Bike as old as me

A

AWFaneuf

XS650 Enthusiast
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Location
Massachusetts
How's it going everybody, if you can bare with me I'm just figuring out this whole forum thing, I an not what you would consider a tech type person.
My name is Adam I have a 79 xs650 Special completely stock including the carbs. It has 35,000 and runs pretty well but definitely needs some attention. I have designs on customizing this bike while not doing much that could not be undone to return it to its original form. First things first is to get it running 100% as it should, we'll maybe 90% , 100% is a bit aggressive for any bike born the same year as myself. That being said ive made the mistake of hoping on a 9 year old thread that I didn't start, oops sorry. My bike is backfiring upon deceleration, I bought it recently from a Manhattan cop that had the bike completely gone thru( carbs rebuilt, tuned up, brakes adjusted, new tires, clutch adjusted) in the late fall of 22 before he garaged it and I bought this past winter. I didn't initially plan on riding the bike until I had done some work to it, but my 76 bobber is down fir repairs and the weather is getting too nice to let the XS just sit. I haven't done much accept adjust the air/fuel mix screw which seemed to minimize the backfire, initially it was doing it just at an idle, since the adjustment it only does it when I let off the throttle and only sometimes at that. I'm trying to build up the courage to take the carbs off as I have never rebuilt a motorcycle carb or done any significant work to bike for that matter. I have however worked on carburetored cars upto and including the rebuilding of carburetors. So begins the journey. Take care thanks for reading. Ride safe
 

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Howdy from Texas and welcome to the forum, Adam!
That bike looks pretty darn good for its age! Very nice. Where did the front fender go? It's gonna be "fun" if you get caught in rain one day or hit a puddle. :)
 
AWFaneuf said:
How's it going everybody, if you can bare with me I'm just figuring out this whole forum thing, I an not what you would consider a tech type person.
My name is Adam I have a 79 xs650 Special completely stock including the carbs. It has 35,000 and runs pretty well but definitely needs some attention. I have designs on customizing this bike while not doing much that could not be undone to return it to its original form. First things first is to get it running 100% as it should, we'll maybe 90% , 100% is a bit aggressive for any bike born the same year as myself. That being said ive made the mistake of hoping on a 9 year old thread that I didn't start, oops sorry. My bike is backfiring upon deceleration, I bought it recently from a Manhattan cop that had the bike completely gone thru( carbs rebuilt, tuned up, brakes adjusted, new tires, clutch adjusted) in the late fall of 22 before he garaged it and I bought this past winter. I didn't initially plan on riding the bike until I had done some work to it, but my 76 bobber is down fir repairs and the weather is getting too nice to let the XS just sit. I haven't done much accept adjust the air/fuel mix screw which seemed to minimize the backfire, initially it was doing it just at an idle, since the adjustment it only does it when I let off the throttle and only sometimes at that. I'm trying to build up the courage to take the carbs off as I have never rebuilt a motorcycle carb or done any significant work to bike for that matter. I have however worked on carburetored cars upto and including the rebuilding of carburetors. So begins the journey. Take care thanks for reading. Ride safe
Click to expand...
That a nice bike you have scored.
Welcome to the forum.
Carbs are not as difficult as the seem at first; be methodical and take your time and you should be good.
Keep us posted with your ownership progress and post lots of pictures as you do so.

Two carb videos from YT which helped me:


There are lots of other too.
Dont forget the forum Tech Section for lots of good info.
 
The factory suggested setting for the mix screws on your '78-'79 carb set is 2.25 turns out, but they often need a bit more, like 2.5 to 2 5/8 turns out. There's also an o-ring on the mix screw to seal it in it's hole. If that has perished, the screws may be sucking air. Take one of the screws out and inspect the o-ring. Through trial and error, I've determined the o-ring size .....

BS38MixScrewO-Ring.gif


78-79MixScrew3.JPG


You can drop a float bowl without removing the carbs using a stubby screwdriver. Having a look inside it will tell you if the carbs need to come off for a more thorough cleaning. If it's nice and clean in there then they probably don't. Your popping issue could just be related to mix screw settings and possibly the sync being off.
 
