No power over 3000RPM - Engine trouble - XS2 1972 XS650

BTW @JimD54 I did fire it up after each check
Wasn't sure from your post, but glad to hear you did that. Congrats on getting it running!
Is the smoke blue or black? blue means it's burning oil, black means it's running rich. Look at the plug. black soot indicates rich running which might explain the pop on shutdown, but that's usually from a lean condition. Kinda odd.... Anyway, congrats again.
 
Oh, man, yeow!
That advance unit is shot!
The little weight ears are severely worn down. Their little rounded nubs should completely fill the slots in the center disc.
xs650LA-WornAdvance.jpg


The proper spark advance operates from 15° BTDC (idle) to 40° BTDC (full advance). A 25° swing, measured at the crank. That's only 12.5° of sweep at the cam, where the advance unit sits.

The amount of wear, with the huge gaps, would allow timing to wander all over the place, most noticeably during radical engine speed changes, like during shutdown.

These are expensive units, if you can find one. Advance units are available from MikesXS, but they're not up to OEM quality, with some reports of them blowing up.

FYI, here's a closeup of a MikesXS advance weight.
Note the size of the ear that fits into the slot...
MikesXS-AdvanceWeight.jpg
 
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WOW I have never seen a advance unit that worn down before ! good catch 2M !
if replacements cannot be found perhaps a light bead of brazing rod on the wore down area
and then filed to shape will get it running properly again..... that won't last super long being softer than steel but it's easier than welding the area..... my 2 coppers !
....
Bob........
 
Mine were worn down like that, but not as bad. I used my mig, with fine steel wire, to *zap* build-up the ears, then ground them to size. Can't explain how, you had to be there...
Yeah, that was my first thought. I'd TIG em' though... but that's just me. I love my TIGer:)
 
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TIG's are awesome ! never had one but watched a buddy of mine weld like an artist with it !
on something that small I think I'ed use Oxi/acetylene gas and weld it up.... I wouldn't trust my 295 amp stick welder not to blow the end right off of it..... or just braze it .... anything to build it back up..... heck , if push come to shove I'ed even try J.B weld and leave allot on it all the way around fer grip.....lol !
2M: good to know it can be done ! thanks !
......
Bob......
 
Just another FYI.
The springs on your advance unit have been modified. Each spring has had 1 loop cut off.

And, since most of us may have never seen one, and probably never will, here's a pic of a new advance unit, p/n 256-81654-10. Notice the weight ears, and how they fit into the center disc slots.
256-81653-10 OEM02.jpg
 
I suggested a look at the timing unit way back on the first page of this thread. There are quite a few fixes that can be applied to get the advance curve back in spec if the wear isn't too bad (those weights are shot, IMO), but there's one that should never be attempted: no matter who tells you to do it, don't try to limit travel by bending or peining the tabs on the timing unit rotor. If you do you'll start tiny fractures, and in a while (often a very short while) the engine will die, usually about 50 miles from nowhere, and you'll find a broken tab lying loose inside the cover.

Problems have been reported with the repop timing units from Mike's XS. A couple of years ago Yamaha produced a run of new ones, and while that stock seems to be sold out, there are still NOS units from that run available at a reasonable price--a bit north of $100 last time I checked on ebay.
 
Use the term "governor" to search. Prices have gone up since the last time I looked; the cheapest NOS unit I found listed today was $154 shipped. Some of the ads gave application lists that ended with the TX650. Ignore that. All XS650 breaker point ignitions take the same advance unit ("governor" in Yamaha parts listings).
 
Other fixes, if weights aren't worn past hope.
1. Add a thin layer of braze to the notch on top of the weights where they contact the tabs. Work the brass down with a fine file until the desired advance is achieved. This refurb held up for over 5K miles on my old F-model and was working fine when I switched to an electronic ignition. I don't know how far it would have gone, but at 5K-plus the curve was unchanged.
2. Clamp the weight in locking pliers, hold it against an anvil, and smack the end of the tip with a hammer until it expands a bit. Then lay the weight on its side and smack the side of the tip, using a flat punch. A lot of light blows will do it, take your time. Repeat until the tip is widened to 4 mm. (.016"). Clean up with fine file and polish with paper if needed. If the base of the tip has deformed and won't allow the weight to come to rest against the disk, relieve the base with a file.
 
No need to collect complete governor assemblies, 2M; the only wear items are weights and springs. Mama Yama let us buy new springs, but she wouldn't part with new weights unless we bought the whole governor assembly. And that brings up a question you might be able to answer. Who makes the decisions on what to offer as a separate part, and what to offer only with the purchase of the whole assembly--greedy accounting trolls or anal retentive engineers?

BTW JimD54, the problem caused by bad weights isn't that they won't let timing advance; it's that they cause the advance curve to stretch because the ignition shaft gets more travel when there's slop between weight ears and slot edges. When the slop is bad enough, you wind up with a situation in which you retard the start/idle timing too far if you set advance timing correctly and pop carbs out of boots on startup, or put the advance timing in the piston holing range if you set start/idle timing correctly. Except for one much abused TCI motor, every postmortem I've done on an XS650 motor with a holed piston has shown a defective advance governor as cause of death.
 
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I suggested a look at the timing unit way back on the first page of this thread. There are quite a few fixes that can be applied to get the advance curve back in spec if the wear isn't too bad (those weights are shot, IMO), but there's one that should never be attempted: no matter who tells you to do it, don't try to limit travel by bending or peining the tabs on the timing unit rotor. If you do you'll start tiny fractures,

Bending the tabs was a (Rescinded? ) Yamaha service procedure. I epoxied shims inside of one..... No longer sure on which bike, but it might be resto. I kinda wonder if the OP's notches were cut in by a PO, never seen a bob weight set worn notched like that......
 
