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Ignition timing

  • Thread starter Thread starter David 750
  • Start date Start date
D

David 750

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Hi guys i have s 1982 gs 750t on hot days sometimes i hear pinging or spark knock i run 93 octane ethanol free gas bike runs great is base timing adjustable and what kind of advance does it have
 
With stock ignition setup, there is not much adjustment available- or needed usually. Check that the mechanical timing advancer is not binding or sticking. Do you have access to timing light? Full advance by 4000rpm is about 38 degrees before top dead center

Honestly, really no need to use anything other than 87 octane . I ride in steep terrain with no pinging issues.
 
tom203 said:
With stock ignition setup, there is not much adjustment available- or needed usually. Check that the mechanical timing advancer is not binding or sticking. Do you have access to timing light? Full advance by 4000rpm is about 38 degrees before top dead center

Honestly, really no need to use anything other than 87 octane . I ride in steep terrain with no pinging issues.
Click to expand...

As I recall, the '82 750 has the 4 valve TSCC cylinder head and probably a higher compression ratio [10:1?] than a 2 valve 650 [9.4:1?]. So what works on one isn't a guide for the other.

I think the 83 on had digital advance and the 82 still had mechanical; easy to look and see. Either way, the only adjustment is to file the screw holes in the 'points' plate oval in the direction of retard - open the holes on the counterclockwise side to be able to rotate the plate clockwise somewhat - and see if that allows lower octane fuel. You could also accurately drill a same size hole to the left of the existing holes and file the 'betweens' out; more adjustment room than needed, but less work.

Having had an '82 4 valve head GSX400, I never managed to really get around the ping on 87 fuel on hot days on hills. I think the owners manual recommended 91 or higher and for that reason. But retarding it 3 or 4 degrees helped the ping factor somewhat. Running colder [#9] plugs may help.

This was also the era of 'lean burn' which is fine on water cooled motors, but not air. Raising the needles a notch and perhaps a slightly bigger main jet may help.
 
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