Camchain tensioner

Im new to the working on your own bike thing. I have an 81 yamaha xj650 midnight specail. I was riding last week and my bike shut down and wouldnt restart. I tried to start it up and it seemed like the starter was locked up, i got it home in a truck and it was cooled off so i tried to start it again and the chain lossened so much that it spun and blew a hole in the cam cover. The chain isnt broke and seems ok just scared, the valve cover is done obviously. My question is do i need to replace the tensioner or adjust it. I know i should replace everything but i dont have the money for that right now i just need to patch it up till i can redo the engine.

 

start by adjusting it. does your adjuster look like this?


remove crank cover turn crankshaft ccw with a wrench until the C on the plate alines with timing mark.
loosen #12 and back out #11 about a 1/4 turn . then torque bolt then nut to spec.

you will then want to check the cams for proper alinement to see if your chain jumped any teeth on the sprockets

 

got a question for you . what color is the label on your TCI.
black or green?

 

TCI?

 

The tensioner is on the back of the engine below the carbs, it looks like that yeah. Why do i have to open the crank case? It says in the manual to lossen the nut on top. It jumped two teeth of the sproket, and is tight now. Will i have to drain the oil to open the crank case again?

 

The starter and electrical is fine, i was reading the manual and if the chain isnt properly tensioned it will cause the bike to just shut down. All of the symptoms match what i read, plus the chain popped thru the cam cover. So i guess the starter is still strong lol i was just wondering if i had to replcace the hole deal or if adjusting the tensioner would solve the problem for now.

 

Since you cam chain came through the valve cover you are looking at much more than just the cam chain tensioner.
The chain either came off because one of the guides broke, the chain broke. Possible the cam gear is also broke. You also have the good possibility of bent valves in the cylinder head since the engine was running when it happened.
Next step would be to remove the valve cover and inspect the chain, guides and gears. Then replace whatever is needed. After the chain is in working order a compression test will need to be done to see if there are any bent valves.

 

When i spin the back wheel (which is hard to do) there is good compression. The chain is on tight again and has very little play. It all seems fine today but i wonder if i can get away with adjusting the tensioner for now? The sprokets seem fine, the chain is scared but other then that seems fine. Do i have to drain the oil to open the crank case to adjust it? Or can i open the nut on the tensioner unit and re-tighten it?

 

You would be lucky if no damage was done.
Be sure the timing marks are lined up on the crank and cams and properly adjust the chain then get a engine compression gauge and test it.
Check that the timing marks are lined up before you try to start it.

 

What damage would you think is done? Like valve damage? If you dont mind is there a way i can give you my number and you call me this board is slow on my phone?

 

black box about 1" thick under left side cover aside of voltage regulator two connectors plug into it

 

Says tid on it? If so then it is black.

 

tid is part of part number
TCI is transistor controled Ignition

thank you for the info. I am trying to confirm that Black label tci are what came on the Midnight XJ650 do the round sidecovers on the motor say YICS on them?

drawings show your bike as Non yics

 

I have no idea

 

What does this mean?

 

2 style motors in the 650 yics and non yics.
Yamaha Induction Control System it is a series of ports in the motor to aid in conforming to epa regulations
80 and 81 650 maxims typically do not have YICS nor does the 82 XJ650 Seca.

you would see yics on valve cover and crank side covers