74' CB125 running issues....

born2expire

let's talk shop
when riding the bike around the block to work the bugs out. once i hit 3rd gear and try to get over thirty mph it just runs suuuuppperrrr rough and backfires a bunch. had a guy tell me he's heard of the coils working for startup and then being POS during mid-range and after. just looking for any input. i got the bike for 125$ so its my little tinker with bike

thanks guys
 
Could be the coil. I had that happen to me on a GS1150 once - would start up fine and run OK for a bit then spit / fart / backfire like crazy. It was a bad coil. If you have a multi-meter you can test the resistance to check if it's within tolerance.

But first, have you cleaned the carb? Could be a partially blocked main jet as well.
 
Im having the same issue on my sl350 ran great the started running like crap kicks over first tey and idles great. Im leaning towards coil failure. Ive read that you cant bench test a coil properly with a multi meter Ohms might be in range but when its eunning the issue develops(cant remember the wording). Good luck let me know what you find!
 
That's true ^^^^ Sometimes the coil can start to fail when they heat up, but not have any apparent problems when cold. Can be hard to diagnose in those instances.

Swapping out to a known good coil is the only certain way to check.
 
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