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Old 02-11-2012, 12:24 AM   #16
lewisjohn
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Swingarm extension

My project bike has a pair of DR forks and a 75 mm swingarm and driveshaft extension,will use a standard length shock.The bike sits level,i extended the centre stand by 100mm
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Old 02-11-2012, 02:50 AM   #17
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Lewisjohn, To me a 75mm extension of the swing arm using the same rear shock that required a 100mm center stand extension means that your forks are a lot longer and the geometry has changed-
but then I'm far from an expert at this, don't know how to use CAD, and am just using high school geometry

Show us a picture of your bike
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Old 02-11-2012, 05:26 AM   #18
Rucksta
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Ontics is on the money with his estimates.
50mm extension = 12- 15mm increase in ride hight.
The final figure depends on the amount of sag you run.

If you use the same spring and lower shock mounting point that you used on the stock setup your ride hight will remian unchanged.

Longer shocks or moving the lower mount forward require removal of metal inside the swingarm to avoid the uni fouling.

The joint itself seems good for the extra angle.
I haven't replaced a uni for 90,000km or ever since I jacked the rear end 38mm on a standard length swing arm.
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Old 02-11-2012, 09:16 AM   #19
cenji OP
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I like that feedback.......

...as it confirms that I don't need the extension to make my Geometry fly. If yours lasted 60K miles and is still going, and the other one that I know off lasted over 100K miles.....it makes sense to me to not spend the $400 on the 50mm extension, not lengthen the wheelbase,keep more off the G/S characteristics and have a blast riding it. The 400 buckeronis can go towards a new u-joint if necessary.

Even thought the 50mm extension will lessen the sharper angle at the U-joint, it would be "ONTICS" geometry or trigonometry skills that could determine the change of angle for the curious, but he has his plate full with his remodel.
My guess, it is not going to be much. I am getting curious actually, so I will measure the length of the swingarm and will come up with some number later.

Thanks so much to everyone for the feedback, it was quite helpful. I am always amazed about the willingness of the forum to share knowledge. I should spend more time on here, but for whatever reason, I am not. Beats me!

Down the line I will post some pics with someone's help, as I don't have any of those accounts. Nothing fancy, just my old bumbler with a KTM fork ready to go more off-road...yipppeehhhhhh.

Quote:
Originally Posted by Rucksta View Post
Ontics is on the money with his estimates.
50mm extension = 12- 15mm increase in ride hight.
The final figure depends on the amount of sag you run.

If you use the same spring and lower shock mounting point that you used on the stock setup your ride hight will remian unchanged.

Longer shocks or moving the lower mount forward require removal of metal inside the swingarm to avoid the uni fouling.

The joint itself seems good for the extra angle.
I haven't replaced a uni for 90,000km or ever since I jacked the rear end 38mm on a standard length swing arm.
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Old 02-11-2012, 09:25 AM   #20
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Quote:
Originally Posted by cenji View Post
The 400 buckeronis can go towards a new u-joint if necessary.

FYI, I had HMPGuy replace my u-joint with a cir-clipped replaceable one for less than $300
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your bike is suitably dirty. Well done.
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Old 02-11-2012, 09:27 AM   #21
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Quote:
Originally Posted by Rucksta View Post
.

Longer shocks or moving the lower mount forward require removal of metal inside the swingarm to avoid the uni fouling.

The joint itself seems good for the extra angle.
I haven't replaced a uni for 90,000km or ever since I jacked the rear end 38mm on a standard length swing arm.

Like I said earlier.........
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Old 02-11-2012, 11:12 AM   #22
cenji OP
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$300 replaceable U-joint

Quote:
Originally Posted by SOLO LOBO View Post
FYI, I had HMPGuy replace my u-joint with a cir-clipped replaceable one for less than $300
well, thats very good news! I like to admit though, that I do not know what your u-joint would look like. Any picture that would give me a better understanding that you can share? Maybe somebody else has the same big question mark on their forehead? Or maybe point out where to find it one of your threads.

As mentioned in other threads of mine, I am just starting to get into the hidden parts of the bike. It is intriguing, daunting, but so far, I would think that I screwed up only half the time. Lessons learned and still ahead of having a dealer maintain an modern GS. I a way, it wasn't too smart to get into this whole front-end conversion with so little knowledge. On the other side, it is fun, I keep plugging away and I hope to have it ready by the end of March.
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Old 02-11-2012, 11:16 AM   #23
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removing metal on the inside.....

