New owner of a 1981 XS650 and I don’t know where to start

JFAIR1

XS650 Member
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Hernando, MS
First of all thanks for this group. I’m brand new to the forum but the knowledge I have found already has been great. So here we go. Ive got a 1981 XS50. Honestly I’m not even sure if everything is original. It was made into a cafe reader/scrambler before I purchased it. I was having electrical charging issues. I replaced the rotor and that fixed the problem temporarily. The bike started acting up again. Battery was not staying charged. I found that the connection from the bikes wiring harness to the rectifier had a burnt wire. It was either the bottom right or bottom left white wire. I was able to fix the wire but again the bike’s charging system failed on me once again. So I cut the connector off of the wiring harness and the rectifier. I wired each wire individually together. Turned the key on, hit the start button and got maybe two cracks before the starter quit working. Told myself that’s fine I‘ll just use the kick stater. Now the kick stater is extremely difficult to use and will not kick over. The bike wants to kick me back every chance it gets. I took the spark plugs out and the kick starter moved up and down smoothly. I put the spark plugs back and the kick starter is back to wanting to kick me back. No chance of kicking over either. The compression I think is good. I was riding the bike less then a week ago With no issues. Please help me out.
 
First, welcome. When you said you replaced the rotor, what did you replace it with? Based upon the information I have from sources here and places like it, a new reproduction rotor is an unacceptable option where I’m concerned. A used OE rotor was a time bomb 20 years ago. They have only gotten worse. I believe the best option is a rewound OE rotor. The only other option is an aftermarket alternator. The former is the only source for me.
 
Thanks for the replies. I honestly am not sure what ignition system is on the bike. Looks stock to me. Ill look under the chrome cam covers tonight and report back. I replaced the rotor with one from MIkes. I didn't know any better at the time that aftermarket is trash. I hope to get the original rewound ASAP. So at this point you guys are thinking it's a timing issue? Possible the aftermarket rotor has also failed? One problem at a time would be nice. Ill start with the timing and go from there. One more piece of information. I noticed that the timing chain tensioner was not set right either. I reset it but that was several weeks ago and the bike was running fine up until the last few days.

Marty from MS. I've been meaning to message you direct. I'm over in Hernando. Maybe we can meet for a cup of coffee or a beer one day and talk about my troubles.

Thanks again everybody.
 
These are good bikes but they're old. One of the first things I do to one when I get it is go through all the wiring. I start at the tail light and work my way up to the front, into the headlight bucket. I clean all the wiring and plugs, repairing any that need it. It seems I always find a few issues, some rubbed bare wires and/or plastic plugs that need replacing. Fixing all this stuff before I run the bike much wards off most future electrical problems. In particular, pay attention to the grounds. There are only a couple on the whole bike and they need to be good. There's the negative battery cable of course, connected to the frame behind the battery, and another small ground wire coming out of the harness around the coil and connected to one of it's mounting screws. This one is very important as it provides a ground for anything connected to the harness that needs one.

If your bike is an '81 then what you're calling the rectifier is actually a combined regulator/rectifier and should have 7 wires coming out of it. I wouldn't wire it directly into the harness, I'd get a new plug for it.
 
Well, to be fair and before you go spending any more money on a rotor. A while back there was a deep dive done on aftermarket rotors when a member was having trouble. The deep dive found that the aftermarket rotors taper was not true causing the brushes to bounce on the lip rings causing a charging issue. This problem could have been just a batch issue but as happens with a lot of these aftermarket parts being made, mostly in China, the quality control is not on par with factory originals.

A member @Jim here decided to help out the members and set up a small Rotor rewind business using the factory rotors on a core rebate system so he always has a rotor. Hopefully the person getting a rewind sends in his old one. The quality of the windings and resin coating is way above what is on an aftermarket one and his quality control is his reputation.

So the chances are the rotor bought from MikesXS is ok but cautions should be used to check the out-put and it won't do any harm to check run-out. If the run-out is ok then...:shrug:..............For piece of mind you could always send your old Factory rotor to get rewound, the cost is very, very reasonable and then you always have a spare if the MikesXS one fails.
 
