SOHC.co.uk Forums > CB750

No Spark

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K2-K6:
Good you've got to the bottom of it.

Those are timed at full advance as you can't set them like a mechanical system that advances the trigger point. They effectively run at full advance with a rpm register internal that allows them to retard only from set point for start and low rpm.

Seems a bit odd if used to conventional mechanical system, but logical once you think it through. 

Should be easier to start now  :)

PHILIP2908:
I've got the same problem; the spindle and nut scribes an oval as the crank is spinning. You can set the timing OK but it plays havoc with the points gap.
As you say its caused by monkeys turning over the engine with the plugs still in: the compression proves too much at tdc and the spindle bends.
I had a look at a replacement but none seem to be available. From the parts diagram it looks as it just screws into the end of the crank.
I also thought about removing it and getting it straightened by an engineering shop but then had nightmares about it snapping off on removal which would probably necessitate a full strip down to get at the crank.
Consequently I will probably go for the Boyer system too. Can you please give some feedback on ease of fitment and what effect it has on the running?
Best regards
Phil

Bryanj:
The 750 spindle is available as a spare and has an O ring on it where it screws in

Lobo:
I removed my spindle recently - not easy. Heat, molegrips, rattle gun (on low) all to no avail. What worked in the end was a roller cam stud extractor, obviously down near the base. But still nail biting…

Saesneg Shaun:
Well dang, its still not sorted.
Got the ignition timed with a strobe lamp to full advance at 4500rpm.
Also did a carb balance whilst I had the bike partly disasembled (I know, I know, should have tackled one issue at a time)

Road tested today and she won't accelerate over 4000rpm in any gear. Tried with the fuel tap on and in res and with the cap open but with the same result.
Starts and ticks over fine.

Any ideas?

*edit, just pulled the plugs, No's 1,3&4 very black and sooty, No 2 tan/clean?

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