SOHC.co.uk Forums > CB500/550
CB500 runs lean and doesn't want to pull through
AshimotoK0:
--- Quote from: Bryanj on February 26, 2022, 09:47:27 AM ---Honda never supplied the springs seperate
--- End quote ---
Correct Bryan .. Yamiya do these though but I wonder what they mean by 'racing' ..pretty pricey too.
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Deltarider probably means these ..but not sure if that German club sells outside of the EU
K2-K6:
For the OP, worth noting that it's not very far away from correct it seems and you're not looking for a big error to bring it within range.
The comments about camshaft timing (if it's been apart before this) are extremely relevant as you'll not solve it if there's an incorrect assembly there.
In addition, when it "fails" to give increased revs, then applying the choke a little to see if it will go further is useful in diagnosing if it's just lean mixture stopping it. Then you'd have to find the cause, but it would confirm it's mostly mixture for some reason.
deltarider:
A member on the German forum has been making the springs for years. They're also in the shop now: https://www.cb-four.de/cgi-bin/shop/__Fliehgewichtfedern-Satz-Z%FCndkraftversteller-Honda-CB350-400F-CB500F-CB550F%2BK-CB750Four-neu__20-059-02_02.03.html
Servus
K2-K6:
Thread here has gone multi-strand :)
I read much of that which Hondaman writes and think he is an original thinker with very good knowledge.
However, I don't understand what he's saying there ("Here's a extract from Marks replies "most likely because the design suffers from a too-soon spark advance that causes the engine to spit back toward the carbs until about 2500-3000-ish RPM, which then makes the carbs run slower and richer than they should at that RPM") as the cylinder has it's inlet valve closed before the ignition timing, sealing off the inlet tract (it can't really work if you fire it with any valve open, can it? ) and so can't really affect the mixture as such.
In engines that use a version of the Atkinson cycle ( Toyota Prius) the inlet cam is retarded at low speed low demand to increase smooth running and efficiency as it bleeds off some compression back out the inlet to reduce effective compression. But it still doesn't interfere with the combustion being sealed from going out there during initial burn phase.
The suggestion to increase camshaft duration for inlet will affect this area of dynamic flow (it usually needs more rpm to work effectively) but no engines I I understand will fire ignition with port open.
deltarider:
First of all, according to not only me, but also to Dave500 in Austalia, to name just one, there is no flat spot. When you accelarate hard from standstill, bike goes like a rocket. I test it every year at least once. What some experience as a flat spot, is something else. If you cruise at say 4000 rpm and then open the throttle, there isn't much in house (as the Dutch expression is). This was already signalled in roadtests back then in Holland and France and IIRC it has to do with the engine design, bore X stroke. This 'shortcoming' can't be helped, but can be adressed by shifting down one or even two gears.
Now, do you see Americans, used to HD's (bikes) and 7 litre V8 blocks (cars), do that?
Until I see proof, I maintain the whole thing is about nothing; it's a created problem. Always good if you want to sell something or establish a reputation.
Note, that, as always, my comment at least can be falsified. Please do.
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