Mechanical help needed please...

I’ve just delivery of a cb500, fairly heavily ‘modified’, it’s this one from Fast Bikes mag:

I went to see it and it started off the button. Since then it’s been mot’d and unfortunately, pressure washed, now it won’t start, but turns over fine.

I took the tail unit and then the tank off to get at the plugs which as far as I can make out are dry, there’s also fuel in the carbs. Since I took it aprt, none of the dash lights work, they did before. Could that be related to it not starting?

I’m sure it’s very simple as I know the bike runs fine - should I be checking fuses etc?

Fixed the dash lights, it was a fuse, still won’t start though…

sounds dumb but look at cut out switch

As in the red engine kill switch on the handlebar? That does seem to work in that it stops it turning over when off. Is there another one that stops it running when bike on it’s side, like in more modern bikes?

a faulty sidestand switch prehaps??

try holding the clutch in while hitting the start button


is the petrol turn on?

or tank empty and not on “reserve”??

Thanks Ratcatcher, yep it has a side stand light on the dash and that’s working correctly with stand being up and down. I’m holding the clutch in (and not), no difference, though I guess theres still a chance of a switch interfering starting to think no spark, but this isn’t consistent with it running ok before…

PS - double checked fuel tap and fuel in tank as well, was on reserve and there was none before.

try putting petrol straight into carbs with a spray bottle

hmmm jetwash and non starting …coincidence …

always watch when jetwashing … does it have alarm ? as water ingress can affect immobilisers or even worse … into the ecu/ignition modules and be farked by it …

or you’ve dislodged a crucial wire

Check for a spark with the plug out

I’m pretty sure there’s no immobiliser (I’ve certainly never seen a fob etc), if there was it would have been stripped out in the build. I keep thinking water ingress but its a basic old carbed bike and its had days to dry, there can’t be much that water can break on it. I can smell its getting fuel, I think my only option is to go back to basics and check for spark - so its down to the mechanic I think, I don’t have the tools here.

Thanks for all your suggestions, if there is no spark then at least we have something to fix.

I’d hold the plug cap with insulated pliers though in case there is a loose wire as it’ll give you a hell of a belt if it can ground through you!

Thanks Alex, yep the plugs are very deeply recessed and I don’t have the socket for the job - my mechanic can test easily enough though.

Got myself the right plug socket and have now been able to take the plugs out and check for a spark. Spark is absolutely fine and the plugs are in good nick. They were a little damp with petrol but unsurprising how much cranking its had. So I have fuel, fire and presumably air, but the bloody thing still won’t start.

As far as I can work out the only thing that can now be wrong is for the timing to be way out, but that makes no sense if it was running fine before??

Take all the plugs out, dry them and leave them out for a while, then stick them back and fire some easy start into the airbox as you’re cranking it.

Will do Alex. The airbox has all been taken out and replaced with DNA pod filters, probably best to take those off and spray directly at the carb inlet? Will get myself some easy start tomorrow…

Yeah might as well take them off, if it’s getting spark it’ll at least run on easystart, then if it stops running you’re looking at a fuel problem.

It lives!

Took the filters off and cranked it on neat Easy Start straight into the carbs and it eventually coughed to life. I ran it for a few seconds to clear while there was still fuel in the carbs, then turned it off, put the filters and tank back on and it started up again fine - what a mission given there was nothing actually wrong with it.

Thanks very much for your help Alex and others, have taken it for a 10 mile ride to get everything working, the induction sound is awesome with the filters on. Next problem is that the cooling fan doesn’t cut in, but that should be just a case of finding a loose connection, at least the thing runs now!

sounds like you filled the carb with water during the jet wash are all of the rubbers intact & clips done up?