can a duff capacitor give starting problems?

Hi All: my '74 Commando is ready, but won't start. Crank, crank, crank..... There's a spark and detonation, but it won't catch. Tried with choke, without..... gas... no gas.... I'm exhausted, and discouraged. The capacitor is probably shot because it is likely very old and has a hole in it, but could that interfere with the bike starting..... (see photo). It ran well last year, though it has never been easy to start. it has the lucas electronic ignition fitted. Finally, the battery is now a couple of years old, and discharged during the last two winters. I've tested it with my multimeter, and it is at 12.5 volts, but could the starting problem be a weak battery exacerbated by a duff capacitor? Ack......... Advice gratefully accepted.

Hi Neilsen.
Just unplug the capacitor.
If the bike then starts, replace the capacitor.
I use 'Capacitor - Panasonic ECOS1JP472CA/DA/EA 4700uF 63v'.
Ta.

I get from what you say that a dead capacitor could, in fact, be interfering with the starting. Correct?

Nielsen said:

I get from what you say that a dead capacitor could, in fact, be interfering with the starting. Correct?

Click to expand...

Correct.
Eliminate to test.
If still not starting, don't replace until starting problem resolved.
Ta.

If your battery is reading 12.5 volts without load don't mean anything its once it has load on it if it still holds that volt and of course that capasiter will be stuffed, they don't like holes in them.

Ashley

I like having the capacitor for emergency starting purposes, but leave it disconnected. If it's connected and you have a short the bike will keep running after your fuse has blown which can then burn up your wiring harness.

Thanks for that. I fear my battery is on its way out, but will report back.

With a good blue can inline one can w/o a battery or one cell dead battery kick start points that only need 5+ volts to fire or push off tow off above 15 mph to start analog boyah. I and others have lucked out to kick off analog boyah w/o a battery but mostly just wear us and the kicker slines down. The cap is essentially an extra battery to suck up rotor pulse and realase as spark triggers line up but if kept spun over 2000-ish can run w/o battery or blue can. So if blue can burnt-shorted inside to fail in open state its already removed itself from the system as its flimsy layers can not stand much voltage flow shorted internally enough to drag down a decent charging system. If battery really trashed so more than one cell bad-shorted then may not be able to start by charger spining alone, unless towed by PU truck to about 25-30 mph it still can but dies pretty easy if not used to dragster like blipping which is better for engine than slow running anyway. Where the biggest capascitors really pay off is powering mobile subwoofer amps supplying instant hi current dumps not to clip off the hard base hit peaks... for bone conduction fidelity.

OK, so I removed the blue can capacitor from the circuit, bridged the wires, and guess what..... The !@#$%^ thing still won't start. I haven't done a load test on the battery, but it reads 12 volts on my multi tester. Having said that, the battery is two years old and I let it run down both winters. When I kick the bike, I get a split second of firing, but it doesn't 'catch' and run. It did once, for about five seconds, then died. The more I kick it, the less it seems to fire. I've tried choke on, choke off..... It has always been a beast to start, but now it won't start at all. Lots of fuel.... fuel tap on.... I'm getting seriously frustrated. Any ideas gratefully accepted.....

Must take ignition system apart and item by item test then step by step go through the TDC and initial timing tedium again wire by wire end point to end point and maybe even check the bar kill switch or bypass for now. I have also had long stored non starters work great after carb floats reset but you likely already have a few times now. Could just be its more complex a motorcycle for you to take care of... as I know it often is to me.

Hi Nielsen.
Re your: "...bridged the wires..".
What do you mean?
Ta.

Nielsen said:

OK, so I removed the blue can capacitor from the circuit, bridged the wires, and guess what..... The !@#$%^ thing still won't start. I haven't done a load test on the battery, but it reads 12 volts on my multi tester. Having said that, the battery is two years old and I let it run down both winters. When I kick the bike, I get a split second of firing, but it doesn't 'catch' and run. It did once, for about five seconds, then died. The more I kick it, the less it seems to fire. I've tried choke on, choke off..... It has always been a beast to start, but now it won't start at all. Lots of fuel.... fuel tap on.... I'm getting seriously frustrated. Any ideas gratefully accepted.....

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If you question the viabilty of the battery, simply hook up to a known good car battery, runs? Buy a batt. No change? Keep guessing. Or TRUB-UL-SHOOT :mrgreen:

needing said:

Hi Nielsen.
Re your: "...bridged the wires..".
What do you mean?
Ta.

Click to expand...

I joined the sets of wires that went to the negative terminal of the capacitor by creating a short length of wire with two male ends. The positive pole on the capacitor goes to earth so I just left that wire as is. Made absolutely no difference--which at least suggests that the capacitor isn't the culprit.

Tip a teaspoon of petrol (gas) carefully down each plughole (after removing sparkplugs )!
Replace plugs and leads, and try kickstarting it again.

If it helps, its gas related.
If it makes no difference, it electrical/compression/timing related.

It does spark on the appropriate compressions ?
With the plugs out, and a thumb over the plugholes, you can see/sense the spark occurs when compression occurs.

If it ran for 5 sec then it should of made enough voltage to help even a poor battery so likely new battery no help unless charging system is not up to snuff with a poor battery. Sometimes the ignition brains go bonkers too or trigger clearance issue with fit on cam tapper. i have my SuVee ready to gas up and try to start after just a tank frain valve replaced but cleaning garage instead to delay risking another perfectly assembled read to go let down. Is it possible too much R factor in Plugs plus leads plus boots?

Thanks for the suggestions. Hopefully I can get at them tomorrow. I'll take the battery in tomorrow to a battery place and get them to put a load test on it.