Re. bending tabs, I had to learn the hard way. First attempt: gentle taps with light hammer and flat punch until curve was restored. Result: DOR in less than 200 miles. Second attempt: removed rotor, heated it with propane torch, applied gentle pressure with water pump pliers (Channel Locks), reinstalled, checked advance, repeated once to get advance in spec. Result: went a little longer, but same as above. Didn't think to try shims; good way to do it!
 
My weights are beginning to show signs of that notching. The slash marks on my unit don't align perfectly but they're not as far off as 650LA's are. I'm still able to dial my timing in properly so it doesn't over-advance but remains in the "F" range at idle. In fact, I'm able to set the full advance a couple of degrees below the slash mark and still remain in the "F" range at idle (over near the right side), which is what I've done. I think the bike runs and performs better with the timing retarded slightly like this.

Abg8svm.jpg


The culprit seems to be that sharp corner on the slot in the little disc. It eventually cuts into the weight tab. I've thought about modding a spare disc I have, rounding that sharp corner off a little with a file or Dremel. Maybe that would slow down the notching effect and wear.
 
No need to collect complete governor assemblies, 2M; the only wear items are weights and springs. Mama Yama let us buy new springs, but she wouldn't part with new weights unless we bought the whole governor assembly. And that brings up a question you might be able to answer. Who makes the decisions on what to offer as a separate part, and what to offer only with the purchase of the whole assembly--greedy accounting trolls or anal retentive engineers?

BTW JimD54, the problem caused by bad weights isn't that they won't let timing advance; it's that they cause the advance curve to stretch because the ignition shaft gets more travel when there's slop between weight ears and slot edges. When the slop is bad enough, you wind up with a situation in which you retard the start/idle timing too far if you set advance timing correctly and pop carbs out of boots on startup, or put the advance timing in the piston holing range if you set start/idle timing correctly. Except for one much abused TCI motor, every postmortem I've done on an XS650 motor with a holed piston has shown a defective advance governor as cause of death.
If you look closely at 2M's pic, it's pretty obvious that the weight could easily hang up on the shaft, causing it to jam. That means no advance. Follow the path the top weight would take. It jams the little wore out depression straight into the shaft.
 
Wow, my advance system is jacked for sure. Good catch. However, that does not seem to be a problem so far... but there's more...

So Saturday morning, the happiest guy I can be, decided to head up to Malibu for breakfast with a buddy of mine. It's about 12 miles from where I am. So first, all runs fine. I got it started in the morning at the first kick. We met at the gas station first here close by, but it was warm enough I even got it going with the self-start (yes, on my XS2 it does work...when warm). I have installed a volt-meter, my battery charges, etc. Floats around 12 when not running to up to 13 when running. We hit the road and there I notice the first issues with the engine. I think it's all gas and maybe jets. The bike runs fine up to 3rd mid-range. Once I revv it up and shift to 4th it starts sputtering - it's like it's missing gas ever so often. It's going fine but sometimes it's sputtering, especially as I revv it up and as it gets to 4th and 5th gears. I've felt this before. From what I have read this is likely that it's running too lean, or maybe my jets are not so up there in the upper ranges. In 1st never seems to happen no matter how high I take it before shifting to 2nd. In 2nd I feel it maybe (maybe) as I am shifting to 3rd when I am pulling it up the higher revs. In 3rd it starts happening halfway to 4th. In 4th if I accelerate I feel it more and more as the speed and revs go up, etc.

Now the kicker (or lack). All is fine. We get to the breakfast place, turn it off. All good. On the way out I got more compliments than I expected by some local guys who build stuff like the stuff you see on TV :) they happened to be there for breakfast too. I guess my paintjob turns heads ;)

In any case, so we get off, start heading back and about 2 or 3 miles in the bike dies on me. As in, flat out, no lights, no power whatsoever. So I look around and I figure the fuse has blown. Interesting. I happen to have been through some of these things before so I had a spare 25. I put it in and start again, all fine. I go maybe not even 1 mile down further and same happens - bam, no power, no lights, etc. No fuses but a friend who happens to be thinking to go out on a ride calls and I ask him to come by and bring some fuses. No dice, it got worse and worse. As I kept putting the fuses, this time it would not even go farther than a couple of revs before me even getting back on the bike... so end result, had to call AAA and got a tow back home...

I guess my major problem now is electrical. Which might as well be it. Since I had on my plans to eventually tackle the electrical and do a complete redo. Debating if I am going to build my own harness or get one of those premade ones - Suggestions?

With that and the info I see in you guy's previous posts, I guess I have to also figure how I am going to fix those weights, or bite the bullet and get whole Pamco thing with the e-advance system too.... there goes the budget babayyyy! :)
 
... Who makes the decisions on what to offer as a separate part, and what to offer only with the purchase of the whole assembly--greedy accounting trolls or anal retentive engineers?

Oh, *those* guys? You have to be a member of a secret society.
I lost track of them after the introduction of $30 inkjet printers with the $65 cartridges.

...The culprit seems to be that sharp corner on the slot in the little disc. It eventually cuts into the weight tab. I've thought about modding a spare disc I have, rounding that sharp corner off a little with a file or Dremel. Maybe that would slow down the notching effect and wear.

That's a good idea. Rounded just enuff to halt the cutting. Of course, once it wears down enuff to contact, it's pretty worn down, but the rounded corner should slow the severe destruction.

... it's pretty obvious that the weight could easily hang up on the shaft, causing it to jam. That means no advance. Follow the path the top weight would take. It jams the little wore out depression straight into the shaft.

Yes, obvious to some, but not to all. It's definitely an "over center" geometry. This would take some descriptive tutorials to explain that...
 
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