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CR750 Set Up

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UK Pete:
I say revert back to points , well set up points system is going to be trouble free

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K2-K6:
I was thinking along the same line's as Pete as you'd see if the kickback problem went away.

But been reading more about their system and realised that it's not clear where the initial timing is set (against that which I thought in above post)  as all the timing mark hardware is replaced.
It became clear ( he says with some confidence  :) )  what they're doing in asking you to set the timing with a check at 4,500rpm is to give the hard set point that is safe for the engine and above which the logic won't pass.
The advance curve fitting in under this is more fluid and exists as a national set of parameters within their logic. They state it can advance the timing even at less that tickover speed to give an anti stall effect and try to stabilise the tickover.
I'd interpret that as having a target for rpm as eg 950rpm and will adjust timing to aim for that figure.  If you advance it, then it will speed up.  If you retard it,  then it will slow down.

If it reads slow rpm as you attempt to start it then it maybe trying to advance it to stop it stalling,  even though it hasn't started, if that makes sense.

But it does also point to the initial setup as being already too far advanced,  so it's probably worth retarding your initial setting by a couple of degrees to try it and see if it improves.  Then a couple more if it seems better in a suck it and see situation to find improvement.

K2-K6:
Forgot to add,  you need to get the use of a strobe that will verify that total advance position to ultimately set it.

Aside from the tacho issue it's probably worth running it,  just a bit of a pain to get there perhaps.

philward:
Lots of info to take in there! thanks for all your research.
Ref the timing marks - the system retains the advance & retard bob weight carrier (with cam, springs & weights removed) so all timing marks are retained. I'm leaning towards the timing as you suggest.
Got a response from Boyer:-'Thank you for your enquiry, you should not get any kicking back, popping out of the carburetors is normally week mixture or having the throttle to wide when starting.  Check the magnetic rotor is not touching the solder pips on the stator plate.
Check the spark plug gaps are around 0.8mm, 0.032 inch'. Regards Tech Dept.
I have my plugs at 0.025inch so that's one thing I can change.
Reference air screws - I've read so much about setting them which contradicts quite often - air screw in for more or less air? 

K2-K6:
Turning the airscrew in will change the idle mixture to richer.  It restricts the air bleed to the idle circuit so a given vacuum in the carb venturi will draw more fuel as you close the air passage down.

Likewise screw out will open the air passage and the same vacuum cannot then draw up the same amount of fuel from the float chambers as it'll just pull more air past the screw so making the idle mixture leaner.

If you warm it then, during tickover, adjust one air screw,  you should here that cylinder go faster or slower. If the airscrew has to travel more than half turn from initial setting,  then it would indicate that you need an idle jet size change. Too far out it wants a smaller jet, too far in it wants a bigger jet.

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