HELP with intermittent starting problems with a CB500

AndyCB500 · L Plate Warrior Joined: 14 Mar 2007 Karma :

Can anyone help? I own a 2003 Honda CB500 which has done about 13000 miles. When I bought it last October the bike had been stood for around 6 months in a garage on trickle charge. The first 3 months of ownership were problem free BUT then it started with an intermittent starting problem. Every so often the bike turns over but will not start, even after about a dozen attempts. I've found that if I leave it several hours/a day then it will start.

I've had a local mechanic look it over and he's replaced the plugs, cleaned out the Carbs and suggested a swig of Redex whenever I fill the tank.

So I got the bike home and it ran/started sweet for about 3 weeks then the old starting problem reoccurred (as I neared the end of a tank of fuel). I recontacted the mechanic who suggested that when it started again I give it a good run out... so over the next few days I put over 100 miles on the clock. Then it failed to start a day or so afterwards.

I only own the bike for transport so it has to be reliable. Can anyone suggest what is wrong?? I've added some more facts which might help you below:

1. The bike is always garaged
2. It always has a trickle charger connected when at home
3. I've got a Datatool Alarm
4. I've had numerous petrol tank changes since ownership
5. The previous owner had it fully serviced by Honda
6. Over the last 10 days it has failed to start (always turns over) on about 4 occasions
7. I generally use it to commute a 20 mile (return) journey each day

ps The Bike is currently back with the mechanic and is behaving itself impeccably.... Help!

kintheuk · Two Stroke Sniffer Joined: 29 Apr 2006 Karma :

When you say it turns have you taken the plug out to check if it sparks? Remove the plug and put it back in to the HT lead and rest it on the cylinder head, try to start the bike and check you get a spark. No spark will mean an electrical problem, spark may mean you have a fuel flow problem.
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Trixie · World Chat Champion Joined: 27 Jul 2005 Karma :

When you do get the bike started and running, does it run OK?
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Marci · Brolly Dolly Joined: 01 Sep 2005 Karma :

Flush the tank out - could be a load of crap in bottom of tank resulting in contamination of carbs etc whenever you run low.
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AndyCB500 · L Plate Warrior Joined: 14 Mar 2007 Karma :

Thanks for the replies and advice.... checked the spark and it looks good. When I get the bike going it starts ok... may be the gunk in the tank needs a clean out... will check my haynes for the know how. Cheers.

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

You know, I'd be very tempted to try a new battery in it, or to try jump-starting it off a car battery when it won't start. I suspect that having it constantly on a trickle charger is covering up the fact that the battery has had it - it's the right kind of age.

finpos.

beefcake · Nova Slayer Joined: 10 Sep 2004 Karma :

Had a similar problem with my CB500. Do you hear the starter solenoid click (under r/h side seat panel)?

If so, check the lead to the starter motor. The insulation had rubbed off the feed to the starter motor and so would short circuit occassionally causing the bike to not start intermittently.
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