barely runs, weak ignition? | Yamaha SR500 Forum

mechcd
New Member

Posts: 2

barely runs, weak ignition? Mar 29, 2006 13:09:58 GMT -5

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Post by mechcd on Mar 29, 2006 13:09:58 GMT -5

I recently bought a '78 SR500 that did not run. I changed the sparkplug and got it going enough to drive around the parking lot. I've driven it about 3 times. Now it tries to start for about 10 minutes and then proceeds to not fire. Occasionally it will start up and idle for about 10 seconds and then die again. It had a very dead battery the 3 times I had it running. Also, the idle was very low and I adjusted it after the 3rd time it ran.

Yesterday I replaced the battery with a 75v 20,000uf capacitor I had laying around. Kicked it over, started right up, then died. As I stood there kicking it, it seemed like it wasn't trying to start at all. No sputters or anything at all.

I don't even know where to start checking things. It keeps fouling the plug (rich or weak ignition?)and I keep rotating and cleaning plugs. I want to get a new plug wire, but my local dealer doesn't carry any. Where can I get parts?

StewRoss
Senior Member

Posts: 2,334

barely runs, weak ignition? Mar 30, 2006 1:25:12 GMT -5

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Post by StewRoss on Mar 30, 2006 1:25:12 GMT -5

Hi,
Try the easy things first. Change the coil over for a known good one...then check...an intermittent CDI can do similar things as well...I had that experience on an RZ350.

It's a matter of trying things out to see what works. As previously indicated there are check that can be done with a multimeter for the coil, CDI, stator etc. Check out a manual.

Good luck.

SR

...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR...

mechcd
New Member

Posts: 2

barely runs, weak ignition? Apr 10, 2006 14:41:25 GMT -5

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Post by mechcd on Apr 10, 2006 14:41:25 GMT -5

Things aren't looking veryg ood. I checked my regulator and all the checks in the service manual for it showed no continuity. Guess I need a new one of those.

My stator reads 1 ohm for each white wire to the yellow, more than the plus/minus 30% of 0.73 ohms given in the manual. The white to white registered 1.6 ohms compared to the 0.80 given. I guess I need to get that rewound....

While I'm at it, what else should I check in the electrical department? I can't find any way to check the CDI box.

This might be a dumb quesion, but is it possible to take the regulator apart and replace the components inside with new parts? The circuit diagram suggests that it contains only diodes. Even if there were transistors I'm sure a newer, more robust component could be subsituted for more reliability.

motomick
New Member

Posts: 19

barely runs, weak ignition? Apr 25, 2006 8:50:13 GMT -5

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Post by motomick on Apr 25, 2006 8:50:13 GMT -5

why check the charging system?,no/weak spark has little to do with the regulator!(initially),a fully charged battery's going to fire it up regardless!,check the stator ignition section,hi low speed etc 1st,also the ignition coil, note the ht lead is integral,rarely gives trouble!,try bypassing the plugcap too,they build up a big resistance with age,try a hotter sparkplug too,(BP5ES)handy while you're playing around trying to start n run the motor looking for faults!,hth,cheers Mick

work,the curse of the racing class