GS850G Won't Start, Electrical Issue, No Spark

[chuck hahn]

does the end of the crank have the pin that engages on the back of the mechanical unit? Im thinking it does and it engages the stock rotor. Im no expert on mechanical advances but i would have to think they are all the same. To me from a manufacturers standpoint it doesnt make sense to have different ones. Just make it a one size fits all to cut down on costs.

[chuck hahn]

I think theyre all the same. Hell try this one. If not resell it or return it....add says 30 days return policy

NOS Genuine Suzuki Advance Governor Assembly GS750 GS 750 1977 1979 33120-45020 | eBay

[chuck hahn]

27 dollars with 30 day returns....

1978 SP370 SPARK ADVANCE GOVERNOR ASSEMBLY SUZUKI SP 370 1978-1979 33120-32410 | eBay

[dandypop]

That's fair. The part number differs only slightly (33120-45110 is the original, while 33120-45020 is the $40 one you sent). The $27 one looks a little different.

[chuck hahn]

One thing Suzuki did that others didnt do was change part numbers on the very identical part from model years. Like say in 82 it was XXXXX-12345 then in 83 they made it XXXXX-12346. Same identical part but 1 number off where as others used the same number through many years until that particular part actually had a change then they gave it the updated number. no harm in giving these a shot.

[dandypop]

I've got one on the way! It's originally the part # for an '81GS1100E (part #33120-49211). I'll resell it as you suggest if it doesn't work. Thanks!

[KiwiAlfa156]

There was a lot of parts sharing between models. The CMSNL website is great as it shows all the models that exact part was used on.


Some parts do get superseded and are issued a new number. But they always follow the same part code format:




With the ATU units, as far as I know, externally they are the same and they can all be swapped. Where they vary is in the initial and full advance ignition timing and the number of degrees advance. This is controlled by spring tension and the metal stops within the unit. A troll through the spec sheets will show that different model GS have differing ignition timing especially at full advance because burn speed is a function of combustion chamber design (swirl and squish) and diameter.

I had indexed the ignition markers during the build as I had to repair the ATU locating pin on the crank. Good thing I did as it was about 3° to 4° retarded which is a lot in ignition timing term.




I had been really disappointed with the bikes acceleration given the work I had done on the engine. Searching for the reason, I found the ATU unit that was fitted to my 750 didn't advance all the way to the full alignment (above 2,750 rpm), when set at the idle mark alignment. It dawned on me, that the ATU was off another bike (this machine was essentially a rolling wreck when I bought it).

I have since set the timing to align at the full advance mark, so at idle the timing is a couple of degrees advanced due to the short advance sweep. The only downside is that it cranks sluggishly as at starter rpm, the early spark means she's compressing more expanding burning mixture. Once she's going its all normal from idle, has really useful mid-range and screams above 7,000 rpm.