So I looked under the chrome caps to find nothing. Just like nj1639 told me I would. Except I didn’t see a cam there either. So that means TCI or some other aftermarket timing system? I’m starting to suspect that the timing chain tensioner might be the issue. When I first acquired the bike the tensioner was backed out way to far. I tightened it so the pin was flush with the 9mm screw bolt. Maybe it jumped a tooth or it’s too tight. My next plan is to back the tensioner out and turn the rotor and crank cam to see if I can straighten out the timing chain. Which direct do I turn the crank cam? Clockwise or counter clockwise? If this doesn’t work then I move to the timing system once I figure out what system I actually have. Thanks again for all the feedback. I’ll also attach the pictures I took this morning.
 

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It's stock TCI, only thing under the chrome cap is the end of the cam or cam end.
Pull the plugs, rotate the engine with the kick starter to find out which way the engine turns.
Have the cap off the cam chain tensioner. The pin in the middle of the cam chain tensioner should have about a mm of up and down motion, near flush with the threaded piece that the pin sits in.
Either use the kick start or a wrench on the crank bolt at the middle of the rotor to turn the engine in the correct direction. Make adjustments to the cam chain tensioner to get that mm up/down travel. By tightening the cam chain adjuster down you could have advanced the timing resulting in your kick back.

Any adjustments to the cam chain tensioner should include a visit to the valves to check and maybe reset the clearances if they're off. Refer to a manual for the clearances. Other opinions welcome.
 
Because you have a TCI system, firing is determined by the alternator rotor.... on the end of the crank. Therefor, ignition timing wouldn't change even if your cam chain jumped a dozen teeth, the relationship between TDC and ignition firing wouldn't change at all.

And I doubt your timing chain jumped timing. More than once someone's pulled the engine 'cause they thought the cam jumped timing only to find out it didn't. Yes, it's possible, but extremely rare.... and even if it did, you wouldn't get kickbacks... as I explained above... crank fired ignition.

Try charging the battery, disconnecting the stator connector and see what happens. Aftermarket junk rotors have been known to cause timing miss-fires because of interference between the TCI magnet and the rotors magnetic field. Disconnecting the stator connector will eliminate that as a source of the problem.

Keep us posted.
 
Yes, I have the original rotor. Are you the member that rewinds them? If so I need to get that done. Please message me.

Just to be clear about the timing chain tensioner. When I bought the bike the tensioner was way to far out. Being brand new to street bikes I didn't think anything of it. After doing some research I figured out that it needed to be tightened down to meet the mm up/down spec. Note: the bike ran fine before I messed with the tensioner as well as after. I already have pulled the spark plugs and used the kick starter to turn the motor over. It's smooth as butter. As soon as I put the plugs back in and kick it, she kicks me right back. One attempt to kick the bike even resulted in a back fire making smoke come out the carburetor.

Jim you are saying the next step is to move on to the rotor.

nj1639 you suggest me checking the valves and reset clearances.

I'll report back ASAP. Thanks.
 
Jim you are saying the next step is to move on to the rotor.
No, I'm saying disconnecting the stator connector will kill power to the rotor (the ground, to be exact). If it runs OK then, then yes, the rotor's the problem.

RE: timing chain and valve adjustment. Adjusting chain tension will not affect valve clearances. I know this is suggested all the time here, but one will not affect the other. The only reason it's suggested is because if the chain needs adjusting, the valves likely do also.... but loose valve clearances will not cause kickbacks. You can worry about them once you have it back to running... jus' leave 'em be for now.... lest you make things worse. ;)
 
It's easy enough to check the cam timing to see if the chain has jumped some teeth. Set the motor at TDC (align the rotor slash mark with the "T" slash mark on the little timing plate) .....


TDC.jpg


..... and remove the little chrome cover on the top right side of the motor. You should see the end of the cam sticking out through the oil seal. Look for a small hole (about 1/8" diameter). This is a throw-back to the earlier points models that had a locating pin there for the mechanical advance unit. If the cam is timed right (hasn't jumped any teeth), that hole will point straight up or straight down .....

CamTimingMarks.jpg
 
I’ll start with the outcome.

We started by putting the bike on the lift and accessing the alternator. The stator was properly installed. I removed the rotor and checked for a woodruff key. The aftermarket rotor has a good trigger magnet and reads just under 6 ohms. OE rotor also checks good.

Timing chain tensioner checks good.

Pulled valve covers. Cam timing checked OK.

Air filters are the type that block the ports on the carburetor. Needs new filters.
 
Compression test good.

Repaired start switch. Starter operation is wonky.

It fired right up. It runs strong. Very strong. It has a 750 kit on it.
 

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