Starter won't turn engine

YellowPeril

YellowPeril

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Jan 18, 2023
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I have always had 750s, so haven't spent much time on the Rube Goldberg contraption that is the MkIII starter.

My 850 came to me with the starter mount blocked off and the starter parts in a box. 3000 original miles, starter will turn freely when connected directly to battery.

I assembled everything according to the parts manual illustration which was pretty straightforward (it seemed). Starter motor wouldn't turn the engine so I figured it must be shot. I bought a new production "gear reduction' starter motor. It does the same thing....I've connected the electrics back up like they should be, the solenoid is working and sending 12V to the starter, but the main (negative) wire gets very hot and the motor will only turn slightly. When connected directly to battery (positive to the case, negative to the terminal) it does the same thing (negative gets very hot after a second). Everything seems to turn fine....bike will start and run with the kickstarter. I'm stumped.
 
YellowPeril said:
I have always had 750s, so haven't spent much time on the Rube Goldberg contraption that is the MkIII starter.

My 850 came to me with the starter mount blocked off and the starter parts in a box. 3000 original miles, starter will turn freely when connected directly to battery.

I assembled everything according to the parts manual illustration which was pretty straightforward (it seemed). Starter motor wouldn't turn the engine so I figured it must be shot. I bought a new production "gear reduction' starter motor. It does the same thing....I've connected the electrics back up like they should be, the solenoid is working and sending 12V to the starter, but the main (negative) wire gets very hot and the motor will only turn slightly. When connected directly to battery (positive to the case, negative to the terminal) it does the same thing (negative gets very hot after a second). Everything seems to turn fine....bike will start and run with the kickstarter. I'm stumped.
Click to expand...
Take it apart and figure out what it is (or isn't).
Hot lead indicates very abnormal current draw, typical of a deadlocked rotor.
>mechanical issue in the drive mechanism in the primary case.
Investigate & report back.
 
YellowPeril said:
I have always had 750s, so haven't spent much time on the Rube Goldberg contraption that is the MkIII starter.

My 850 came to me with the starter mount blocked off and the starter parts in a box. 3000 original miles, starter will turn freely when connected directly to battery.

I assembled everything according to the parts manual illustration which was pretty straightforward (it seemed). Starter motor wouldn't turn the engine so I figured it must be shot. I bought a new production "gear reduction' starter motor. It does the same thing....I've connected the electrics back up like they should be, the solenoid is working and sending 12V to the starter, but the main (negative) wire gets very hot and the motor will only turn slightly. When connected directly to battery (positive to the case, negative to the terminal) it does the same thing (negative gets very hot after a second). Everything seems to turn fine....bike will start and run with the kickstarter. I'm stumped.
Click to expand...
Is your bike still positive ground? If so, does the motor match?
 
What guage of wire are you using for the battery to solenoid, solenoid to starter and starter to ground lead.

And battery to ground.
 
Becaflreful of overly wetsumped crankcase with the electric leg setup...it is marginal to begin with and extra load of trying to compress significant oil in sump will cause proba like blown sprag or anti kick back device...seen it happen...yes mk3 has antiwet sump pressure side valve etc but can still happen.
 
I've had the inside of the primary apart and back together 4 times now, nothing is binding up and I can't see how anything could be installed wrong. I've got a new sprag clutch, the old one doesn't look bad but I've swapped them both in and out several times with no difference. Tried my new starter on another 850, it turned over like a champ. Mine won't make half a revolution before it stops. Battery is at full charge, and I'm going direct from the battery to the starter. It's positive earth, spins in the right direction and as I stated turned the other bike over fine. Not a deadlocked rotor, that's been on and off a dozen times now and everything there rotates freely. I've attemped to isolate the problem by removing things to see if they affect the rotation of the engine- started with the stator, then the rotor and stator mount. There's nothing obvious at all....all components move freely, and I have just discovered the starter turns the engine over fine with the spark plugs out. This bike came to me with no information on its history, I've had to guess at it. It hasn't been tagged since 1983 and has 3000 miles on the odometer. It had a single Mikuni on it, and the starter with the gears, sprag clutch, bearing sleeve etc were all in a box. I'm sure that everything is there and installed properly, and am starting to wonder if the compression wasn't raised significantly by the previous owner. But, it's not hard to kick over and I've had it running so I'm dubious on that. It's not wet sumped, that I'm sure of as of this writing (if anything, there's little oil in the sump as much of it has drained out from the several times I"ve removed the bottom stator mounting bolt which threads into a 'through hole' in the crankcase). Still stumped.
 
