SOHC.co.uk Forums > CB350/400

starting issues

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Ariel-KH-500:
Having problems starting the bike when its stood for a few days. When trying the start the bike I turn on the fuel about 5-10 minutes before trying it turns over ok and for about 4 presses of the button it makes no attempt to fire, after more presses of the button it fires once this then happens a few more times until it starts to run but very lumpy eventually it will chime up on all four cylinders and run. When ridden it performs as it should and when left for a few hours it stars as it should. So the jobs that I have done so far are Timing checked, valve clearances checked, balanced carbs, fitted new battery, checked petrol tank fuel filter, also only E5 fuel been used. I've now removed the carbs and have stripped them ready to ultrasonic clean them upon initial inspection they look spotless. The bike has only done 13,000 miles from new, I will post again in a few days to let you know if the cleaning was a success but in the meantime any ideas  or advice gratefully received . PS bike stored in my dining room during the winter after draining the tank and putting fuel solutions storage fuel in it and running it through the carbs bike started ok after winter lay up.

McCabe-Thiele (Ted):
My 400 was the same when I first had it running after 10 years of being in POs garage.

Turned out to be low compressions, all were even but not enough.
Try the Easystart spray test on the air box.

Oddjob:
First off why turn the fuel on so early and leave for so long? It could be the problem or part of the problem. There should be enough in the float bowls to start the engine, unless you’re one of those that turn the tap off a few minutes from home and run the bowls dry, not knocking that practice but would go so way to explain the tap turning on thing. If the float levels are wrong it will start to flood the cylinders, that could mean it fails to start or it runs lumpy for a while until it’s burned it off.

How are the plugs looking? Are they new? Odd question but what make are they? Reason for that is there are a lot of fake NGK plugs around and a mate of mine had a similar problem on his Harley. He kept saying the plugs are new it’s not them. I kept telling him to refit the old ones and see if it was ok or the same but he was stubborn and stuck with his new ones. Of course they turned out to be fake, bought from a motorcycle shop btw not eBay. A month with no bike just because he thought new meant they couldn’t be the problem.

I’d really check the idle jets when you remove them, hold them up to a strong light and see if they are blocked.

Report after that or when others ask questions.

Ariel-KH-500:
It dose not make any difference if I just turn the fuel on or turn it on early the problem is still the same, its probably an old habit riding my old classic bikes as if they have stood for a few days the old Amal carbs tend to evaporate.. spark plugs are new and purchased from David silver along with air filter and oil filter. Just waiting for cleaning fluid to arrive will post results when carbs have been cleaned refitted and balanced

K2-K6:
If float valves (controlling fill from tank) are a OK, then it shouldn't matter how long the tap is left on prior to start.

As most things are checked, and carbs cleaned too, then if it persists a check of compression psi would be helpful in establishing whether anything is out of range there.

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