Custom XS 650:

I'm 50gary. I actually call the bike "Arte Primitivo" Latin for Primitive art. Auto Didact means self taught, as this is the first custom bike I've ever done. I built that bike over about two years part time, finished it in 2005.   Most guys never change the geometry unless they're making a chopper I went the other way.  27" down to 24" as that's the same as an Yamaha R6 which is the front end (complete) that I used.  The frame was cut off just below the front engine mount and at the rear end of the top tube.  The rear sub frame was also cut off and chromoly tig welded for the new parts. Made  everything myself.  The rear brake is operated by a thumb brake that I made up. I did that so I could have semi-rear sets (pegs located just below  the swingarm pivot) and still use the kick start lever.  The right side foot peg folds up for starting.  Steerer tube is chro-mo and turned by a machinist  I don't own a lathe.  My new welded on frame front end saved 9# alone, the bike only weighs 340#  The front engine mount saved  5# I used the header pipes from an old Mac set and made my own exhaust it's ceramic coated without any baffles.  Yep it's loud.  The tank is an RD 400 with a new tunnel so that it fit the new frame it also has a racecar quick fill cap, not a sport bike cap.  The tank is stuffed with fuel cell foam to prevent fuel slosh while cornering.  The rear suspension is '94 FZR 600 swingarm with same linkage using a Fox twin clicker that I made ride height adjustable myself because I couldn't afford the Penske or Ohlins. The axle slot is machined to match the rear wheel. Interestingly the front  wheel is R6 Yamaha 99/01 and it matches with the rear pattern which is 2002 Suzuki  SV/Bandit/Katana 17" x 4.5" using a 160/70 17"  and that's the widest that will fit in the rear without widening the rear of the frame. Tires are  Metzeler Sportech M1 the front is 120/60/17" This bike rides straight and true I can let go of the bars at 80 mph and zero shake or wobble without a steering damper.  This combination took a very long time to figure out and lots of planning and thought, that's why I mentioned "Auto Didact"  The bike rides much like a 250, change of direction and cornering is a blast very nimble.  Sorry to run on like this, there so much more but it gets boring listening to other people's stories.  I included an "Arte" shot, ha ha.  BTW, I have a photo story of how to do the front end without an expensive frame jig and still get the numbers correct. It cost me only about $50.00 for my self made fixture. Thanks for your great site, so many people from around the world get so much pleasure from it you should be proud to share with fellow XS 650 enthusiasts.