"and I have just discovered the starter turns the engine over fine with the spark plugs out."

Ok, back to the starter.

I have seen offered for sale copies of the DynoDave starter.
Perhaps you have a poor quality Chinese knock off.

Originally, high quality Japanese Nippondenso automotive starters were modified to be the DD starter.
 
YellowPeril said:
I've had the inside of the primary apart and back together 4 times now, nothing is binding up and I can't see how anything could be installed wrong. I've got a new sprag clutch, the old one doesn't look bad but I've swapped them both in and out several times with no difference. Tried my new starter on another 850, it turned over like a champ. Mine won't make half a revolution before it stops. Battery is at full charge, and I'm going direct from the battery to the starter. It's positive earth, spins in the right direction and as I stated turned the other bike over fine. Not a deadlocked rotor, that's been on and off a dozen times now and everything there rotates freely. I've attemped to isolate the problem by removing things to see if they affect the rotation of the engine- started with the stator, then the rotor and stator mount. There's nothing obvious at all....all components move freely, and I have just discovered the starter turns the engine over fine with the spark plugs out. This bike came to me with no information on its history, I've had to guess at it. It hasn't been tagged since 1983 and has 3000 miles on the odometer. It had a single Mikuni on it, and the starter with the gears, sprag clutch, bearing sleeve etc were all in a box. I'm sure that everything is there and installed properly, and am starting to wonder if the compression wasn't raised significantly by the previous owner. But, it's not hard to kick over and I've had it running so I'm dubious on that. It's not wet sumped, that I'm sure of as of this writing (if anything, there's little oil in the sump as much of it has drained out from the several times I"ve removed the bottom stator mounting bolt which threads into a 'through hole' in the crankcase). Still stumped.
Click to expand...
With the plugs out, how "fast" does it spin the engine.

With one plug out will is spin the engine? Much slower?

If you have a voltmeter, connect it across the battery and note the voltage and then press the button. Do that with no plugs installed, one plug installed and both plugs installed.

Some batteries, especially AGM can seem to be fully charged but cannot deliver current once the voltage drops to a certain level. I have one that is one year old, seems to charge fine, but when put in a bike without e-start and with lights off, will not provide enough current to spark the plugs - it's a 9AH AGM.

A quick test, is to use car jumper cables between your car battery and motorcycle battery. Black to - on both and red to + on both and make sure the bike does not touch the car.
 
Do you have the heavy “ground” wire that goes from the engine case back to the battery installed? It should be located on the left rear side of the case, right below the barrels
 
YellowPeril said:
I"ve removed the bottom stator mounting bolt which threads into a 'through hole' in the crankcase).
Click to expand...
I don't understand that as the Mk3 stator mounting studs don't screw into the crankcase. And why did you remove it?
andover-norton.co.uk

Andover Norton - STUD - STATOR FIXING - 06.4716

STUD - STATOR FIXING
andover-norton.co.uk
Do you mean one of the outrigger studs, item 20? None are bolts.
andover-norton.co.uk

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
 
YellowPeril said:
I've had the inside of the primary apart and back together 4 times now, nothing is binding up and I can't see how anything could be installed wrong. I've got a new sprag clutch, the old one doesn't look bad but I've swapped them both in and out several times with no difference. Tried my new starter on another 850, it turned over like a champ. Mine won't make half a revolution before it stops. Battery is at full charge, and I'm going direct from the battery to the starter. It's positive earth, spins in the right direction and as I stated turned the other bike over fine. Not a deadlocked rotor, that's been on and off a dozen times now and everything there rotates freely. I've attemped to isolate the problem by removing things to see if they affect the rotation of the engine- started with the stator, then the rotor and stator mount. There's nothing obvious at all....all components move freely, and I have just discovered the starter turns the engine over fine with the spark plugs out. This bike came to me with no information on its history, I've had to guess at it. It hasn't been tagged since 1983 and has 3000 miles on the odometer. It had a single Mikuni on it, and the starter with the gears, sprag clutch, bearing sleeve etc were all in a box. I'm sure that everything is there and installed properly, and am starting to wonder if the compression wasn't raised significantly by the previous owner. But, it's not hard to kick over and I've had it running so I'm dubious on that. It's not wet sumped, that I'm sure of as of this writing (if anything, there's little oil in the sump as much of it has drained out from the several times I"ve removed the bottom stator mounting bolt which threads into a 'through hole' in the crankcase). Still stumped.
Click to expand...
Try your battery on the same bike
Even if they look ok, clean and make sure the terminals/cables are tight. Loose battery terminals have caused me grief in the past (and probably will in the future!)
Problems caused by a 'not tight enough' battery terminals
Weird charging issues,
Non starting (solenoid clicking) but lights all worked ok
Ignition light lit when key turned to on then ignition light faded out (not enough to pull the solenoid in)
Engine able to run, won't start on the button but would bump start (or kick start, if it had one fitted) I removed it as it got in the way of the rearsets i made.

