Electrical issue

E

eholster

New member
Location
Denver, CO
Hello folks,
I bought an SFC Replica a while back and have experienced intermittent electrical issues since first day.  Initially, on a fresh battery the bike would start up without issue (with some protest from sprag assembly, though I've replaced the rollers, pins and springs - thank you Wolfgang!).  I could make it down the road a ways, get a coffee, stop for a sandwich, and then bike would just die going down the road.  Usually after I took a taxi home and back wherever the bike stopped with a new battery I could make it home... frustrated.  The last time the bike died it would not even hint at starting again with a new battery.  Last night after getting starter rollers and parts installed I put in a fresh charged battery, turned the key, heard a click followed by the battery gurgling... went from ~13V to 10.5 after a couple attempts, so am assuming a massive short somewhere.  Strange thing was the night before I tried to start without the starter chain connected and got the motor to turn.  Prior owner rewired bike and it all looks quite clean, though wire to the starter does look a little anemic, guessing is 14 gauge, so am replacing that. 
The bike would start effortlessly before and now no go... eating batteries now with 2 dead Shorai batteries (will not 'come back' with their hi-tech chargers).
Am bringing the multimeter home from shop tomorrow for further testing, but any thoughts in the meantime?     
 
Sounds exactly like the symptoms my Jota had when the starter motor died. Turned out the stator windings were basically short circuiting, so it would pull massive current but not do anything. Starter motor still had enough active windings to spin OK under no load (as with yours when you took the chain off) but it wasn't making enough torque to turn the engine over. It would just stall.

You can't really tell if the starter motor is buggered by testing the windings with a resistance meter, because the resistance is very low normally. The difference between a good one and a buggered one might only be one or two ohms. Most multimeters don't have the accuracy to tell the difference. But if it's pulling enough current to depress the battery voltage but not cranking, you can be reasonably sure it's knackered.

One way to check it is to feel how hot the starter motor gets after you've held the button on for a few seconds. If it gets quite hot quite quickly, then then you know the electrical energy is being dissipated in the windings, rather than going to turn the output shaft.

Could be stator or rotor windings. I suspect what happens is that the lacquer insulation on the winding wire breaks down after a time (these bikes are 30+ years old) and adjacent coils short against each other. The shorted windings draw more current, get hotter and more insulation breaks down, making more short circuits, etc. So it's a kind of runaway effect. Eventually it gets to the point that it won't work at all. 

You may be able to get it rewound if there's someone who does that in your area. I got a refurbished starter motor from Malcolm Cox in UK. My bike now starts better than it ever did. I'd suggest you try Wolfgang.
 
Shorai batteries are LiPO4 type, no?
Are you still running the original dynamo and regulator systems?
Might be that the battery charging is too spiky.
LiPO4 batteries need a finely controlled charge flow.
 
The mega old Auto sparky bloke I used tested my starter motor by holding it in his hands and activating it and using the cog on the end as a timber router on a 4x4 lump of pine, softwood. It did a good job ripping chunks of timber out and not stopping. impressed me no end. He could have been 50 but I reckon he was closer to 70. That family-owned business had been there since the early 1930s, 3 generations worked there. They closed up and bought a Battery World Franchise.
 
Paul Marx said:
What components have you got in your electrical system.
Relay?
Regulator?

Who wired it  :D

Paul
Click to expand...

Components are all original to the SF donor bike.  I have a replacement regulator to install.
I didn't wire it... but may have to!
 
Dellortoman said:
Sounds exactly like the symptoms my Jota had when the starter motor died. Turned out the stator windings were basically short circuiting, so it would pull massive current but not do anything. Starter motor still had enough active windings to spin OK under no load (as with yours when you took the chain off) but it wasn't making enough torque to turn the engine over. It would just stall.

You can't really tell if the starter motor is buggered by testing the windings with a resistance meter, because the resistance is very low normally. The difference between a good one and a buggered one might only be one or two ohms. Most multimeters don't have the accuracy to tell the difference. But if it's pulling enough current to depress the battery voltage but not cranking, you can be reasonably sure it's knackered.

