80's colt sputters & misfires

[Tacoma01]

I have a 20 yr old 1.25 hp Johnson Colt that worked well when it was put away a few years back. Now it won't stay running below the start mark on the throttle. It also misfires badly and frequently at all but wide open. I've replaced the plug and am using fresh 50:1 gas. I've used a timing light to check the spark. It pulses brightly until the misfire then goes black for the duration of the skip. ( Skips happen every 2-30 seconds. Some are minor, some almost stall the motor.)I've also tried spraying gas in the airbox intake and it seems to have no effect.<br />Is the lack of spark during the skip a symptom or the cause? Any help troubleshooting is appreciated.

 

[11craigt]

Re: 80's colt sputters & misfires

Just curious, no expert here, but I owe something back to this forum. Have you ever cleaned the carb? It did sit for a while, probably schlacked up the jets in the carb, especially the low-speed idle jets? Probably uses other jets [passage-ways for the air and gas to go through to get to the engine] at high throttle levels. That's my guess. Hang out for an expert to come along. Good luck.

 

[Tacoma01]

Re: 80's colt sputters & misfires

Thanks, I'M on the verge of pulling at least the bowl and cleaning that out. just thought that I'd like imput on the spark findins before i go adding another variable.

 

[Goodoleboy]

Re: 80's colt sputters & misfires

I would check the ground wire going to coil. See if spark will jump 1/2 inch gap. Make sure their is no corrosion inside rubber boot on plug wire. If all this results in no improvement, then try new coil.<br /><br />Are you useing champion plug. of the correct heat range. ( very important).<br /><br />After fire issue is settled you will also want to clean and rebuild carb. Soak good in cleaner and blow all passages clear with compressed air. Be sure to remove welch plug and replace with new.<br /><br />You will most certinaly need to replace water pump impellar.<br /><br />If it were me I would also do a decarb on this engine. You can read as how to do this in the FAQ at the top of forum page.<br />I would also recomend you read the article on<br />( wakeing a sleeping engine.)<br /><br />Good luck!

 

[Tacoma01]

Re: 80's colt sputters & misfires

Thanks , I actually just put a new plug in ( NKG J6something). I'll try it again with teh old plug just to be sure. I'll check the coil ground and will likely just install a coil, wire and tune up when I get in there. I was hopeing not to have to dig into it too far but I guess I'm doomed to be messing with rusted bolts. Hope I don't snap any.