Cheers,  Gary F. Westendorf - Saginaw, Michigan

The rear end is FZR600 swingarm with a Suzuki rear wheel assembly from the SV/Bandit/Katana600 17"/4.5" this is maximun width with the stock frame.  I used 520 sprockets and chain for narrow width as well as weight savings.  The modern 520 X-ring chains are used on very powerful 600 cc sportbikes with in excess of 110 hp so strength is not a factor in our 650s.  Once the swingarm is fitted to the frame (which requires milling off about 5 mm from each inside S/A mounting boss. I milled mine in a very large Boko (SP) mill).  It's off to the machine shop to have the axle slots made longer (by .5" and larger to accept the Suzuki rear axle (20 mm I think) this is very important if the axle slot is not exactly the same from side to side the rear tire will tip to the left or the right measured from top to bottom.  The axle must be parallel to the S/A bolt.  Another thing I did was to weld on a 6 mm hexagonal coupler to the bottom of the arms (one each side) to allow the use of spools for paddock stands about 3" from the rear end of S/A.  This saves 6# of "non- sporting" weight by cutting off the center stand and mounts also giving better ground clearance and a cleaner appearance, after all this is a sporty type motorcycle.  The Suzuki sprocket carrier must be milled by .375" on the sprocket mounts side, the engine counter sprocket must be offset by .375" and the drive chain must be 520 .125" narrower than 530 chain and sprockets. Note: how I made my offset counter sprocket.  I took the original off and ground off  all the teeth  then took it to the machine shop and had it made round again. Then the new sprocket get a "dish cut in as large in diameter as the lock washer that goes on the out side.  Then I put the new sprocket on the counter shaft with the dish cut facing in towards the engine along with the old toothless round  sprocket on next and tac welded them together in four places 90 degrees apart.  Then I slipped it on and off to make sure it was concentric and then TIG finished welded it in the bench vise.   The stock sprocket is 530 which is .375" thick giving that much offset, perfect for this application.  This adds up to .875" x 2 = 1.75". This is perfect as the stock XS rear wheel is 3" and the new wheel is 4.5" I get no chain rub on the tire or the frame.  The rear wheel is centered and no chain rub.   I used the Suzuki rear brake caliper and hanger as it's low mounted and modern.  I had to make a torque arm to hold the caliper and a mount to the underside of the FZR S/A.  Make sure the alignment is spot on and the torque arm as long as reasonably possible.   I also used a hugger type rear fender to make the bike more modern looking and keep it clean.  The S/A is FZR600 so just ebay an FZR600 hugger simple right?  Mounting the mono shock linkage is a bit more work.  Luckily the lower rear of the main frame has a cross member and that is where you will mount the parallel tabs for the linkage to frame pivot point (10 mm bolt)  Mine mounting brackets are .1875" chromoly made from a small sheet I bought for the project to make all my tabs.  I have very little equipment in my humble garage so I hack saw them out , tac weld them together that way the holes are in the same location.  Drill press the holes and finish them with a bench grinder then hand file them prettyl  The shock (I used a Fox twin clicker from a Honda F4 and made it ride height adjustable myself)  I made a strut the proper length for the mock ups as it's easier to work with and it's about one inch shorter than the actual shock.  The reason for this is you have to allow for the static sag of the bike fully built and the bike weight compressing the shock the proper amount (25 mm)  Full on sport bikes use about 12/13 degrees of swingarm angle measured from the S/A pivot to the rear axle center. I settled for 8' that's all I could get as the layout of the old style bikes do not have the S/A pivot and counter sprocket close enough together to get greater angle.  My S/A pivot is 13.5" to the ground.  The shock must be centered in the shock well of the S/A so the spring doesn't rub on the S/A.  Above the shock are the stock "Vee" brace tubes, I welded in a cross tube (1" dia.) so it centered the shock for and aft, then two more mounting tabs (again 10 mm) down to the upper shock eye. Note: the shock you choose for this set up has to have an upper eye and a lower clevice for the FZR linkage.  It also must not be too long or else you cannot use the upper mounting as I explained.  A lot of planning has gone into this design you must always think two steps ahead.  I mounted the battery on top of this vee brace and shock mount.  Keeping the weight towards the center as much as possible helps the bike change direction much more quickly.  The engineers call it "Mass Centralization"  This is one of the many reasons mono shock bikes works better.  Instead of having two shocks and two springs way out on the end of the wheelbase you have one shock/spring (half the weight) but also located very near the center of the wheelbase and lower.  Many mono shock linkages use a two to one ratio, that is, for each two inches of upward axle travel the shock/spring will compress one inch due to the built in leverage of the linkage .  The FZR600 is one that uses 2/1 ratio.  I use a 450# spring by Hyperco but everyone has different body weights and will have to adjust the spring to match.  One thing I did  when laying out this design was to look at other sport bikes using the same or similar designs.  It took me a long time to figure this out.  This was my first custom bike project and  I learned a lot.  Nothing on this bike is stock from end to end everything is changed or modded, fun stuff. 

P. S. In the file attached you can see the shock linkage and the reservoir, note that the reservoir is also mounted in the center rather than up the rear frame tube as many do.  On a full on race bike cooing may make a difference but not in this case IMO.   

P. P. S. In the second file you can see the low mount rear brake, torque arm, and torque mount.  Also the blue paddock stand spools. I hope this helps.     Cheers, 50Gary