two valve advance

[greg becker]

some time back i found an 81 750kat with a 1000 two valve.i still do not know what year this motor is.there is no mechanical advance on this motor so i assume the advance is usually looked by the ignition black box.my issue is that i seem to have a 4 valve [mechanical]black box.can any tell me the ins and out of this situation.part numbers etc.ta

[salty_monk]

The advance is going to be different between an 8v & a 16v for sure... That's not to say it wouldn't work but you might not get the best out of the engine & worst case you could do it damage if it was running too much advance...

[49er]

The advance is going to be different between an 8v & a 16v for sure... That's not to say it wouldn't work but you might not get the best out of the engine & worst case you could do it damage if it was running too much advance...

Quite true. Stock total advance on the 4 valve engines is around 34 deg. The 2 valve total is 37 deg and some 2 valve specs will live at 40 deg.

[greg becker]

gs advance

Hi and thanks.Ive checked the number on my black box and it IS a 16 valve unit.So as i see it this motor is not enjoying any ignition advance.My normal routine is to go Mr Motorcycle .com and check out the flitch files when ineed info on a scoot. but i can not find a model that DOES NOT HAVE mechanical advance.can anyone help?

[49er]

Hi and thanks.Ive checked the number on my black box and it IS a 16 valve unit.So as i see it this motor is not enjoying any ignition advance.My normal routine is to go Mr Motorcycle .com and check out the flitch files when ineed info on a scoot. but i can not find a model that DOES NOT HAVE mechanical advance.can anyone help?

I think the GS's changed over to electronic advance in either '82 or '83. They went electronic ignition in '80.

[salty_monk]

82 was the first year. The 82 850G was one 8v engine with electronic advance in the box.

What part number is your 16v box?

Wish you could find out what the differences in the curves were, be interesting to know as even the 82 GS750 is different to the 83 GS750 which is a different part number to the 84 GS700....

Looking at the instructions for a dyna 2000 it would seem that most units if they are 8v or 16v end up approx the same total advance (i.e. any 8v will be similar to any other 8v engine, any 16v will be similar to any other 16v engine). I guess this is within reason as a 16v GSXR is going to rev a lot higher than a 82GS750.
I would suspect that the similar years would interchange for example the 3 mentioned above, plus the 1150 but it's just guesswork without seeing a plot of the curve. You should be able to run the engine & measure the advance with a decent timing light...

Dan

[greg becker]

G S Advance

bingo.thanks Salty.The stator plate and the trigger look the same as my motor,mind you the box looks like the unit on my 750ES.The number of the unit in service at the mo is32900-45120.I have actually been riding a 81 GSX750 with this motor [1000 gs]in it for a few months while I rebuild the 750 ready for the Katana which has also had a ground up recon.Gee,NO ADVANCE!!!!!!!!!!!!She will pull like a train when this is sorted.Not to mention fuel economy,the reason tumbled to the problem.thanks all.By the way WHAT motor is this that has the same ignition as the 82 850G???