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Possible starter clutch problem.....?

  • Thread starter Thread starter turbo_billy
  • Start date Start date
T

turbo_billy

Guest
Hi all,

Firstly, I`m sorry if this subject has been covered to death in the past but have used the search feature and still not answered my question fully.

So, the bike is a 1979 GS1000S. The bike has always seemed very laboured to turn over on the starter. Almost seems like a flat battery. However,the battery is fully charged and kept on an optimiser when the bike is stood.

Have removed the starter and this spins freely both by hand and on the button. Have taken it apart to check brushes etc and all is fine.

Take the plugs out of the engine and without compression the motor spins faster and freely. Don`t know if the motor is standard or wether it has higher compression/cams/big bore etc.

Have taken the cover off and turned the starter gear by hand, spins freely clockwise and bites if you try to turn it anti-clockwise, so that appears to be in order.

HOWEVER, tried to start it today and very slowly it turned over and fired with the choke on. Popped the choke back in and the motor died. When I tried to restart the bike, the starter seemed to spin over at what you would assume to be a good rate but the motor did not turn over with it, like the starter clutch was not engaging and turning the crank over.

Bump started the bike no problem and when running the engine pulls like a train and doesn`t miss a beat. Turned it off and tried to restart but same again. Bumped the bike again and took it out for a 6 mile round the block ride. When I turned it off and tried to start it again, this time the starter worked fine and turned the engine over, albeit slowly again.

Anyone got any ideas as to what I should be looking for? Could it be the weights sticking? Any pics of how it all works?

Any help greatly appreciated.

Kind regards

Tim
 
Tim, if the starter motor only spins slowly you need to check the following:
Is the battery good?

Good connections in the wiring - especially the earth to the engine and the lead to the starter motor (note it's a heavy gauge wire that may be partially broken inside).

Solenoid working OK?

Are the starter motor brushes in spec - I think it's something like minimum length 5-7mm - check the manual. If they're too short they won't make a good contact.

Is the SM armature clean? A bit of T-Cut cleans them up nicely.

The starter clutch is a pretty good design on thse bikes (unlike on my CB1100F!). However, the springs (pt no 6) do lose their tension over time. Also the driven gear can get worn - hammered by the rollers is what usually happens. Or the parts 5,6 and 7 can just disintegrate and end up in the sump. Definitely worth having a look at if your electrics ar ok.

46.gif
 
I'll take a stab.

Sounds like two separate problems.

First Do you have a big bore kit in the bike? Sounds like either the starter is overloaded or it is weak. Have you tried a different starter with perhaps less miles. Kinda a stretch but I had an old motorhome with a poor cranking starter. Bought a rebuild and the new one cranked like new with no other changes. Could have been a shorted winding potentially reducing the EMF in the motor.

Second issue seems to be with the starter clutch. Not sure what to say, except if it is barely catching, it might be on the way out and depending upon temperature it might be able to grab. What ever the clutch problem is it will only get worse and will not be a mystery for long. Once it quits you will be pulling the stator cover.

I would get the motor to spin fast first.

Good Luck

Pos

P.S. Hampshire beat me to it, but I'm assuming you have all clean connections (including the shorting bar inside the solenoid)
 
Hampshirehog, Everything checks out ok and as I said if you remove the starter it spins just fine with no load.......thanks for the reply

Posplayr, again, I don`t know for sure if the motor has a big bore but the engine turns as if it is at higher compression and the performance would also give me that impression. ( way more power than any of the 3 I had before)

Regards

Tim
 
Last edited:
Tim,
The starter motor spinning without any load isn't really a decent test for it as there won't be anywhere near the load when you're spinning the engine over.

I've checked the manual and the service limit is 6mm for the brushes with std length being 12-13mm. And the armature needs to be nice and shiny.
 
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