Someone asked me today on how to do this so this tutorial covers the motor belt replacement on the majority of Kenmore 158 series sewing machines. It does not apply to the 158.1030 or 158.1040 sewing machines because the motor attaches differently. Depending on the model of your machine, you may or may not need to remove the balance wheel or a bottom cover, but the steps to loosen and replace the belt are essentially the same across the board.
The machine here is a 158.1430, but as I said, the process is straight forward and applicable to most Kenmore machines so I will explain it in steps. If your Kenmore has a bottom cover (convertible or free arm machine) you will need to remove it first before proceeding thru these steps.
Step 1. Remove the top cover of the machine. There are no screws holding the lid on and it is held with spring clips… simply pop the cover off.
Step 2. Remove the two screws attaching the rear cover to the machine.
Step 3. Tip the machine up on its nose.
Step 4. Loosen the screw in the balance wheel stop motion knob (but don’t remove it). Unscrew the stop motion knob and remove the large washer from underneath it.
Step 5. Looking at the bottom of the machine, loosen the bolt on the motor bracket with a large screwdriver, 12mm wrench, or a crescent wrench. This bolt may be very tight. Shift the motor bracket up as far as it will go to loosen the belt and remove the belt from the motor pulley.
Step 6. With the belt removed from the pulley, gently pull the balance wheel and the rear cover away from the top of the machine and away from the upper arm shaft bushing. The rear cover has clips on the bottom that disengage when the cover is pulled away from the top of the cover. The motor belt is captured between the balance wheel and the cover. As soon as the balance wheel is free from the sewing arm shaft bushing, remove the belt from between the balance wheel and the cover.
Step 7. Remove both belts from the large double pulley found behind the rear cover. This pulley is actually a reduction pulley and it magnifies the motor’s power to the sewing mechanisms… a nice feature!
Step 8. Grab your new belts. You will notice that they come in a set and there are two sizes.
The smaller belt goes on first. Install the small belt on the large pulley groove and the motor pulley. Next, put the longer belt on the smaller pulley and lay it over the upper arm shaft bushing. Replacement motor belts are readily available and can be found at any online sewing machine parts store. They are usually sold in sets and you should replace both.
Step 9. With the balance wheel inserted thru the hole in the rear cover, engage the rear cover bottom clips and guiding the balance wheel towards the upper arm shaft bushing, guide the belt back on the groove in the balance wheel. Keeping some tension on the belt, put the balance wheel on the bushing.
Step 10. Adjust the tension on the motor belt by pulling the motor bracket down so the belt is snug. It does not need to be tight but it should not be loose… Just snug. Keeping the motor bracket snug against the belt, retighten the motor bracket bolt.
Step 11. Replace the large washer and the balance wheel stop motion knob on the machine with the wings pointing out and engaged in the slots on the sewing arm bushing. Screw on the stop motion knob and tighten the small screw.
Tip of the day… Because the large washer has two “wings”, it can be put on in the wrong direction. If after tightening the small screw the stop motion knob does not loosen enough or at all (as in what you would do to wind a bobbin), loosen the small screw, remove the stop motion knob, rotate the large washer 180 degrees and put it back together. You would think there is a 50/50 change of getting it right the first time, but somehow I usually get it wrong 80% of the time (go figure…).
Step 12. Set the machine upright and reinstall the two small screw that hold the rear cover on. Don’t make them too tight or they can crack the plastic cover.
Step 13. Replace the top cover and snap it into place.
Step 14. Test the machine out to make sure the belt does not slip… snug it a little tighter if it does.
That’s it! Step 14 is really self explanatory, but stopping at 13 steps in a tutorial is bad luck… I just threw step 14 in there to avoid any calamity this may cause (just kidding…) Anyway, that’s all there is to it!
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Thanks for reading and I hope this helped!