1972 XS650 Heavy Metal Sled

irk miller

You've been mostly-dead all day.
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The last project to come out of my Mid-Ohio haul is a ‘72 XS650. We were hanging out at our swap spot when a dude approached us figuring we were the perfect suckers to take his buddy’s XS pile. BradJ’s freshly painted ‘77 was for sale and our spot is right at the back entrance to the parking, so the dude didn’t have to look hard. Later that day his buddy drags BradJ and me out to his truck. I’m thinking it’s a pile of parts for Brad to buy cheap, but somehow I walk away with a $200 handshake.

I have zero experience with an XS, so it will be somewhat of a learning curve. I have one complete bottom end and enough to build two complete motors. The mostly complete chunk will have to be a map for the initial build up.

My plan for when I finally got an XS was to build a chopper. Yes, the eleventy billionth XS chopper. Then the peer pressure and drunk talking set in and we are staying away from a chopper. It’s been my desire for quite a while to build a vintage desert sled style bike and with such a close resemblance to a Triumph engine, I think this XS would be perfect. Plus, there’s enough meat that I can take the other engine pile and stuff into another XS hardtail frame later.

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Well, the shit show begins. I’ve apparently become the guy that buys bikes completely disassembled by other guys who can’t put them back together.

Lots of vapor honed parts and it appears as though every bearing, seal and gasket has bee bought for the whole bike.



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I’ve decided to take this motor and put it back together for an assessment. I assume this was the parts motor, or he bought parts for this motor. I’m not sure. Regardless, before I go and dig in with Legos that may or may not have all the pieces, I prefer to find some known quantifiers.


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The motors are pretty basic. Looks like you have the puzzle figured out. The major issues with these bikes is the charging and ignition systems. Replacing the carbs generally eliminates some headaches too!
 
I can finally move forward on this engine. A guy from the XS650 FB page sold me some good jugs that took to a nice hone.

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irk miller said:
Well, the shit show begins. I’ve apparently become the guy that buys bikes completely disassembled by other guys who can’t put them back together.

we all need that guy.
 
Got the head all cleaned up, but discovered a mystery in the process. Someone took a burr bit to the intake sides of both chambers. Haven’t found a reason why.

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That's easy. It's a way to relieve the pocketing around the valve and to allow it to flow out to the sleeve. It must not go further than the bore or gasket surface of course. Some of us have been doing something like that for years but hopefully a bit better than that. Admittedly that isn't very well done, but that's probably what is going on there.
 
teazer said:
That's easy. It's a way to relieve the pocketing around the valve and to allow it to flow out to the sleeve. It must not go further than the bore or gasket surface of course. Some of us have been doing something like that for years but hopefully a bit better than that. Admittedly that isn't very well done, but that's probably what is going on there.
Thanks, Teazer. So badly done beyond good performance? Not expecting enhanced, but I don't want to be burning up my head gasket either. It's definitely inside the metal lip of the gasket. I can clean that up myself- smooth it out, soften the transition, etc.. I have the skill and tooling, but I don't have visual examples to go by.
 
Not sure how I missed this thread. I'm in.

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Slowly getting it put together. It’s a bit of a challenge finding parts in random bags and paper cups. Hopefully, I haven’t missed anything so far. LOL. I’m actually impressed I was able to find the advance locating pin, which was in a torn, oily bag at the bottom of the bin.

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