5twins said:
The factory suggested setting for the mix screws on your '78-'79 carb set is 2.25 turns out, but they often need a bit more, like 2.5 to 2 5/8 turns out. There's also an o-ring on the mix screw to seal it in it's hole. If that has perished, the screws may be sucking air. Take one of the screws out and inspect the o-ring. Through trial and error, I've determined the o-ring size .....
Click to expand...
Cool, thanks for the help. 2.5mm ID / 5mm OD O-ring, gotcha.
Now ... what's that in Queen's archaic units for us new continent dwellers? :D
 
Lou_TX said:
Howdy from Texas and welcome to the forum, Adam!
That bike looks pretty darn good for its age! Very nice. Where did the front fender go? It's gonna be "fun" if you get caught in rain one day or hit a puddle. :)
Click to expand...
I actually removed the front fender to make it a bit smaller. Thank you for the greeting, must be some nice riding down there, I live in the northeast and still ride year round weather permitting. I had an 85 maxim 650 years ago, it had a small removable windshield that worked wonderfully, it didn't look amazing but sure did work amazing. I was thinking about looking into something similar.
 
Yes, you need something on that fork, either a fender or a brace (both is best). When you grab that single front disc brake, it puts lots of twisting force on the fork.
 
AWFaneuf said:
How's it going everybody, if you can bare with me I'm just figuring out this whole forum thing, I an not what you would consider a tech type person.
My name is Adam I have a 79 xs650 Special completely stock including the carbs. It has 35,000 and runs pretty well but definitely needs some attention. I have designs on customizing this bike while not doing much that could not be undone to return it to its original form. First things first is to get it running 100% as it should, we'll maybe 90% , 100% is a bit aggressive for any bike born the same year as myself. That being said ive made the mistake of hoping on a 9 year old thread that I didn't start, oops sorry. My bike is backfiring upon deceleration, I bought it recently from a Manhattan cop that had the bike completely gone thru( carbs rebuilt, tuned up, brakes adjusted, new tires, clutch adjusted) in the late fall of 22 before he garaged it and I bought this past winter. I didn't initially plan on riding the bike until I had done some work to it, but my 76 bobber is down fir repairs and the weather is getting too nice to let the XS just sit. I haven't done much accept adjust the air/fuel mix screw which seemed to minimize the backfire, initially it was doing it just at an idle, since the adjustment it only does it when I let off the throttle and only sometimes at that. I'm trying to build up the courage to take the carbs off as I have never rebuilt a motorcycle carb or done any significant work to bike for that matter. I have however worked on carburetored cars upto and including the rebuilding of carburetors. So begins the journey. Take care thanks for reading. Ride safe
Click to expand...
For back fire on deceleration - check for air leaks. Mine had a leak on the old gaskets between the carb boots and intake. Replaced gaskets and issue solved. I found leak by spraying carb cleaner in area where I suspected a leak. Engine rev’d due to leak.
 
5twins said:
Yes, you need something on that fork, either a fender or a brace (both is best). When you grab that single front disc brake, it puts lots of twisting force on the fork.
Click to expand...
Thanks ,the fender is back on, had it off for a day or so, didn't even ride it with it out. I do appreciate the advice though. Just out of curiosity, what benefits would a brace in addition to the fender have, would it be more of an improvement for performance and or handling or merely a safety thing? I'm not a very aggressive rider I basically just like cruising around. Thanks again ride safe.
 
Wrenchmorethanride said:
For back fire on deceleration - check for air leaks. Mine had a leak on the old gaskets between the carb boots and intake. Replaced gaskets and issue solved. I found leak by spraying carb cleaner in area where I suspected a leak. Engine rev’d due to leak.
Click to expand...
Thank you, someone else had also suggested spraying starter fluid or carb cleaner around the carbs(avoiding the air filter side) as a way to check for leaks. I appreciate the help and will do that this weekend. Aside from that the bike is running great, I took it out twice today after doing some minor adjustments and I am very happy and excited with it. Wish I has gotten an XS years ago. I have a 76 cb500t bobber, thinking about selling it and bobbing out a less than desirable XS to replace it, I'll keep this one as close to original as possible. What a great motorcycle I definitely understand what all the fuss is about.
 
