SOHC.co.uk Forums > CB500/550

Hello everyone

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chrisr58:
Hi all, after getting found out immediately on the US site (for using the word petrol!) I was directed to the UK site. I'm just trying to get my 78 550k3 back on the road, it has been MOT'd and serviced a few times over the years but hasn't really been used much since about 1981 (usual story-family, car, more sense!) so less than 8000 miles on the clock. Problem is now it won't start and petrol just runs out of the carb overflow pipes, plugs stay bone dry.I presume this means a carb stripdown and clean - unless anyones got a better idea? Looking forward to getting all your words of wisdom/encouragement/empathy over the coming months (years?)
Chris

Dave M:
Welcome Chris.

Yes, you're looking at a complete stripdown of the carbs.

All the jets and passages will need cleaning and blowing out and you'll need to clean and check the float valves which is the most likely cause of the leak unless you've got a punctured float.

I've got a '78 550F2 which has done 16,000 miles and runs fine apart from a poor idle and running very rich. I need to strip and clean my carbs but keep putting it off because I'd rather ride it! Especially now the sun's out.

Good luck.

chrisr58:
Thanks for the advice Dave- just had an idea (maybe a stupid one, but anything to save work!) what if I bung up the overflow pipes and fill the carbs with carb cleaner and leave overnight? Has anyone tried this or is it too daft to contemplate?

SteveD CB500K0:
Hi Chris.

I do keep an eye on the US site for obvious Brits!

The problem with your idea is really around the strength of the carb cleaner required.  Anything strong enough to do the job that quickly will probably dissolve the rubber bits as well.

The most popular carb cleaner is that branded by Yamaha as it doesn't affect any rubber parts - but I've never found it for sale! Even my local Yamaha dealer said "no - we use Wurth in the workshop; and it's only available retail in aerosols!"

I bought a gallon (remember them?) of cellulose thinners at Kempton Autojumble last year. It's carcinogenic and probably illegal - but it will dissolve fuel varnish. It will also dissolve aluminium if you leave it in long enough!

You could try Redex Fuel Injector cleaner (from Halfords) and leave it in the carbs for a week or so.

Let us know how you get on.

Bryanj:
78 K3 has push in pilot jets which can be awkward to remove and refit BUT bad starting/running is almost certainly down to those being blocked, Over flowing is stuck floats, total strip and clean is only way, be carefull with the rubbers between airbox and carbs as they are unobtainium

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