Chain tensioner broke - Razor E300 Scooter

It sounds like you may need a timing chain tensioner.
I looked on e-bay and found a kit which includes an "upgraded" tensioner, and includes all the pieces, for only 60 dollars.
God bless your efforts.

place no 1 piston at TDC compression stroke. There are procedures for the timing of the balance shafts but if it is only the timing chain I will go to that
Align uniquely coloured chain link with intake camshaft sprocket timing mark-- INT--. ( this will be pointing at the 2 o'clock position)
install timing chain and sprocket as an assembly
align first matching coloured chain link crankshaft timing mark (5 o'clock position)
align the second matching coloured chain link with exhaust cam shaft timing mark--EXH ( at the 11 o'clock position
There is a special procedure to reset the balance tensioner and it is different to the timing chain procedure.

To reset cam shaft timing chain tensioner push piston fully and turn clockwise until locked
Once the tensioner has been compressed ensure the distance from end to end is 2.83 inches . If not repeat the resetting process
vehicles 30.000 miles the tensioner is released when the engine is first started . In vehicles over 30.000 miles manually release tensioner by tapping the plunger
Note cam shaft and crank shaft sprockets bolts MUST only be used once. If you want details on the balancer chain procedure then make a comment in the box
use tension wrench and a degree gauge
cam bolts are tensioned to 63 ft lbs + 30 degrees
crank shaft pulley is tensioned to 74 ft lbs + 75 degrees

Your chain could have worn and lengthened may need new one.

You told us the issue or problem

Now what is the question ?

The chain tensioners got loose ,maybe &
I would guess that the chain guides broke,
because they are plastic & that is what they do
So off came the chain

Now you have a lot of work to do or
someone does

Release the door from the opener by pulling down on the rope. It will be very hard to pull. This should release the tension on the chain but I think you need professional help with this opener. It sounds like it is badly out of adjustment. The chain coming off is an indication of a worn bearing that will have to be replaced.

Other than the chain breaking? I would recommend replacing all the chains while it is apart. Also all timing chain tensioners, tension arms & guides.

I don't have an answer to why, your specific parts,wore or broke.

The timing chain should of been changed at 30,000 or 60,000 miles it's in the owwners manual.

not true. SOHC 4.0 tensioner and rails fall apart, allowing the chain to slap and do damage, or even break. book it. in order to replace rioght side cam chain and tensioner, the engine MUST BE REMOVED! if it has balance shaft chain in oil pan, there are a total of four chains in this engine.

i had the same problem. had a knocking on the engine and let the vehicle sit until i had time to look for the problem. my unknowing mom took the car without permission and the car broke down on her. as it would turn out the upper timing guide rail broke off and damaged the cam gears and broke the upper timing chain along with damaging both the right and left lower chain guides, and the tensioner was also damaged. i would recommend that u inspect the lower chain to make sure that everything is good.

you need to replace the tensioner with timing chain. the tension er is the one that keep the chain in place.