try to make a" Budget HPN like build based on a similar frame" thread but I need to gutter some information before I start just not to make a complete full of my self . so if you know something I should know please shere it if you can point me int the direction of some solid information I will be very grateful.
Regards to everyone on this website BART:beerjug:
 
I wouldn't worry too much about headstock angles if your putting a wp front end in. You'll be screwing things up to such an extent a few degrees of rake won't make much difference.

You will end up with a monstrous unwieldy bike with a very long wheelbase and high centre of gravity. Is the bike for riding or just a design excercise?

the twin shock and mono shock are different machines that share some common components.

You won't do it on the cheap either. You'll kiss that 5k goodbye in very short order.
 
Rob's 100% right.

Please dont ruin yet another airhead - they are starting to become a bit scarce.
 
There are many excellent reasons to build a custom motorcycle.
Saving money is not one of them.
 
Thanks everyone for the replies .
At the moment I am only gathering the informations . I am still fighting myself in spoiling that /7 but will se .
I know what you are saying about the rake being altered when chenging the suspension components but in order to take exemple of the others HPN builds
I have to know if there is a diferance in rake of my frame becouse couple o degres with a fork this long makes a massive diferance .
And lastly there is plenty of reasons to spend money but if there is no reson I am not going to spend them . I have build several custom motorcycles from scratch
And my labour and the second hand parts ware posible should be a point of saving.
Thanks again Bart
 
don't listen to the haters, an extended swing arm "HPN" bike is a gem in the dirt

from what I understood the HPN frame mods do not seek specifically seek to change headstock angle, but some variance does occur as a by-product of the frame strengthening near the headstock - from post welding shrinkage.

I have a TAG modded frame which does alter the headstock to decrease the rake. This extended mono lever bike handles great, but have not ridden one with a 'standard' frame enough to be able to tell you how much of a difference it makes.

If you compare the rake of an airhead GS vs a modern bike there is a big difference
 
Thenks for your input Ras Thurlo
I do get what you are saying about the HPN frame reke and I know that it is a bit of a mistletoe but my primary quastion is a diferance betwin the rake of the stock Gs frame and the frame on r100/7 just to know if I have the same starting point if you know what I mean .
Also since you expirianced riding a HPN style frame could you tel me how it behaves on road and what is your opinion about it as a rough touring machine .
As to the opinions about this bikes ...everyone is intilted to his own but thi is not what I would like this thread to be about .
Thanks again Bart
 
Are you that copper out of Allo Allo by any chance Of?
 

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bartek_ns said:
Thenks for your input Ras Thurlo
I do get what you are saying about the HPN frame reke and I know that it is a bit of a mistletoe but my primary quastion is a diferance betwin the rake of the stock Gs frame and the frame on r100/7 just to know if I have the same starting point if you know what I mean .
Also since you expirianced riding a HPN style frame could you tel me how it behaves on road and what is your opinion about it as a rough touring machine .
As to the opinions about this bikes ...everyone is intilted to his own but thi is not what I would like this thread to be about .
Thanks again Bart
Click to expand...

I think you need to understand how Much Ras spent on his bike before considering going down that route Bartek.

If you want to do it on a budget then this would be a good starting point but even this isn't going to be cheap. For my money id buy a Suzuki DRZ front end (not the upside down ones). This bike has exactly the same frame as yours. A G/s subframe. The swinging arm and driveshaft is extended (this is where the money goes).

70a7_3_zps376ea0f0.jpg


9cc7_3_zps7e3b0f88.jpg
 
Hi Rob
I am not by any means making an expert in building motorcycles out of myself and I hope you didn't take it that way . I am not English and sometimes what I am writing just not coming out like I would like to .
I am really impressed by any one that attempted this kind of build and I have a great respect to them .
 
Bartek,

I wasn't criticising you for trying this at all. Having built a few Airheads myself I'm only to aware of how quickly the bills build up. I looked at fitting a Wp front end in a twin shock myself a few years ago but the expense soon builds up

Frame.jpg


Boxer supplies make a yoke to fit the wp forks into an Airhead frame but again it isn't cheap http://www.bmwboxersupplies.com/for...d-p-91.html?osCsid=a72961oij4bppj5s2hch649au1
 
Rob I really like the clash of old and new I the photo of this frame .
Would you go for drz fork instead of WP just becouse of the finances or just becouse the conventional fork is just more period correct .
Also if you considered WP did you go deeper into revalve and respring accordingly to the higher waight .
Is any of tis yours ?
 
