Parts Question
i bought 338xpt chain saw at garge sale did not run found...
Parts Question posted October 31, 2015 by jim cecil
204 Views, 8 Comments
Question:
i bought 338xpt chain saw at garge sale did not run found flywheel nut was loose caused pin sheer off order new flywheel on ebay but it came it,s much lighter then original one is ok to install
Answer
I found two different flywheels that are available used in this 338 xpt series. Please upload images of the flywheels that have with them as to which is the one that was on the saw.
I got parts numbers 503790603 and 537233901. Since neither number is a supercede of the other I would think they timed differently.
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The last three pictures were the original flywheel. The other flywheel is currently bolted into the saw. The new fly wheel was noticeably lighter. I turned on the chainsaw with the new flywheel attached. Does the weight make a difference?
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Yes the weight normally makes a difference. The flywheel beside providing cooling and ignition timing is a like gyroscope it help to keep the engine turning at steady speed and to balance out harmonics. On larger mower engines for example this resist to speed changes help get engine past compression strokes easier with starting.
Take a push mower engine without the blade attached (which is also a type of flywheel) with a light weight flywheel and engine compression can literally jerk the pull rope out your fingers by backing up. It the reason why engines that don't use full time heavy load use heavier flywheels.
Another example of the heavy flywheel use is old hand crank tractor that flywheels that in 10's pounds. I seen an old farm tractor when I was a kid that had 100 pound flywheel.
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Jim,
I would definitely recommend getting a flywheel the same as the original, and the correct part number too. I can visually see you setting yourself up for a bunch of different problems, and unless you just like to experiment to see what kind of problems you can get into, I would not recommend it.
But If you really want to experiment, then I would make sure that the overall diameter of the flywheel is exactly the same and measure it with a Vernier caliper, I would check the thickness of the flywheel and the placement of the magnet in the flywheel so it will line up with the armateur of the ignition module when mounted, I would check that the tapered shaft hole and keyway are the same, and that the keyway is the same distance from the magnets on the flywheel to the keyway are the same, as far as weights that would be a little more difficult to figure out because the engine speeds are so fast, I definitely wouldn't recommend trying to add weights to the flywheel to get them the same, or know how the balance and vibration would turn out.
Nope, I think I would just make sure you get the same as the original part.
I am not a Husqvarna Representative or Sales Person, just an experimental chainsaw person.
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