I find the batteries that have the lead terminals worse for the cables getting loose, I prefer the batteries that have the sheet metal terminals (like motobatt) etc
That said the battery on Mitzi has lead terminals, Just what was available at the time.
 
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I don't see any mention of the battery's age. The symptoms suggest to me that the battery could be at fault. Why not try the battery from the other Mk3 (on which you tested the starter from your bike) on yours? If there is still a problem with the borrowed battery, I would look at the wiring.

The standard starter cables are rubbish, as is the standard solenoid. Even a new well-charged battery can struggle due to the electrical losses in these parts. I use a solenoid for a British Leyland Mini and the cables are much thicker multi-strand stuff as used with fork lift truck chargers. There are sellers on Ebay in the UK who will make custom lengths.
 
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Any chance of clutch plates being stuck causing excess drag when trying to start? Put in neutral on CS and try turning rear wheel by hand...should be easy spin.

What excatly happens while you watvh the mechanism with primary cover off and starter being triggered?
 
When my mk3 is wet sumped the starter struggles and I have a 4 brush motor with 26 amp hours. Just a thought, unlikely but could be!
 
YellowPeril said:
I don't seem to have explained things clearly so here's some video of me putting it back together and showing what's happening when I try to turn it over with the starter.

Dropbox

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Dropbox

www.dropbox.com www.dropbox.com

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www.dropbox.com www.dropbox.com

Dropbox

www.dropbox.com www.dropbox.com

Dropbox

www.dropbox.com www.dropbox.com

Dropbox

www.dropbox.com www.dropbox.com

Dropbox

www.dropbox.com www.dropbox.com
Click to expand...
Several people have asked questions, and some have given simple tests to do. It appears to me that you've ignored most of that. IMHO, me creating a dropbox account and watching you redo it, is very unlikely to provide you with answers.

There is a thing in troubleshooting known as a binary split. If you do and report back the results of my tests in post #8 you may or may not have an answer but at least will know some things that are not a problem and will be pointed towards what to check next.

BTW: "It don't work" = "We can't help!"
 
Have you got any thicker wires? If the wires are getting hot then they're not up to the job and the original starter wires were barely good enough so should be replaced. I can't see anything wrong with the assembly.
 
marshg246 said:
Several people have asked questions, and some have given simple tests to do. It appears to me that you've ignored most of that. IMHO, me creating a dropbox account and watching you redo it, is very unlikely to provide you with answers.

There is a thing in troubleshooting known as a binary split. If you do and report back the results of my tests in post #8 you may or may not have an answer but at least will know some things that are not a problem and will be pointed towards what to check next.

BTW: "It don't work" = "We can't help!"
Click to expand...
Thanks for scolding me, I hope that makes you feel high and mighty.

I detailed these things in the videos, which I thought made it more clear.

The engine will spin with the plugs out, but not with one in it. You can see how fast it spins in one of the last videos, they're not long at all but forgive me for offending you by posting them rather than answering 'how fast does it spin'.

I have tried several batteries, all with the same result. These batteries work fine in my other bikes. I also have another 850 with no starter issues- I took the starter out of that one and tried it in the trouble bike. Same issue. I tried the old starter and the new gear reduction starter from the trouble bike in the 'good' 850- the old one turns it over fine, the gear reduction turns it over twice as fast.

I had everything hooked up through the solenoid and starter button, then decided to eliminate that for testing and have been using jumper cables to go direct from the battery to the starter with the positive grounded where the original positive wire was at the case stud next to the starter and the negative direct to the starter, touching the negative to a battery. The engine will turn about half a rotation and then stop. When the negative cable is touched to the battery it makes a big spark, so obviously something is stopping the motor from turning.

The engine is not wet sumped.
 
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