no cam chain tension???????????

[350rwhp]

hi guys iv just bought my first pit bike. its has a 140cc lifan engine that needed some new rings. now iv never worked on one of these engines but they are pretty basic looking so i pulled it down, gave it a hone and replaced the rings assembled it and set the timing from some info on this site. the only problem im having is apon replacing the rod and spring for the tensioner the chain didnt tighten. when i remove the spring and push on the rod with a screw driver the chain tensions.

what am i missing?

also where is the crankcase breather on these motors?

cheers jake

 

[bulldog93]

http://www.miniriders.com.au/tech-talk/21042-how-tear-down-head.html

try this.

OR

this

http://www.miniriders.com.au/tech-talk/21075-how-tear-down-head-cylinder.html

should be in one of these havn't read them and never pulled a motor apart but it might be worth the go, good luck.

 

[350rwhp]

cheers mate. it nearly answers every question one could have, but not mine.

 

[bulldog93]

owell sorry mate, hope you find your answer soon

 

[7deanos1993]

Crankcase breather is near the back of the engine. Should have a rubber hose coming out.

 

[coolmodee01]

crank case breather is at the back and on the top depending on your frame it might be hidden behind the mounts or cradle

as for the timing chain being loose you either havn't got it on the bottom sprocket which means you will have to take the stator plate so you can see and put it back on
also there is a timing chain tensioning bolt next to the sump plug under the motor it could be missing the spring or something dunno but be careful checking it's a bit fiddly

good luck

 

[headsmess]

from what ive heard the tensioner is hydraulic or something...if you put the spring nd piston in, itll stay fairly loose until the engine runs and builds pressure... i assume anyway. the spring just holds minor tension. theres always a big gob of oil that comes out when you first pull the bolt i notice.

honestly ive never checked my tension after replacing the spring n bolt... before starting...

dont take my word for it though. unless someone else confirms my suspicions

 

[350rwhp]

i thought it might be hydrolic but i swear it had tension on it when i pulled it down. it is definatly on the bottom sprocket as it starts and runs. maybe it is hydrolic and i have the cam advanced a tooth and it isnt chain rattle its pistons and valves hitting.
can anyone confirm that the chain is loose when motor is stationary.

 

[headsmess]

rattle could just be the valve clearance... try taking off just the sprocket cover and seeing if its got tension now you ran it... if valves are hitting, it wont be running very well. and not for long either
set your clearance to .004 or about two sheets of paper. i havent measured a coke can yet but thats probably the right thickness too... hey, feeler guages are like 30 bucks rip off.

you also might have put the tensioner piston in upside down... should have a hole at one end for the spring to sit in... thats the bottom.

 

[350rwhp]

is that the gap hot or cold? i have feeler gauges so ill check it out but it wasnt ratling before the re-ring.
i just retarted the cam timing one tooth and there is no more rattle but it wont rev past about 2 grand so im confident the timing was right and it is valves and pistons kissing from the lack of chain tension.

ill go checkout the tensioner rod and see if thats the problem.

cheers

 

[350rwhp]

thanks headsmess that was it. rod was upside down.
reset the timing and swaped rod around and tension was back and noise was gone.

thanks everyone for your help

 

[Kingers]

valve clearances are from cold

 

[headsmess]

now, a hint (if anyone else reads this) DONT pull out the piston...just the bolt and spring, then put the bolt back in...saves dumping the oil as well

i really gotta get off my butt and write up this timing tute... but my pics are lousy as