Cb500 doesn't start.

pikey666 · Borekit Bruiser Joined: 18 Jan 2013 Karma :

I cant get my wife's cb500 to start.
A couple of weeks ago the reg rec failed and fried the battery, I fitted a mosfet reg from a 04 Yamaha and a new battery that I charged fully before use. The bike started fine and was used for a 30 mile trip, the battery showed a voltage of 14.6 while running.
The next time she went to use the bike it wouldn't start, the battery shows full charge, all fuses are ok, the starter relay clicks and the engine spins but doesn't catch.
The air filter is clean, fuel flows through the tap when a vacuum is applied, the plugs spark when held against the engine and were wet with fuel when I took them out. The side stand and neutral switches work properly.
I am poor when it comes to electrics so hopefully some can talk me through troubleshooting.

Sorry for the tef like essay.

davebike · World Chat Champion Joined: 15 Nov 2013 Karma :

Fuel ?
Drain and refill carbs

Is there a spark at the plugs ?

CB500 inigtion module is very tough but if no spark could be
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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Kill switch?

But you say you're getting a spark.
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davebike · World Chat Champion Joined: 15 Nov 2013 Karma :

Ignore last Brain fade!!

Choke on
crank hard and contentious Aladdin and removing throttle

Classic cb500 not been used

After longer periods you may need easy start
I think exhaust valves don't seat correctly after standing and once run all will be well again My high silage (140K) one dose this if not run for a few weeks
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MCN · Super Spammer Joined: 22 Jul 2015 Karma :

Wet plug inicates flooding (over-fueling). But could simply be tons of un-ignited fuel due to ignition problem.
For a flooded engine the remedy is alwys the same.
You need to clear the extra fuel or the mixture will be too rich to burn. (Not enough oxygen for combustion)
Choke off (if a manual choke)
Hold the throttle wide open against the stop.
Crank the engine over several times.
Set the choke.
Crack the throttle open (about from 12 o'clock to 1 o'clock) this ensures that there is sufficient air for combustion.
The engine should then start. If ignition, timing is ok.
Another wild card is that the battery cable terminals are dirty and the engine isn't turning over faat enough to start.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

UncleFester · World Chat Champion Joined: 30 Jun 2013 Karma :

When you put it back together, did you check that the leads were on to the plugs securely?

I knocked one of them off mine and it did exactly this.

Are both down pipes hot after trying to start it or just one / none.
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MCN · Super Spammer Joined: 22 Jul 2015 Karma :

pikey666 · Borekit Bruiser Joined: 18 Jan 2013 Karma :

Tried stinkwheel's flooded technique tonight but no dice, checked plugs and cables again and the spark looked a little dull In the half light so I am going to get a new set of plugs tomorrow and also trim the leads. Here's hoping...

pikey666 · Borekit Bruiser Joined: 18 Jan 2013 Karma :

Trimmed the leads where they looked a little crusty, new plugs and it fired up straight away. Voltage over the battery a constant 14.1V when running.

Fingers crossed the problem doesn't come back.

Thanks for the advice.