Generac 4270 7.5kh noises

[taylorham420]

I have a generac 7.5 k guardian. When I start the motor it runs but there is a slight rattle. Then when I put a load on, aka the Air conditioner, the noise becomes super loud. Sounds like a grinding sound.
I have been told so different things.
1. Carrier bearings.
2. Bad brushes (even tho it creates good power)
3. the fly wheel or flex plate is cracked or broken.

Any one heard or have had this problem?
Thanks

[Randy125]

I would go with bearing issue.

[tubeguy]

Almost for sure the rear carrier bearing has eroded into the aluminum carrier housing causing the spinning rotor to become off center and now rub into the stator winding. IF you still have output, consider yourself real lucky! Stop using the genset immediately and check the rotor to see if there is zero clearance on one side and lots of clearance on the opposite side where it spins in the stator windings. This is viewed on the brush end of the alternator. You'll probably also notice it you look at the bearing end of the rotor where it is visible in the rear carrier that it is no longer centered in the housing. You may also see very fine metal dust all over the area caused from the rotor rubbing on the stator poles. Rip out the alternator and see how much can be salvaged if anything. You'll definitely need a front and rear bearing carrier. Possibly a new stator and rotor to. Brushes are cheap and should also be changed as well as both belts and maybe the bearing in the cooling blower. If the belt tensioner pulley's are noisy may as well replace them at this time.

In my opinion the two carriers are extremely weak for handling the load that is imposed upon them from the side pressure of the belt drive and the loading from the current draw of the alternator. At the very least the bearing insert holes should have had a steel insert in them instead of the bearings just being supported in the aluminum. The bearings fit in the housings very loosely and this also contributes to the outer shell "waking" in the aluminum slowly eating it away. They should have been press fitted or "Loc-Tited" in to prevent rotation.

I've been down this road already with a unit that had about 2400 hours on it of pretty light loads. Had since new and was really surprised at what I saw with mine. Bought a nice little three cylinder Kubota set now that runs at 1800 RPM and installed that instead. Small, efficient and quiet. Much better unit and with a brushless alternator too that is 4 pole and directly engine mounted.

Drop me a note if you got yours going again and if not, maybe you want to sell it for parts.

AB