Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Ashdowner on June 01, 2015, 09:30:50 AM
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I'm sure this has been flogged to death but can I please have the definitive answer on whether it's actually possible to get a smooth tickover under 1400 rpm on a 1977 CB550K3 and what is the true source of the cacophony of noise from the crankcase at anything lower than 1400. My "new" bike has exactly the same as my old one and I've done everything I can to balance my carbs (gauges, airsscrews, prayer) and it's still lumpy below 1400. Also how much choke do I need to use to start it from cold because if I open it full it refuses to fire? I'd add that on the main jets over 2000rpm it flies like a bird. In passing I read an MCM article some 30 years ago that said words to the effect that 550K owners simply have to accept that on tickover it sounds like someone has thrown nuts and bolts into the gearbox.
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Yes Oddjob but the 400s & 500s never had the problem that the 550s have. Different animals
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My 550 could run ok / run quiet at 1k rpm, but only when it felt like it. - true of both my 550k3's, and both had a habbit of randomly stalling if in neutral waiting at lights. I am of the oppinion that the carbs might have been why mine were shall we say tempremental. Probably primary chain and cluch baskett contribute to the noise, at least 1 of my cb550k3s had a new camchain, but both would have run their original primary chains and cluches.
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My 550 ticks over fine at 1500 rpm, there's nothing wrong with this, don't try to get it too low, there is no point at all despite what some will say. The 550's and some 70's Hondas were prone to 'low end clack'
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Does it have those stupid PD carbs the late 750,s have?, if so your flogging a dead horse they are shite
peter
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Does it have those stupid PD carbs the late 750,s have?, if so your flogging a dead horse they are shite
peter
Plus 1 on the above. Couldn't have put it better myself.
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If you can get the carbs working right, the bikes are amasing on fuel use. I once did Fort William across A9? I think, anyways over to the east coast of Scotland, then down to Edingbourough, on to Glasgow and a bit more on one tank of fuel, before comming the rest of the way home on the next tankfull, and as I seem to recall it bumbled around for nearly a week of commuting before requiring a futher fill up. Odd as it started the trip matching my mates 250N to the penny on consumption but was using a good gallon a tankfull less by the end of the trip- I was carrying a 1 gallon can in my top box, which the other bike ended up using. I think the k3 carbs were always fine unless the bike was not used reguarly, at which point they are indeed inclined to give issues.
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I think they all have a tendency to be a bit lumpy at low revs; I just turn the tickover screw until it's smooth and ignore the rev counter. (actually mine's been disconnected for several years since the cable broke) On a long run when my bike gets fully warm I sometimes find myself doing a quick adjustments at traffic lights as I arrive at a town or something. The primary chain and clutch are not the best design really and seem unhappy with low revs.
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Yes I've got the PD carbs. Yes mine stalls every now and again for no apparent reason. It also suddenly races for no apparent reason. Guess I'll just have to keep the tickover at 1400 and live with it. Thanks for all the comments.
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Before you do anything, verify your tachometer is telling the truth. I remember I was once working on a CB550K3 trying to get a nice idle. In despair I reached for my automotive DMM to soon find out that a true 1000 rpm (DMM) showed 1400 on the Honda (I believe it was ND) tachometer.
I do not recommend idles below 1000 rpm. You want that oil up there.