Run push mower w no blade - Walking trimmer motor?

[rickf]

So, I was gifted a walk behind string trimmer that had a blown engine, thought it'd be just the ticket for doing the fence lines etc.

It was a craftsman with a 5hp tecumseh, motor, had a couple regular pushmowers with 5-6hp tecumseh's on them (that hadn't been run for a bit. On the trimmer, there is no blade, just a pulley. Trying to start either of the replacements it rips the pull cord out of your hands (flywheel keys are fine).

From my reading, it looks like this can happen if you run a push mower engine without the blade? I thought it'd be a simple fix to drop a new motor on the string trimmer, but now wondering if you need one that's specially designed for that application rather than a generic mower?

Any thoughts on that? Anyone use a lawnmower vertical shaft for a go cart or such?

(not tractor related but couldn't spot a better place)

[humphrey]

Honestly it shouldnt matter. The blade only functions as a fly weight to help spin the motor over. The pulley should serve the same function, just creates inertia.

[simple_stan]

You need a heavy flywheel. Maybe the flywheel off the old engine would work on the replacement engine. Without the extra weight, the pull cord will snap back every time. I doubt that you have even gotten it to start.

[Dan123]

Most Tecumseh engines require an advanced timing, which must be set using a TDC dial depth gauge. Some gauges allow the pistons TDC to be verified with the engine head on. It's done thru the spark plug hole. Also the engine should run w/o anything mounted to the crankshaft. The flywheel is enough to carry the piston through all cycles. Tecumsehs are the only one I know of that have made engines that have a keyed camshaft gear in them.

[littlefan]

all that is needed is more wieght on crank try a case iron pulley or add some kind of wieght

[rickf]

quote:Originally posted by simple_stan

Without the extra weight, the pull cord will snap back every time. I doubt that you have even gotten it to start.

---

id="quote">

id="quote">yeah, and it can be dangerous!Well I put a working motor on the trimmer, and same thing. It almost started, but had the same habit of ripping the cord out of your hand... back on the original mower deck with blade started first pull ran fine. Actually put the original donor motor back on the mower deck (hadn't really started it before the transplant) and it started and ran fine on the second pull. Both motors where tecumsehs. So yeah, need some more mass I suppose, makes sense. Most of my motors around here have cast iron flywheels, so never really considered it. Looks like I tossed the flywheel that came with the busted motor, dang. Live and learn, Never imagined that would be an issue.Thanks for the help.