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"Gen-Set Vibrations"

10/8/00

This "Tip" may be a little more involved than many should try but it's something to consider having your local shop look at if you have a problem. If you have a generator that vibrates excessively and has breakage of engine shrouds, carb intake manifolds or mufflers, think about this.

The engine has it's own set of counter balance features as does the generator. Trouble is, if the two are not matched, you will still have excessive vibrations. I was made aware of this about 2 years ago by my Briggs rep. There are some gen-set manufacturers who don't want to take the time on the assembly line to make sure the two are matched. Briggs was concerned about vibration breakage and wanted to make sure if we ran across it that any repair we made didn't come back as a result of something we or they had done.

The rotor part of the generator is bolted on to the engine crank via taper fits, much the same as the flywheel mounts to the opposite end of the crank. Unlike the flywheel, they are not aligned with a key, but they still need to be aligned. The rotor poles, those big heavy electro-magnets, will spin in balance by themselves but when coupled with the engine they can cause vibration if not properly aligned to the power stroke. This is something that should be done by the gen-set manufacturer but not always done. Unfortunantly the gen-set manufacturers like to blame the engine so they may not accept responsibility, but try to get them to anyway. The engine manufacturer has no control of the situation after their engines leave the factory. For the most part, neither Briggs or Tecumseh have many vibration related failures on other applications so it's not fair to blame them.

If done correctly, the rotor poles should be horizontal when the engine piston is TDC. If your gen-set has vibration problems, carefully remove the end cap far enough to see the rotor poles and turn the assembly until horizontal. Then look down the spark plug hole to see if the piston is all the way to the top or all the way to the bottom. If it isn't, the rotor should be removed and re-orientated with the crankshaft so the engine and rotor are "Timed". As I stated at the top, this may not be the kind of job the average DIY'er should attempt, but it is something you can probably handle at least finding out if a correction needs to be made.
LMRM;Bob :<=

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