81 xs650 dies while cruising.

[LeftyKash]

My 81XS650 SH has an intermittent problem that is giving me fits! Every few miles (like 4-10mi) the bike will stop running. Usually I'm on the highway, cruising along in 5th @ 4-5K rpm. Often it backfires 1x upon stopping. If I pull in the clutch and coast along for 10-15 seconds, I can usually drop the clutch and it starts back up. It's never happened at idle or when just riding on surface streets, but most of my miles are highway so ¯\_(ツ)_/¯ Also, when the bike dies, the electric seems to keep going. The gauges stay lit and the headlight stays on.

Here's some background:
I bought this bike about a month ago, it's a very clean 81 XS650. When I bought it, it wouldn't run off of Choke. I cleaned the carbs (but didn't mess with the floats or the float valve.) Honestly, they we're pretty much sparkling clean. I also found that the left intake manifold barb was all leaky and barely in place, so I replaced both intake manifolds. While I was at it, I replaced the spark plugs. Once I put everything back together the bike started right up! I sprayed around with carb cleaner and couldn't find any leaks. Now it idles and runs fine, except for the aforementioned problems.

I thought it was likely a fuel delivery issue, so I cleaned the tank vent and replaced the filter with a piece of scotch brite. I also replaced the sealing gasket. The issue was still present afterwards. Then I tried just leaving the tank open to confirm that it wasn't the vent. Still no good.
Then I thought maybe it was the vacuum petcock. It seems like most of the failure modes were with the petcock leaking, but I wasn't sure. I bought a non vacuum replacement of amazon. It bolted right up, but honestly, it's a piece of crap. The fuel line barb is 3/16 instead of 1/4 and the right angle barb was just a press fit that leaked. I brazed it, and made the 3/16 fuel line fit to the inline filter that I installed.

I used a clear filter and replacement line, and I can see gas flowing through it, although the line doesn't seem to 'fill up'. Looks like there's always air in there. Anyways, I started the bike up and hit the highway. Same thing happened again. If anything it was a bit more frequent. Now I'm not sure what else to check or look at. Any ideas?
Thanks!

 

[Jan_P]

I would guess a ignition problem
I would check the fuse holder and connections servicing if needed ... downstream
Also check the kill switch ,,not likely the fault here but might as well check
Then I would connect a Voltmeter on the bike to see that it is not overcharging out there on the road.
If i recall right this can be the coil .That when it gets hot shorts out.
This having an electronic Stock ignition .. I don't know much about.
I have not heard of any simple fault finding on that..

 

[jetmechmarty]

The TCI box is 40 years old. I sent mine to a friend who could fix it and he simply re-soldered all the board connections, AFAIK. Whatever, I got it back and the bike runs just fine. Check the Gonzo thread. You could try that. Easiest if you had a spare TCI box to try. It does sound like you have an intermittent open circuit somewhere in the ignition system. Without parts to swap, this will be a little more trying.

 

[Team Junk]

I would temporarily hookup a light or led to the r/w coil wire near the coil. That way you can confirm power through the key switch and the kill switch when it dies. If the light stays on when it dies then if it is a ignition problem that narrows it down to the coil, the TCI box or the pickups.

The Gonzo makes a good tester for all the above.

http://www.xs650.com/threads/gonzo-diy-tci-system.57694/

For questions about the Gonzo box.
You don't have to read all 60+ pages.

http://www.xs650.com/threads/tci-replacement-2020-it-works.57388/

 

[LeftyKash]

I would temporarily hookup a light or led to the r/w coil wire near the coil. That way you can confirm power through the key switch and the kill switch when it dies. If the light stays on when it dies then if it is a ignition problem that narrows it down to the coil, the TCI box or the pickups.

The Gonzo makes a good tester for all the above.

http://www.xs650.com/threads/gonzo-diy-tci-system.57694/

For questions about the Gonzo box.
You don't have to read all 60+ pages.

http://www.xs650.com/threads/tci-replacement-2020-it-works.57388/

This is good advice! I wasn't sure how best to check through the keyswitch and ignition for an intermittent fault. I'll start with that, and I'll check the fuse box when I get a minute.

I also ordered a Honda mp08 coil (I'll grab some plug wire and 5k resistor boots at the auto parts store) my plug wire and boots aren't in the greatest shape, and it's a cheap thing to try.

 

[Team Junk]

I think you are well on your way to resolving this. The coil & plug wires are the most likely candidates in this scenario. Check your ground at the battery. The pickup seldom fails so if it's not the coils it's a TCI box or wiring. Or something weird.

