SOHC.co.uk Forums > CB750
1978 CB750F2 - Poor Starting
blackeagles:
ok, almost finished this rather easy 'restore' but not been at it for some time - too cold and too old.... well mainly the latter.
still seem to have a problem, when its hot the bike ticks over at 1200 and revs up without hesitation to settle back to 1200 again BUT getting it to start is something of an art form. I checked the jets and sprayed them with cleaner and even the pilots were clear! (in fact they all look new), they are the correct size, pilot screw is now 2 3/4 out and all the pump jets fire a jet of petrol into the venture. press the button and it fires up after a few tries (twisting the throttle to get the pumps to jet petrol into the venture helps) with the choke on and revs at about 4k (I know I have set the grub screw a bit too high at the moment) and I can rev it as much as I like but as soon as I let go of the throttle the revs start to die and the bike stalls.
any suggestions?
royhall:
They all do that until fully warmed up. Mine starts on the first touch of the button but takes about 5 miles to tick over correctly. I keep a touch of choke on until it's warm, just enough to raise the revs but leaves the butterflies open.
K2-K6:
As Roy says, sounds about normal.
Right from new they were like this, in weather that's cold like now and from stone cold, then two twist of throttle to use the pump, pull choke fully out and fire it without touching throttle as you do.
It'll tickover fast and be reluctant to accept no choke until it's good and happy at its normal running temperature.
A friend with one was always dismayed that on his way to work he'd stop off to get a motorcycle news and in winter he'd need to choke it again to pull away.
:)
UK Pete:
Yep that is classic f2 behaviour, the carbs on these bikes are shite.
Sent from my SM-G950F using Tapatalk
blackeagles:
ok, thanks for the info.
i get most of it but i'm still a bit unsure why when its cold and on full choke I can start it and I rev it up and it initially settles to about 3k but (with the choke still on) I let go of the throttle and the revs drop back and the bike stalls. as I said its ok when it starts to warm up and good when hot - I guess its one of those things you get used to.
thanks again
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