Hello everyone

[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

[matthewmosse]

neat redex fuel system cleaner can do the trick, (left to soack for a week or so) plus undo the drains in bottom of float camber to flush the crud out before plus after, can save risking them unobtanium airbox rubbers as well as an evening cursing to fit it all back together. Incidentally can anyone tell me if I'm right in thinking the carb to airbox rubbers are shorter and easyer to fit on the 500/4 than the 550/4 k3 and that they grew longer to fit in the choke cable arrangement on newer models? Ps I've 2 550 k3's from '78 in bits as spares/ projects but still use the carbs +engine in my 500/4 as the fuel economy is best on k3's. Good luck

[Bryanj]

Matt, do you run the 500 air box with the 550 engine and carbs? I was under the impression that the carb spacing was different, i know the intake rubbers are different (carb to head)

[chrisr58]

Well I've just managed to get the carbs off, only to come home and see Matts post confirming Steve's thoughts about the redex! I decided that knowing my luck it probably wouldn't work anyway so I should do the job properly. It was quite a squeeze getting the carbs out,though managed to keep all rubbers intact (so far) I'm not looking forward to trying to get them back in!

[matthewmosse]

Brian, so far as I'm aware (I've had loadsa 500/550 bits thru the years) although the parts look / measure up differently they will all interchange quite happily as long as kept as a set (ish) I can take a closer look but from memory the airbox top, airbox to carb rubbers are the only bits I know are different. Some of the cast alloy inlets that bolt to the cylinder head have drillings for attaching carb balancers and I tend to use these just in case but I've no idea which bikes donated these. Current set up is 500/4 airbox rubbers on 550/4 k3 airbox and carbs but this leaves little room for the carb cable linkage but is much easyer to fit together on the bike. (plus I've more carb to airbox rubbers for the 500/4 in good order.
A useful hint fron cmm mag is to heat the rubbers using a bowl of hot water and washing up liquid on removal and refitting. Works well as heat softens the rubber temporarily. For similar reasons I try to fit new tyre in summer, on a hot day, having a few spare wheels to get thru winter helps. Ps for getting the family on side, fitting a sidecar really helps. Young kids and ladies of a cirtain age just love outfits plus a 550 outfit is a scream for power sliding, particuarly in rain or snow.........

[Bryanj]

Thanks Matt, according to the parts book the inlet manifolds and manifold to carb rubbers on the K3 are 404 middle numbers which makes them unique to the K3, i suspect you are using K3 manifolds and rubbers, I only owned one K3 and that was sold to Ireland in a "chop" and didnt have an Airbox only pods and that i had to pull the pilots 3 times to get them clean!!

As to chairs I only drove one and that was a Cossack Urinal with the posh Dneper chair as against the "fit a machine gun" original, Unfortunately they were RH chairs putting the bike in the gutter making for "Interesting" handling and impoved muscles in the left arm-----swore that would be the only time and so far i kept to it

[Dave M]

I removed my carbs yesterday and stripped them down.

Not easy to remove and not looking forward to getting them back in again!