I need something like a guitar string, about 18 inches. Preferably from a local store.
Maybe it can be a plastic wire.
It is for lengthening the throttle cable on a grass trimmer that I'm using for a project. I tried straightening a wire, but it needs to be perfectly straight so that it doesn't act like a spring. Under stress, the engine sputters rhythmically. I'm sure it's the wire acting like a spring.
Then I will need to find a sheath, but I will go for the wire first.
Thanks.
Find a hobby shop that has straight lengths of music wire. It's used by model-airplane folks. It's typically available in diameters ranging from 0.006" or so up to 1/8". Over 1/8, it's technically not music wire, but hobby shops may have thicker pieces.
It's plain-carbon steel; extremely strong (from 100,000 psi tensile to well over 200,000 psi) and it rusts like hell, so you'll need to coat it.
A hobby shop should have an assortment of "music wire" in various sizes, it's tough stuff.
You're saying that when you grab the throttle tab on the engine and hold it steady, the sputter goes away?
second the hobby shop. Or get the wire and sheath as a bicycle brake cable. I'm betting neither solves your problem.
I'm going to try 1/16" (or so) diameter nylon string. If that causes the same sputtering that is probably due to some sort of throttle system oscillation, or if it stretches too much, I will carefully moisten it with superglue in order to stiffen it while it is under tension, and try again.
If that doesn't work, a hobby shop is nearby.
Hobby shops and real hardware stores sell piano wire, which is steel wire, usually in straight 36" lengths.
Bicycle, motorcycle, and hobby shops sell push-pull cables for controlling stuff like throttles and brakes, and they come sheathed. The cables inside are flexible, but the sheath can keep them very stiff.
Not that matters, but...
Being a push-pull cable would be even more difficult to extend. In this case, I think the carburetor tension is significantly more than the hand throttle tension pulling in the other direction, so the cable is always being pulled in only one direction, fortunately.
McMaster or Amazon
Doesn't sound like a cable problem unless the engine/carb can flex relative to the throttle control.
If you want a good cable just hit a bike shop. That gives you easily modified cable with protective sheath. As long as the ends of the sheath are secured to the respective control areas the motions of the cable will have no impact on engine stability.
What it sounds more like is that you are running the engine lean or under a load that it cannot handle.
Even though I know little about gasoline engines, those are the two thoughts I first had, but... Everything else is the same as when it was running fine, before extending the throttle cable with a slightly crooked wire. In my view, some sort of feedback caused by a springy throttle wire (that causes sputtering) is the best lead. It is easy to try and it should be obvious if it is.
Generic lawnmower throttle cables are available just about everywhere you can get lawnmower parts, big box home improvement places, hardware stores, outdoor power equipment joints, etc. If you insist on making your own, Ace hardware carries a line of short music wire pieces, 18" and 36". I've run into the galloping idle on lawnmowers, it's usually a fan governor with a stretched-out spring or one hooked up wrong(AND stretched-out because of that). Lots of ways of governing a small engine, of course.
Stan
Agree with Steve. The problem is not the wire, it's the gas/air mixture and there should be an adjustment for that where the gas and air come together before they go into the engine. That used to be inside a device called a carburetor; but maybe it's called something else on that type of engine.
Tomsic
Or given that it's spring, maybe old gas.
I replaced the throttle extension cable with a 3/32" nylon string.
Or the ignition kill switch wire might have been shorting. I suppose that could have been rhythmic. Trying to rev the engine might have caused the shorting. I suppose that could have caused an oscillation.
In any case, now the acceleration is normal and smooth, no sputtering.
I'm aware of the need for a fuel stabilizer.
Thanks to the replies.
Biggest problem I have with string trimmers is the little rubber flapper valve in the carburetor curls up and leaks.
What is that a picture of?????
For pulling or for pushing?
Either way, find a junk bicycle and use the brake or shifter cables and sheath. If for pushing, you have to clamp the sheath in place close to the end.
Hmm ... can you use some of the trimmer string itself? Depends on whether the cable is under tension all the time or has to push, I guess.
Is there a piano repairman in town? If so, ask him for strings which he has replaced.
Good Luck, DoN.
It's my current push stick for inline street skating.
To get a very clear idea, you can see similar devices in action on my Youtube playlist.
Get a lawnmower throttle cable - music wire in a coiled sheath. Made for the job.
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