Razor troubleshooting HOW TO TIGHTEN THE CHAIN, IT BECAME LOOSE DURING A SUDDEN BRAKE.

Tighten the adjusting screw with the two nuts loose but snugon the middle of the chain on the top of the bar. Tighten the chain screw until the chain is loose enough to raise the chain up about 1/2 inch then tighten the mounting nuts tight. Then see if it is ok.
Terry

Razor E300 chain adjustment fix

Loosen both rear axle nuts, pull wheel back but keep it straight in the frame. retighten bolts

These are the instructions for adjusting the chain. They are taken directly from the manual available at http://ep.yimg.com/ty/cdn/razorama/e100e200e300manual.pdf

To adjust the chain:
1. Loosen the axle
2. Loosen the brake anchor (this is attached with the small bolt in the long slot on the left side of the rear fork)
3. Tighten the tension adjusters on the axle 1/8 to 1/4 turn to tension the chain. Tighten both adjusters the exact same amount to maintain the wheel alignment.
Note: this system of adjusters is common to motorcycles and BMX
bicycles so I your are not familiar with it, if you know anyone who is,
they would not have a problem adjusting it for you.
Chain tension: The chain should be "just not-quite snug" in other
words, not taut or sloppy loose. BE CAREFUL NOT TO ADJUST TOO TIGHT. The tensioning system can easily impart too much tension and snap the chain or bend the motor output shaft. Turn the adjusters 1/8 to 1/4 turn at a time and recheck the tension each time.
4. Once the tension is good, tighten the axle and brake anchor bolt. Test run the scooter. Readjust as needed.

If the brake has come on, the band is now smaller than the drum, you need to load the brake, there are a number of ways to do this, remove the clutch and sprocket, the cover will then go back on easily, now use the hand guard to pull back fully to the top handle to load the brake, or remove the hand guard from the saw, clamp the brake in a vise, be carefull not to damage the cover, now use the hand guard as a tool to load the brake.

If the chain is too long than shorten it by using a chain breaker. Or you don't have a chain breaker take the scooter to a bike or more preferable a electric scooter shop and have them do it. The problem could also be your chain tensioner check to see if it's tightening the chain.

it sure can happen. You can also take a link out of the chain to shorten it also, best thing buy a new chain.

Like this:
Chain Adjustment

1. Make sure the chain brake is off (gloves will protest your fingers).
2. If necessary, loosen the bar nuts that are clamping the clutch cover in place (or whatever holds the clutch cover and bar on). They don't need these really loose - finger tight will do.
3. Ease the tension adjustment until the chain is obviously loose.
4. Using one hand, hold the nose of the bar up.
5. While holding the nose up, adjust the tensioner so that the center of the chain just touches the underside of the bar, add a touch more.
6. Continue holding the nose of the bar up & tighten up the bar nuts / bolts / quick-release system. HTH

Lou

You didn't say what kind of saw you have but they are all generally alike. This happened because the chain stretches when it gets warmed up and it also gets a slight amount of wear in the pins so it lengthens as it is used. There should be 1 or 2 nuts on the side cover over the drive sprocket that you need to loosen just so the bar is loose and there should be a screw on the inside of the bar that faces the tip of the bar. When you turn this screw it will adjust the bar outward which will then tighten the chain up. Tighten the nut or nuts back up with upward pressure on the bar. It should be almost snug when cold. Make sure you have bar oil in the oil tank to lubricate the chain or it will soon stretch and come off again. This can ruin your chain and they aren't cheap

check the cog that the chain runs on, the one on the back of the centrifugal clutch they are supposed to be changed when you change the bar ((i dont bother until iget symptoms like yours or the chain starts to get tight and loose tight and loose)