SOHC.co.uk Forums > CB350/400

Occasional stall it idle...

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exvalvesetdabbler:
1200 rpm for the 400F idle.

That's assuming the tacho is spot on at that reading. Could be 200 out either way.

If it's a bad connection it might get around it without stalling at normal riding rpm, if the idle is set too low it might just trip it up

Wiring seems more likely or grubby contacts breakers.

Regards
Dave

exvalvesetdabbler:
Worth noting that the tacho I am currently restoring was reading 500 high at 5000 rpm so if you have one like that it could easily screw things up.

I used to have a timing trobe that could measure rpm but haven't seen one like that recently. 

Regards
Dave

Oddjob:
Idle speed as set by Honda is 1050 + or - 50. It's best at 1000rpm in my experience. It shows up problems much better rather than disguise them by a fast idle. If the engine is in really good condition you can get one down to 600rpm easily. At 500rpm they do start hunting a little and making a bit of noise as things start to lash about inside. I'm not saying run at those speeds, just that it's an indication that all is well if the engine can do them. At 600rpm my 500-4 was still silent, at 1000rpm you couldn't hear it from 6ft away.

Could also be a small air leak, check the carb clamps. 

K2-K6:

--- Quote from: exvalvesetdabbler on August 14, 2026, 06:18:28 PM ---Worth noting that the tacho I am currently restoring was reading 500 high at 5000 rpm so if you have one like that it could easily screw things up.

I used to have a timing trobe that could measure rpm but haven't seen one like that recently. 

Regards
Dave

--- End quote ---

Some of the relatively cheap DVM have a frequency read, across one set of points will count crankshaft revolution on these.

Mikep328:
Good info guys, thanks!!  I'll check out the carbs AND the actual RPM!!  :)

Am I correct that reading "frequency" across one set of points would indicate 1/2 of engine RPM?  IOW, double that reading would be actual engine RPM?

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