1981 XS650 Special - Build Thread

ssjody

Piston Addiction
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First post, new member. First let me say that I'm blown away by the information on this site! Nice work!
My name is Jody and I absolutely love these XS650's. In 1981 I bought a new XS650 Special II. It was the 1st Brand new anything with a piston that I'd ever bought. Rode the wheels off of it, then family life kicked in and I ended up selling it. Fast forward to now and as of 11/4/2023 I now own another one! I wasn't planning on buying one when I woke up on that Saturday, but I was going with my Brother in-law Jim to look at one he wanted to buy.

The bike we were going to look at was about an hour and a half away and we talked bikes for the entire trip. Jim too had bought an 81 XS650 back in the day with only a few miles on it, and like myself, he rode the wheels off of his too! On our trip he was telling about another 81 he had looked at a couple days prior that had good bones but needed some attention. Unlike me, he was looking for more of a completed bike (obviously Jim's the smarter one) but the bike he was describing sounded like it was in pretty good shape. The more we talked, the more the fever started kicking in. By the time we got to his bikes location I'd already sent a message to the owner of the bike that needed work. Fast forward a couple of hours and between Jim and I, we now owned two bikes. 😁 So it begins..

Day 1
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Glad I could plant the bug that ended in you getting the other one I had looked at!! Great intro here and like you I love my original 1981 XS650 Special and my newly restored one too! Here’s a couple pics of my two. Can’t wait to get out there riding these together Jody!!
 

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My ‘81. Deviations from stock are ‘80 seat, ‘80 badges, early rear signal red lenses, early stock shocks and U.S. market Triumph T120 handlebars.

One of my friends rode it 500 miles over the weekend. It tours just fine. If I were to suggest fixing anything that isn’t broken, it would be the alternator rotor. If it’s OE, I recommend sending it to @Jim for a rewind. Then, you can ride it to the end of the Earth and it will outlast you. Otherwise, outside of consumables, this bike is anvil reliable.

I wish you a successful resurrection! It sure looks good!
 
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My ‘81. Deviations from stock are ‘80 seat, ‘80 badges, early rear signal red lenses, early stock shocks and U.S. market Triumph T120 handlebars.

One of my friends rode it 500 miles over the weekend. It tours just fine. If I were to suggest fixing anything that isn’t broken, it would be the alternator rotor. If it’s OE, I recommend sending it to @Jim for a rewind. Then, you can ride it to the end of the Earth and it will outlast you. Otherwise, outside of consumables, this bike is anvil reliable.

I wish you a successful resurrection! It sure looks good!
What bars are those on your black beauty??
 
What bars are those on your black beauty??
Those are Emgo replica U.S. market Triumph T120 Bonneville. 1975 or so. The rise is 8 inches. My buddy did 500 miles with them over the weekend. He approved.

Lowbrow Customs sells the same bar as “mini apes”.
 
Been a long time since I originally owned and rode a XS650 Special. Interested in what most of you are showing as RPMs on the tachometer at 50 mph.

I’m showing about 3k-3200 RPMs. Bike vibrates a lot more than I remember at speed.
 
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Been a long time since I originally owned and rode a XS650 Special. Interested in what most of you are showing as RPMs on the tachometer at 50 mph.

I’m showing about 3k-3200 RPMs. Bike vibrates a lot more than I remember at speed.
Yes. You’re running 17/34 sprockets I do believe. Much of the bad vibrations can be tuned out. I ride comfortably at 4,000 RPM. I’m not saying there is no vibration, just that it’s not uncomfortable. I expect what you’re experiencing is an issue.

Adjust the valves and cam chain.
Carburetors. They must be performing equally. I had a very heavy vibration in my ‘81 at certain RPM range. It went away when I cleaned the pilot jet in the left carburetor. I had a friend on my bike all weekend. He’s not a vintage bike guy. He said nothing of the vibrations and if I put him in front, he ran a good bit at 70 mph. That speed can make your fingers tingle on a well tuned bike.
 
Yes. You’re running 17/34 sprockets I do believe. Much of the bad vibrations can be tuned out. I ride comfortably at 4,000 RPM. I’m not saying there is no vibration, just that it’s not uncomfortable. I expect what you’re experiencing is an issue.

Adjust the valves and cam chain.
Carburetors. They must be performing equally. I had a very heavy vibration in my ‘81 at certain RPM range. It went away when I cleaned the pilot jet in the left carburetor. I had a friend on my bike all weekend. He’s not a vintage bike guy. He said nothing of the vibrations and if I put him in front, he ran a good bit at 70 mph. That speed can make your fingers tingle on a well tuned bike.
Are 17/34 sprockets OE?
 
Some Canadian Specials came with 17/36 gearing, talk about a stump puller, lol.

And yes, check ALL the engine mounts. Most were loose on both of mine when I got them.
 
Day 5
This was the 1st full day I got to tear into anything. My goal is to get this bike running good before I go to tearing it down. It sorta ran when I got it but it was definitely struggling. It would run a little better with the choke pulled out to the 1st notch so I had to figure out what's going on there. The PO also said he had "rebuilt" the carburetors but I wanted to take them apart and see what was rebuilt. I expected the worst but was pleasantly surprised to find that all the factory parts were still there. The needle and seat had been replaced at some point but everything else was original.
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I already had a Carburetor kit so I got to work and it was pretty nasty on the inside
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End the end they turned out pretty nice
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I also found that the PO had put a set of NGK BPR5ES (resistor) Spark Plugs. The 5k ohm end caps tested good. I changed the plugs out for a set of BP7ES (non-resistor) Spark plugs.

The Carburetor boots looked like they were the originals. I could see some light cracking which didn't give me much faith they'd be any good. My hunch was right. I cleaned them the best I could and stuck em back on, mounted the Carburetors. I checked valve clearance .006(exhaust) and .002(intake). I looked for some specs on the clearance and found more than a few opinions but I think that should be fairly close. Feel free to chime in if you have had better luck with something different for the valve clearance.

I drained and refilled the gas tank, which to my surprise was absolutely spotless on the inside. I buttoned everything up and fired it up. It cranked over right away and I synced the carbs, set my idle mixture to right about 2 1/4 turns and let it warm up to running temp. I did a dead cylinder run with a spark plug still plugged in and grounded to the block. When I ran it on the Left cylinder it cranked right up and I was able to adjust the idle mixture pretty good right at about 2 1/4 turns. Switched over to run it on the Right side and it wouldn't even fire up. hmmm..
I hooked the Left cylinder back up and fired it back up. I had some spittin' and sputtering going on out the right side. When I shot some Carburetor cleaner where the boot meets the head on the right side, she raved up. Looks like I'm going to need a set of boots. I'm guessing that's what's causing the Right cylinder to act that way it is.

Figure while it was running I'd see if it was charging. Nope.. There's another project!

Well, I'm gonna get it running good then I'll tackle that. Before I tear into the charging, does anyone have thoughts on what someone was trying to accomplish with this splice hack?
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All in all it was a productive day!
 
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Anyone have a good source for the Carburetor Intake Boots?
Look for ARS branded boots. All the others seen here over the years were Chinese junk. ARS is Japanese. They made the original boots for Yamaha near as I can tell.
 
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