 

[jetmechmarty]

The pickup seldom fails

At least not intermittent.

 

[LeftyKash]

Thanks everyone for the advice! I didn't have time to check through the key switch last night, but I did inspect the fuse box (all OK) and I rang out the ignition coil, with the bike cold.
The primary was fine at 2.6ohms.
Everything was OK to ground and between primary and secondary.
Secondary resistance was high- 28.6k ohms, as measured through the spark plug caps.

My Clymer manual has the spec at 10,500-15,500 ohms. Perhaps this is causing my intermittent problem.

 

[nj1639]

Pop the caps off and check through the secondary.

 

[LeftyKash]

Through the secondary, sans spark caps, is about 12.2k ohms. That's in range for the coil in the Yamaha 650SH supplement. The clymer manual said to check the secondary wires, but the illustration showed testing through the wires and spark caps. Kinda ambiguous if you ask me!
Left plug cap is 7.9k ohm
Righy plug cap is 8.3k ohm.
Both are a little high.

So, I think the coil's testing ok. But it's an intermittent problem so..... It doesn't really mean anything. I'm still going to replace coil, caps, and wires when my new stuff gets here next week.

I set up a temporary volt meter to monitor charging, and i put a couple of wires in series before the coil primary to monitor the kill/ignition switches. (That's the green and white alligator clips in the picture). Now I've just got to go grab a 12v led and I can test that stuff, likely tomorrow.

 

[Jan_P]

Through the secondary, sans spark caps, is about 12.2k ohms. That's in range for the coil in the Yamaha 650SH supplement. The clymer manual said to check the secondary wires, but the illustration showed testing through the wires and spark caps. Kinda ambiguous if you ask me!
Left plug cap is 7.9k ohm
Righy plug cap is 8.3k ohm.
Both are a little high.

So, I think the coil's testing ok. But it's an intermittent problem so..... It doesn't really mean anything. I'm still going to replace coil, caps, and wires when my new stuff gets here next week.

I set up a temporary volt meter to monitor charging, and i put a couple of wires in series before the coil primary to monitor the kill/ignition switches. (That's the green and white alligator clips in the picture). Now I've just got to go grab a 12v led and I can test that stuff, likely tomorrow.

Yes sir this is on track . We have not failed Yet -- Or should I say those here that knows these things have not failed
You are listening to advice and replaces the " Usual Suspects " and are doing the right things.
Usually within the week .If not quicker..Please report.

That voltmeter display 13.3 at ca 3000 .. Please check that it goes a bit higher if revving.With lights HI on and a turn signal perhaps braking also
might be right 13.3 ..but it is easy to check once it is hooked up.

 

[650Skull]

Or something weird.

Nothing like good advice.......

Sorry couldn't help myself

 

[5twins]

Actually, the plug caps probably aren't reading too high. Yamaha used some rather oddball caps on these rated at around 8 or 9K ohms. But, new NGK 5K ohm caps wouldn't hurt a thing. I always get rid of those 40 year old originals. It's like a less than $10 "fix" that may very possibly ward off future problems. I have found bad original caps on these. Usually, their resistance begins to climb when they go bad. You'll find them reading 10K, 12K, or even higher. They will start choking off the spark eventually.

 

[LeftyKash]

So i got my replacement ignition coil in the mail today. It's new, listed on eBay as for a Honda cb. The primary is 1.5ohms and the secondary is 14k ohms. That's too low on the primary for an TCI, right? I need 2.5ohms or more? Just want to confirm before I accidently fry the electrical system.

Edit: my clymer manual says 2.5 ohms for the primary but the Mike's xs replacement is 1.6, so maybe i am fine.

Edit 2: the connection from the secondary side of the coil out to the plug wire is not what i was expecting. Instead of a 'wood screw' looking thing there is a straight pin. Kind of like a coax cable. I pushed the wire into it, and then tightened down the strain relief, but that doesn't seem right. Is there some type of terminal for this side or something? Thanks!

 

[LeftyKash]

I finally had the opportunity to test the bike out today. It ran great! No stopping, for my first ride.(about 30 minutes) on my second ride (heading home) the bike was breaking up and lurching after about 3k rpm. I went under a tunnel, and in the dim, saw that my high beam indicator was lit. I turned off the high beam and everything was good! Looks like I've got something going on with this bike electrically. Brushes looked good, the caliper says they're both right about 14mm. At least it's rideable now though. On to the next problem!

