ron

[ron]

Hi all can any one help me as now proper confused, 1980 gs 850 GT electronic ign . I took off cover put a snap on timing light  first on no 1 then on no 3 to check auto advance, both pic ups. appeared to be very erratic at tick over and higher revs. (now the confusion ) my Haynes manual says check the atu fittd to both electronic ign and points ign, so i undid the center bolt and took off what i call the rotor then the three screws holding the back plate removed the back plate and nothing is there just end of crank shaft and a small locating pin that fitted in the bottom end of magnetic rotor arm   ive added some pics the rotor the pick ups and back plate and lastly what is behind them . have i got parts missing this may account for back firing etc or is there any other device that sets the auto advance .

thanks for any help advice etc  

[wraith]

It's not a standard ATU  you have. Not seen that type on a GS before.

Most I've seen even when using a Dyna ignition you still have the standard manual advance/retard that bolts onto the end of the crank (your pic 3) if I get chance tomorrow afternoon I will take a pic for you, unless someone nice on here can do it first 

[Gixer1460]

Similar to the ignition on the EFE models - they don't need the mechanical ATU as its all done electronically in the 'sparky dark arts' box - see here......

 

So it looks like someone has done an 'upgrade' as the 1980 GS850 should be like this.....

[wraith]

There you go @ron

[ron]

ok thanks seems its an upgrade then, perhaps its the box thats playing up giving me erratic movement on the rotor with the timing light fitted . the problem is im getting up till the engine get really hot backfiring in the exhaust and popping in the carbs IE you can see the carbs moving backwards as they make popping noise , tick over is ok, quick revving makes backfire slowing down, holding on 3to 5 thou reves makes backfires and the popping in carbs , so im not sure if its the carbs making the engine run ruff showing erratic advance movement or dodgy advance making engine run ruff, but when engine been running parked for 10 15 minutes it must be quite hot by then and it not as bad then but then im getting worried in case im over heating it. car engines are much easier.  I have cleaned all the jets in carbs float levels checked all good compression is over 160 psi all 4  inlet boots now not leaking but do need new only thing not properly sonic  cleaned is carb bodies im sure just that would cause all the problems  

Edited March 19, 2018 by ron
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[wraith]

Hi Ron, 

If it's backfires on slowing down (shout off) it may be running lean or a air leak on the exhaust, 3-5 rpm is where the advance should be coming in.

I'd try three things,

1. Check valves clearance (be shims on the GS)

2. What colour are your plugs when worm?

3. You could slot the timing plate on the 3 holes that the bolt/screw hole it to the crank case you could then advance/retard the engine if needed.

4. Balance the carbs, as that can make a big difference.

5. You could put a Dyna S ignition on, you would still need to get a manual ATU part for it but it removes the need for a cdi (black box) as it wires strate into the coils.

But when I can get to the shed I will see if I have a ATU. Did have some spare ones but I can't remember if I gave them to a mate.