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Discussion in 'Old's Cool' started by cgoodwin, Jul 17, 2009.
Does anyone know which KTM USD forks can be made to fit a 1983 R80GS???
Any idea where I can find triples like these, I have fouynd several sets of KTM USD forks but do not really know which ones to get and judging from the caliper mounting differences, I would rather know for sure than spend money on forks I can not use. Distance between forks, caliper mounting, fork diameter....
Similar thread but no real answers...
I wouldn't buy KTM forks and plan on using the beemer wheel and brakes. You're better off replacing the WHOLE front end. WP USD forks are going to jack up your front end quite a bit. Have you looked at lengthening your swingarm and also hopefully reinforcing your frame for using longer forks?
Another thread with many photos of HPN bike porn...
Yes, the frame reinforcements are basic and well outlined in the last post I referenced, I have a complkete fab shop and plan on making patterns for the front frame/steering head plates then welding them in as well as the swing arm pivot point reinforcement.
Any idea which fork set is most easily adapted???
I am going to cut a spare mono I have and add 100mm, then have the shaft lengthened similar to what was done here.
Both touratech and HPN sell kits to fit the WP 4860 forks which are used on the KTM 640 950 990 Adventures as well as many others.
Here is a photo of a similar extension from a company in Europe
I can find nothing for the early r80gs in the touratech catalog... Got a link?
You also might consider reinforcing the shock mounts, both on the frame and the swingarm.
Post 6th from the bottom points out that the point of lengthening the monolever is partly to reduce "Shaft Jack". Interesting.
It appears that the BMW R1200C had a monolever that was 90mm or 3.54" longer, similar to the HPN which was 100mm or 3.94 longer, I wonder if I can just find one and swap it out???
Extra-long Monolever instead of the Paralever. Apart from the lower angle of the Telelever fork, the rear-wheel swinging arm extended in length by 90 mm or 3.54" also contributes to the much greater wheelbase of the BMW R1200C. Since a long swinging arm is just as efficient in balancing the reaction of the shaft drive as a short, but more complex double-joint single swinging arm, the BMW Paralever, BMW’s suspension and running gear experts have chosen a longer version of the original single swinging arm, the BMW Monolever, for the R1200C for reasons of function and design. Here, too, smooth and superior suspension is ensured by a central spring strut with a single-sleeve gas-pressure damper mounted on the swinging arm. Yet a further feature is that pre-tension of the coil spring may be adjusted mechanically according to load conditions, spring travel being exactly 100 mm or 3.94".
Looking at images, it appears to be a paralever bike some years, and mono others...????
One big thing those FJ forum guys missed: The other reason that driveshaft splines need to be able to slide (apart from swingarm travel) is that whenever a UJ rotates with a bend in it (ie the two segments are rotating non-coaxially) the shaft lengthens and retracts at the joint with every half rotation. This inherent behavior of universal joints intensifies with sharper angles. If the splines don't slide smoothly, you're putting a rapidly pulsating load on your UJ's bearings.:eek1
Although I will encourage the destruction of as many R1200Cs as you want, I'd stick to the known good solution for this. Reinventing the wheel like that brings a BUNCH of unknowns into the equation such as swingarm pivot bearing spacing, final drive attachment, driveshaft fit, shock mounting points, etc.
Three answers here...
1. Pick the best forks - one with both on-the-fly tuneable comp and rebound and use the complete front end off of a KTM.. pay somone to shorten and tune the forks... loose steering lock using the stock KTM 18mm or 20mm triples..
2. Buy the triples from Boxer toko that go with 1999 and 2000 KTM conventional WP "Extreme" 50mm forks and be able to use the stock wheel, headlight bucket, etc (I think)
3. Contact member HPMGuy to have him make another set of R-Dubb's custom triples that can be machined to run the Extreme's or the modern KTM USD's...
Stock from the BMW?
No, it's an aftermarket BMW guy in the netherlands...
click on the "stainless steel modifications" link to see the triples
Wow, he is proud of those! I contacted HPMguy to see what he is offering. Ebay is full of KTM forks for cheap. It looks like making an aluminum 100mm space is simple enough and lengthening the driveline should be straight forward.
Remember to take off the 19% VAT so $638 plus shipping ... when HPNGuy made fie or eight sets of these for R-Dubb, I think they were around $500-ish...
roadsacallin used a set and put the WP 50mm's onto his G/S and is making his way around the world right now.
Any idea what bikes the 50mm units come off or if there is a thread about roadsacallin