One way to check it is to feel how hot the starter motor gets after you've held the button on for a few seconds. If it gets quite hot quite quickly, then then you know the electrical energy is being dissipated in the windings, rather than going to turn the output shaft.

Could be stator or rotor windings. I suspect what happens is that the lacquer insulation on the winding wire breaks down after a time (these bikes are 30+ years old) and adjacent coils short against each other. The shorted windings draw more current, get hotter and more insulation breaks down, making more short circuits, etc. So it's a kind of runaway effect. Eventually it gets to the point that it won't work at all. 

You may be able to get it rewound if there's someone who does that in your area. I got a refurbished starter motor from Malcolm Cox in UK. My bike now starts better than it ever did. I'd suggest you try Wolfgang.
Click to expand...

This sounds about right...  I'll start with exploring the starter.  I recall motor did in fact get quite warm. 
Will update on what I find.

Thanks everyone!

Erin
 
Such a severe problem, I reckon the culprit should be relatively easy to find. Good luck and keep us posted. Cam's post indicates the starter is definitely looking like a good place to start. And get a big fat cable onto it pronto. They are hefty beasts those ND starters and must pull some amps to produce 1hp!
 
Great points from Cam per usual & he's probably spot on w/ the starter amp draw but you will probably still have the stall issue. Consider checking ignition switch and fuse box contacts & circuit grounds. Congrats on the purchase! 
 
You mention that the bike would just die going down the road, riding it after a stop so more than a starter motor issue. Charging system should be checked, and as Grant points out, if these hightech batteries are so fussy, how can they cope on our old bikes. AGM work great on these bikes.
 
Lithium works fine on my bikes. BM has had one in it for 5 years and no problems so far. Even after a few months of sitting it'll fire right up.
Motodd has a smaller version, brought the same time I brought the BM battery and sat on the shelf for 18months while having the frame repaired and showed full charge after that time.
The batteries I use don't require special chargers or tenders. The fact that it weights less than a kg is a bonus as well. Must be having a moment as I can't remember the brand name!!!
 
Grant said:
Modern r/r too?
Click to expand...

Ah yeah, up grade with the kawasaki alternator. The battery is a SSB.
I guess we're talking about a dynamo and regulator so my comment is erevelent. Haven't tryed a lithium on the SFC yet so can't comment.

 
I have had mixed experience with LiPO4 batteries, and for the foreseeable future I will stick to AGM ones.
 
stator windings were basically short circuiting
Click to expand...

Dellortoman: Been there a couple of times with various starters - Mostly Automotive - Often the bolt that holds the windings to the starter case comes loose and the the windings vibrate and sheaf against the case shorting out. Generators can have the same issue.
 
Laverda SF said:
Often the bolt that holds the windings to the starter case comes loose and the the windings vibrate and sheaf against the case shorting out. Generators can have the same issue.
Click to expand...

Thanks Ron. That failure mode hadn't occurred to me, but it sounds quite plausible.

Cheers,
Cam
 
That issue is a "Battery Short" through the starter solenoid and the starter Stator Windings to ground or perhaps a Generator.
 
I've been off the charts busy... so haven't had the bandwidth to lift a wrench. 
However, I did spend a few minutes re-assessing things and am putting fault on the starter.  I went ahead and attempted to start and rather than feeling the starter body get warm as Cam suggested may happen, I could feel things grinding inside.  I may disassemble it once I get home from the office this eve - and I know, pictures, or it didn't happen.
More to follow - thanks again for the input.

Erin
 
Removing the starter motor is quite easy. Just disconnect the big wire and remove the two flange bolts and it comes out.

Only issue you might have is getting at the flange bolt on the front side of the starter motor. It's jammed down between the starter motor and the back of the cylinder block, so there's barely room to swing the Allen key. I made a special tool to do it. Cut a straight piece of Allen key and welded it to a long extension with a T-bar on the end. It enables me to reach that socket head bolt from the other side of the engine. Makes removing and installing that bolt very easy.
 
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