Boardtracker-ish build

[barncat]

Or boardtracker influenced... This will likely be the last XS I'll do. Used up my supply of old Yamahas.

Objective is to make it as light as possible. Using MX wheels- the knobbies are being swapped for new dual sport rubber. It'll get a low tractor style solo seat above forward slanted rear shocks. I'm seriously considering custom fabbing a leading link front fork. Have been saving an XS-1 tank for the build and it'll get upside down bars.

Tore most of it down some time ago and finished it off today. Swingarm bolt was broken and chain side end totally seized into frame. Had to carefully sawzall the swingarm out- not easy... will deal with stuck bolt end tomorrow while de-tabbing and cleaning up frame.

 

[barncat]

It gets this motor, already rebuilt and race ported. Will probably paint frame matching Chevy orange.

 

[barncat]

Just spent the last four hours removing the seized up swingarm bolt end.... what a PITA. Tried drilling it out but hit some hard or work hardened steel. Even took it to my car mechanic who tried an air hammer and O/A torch. Nothing. Purposely broke the head off trying to spin it with big crescent wrench and cheater bar. Finally went low tech and spent 1/2 hour filing through it with a chainsaw file. Tapped out no problem after that...... so in the unlikely event this ever happens to you that's one way to deal with it.

 

[mrtwowheel]

Wow, that's a lot of filing.

 

[halfmile]

"Wow" What a racy looking motor. It`s good to see someone achieving contrast by using some color for a change instead of black. Keep posting pics and good luck with your build.

 

[barncat]

Not many metals you can't file through. Access was the problem here. It was a last resort.

The motor color scheme does pop. So far the plan is do the gas tank in the classic "Gulf" light blue and orange.

 

[barncat]

Sawzall stage complete. Lotta grinding, cleanup and welding next to get frame finished before paint. I'll be adding some sort of tube arrangement that replaces the chopped out horizontal V tubes that also acts as a solo seat mount and upper shock mounts.

Have a pair of vintage Marzocchi shocks that need paint but otherwise good. They're very light but wish the springs were 7mm not 8. Will try them first and substitute Chinese shocks if over sprung.

Anybody have a bike with an Earles or Greeves front end? Never ridden one but it would have a cool preying mantis look that would compliment the back end. Still debating whether to build one. Boardtrackers either had reinforced bicycle forks or leaf spring front ends. Not suitable for real world riding.

 

[barncat]

Chipping away at frame work... had to take several days off since i tweaked the hell out of my lower back from leaning over the frame with all the cutting and grinding.

Have to weld a pair of struts back in and fab up a seat pan that will mount to same.

Went with an XS1 swingarm since it's 1 1/2" longer and works better with shock length and tire/seat clearance.

Scrapping the linkage fork idea. Too much time, no weight savings, high complexity and part count, etc...

 

[NastyBeads]

Nice work Barncat! Can wait to see the progress on this.

 

[TwoManyXS1Bs]

...Went with an XS1 swingarm since it's 1 1/2" longer...

Longer?
You have an early style 70-73 frame.
Should be the same length...

 

[barncat]

A bit more progress... Will put the forks and front wheel back on to finish the mock up and get all the geometry right.

Pretty sure this is the earliest swingarm TwoMany. Please correct me if wrong. It's about 1.500" longer than all the other ones I've been using on various builds.

 

[TwoManyXS1Bs]

That doesn't look like any XS650 swingarm I've seen.
Here's a closeup of my XS1B's 8mm thick axle plate:

 

[fredintoon]

A bit more progress... Will put the forks and front wheel back on to finish the mock up and get all the geometry right. - - -

Hi barncat,
The photo shows a sprocket with way too many teeth for an XS650, how small of a rear sprocket can be fitted to that MX wheel?

 

[barncat]

Then we'll call it a mystery swingarm. Got it with huge batch of bikes and parts. Pivot area all the same dimensions.

You raise a good point Fred re the sprocket. I have a 40T which is minimum for that hub plus will run 18T up front and may need to put an idler pulley under the swingarm to not saw into shifter... the 18/40 with the larger diameter 19" wheel and tire should be about right.

 

[Wingedwheel]

barncat, that tank looks like a '72 XS2. Is the frame from the same bike?

 

[barncat]

Probably not. It's a '73 frame so it's a mix and match build.

Will put in a few more hours tomorrow. This wheel swap is easy in terms of axle diameters but complex in final drive ratios and brake setups. Super light wheels though, and that's where you want reduced weight.

Current plan is dual 34mm TM carbs on short aluminum intakes and custom exhaust TBD...

 

[TwoManyXS1Bs]

Finally got a pic of my swingarm, for reference.
From the pivot center to axle center (axle full forward).
'71 XS1B swingarm length = 16.5"

 

[fredintoon]

- - - You raise a good point Fred re the sprocket. I have a 40T which is minimum for that hub plus will run 18T up front and may need to put an idler pulley under the swingarm to not saw into shifter... the 18/40 with the larger diameter 19" wheel and tire should be about right.

Hi barncat,
seems to me that 18T/40T, even with a 19" rear, will give you 4 speeds + underdrive; you sure you can't get a 38T on there?
When I had an 18T front on my bike the O-ring chain's massive sideplates left gnaw marks in the shifter shaft.
If you use ordinary chain instead there'll be a better chance of getting clearance.

 

[TwoManyXS1Bs]

That 40 tooth rear is in the ideal range with the high ratio primary gearset.

http://www.xs650.com/threads/is-there-any-interest-in-high-ratio-primary-gears.20073/

 

[650Skull]

Looks to be a Special swing-arm, the bolt hole for the chain guard is the same. The axle plates have an extra piece welded on the side to take some kind of different adjuster