Starting the engine

[paul G]

It should be 0.3 to 0.4mm either missed the 0. Or set them wrong

[El__burro]

I guess it's 0.40 on the feeler gauges.
the points start opening just after the F  mark on the plate passed the window and it coincides with T being in the window once fully open.
Tried to turn the plate but can't get them fully open with the F in the window.

[ka-ja]

Hi,
    The old fashioned way is to line up the "F" mark to the pointer and a piece of cig rolling paper should just pull free from between the points!----Ken

[Lobo]

Hi again,

As mentioned... the points gaps should be 0.3 to 0.4 mm. Ka-Ja suggested a good tip to set the (points) opening time. Reading your 'set up' comments.... it just doesn't sound right, ie I wouldn't expect the points to be fully open @ the adjacent T mark, and certainly not expect them to be fully open at the F. (or are you talking opposite F & Ts - ie cylinders 2/3?) Have a good read of the set-up literature, and if in doubt post back... if the points are not set properly it'll explain your starting problem all along...

The coils.... there should be no continuity (connection) between the primary & secondary windings ... they are completely independant of each other. Any continuity here implies a problem.

I said it on the other thread too.... but if your secondary (HT) winding only has a resistance of 14 ohms.... then this it is duff. It should have a reading of abouts 1000x that ... I can't find a specific CB750 value... but generic coils come in at 10-20 KILO ohms.  Re-check the reading on your meter, if in deed its 14 ohms I'd start looking for new coil(s)

It has been said before (K2-K6) - ie oil pressure. My suggestion is purely one to see if you can get the bike to fire up. If you do, and assuming you've no oil pressure indicator, run it for only a couple of seconds - don't get carried away revving it up / playing. (Rather stop it, reinstall the original wiring & try again)

Simon

[El__burro]

Here are some pictures of the readings.
Hopefully i just read it the wrong way.

Thanks
Ek__burro

[Lobo]

Ah! That looks fine... though I say again, I'm not certain of CB 750 coil values... tho they do seem in the right ballpark.

The points. Rotating the crankshaft (only ever) clockwise, set #1/4 breakers to a maximum opening of 0.012 - 0.016 inch, OR 0.3 -0.4mm using your feelers.

Now set the crankshaft to align the F 1:4, and rotate the whole back-plate so that, at this point, those breakers are just beginning to open... using Ken's fag paper trick, borrowed from some school kid if necessary. Its fiddly, and may take a few goes.

Now rotate the crankshaft to F on cylinders 2/3

Now loosen BACKPLATE of points 2/3 and move them until they just begin to open at F mark.
Once done, by default, these too will have the correct t gap of 0.3-0.4 mm as they follow the same cam - ie no need to gap them.

Keep plugging away!

Simon

[ka-ja]

Hi,
    The fag paper was later superceded with a 12v bulb soldered on two wires with croc. clips (stopped smoking) -----Ken

[El__burro]

Finally a tiny step forward.
I have seen a few very shy sparks at the points. Mainly 1-4.
Still trying to have the points fully open with F 1-4 in the peephole. Can't get there.
Will keep trying.
Thanks

[Trigger]

Hi,
    The fag paper was later superceded with a 12v bulb soldered on two wires with croc. clips (stopped smoking) -----Ken

I still use a old indicator holder with two wires but, I kept the bullets on them   

[Johnwebley]

Finally a tiny step forward.
I have seen a few very shy sparks at the points. Mainly 1-4.
Still trying to have the points fully open with F 1-4 in the peephole. Can't get there.
Will keep trying.
Thanks

 NO !! the points are JUST opening at F position,


 try that

[ka-ja]

Hi,
    The "spark" is made when the points start to open ie. as soon as there is an air gap when the crank is at the "F" point, yours sounds as though it is well in advance, if the points don't close properly or for long enough, the spark suffers!

[El__burro]

No way,  the points open at the T mark.
what if I rotate the plate behind the one with the points on
can I, should I?

[ka-ja]

Hi,
    Can only go on general set up advice (as per 400/4)     set the gaps on the two sets of points to the book settings say 0.3-0.4 mm at maximum lift, line up the 1/4 "F"mark to the pointer, then turning the main backplate, set the 1/4 points to just cracking open using a bulb or even the thinnest feeler gauge you have, lock the backplate, timing should be near enough to run the motor, after that , set up with a strobe----Ken

[royhall]

Did you remove the points back plate and check the timing advance mechanism behind. Its a set of bob weights that throw out to advance the timing as engine revs build. Sounds like they may be jammed or sticking. Long shot but worth 10 minutes work to make sure. Cheers.

[mike the bike]

Check the points cam isn't on backwards (180 out of phase)  done that once.