Unless your racing and taking the bike to its limits then a fork race is of little help. Sure it does stiffen up the front but the 35mm forked bikes front guard has extra bracing incorporated into it from the factory. This will give the average rider more than enough for bracing.

Just like the average person rides with factory suspension and survive's others who want to give it a bit more will upgrade.
 
Adamc said:
That a nice bike you have scored.
Welcome to the forum.
Carbs are not as difficult as the seem at first; be methodical and take your time and you should be good.
Keep us posted with your ownership progress and post lots of pictures as you do so.

Two carb videos from YT which helped me:


There are lots of other too.
Dont forget the forum Tech Section for lots of good info.
Click to expand...
Great thank you for the videos, I've watched a bunch on YouTube I'll check these out asap and take a look at those carbs. If you figure those out it opens alot of doors on Marketplace around here. I'm confident that I can do it, I hope, as I have rebuilt carbs for many Chevys since I was a kid. Take care I'll try to jeep you posted.
 
650Skull said:
Unless your racing and taking the bike to its limits then a fork race is of little help. Sure it does stiffen up the front but the 35mm forked bikes front guard has extra bracing incorporated into it from the factory. This will give the average rider more than enough for bracing.

Just like the average person rides with factory suspension and survive's others who want to give it a bit more will upgrade.
Click to expand...
Thanks, I would imagine the fender will suffice with my current riding habits, it's good to know though, if I ever step it up I will most certainly listen to your advice.
 
drgonzo said:
That looks like a pretty nice bike. Myself, I wouldn't make any radical changes, get it in good tune, tires and suspension improvements, etc.
Welcome to the forum.
Click to expand...
Thank you, Any suggestions on the suspension?To the best of knowledge it has the original suspension now, I am strongly considering lowering the bike 2 inches front and back. I like the lower stance and the look of a lower bike, but I'm apprehensive because it does a have a really nice ride now as opposed to my other bike which is a rigid. I'm also not in a huge rush to do much with tires quite yet being they only have a couple hundred miles on them, I'll eventually get some different ones there, I'm most likely switching to spoked wheels maybe 21 in the front and 19 in the back with a tire that has a more vintage look like shinkos or something. I don't ride very hard just alot and looking to keep the ride fairly soft and forgiving as I basically just cruise anyhow.
 
650Skull said:
Unless your racing and taking the bike to its limits then a fork race is of little help. Sure it does stiffen up the front but the 35mm forked bikes front guard has extra bracing incorporated into it from the factory. This will give the average rider more than enough for bracing.

Just like the average person rides with factory suspension and survive's others who want to give it a bit more will upgrade.
Click to expand...
I'm in agreement here. If you add straight rate springs for precise laden sag and also cartridge emulators and you're looking for performance, the fork brace will become necessary. For stock damper rod forks, not so much.
 
AWFaneuf said:
Thank you, Any suggestions on the suspension?To the best of knowledge it has the original suspension now, I am strongly considering lowering the bike 2 inches front and back. I like the lower stance and the look of a lower bike, but I'm apprehensive because it does a have a really nice ride now as opposed to my other bike which is a rigid. I'm also not in a huge rush to do much with tires quite yet being they only have a couple hundred miles on them, I'll eventually get some different ones there, I'm most likely switching to spoked wheels maybe 21 in the front and 19 in the back with a tire that has a more vintage look like shinkos or something. I don't ride very hard just alot and looking to keep the ride fairly soft and forgiving as I basically just cruise anyhow.
Click to expand...
What I was suggesting was stuff like better quality shocks, sprung for your weight and equivalent fork springs, fork oil, bronze swing arm bushings and tapered steering head bearings or new ball bearings properly torqued. Basic suspension upgrades. Nothing radical.
 
Yes, there are many little improvements you can make to these bikes and most don't cost much. Just adding another ounce of fork oil makes the forks work much better, and a little "tweak" called the "Minton Mods" will improve their damping action and smooth out the ride. You can "upgrade" the stock charging system by swapping in an automotive regulator and a newer more modern rectifier from the electronics world.
 

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