Also wouldn't it be posible to fit a complete front end of lt say 660 and just machine the correct stem for it . Or maybe the yoke offset is completely wrong .
Thanks for all the info
 
bartek_ns said:
Would you go for drz fork instead of WP just becouse of the finances or just becouse the conventional fork is just more period correct .
Click to expand...

as Rob Mentioned do your homework on the various unholy union threads.

if you stick to modern forks then WP and conventional DRZ are the obvious choices. Both options are plentiful on ebay where you can piece together a whole front end and have things like supermoto kits for larger disks etc.

I think the DRZ is prob the cheaper route, and I am told has lower unsprung weight than the WP (which is counter-intuitive as the WP is a USD). Also you hear people mention stiction issues on the pre-2010 WPs.

Also be aware that the triple clamps for these forks will have small offset, which results in crappy steering angle on the airhead. This can be improved if you file off bits of the clamps and is totally solved by special triples made for the 'HPN' conversion, but these are expensive.

bartek_ns said:
Also since you expirianced riding a HPN style frame could you tel me how it behaves on road and what is your opinion about it as a rough touring machine .
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The 'HPN' bike ends up being tall (+/- like a KTM 990 Adventure). wheel base obviously longer which makes it less flickable than the OEM bikes.

They are still great on road and no problem for a road trip. Remember that these bikes have been used a lot as overlanders (which is more do-it-all roadtrip than hard enduro).

Its more that they are such a gem on dirt, that you end up wanting to spend your time off tarmac
 
Thanks Ras your posts somehow make me wont this bike even more .
I had in my mind for a long time so it's not a fresh idea I did some research but thare is so many people writing about this thinks using worlds like "I think or maybe " ending up not giving any solid info . I really appreciate you pointing me into the informations I need . I know there is no one right way but I would love to make a list of esensial information that people like me could use without asking all of the quastions I do.
 
WP front end

I have done a few bickes my self and the way round it all is by fitting supermoto forks they are around 70mm schorter than standard eduro for exampel ktm 660 sm or ktm 640 sm with a front wheel from the enduro same year total cost just time if your gona sell your old set up geometry stays prity much the same ;) I have a nice exaust system up for grabs if your interested or a bracke upgrade if your interested in keeping your standard front end !!


Rob Farmer said:
I wouldn't worry too much about headstock angles if your putting a wp front end in. You'll be screwing things up to such an extent a few degrees of rake won't make much difference.

You will end up with a monstrous unwieldy bike with a very long wheelbase and high centre of gravity. Is the bike for riding or just a design excercise?

the twin shock and mono shock are different machines that share some common components.

You won't do it on the cheap either. You'll kiss that 5k goodbye in very short order.
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Hi Litelfun. Correct me if I am wrong but would the setup that you mentioned using KTM supermoto shorter WP was a corect way of getting a nice geometry on a motorcycle with a stock paralever swingarm with I believe is 50mm longer then monolever and 50mm shorter then HPN setup in any form (monolever or paralever).
Are the parts you mentioned on the motorcycle on your photo ,is this exhaust a one of your design or a production part specifically design for that application .can you send me some prices on PRIV.
Thanks Bartek
 
Hi
The Unholy Union threads you recommended to me are fantastic source .
Do you know any god ones about frame reinfocemants swing arm extension and rear suspension setup.
Thanks Bartek
 
Rob Farmer said:
I think you need to understand how Much Ras spent on his bike before considering going down that route Bartek.

If you want to do it on a budget then this would be a good starting point but even this isn't going to be cheap. For my money id buy a Suzuki DRZ front end (not the upside down ones). This bike has exactly the same frame as yours. A G/s subframe. The swinging arm and driveshaft is extended (this is where the money goes).
Click to expand...

Rob's got a point...and I'll start another thread with this....
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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