I can grasp that, because the U-joint will be closer to the wall. Do you remember how much metal needed to be taken off? Maybe some pics? Did you modify the cross-brace where the battery is mounting too? Anything that comes to your mind, that a noobie could screw up easily? Thanks for your input.

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Like I said earlier.........
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Old 02-11-2012, 12:06 PM   #24
SOLO LOBO
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Originally Posted by cenji View Post
well, thats very good news! I like to admit though, that I do not know what your u-joint would look like. Any picture that would give me a better understanding that you can share? Maybe somebody else has the same big question mark on their forehead? Or maybe point out where to find it one of your threads..
Stock



and the finished HPMGuy product

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Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 02-12-2012, 12:09 AM   #25
lewisjohn
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Quote:
Originally Posted by lewisjohn View Post
My project bike has a pair of DR forks and a 75 mm swingarm and driveshaft extension,will use a standard length shock.The bike sits level,i extended the centre stand by 100mm
I should have mentioned i am converting the bike from an RT donor bike,and using a standard RT bevel box,so have moved the lower shock mount onto a bracket welded on to the monolever armhttp://lewisjohn.smugmug.http://lewisjohn.smugmug.com/Motorcy...rden-002-M.jpg
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Old 02-12-2012, 12:49 AM   #26
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let me fix that image for you
Quote:
Originally Posted by lewisjohn View Post
I should have mentioned i am converting the bike from an RT donor bike,and using a standard RT bevel box,so have moved the lower shock mount onto a bracket welded on to the monolever arm


Awesome, looking good.
love the /6 tank on a dirtbike airhead. You are doing similar to what I was planning to do before I found a G/S to butcher- except I was going to do a twin shock. I have an old RS twin shock frame, spare 90/6 motor, /6 tank like yours, choice of gearboxes and final drives. That pile of parts was going to become a GS type thing but will have to wait until I sell it all, or more likely hang onto it for a rainy day (and budget-build).
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Old 02-13-2012, 07:04 PM   #27
cenji OP
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cool bike...

and you bought the 75mm extension from the Australian guy?
Where exactly did you extend/weld the center-stand, midsection, did you use a larger sleeve or smaller sleeve to bridge the existing tubing? Do you have a pic, any hints what to do what to avoid? Thanks a bunch.
What is the length of your shock from eyelid to eyelid?

Quote:
Originally Posted by lewisjohn View Post
I should have mentioned i am converting the bike from an RT donor bike,and using a standard RT bevel box,so have moved the lower shock mount onto a bracket welded on to the monolever armhttp://lewisjohn.smugmug.http://lewisjohn.smugmug.com/Motorcy...rden-002-M.jpg
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Old 02-13-2012, 07:05 PM   #28
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G/S that won the PD in 81

Was wondering if anyone knows , what the shock length (eyelid to eylid) of PD winning G/S measured? Just trying to learn of all the parameters that go into added ground clearance. Thanks.
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Old 02-13-2012, 08:34 PM   #29
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Quote:
Originally Posted by cenji View Post
Was wondering if anyone knows , what the shock length (eyelid to eylid) of PD winning G/S measured? Just trying to learn of all the parameters that go into added ground clearance. Thanks.
That info won't help much without knowing the geometry of the mounts on the main frame and swingarm both of which were modified from stock. It used a double sided swingarm
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Old 02-13-2012, 09:05 PM   #30
ontic
 
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Quote:
Originally Posted by cenji View Post
and you bought the 75mm extension from the Australian guy?
At some point Paul Rooney the australian guy played with 50mm, 75mm and 100mm extensions, but now only offers 50 and 100. I can't remember which way it went, but for him he couldn't really tell the difference between the 75mm and one of the other ones (50 or 100) so for all the extra complication of offering three versions it wasn't deemed worthwhile.
The 50mm is a bolt on affair like Lewisjohn seems to have and the 100mm is a completely different welded extension (much more expensive too).

I'd be interested in seeing the center-stand extension too as I'll have to do that soon (and figure out a side stand solution).
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