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CB550F2 '77 slow to rev when starting

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Oddjob:
My L reg just after being rebuilt used to idle at 600rpm, below that it used to start to knock a little, it would go as low as 400 before it stalled out. Must say though it didn't really sound that nice that low down, lots of knocks and bangs going on.

I've just done a members bike on here recently that was a bitch to start, I did a full rebuild on his spare bank of carbs and it now starts on the button everytime, I must ask him if it will start JUST on the button, no throttle movement at all. From all accounts it's now running extremely well and touch wood no flooding. He intends to post a few pics in a short time when he's finished doing a few other bits.

1200 is normal these days for a four to tickover at, at 1000 it can sound loud, at 1200 most of that noise seems to go, that's because the engine loads up more of the components that are making the noise, primary chain especially on the 500/550, clutches on the 400. If the engine sounds better at 1200 I'd leave it there, 1000 is just an aspirational figure, if it ticksover at that speed and it's quiet then all is well inside that engine IMO. The lower it can go the better the engine is inside.

robvangulik:

--- Quote ---The lower it can go the better the engine is inside.
--- End quote ---
True, but as these engines need oil pressure to run, it's wise to only try this once. The lower your revs go, the lower your oil pressure goes....

Oddjob:
I'm not advocating a tickover that low Rob, just that's it's a sign of a well set up engine IF it can go that low. I only did it occasionally to see how the engine was faring, I'd say 1000 was as low as I'd go normally, when they were new the tickover was always set at 1000, it's only as they grew older and more worn that the tickover seemed to creep up as well. Saying that, those were the days of decent petrol.

K2-K6:

--- Quote from: robvangulik on June 18, 2023, 12:12:20 AM ---
--- Quote ---The lower it can go the better the engine is inside.
--- End quote ---
True, but as these engines need oil pressure to run, it's wise to only try this once. The lower your revs go, the lower your oil pressure goes....

--- End quote ---

The oil light can be out just from kicking them over on the kick-start, that can't be more than about 150 rpm. I dont feel thats an issue in pump delivery terms.

I don’t ordinarily chase a particularly low idle speed, not for any real reason but just dont mind them running a little faster.

Older engine than these normally had heavier flywheel to keep them going, also now with injection they can measure crankshaft pulse to smooth out low load idoe speed.
Generally much new stuff has a cutoff of about 500 rpm with target more around 6/700 minimum in ecu. Saves a little fuel and heat Generally if low.
As noted Ken, when hearing a new one originally they always sounded so smooth naturally, along with dead steady tacho needle. I think one of the things that most impressed buyers coming from brit bikes etc.

McCabe-Thiele (Ted):
I've never understood the variation of standard oil pressure amongst different brands of vehicles. In the days when oil pressure gauges were fitted to cars Mercs would have a maximum of 45, Minis liked 75 plus, Jaguars were around 40.iirc

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