RedMax Trimmer Overspeeding and Overheating

[MBDiagMan]

I have a low hours, commercial Redmax, gearhead string trimmer. I don't remember the exact model number. It has been very impressive until yesterday. It got to where it would run at a pretty good speed even with finger off the trigger. I could look and see that the cable was snapping back to closed throttle position.

It seemed to be getting hot and it started running faster and faster even though I could see the cable allowing the throttle to close all the way. It was running pretty much full speed and I killed the ignition. It kept running with no change. I put it against the ground and managed to stop the engine.

My concern is over the fuel mix. I mixed the fuel this year and there was probably a quart or less left in the jug. I shake it well before filling the trimmer and I always watch the color to make sure that I'm not pouring in straight gas by mistake.

Could the problem be the fuel and do you think that I damaged the engine?

I plan on getting some oil and mixing up a fresh batch of fuel to see what that does.

Thanks for your replies,
Doc

[pugs]

Take the air filter off. Look into the carb. Move the throttle lever. check to see that the butterfly or the black round valve setup is actually opening/closing inside the carb. Sounds to me like the cable is attached and working on the outside but its not connected to the inside.

Or someone screwed with the idle speed screw.

[MBDiagMan]

Thanks for the reply. I will do as you suggest. I am the only one that has operated this machine and I know that no adjustments have been made.

It sounds like you don't think it's a fuel issue.

[Ben's Landscape]

How long have you had the trimmer?? I would think that the carb is messed up. If it is still under waranty i would go back.

[MBDiagMan]

The trimmer is out of warranty.

I poured what gas was in there into my mower. I mixed a fresh can of gas and it started and ran fine. I had burned several tanks from that same batch of mix, but something happened with the last tankful.

Now it doesn't seem to want to idle, while when I was having trouble it was running away. In the course of all this I pulled the air cleaner and peered into the carb. It seemed to be opening and closing fine. I don't think I did anything that could have changed anything, but I don't know.

Since I had the trouble with it I haven't used it more than a few minutes at a time. Once it warms up thoroughly, maybe it will idle better.

[mcdc6]

i would think fuel with the high idle. running lean could cause that. if clears up at all under some partial choke, check your fuel filter, then off to the carb. maybe a clogged fuel screen.

[treemeat]

sometimes the carb gets loose on these and motor sucks air causes similar symptoms . . . grab air cleaner and wiggle to check.