6-speed options for XS650?


XS650 New Member
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Washington, DC
I realize this may be considered blasphemous by some but I'm wondering if anyone knows of a reasonable (i.e. not custom race parts for $$$$$) way to add a long 6th gear to the platform. For example, is it possible to swap the transmission parts from another bike into the case (maybe an XS400 or similar donor?) or modify the existing shifter mechanism and add one more gear?

I have a 1979 model that I rebuilt nearly completely and have been loving, but I would love to take some longer rides on it and just really want that one more gear, badly. My spockets aren't original, she's pretty good up to 65 and tolerable to 70 but no more and I'd really like to get 75 and bring the revs down a bit if possible. There's no lack of power and I like the current gearing, I just wish she had one more highway gear.

I don't really want to make the 1st gear any taller, and generally I like the ratios I have currently so would prefer to add a gear if possible rather than simply replacing the 5th or some such, though I suppose that's an option too potentially.

Any suggestions welcome. Apologies if this is an old and tired topic - I wasn't able to find any good info though I did take a look around before posting. If I missed it though, forgive me please.
The XS is a dinosaur. Modern bikes spin the transmission pretty fast with little torque multiplication from the crank. They get the torque multiplication via a small countershaft (drive) sprocket and large rear wheel (driven) sprocket. XS trannies are big beefy gears that go clunk, clunk. Modern motorcycles multiply torque after the transmission and the lightly loaded gears go snick, snick on the shift.
There is an overdrive 5th gear kit out there somewhere. Also you can change final drive. I have heard of rear sprockets as small as 30 teeth (down 3 or 4). The front sprocket can go up 1, the clutch push rod prevents going any larger.
If cubic dollars is not an issue, people say 277 motors are smoother. While it is apart for rephase, a 750 BBK and an overdrive 5th would give you a lot of torque to handle that 18/30 final gearing. :)
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I’m not sure of any transmissions to swap over. I’m sure if this was possible, some of the nuts on this forum would have done it already and modified it multiple times by now. As mentioned there is a 5th gear overdrive, but it can only do so much. The XS is what it is. Go 34, 33 or 32 in the rear, perhaps do the 5th gear overdrive, big bore it, or the more reasonable choice, get a bike better suited for longer miles. Whether that’s selling your current bike or adding one to the stable, this bikes niche isn’t sustained highway rides, but the road less traveled
I think you want a 17/33 sprocket set and a 24 tooth 5th gear from MikesXS.
Or a high ratio primary gearset from Ivan Hoey in OZ oe maybe Smedspeed in the UK.

As for 6-speed box, I was visiting Jerry Heidens workshop in the Netherlands some 10 year ago. He, or one of his employees was working on adapting a 6 speed box from a new-ish Laverda twin. Either a 650 or a 750.
https://www.motorcyclespecs.co.za/model/Laverda/laverda_650_sport 94.htm

Whether the effort is worth it, is up to the individual I guess. It is doable, that's all

I have also read about a guy in Norway that wanted a 6 speed in his Yamaha TRX 850 (a very cool bike by the way)
He welded up parts of the cases and re-machined. Then used a tranny from a 750 or 1000 cc Yamaha four (FZR, R1, I am not sure)
I'm in the middle of putting a 6-speed transmission from a KZ550 into my GPz750.