 

[LeftyKash]

I thought it might be worth an update-
I was out of town/it was raining for a bit so I wasn't on the bike. I took it for another ride and it died again about 1.5miles in, right at the end of the freeway ramp. It didn't want to start back up right away so I pushed it for a bit before it started. I did a little bit of exploration, but couldn't find a clear culprit.

Here's what I did:
Inspected headlight bucket/harness for bad connections/loose/pinched wires- everything looked ok.
Checked slip ring resistance 5.2 ohms- OK
I noticed that a previous owner had glued a magnet to the the slip ring (pictured). There were a couple of flakes of the rotor insulation in the bottom of the left side cover.
.759k ohms on pulsar coil, both sides to black. seems ok.
I quickly checked the voltage before the ignition coil red/white and at the TCI. both were showing 11.8 when the battery was at 12.4 I'm thinking that's ok. Jumped the safety relay to see if that was causing any voltage drop and no, it's ok.
When I checked voltage at the TCI, I saw that it had been removed at least 1x previously- one side of the case is held on with a wire tie.


I noticed that the bike's voltage seems low while running. I temporarily put in a voltmeter at the ignition coil (to show me next time the bike dies if the coil is losing power through the kill switch/ignition) and it was running with pretty low voltage- maybe 11.4vdc
I also got the following, with no headlight on the bike:
12.2v at 2k rpm
12.9v at 3k rpm
13.0v at 4k rpm all measured at the ignition coil.
Additionally, my idle seems to be running fairly low lately. Maybe 800RPM. definitely not where it was earlier this year.
I tried unplugging the R/R while the bike was idling to see if the rotor was overwhelming the magnet signal, and the idle did not pick up any speed. I'm thinking that means that the magnet and pickup coil is ok, at least at idle.

I bought a new battery (just to try) and a GN250 ignitor to see if that takes care of my ignition. Fundamentally, now I'm not sure if I have a charging problem or an ignition problem. Any advice on next steps?

 

[nj1639]

In post #1 you stated that you didn't mess with the floats or the float valve because they were sparkling clean.
Sparkling clean isn't a measurement of float height, might want to get that checked off the list. It costs nothing but time to confirm.

 

[Downeaster]

Also - check your voltage at the battery. Low battery voltage will result in funky ignition with a TCI.

Voltage at the battery with the bike in neutral, headlight off and at high idle (2-3K) should be north of 14 volts. If it's not, you have charging issues. Good brushes and a clean slip ring with proper resistance values are good signs, but there's more to it than that.

Things to check next in that department are stator coil values and the regulator/rectifier.

 

[LeftyKash]

I went through Curly's charging checks last night after putting in a new battery. It looks like I need a new regulator/rectifier.

"slap" test- a wrench hanging off the end of a screwdriver will slap the cases when I turn the key 'on'

Regulator/regulator ground check- with no changes voltmeter at the batter shows 12.9v off, 13.1v@2k rpm 13.6v max @4k rpm. With the green regulator wire jumped to ground, the voltage will go all the way up to 16v when the bike is revved up. I read that the regulator grounds through it's mounting bolts, so I put a jumper on the heat sink out to the engine. Still maxed out charging at 13.6v. Conclusion- BAD REGULATOR. I kept going with the rest of the tests, just to see if anything else was weird.

Wiring to brushes check- battery shows 12.7v positive brush shows 12.3 Document shows a maximum drop opf .3v, this is .4v. It's probably fine though.

slip rings check- 5.2 ohms ok. rings to ground open ok.

stator voltage check, between the wires. 11.2v 11.5 v 11.5v @1800rpm OK.
stator resistance check, .6ohm .6ohm .7ohm OK.

I've got a new regulator/rectifier from ebay on the way:
https://www.ebay.com/itm/290798826230
So I'll go for a ride once it's installed. I still have my meters at the ignition coil and one at the battery so I'll monitor them when I try out the new R/R
I'm working on a permanent meter install so that i can keep an eye out for this kind of problem in the future.

nj1639- Not a bad idea! I'll check the float height when I have a minute.

 

[LeftyKash]

Just a quick update- my new regulator rectifier arrived today and i tried it out. It didn't work. When revving the bike, my voltage didn't go up at all.
I read that the unit needed grounding to the frame so I ran a jumper to the main ground, still no increase.
Then I did a resistance check through the connector, all good.
I'm going to have to return the R/R and order another.
My new cdi arrived to try the gonzo cdi also. I have to write up a connector and plug it in, but it's crazy hot in the garage right now, so I'll try it later this week.