Reply To: Valve clearance, camshaft, camshaft tensioner – a problem or a serious fault?
I can’t edit the previous post, so I’m writing another one.
I have done my homework properly and know that valve lash affects piston compression.
I have checked them and they are:
FRONT – 6,73kg/cm2
REAR – 7,65kg/cm2
It should be 8kg cm2 minimum, so i suspect you have gone over the “safe limit” , as per service manual but the bike is still operational.
Next time you do this ===> Pour a tiny bit of oil inside the RUBBER intake pipes , so that oil will go inside the cylinders
Then see if the compression improves?
this will help determine if we have to look at piston rings or a possibly scratched cylinder (A cylinder is easier to replace)#
Keep in mind also, if you or previous owner ever removed the cylinders or changed cylinders (they did, i can see you have mixed size cam tensioners) , then it is possible some compression loss is due to bad gaskets ? It is just a thought . Very common on cars , but you are lucky that if a gasket has problem, your engine is not burning blue smoke (water radiator coolant has mixed with oil!) – Your GT125 only uses oil, so the worst is burning oil (plugs will be oily and very sooty) and loosing compression overtime. It is advised to check ebay for a cheap piston and cheap cylinder as emergency back up. Korea is not making any more cylinders for carby 125cc bikes , so they only make parts for Fuel Injected GV125 now (it wont fit GT)
Also it will be advised 100% to buy spare cam tensioners , it looks like we cannot trust the ones you have. So buy a backup on ebay that’s cheap.
Also don’t forget to get tensioner gaskets! (I have loads), if you re-use tensioner gasket, you will burst oil there, the chains spin a lot of oil!
Also, if you ever get time, remove clutch cover ===> look at the rear cam chain crank, hopefully the right side of the crank does not have damaged teeth causing chains to dance and skip around and knock#
The left side is tricky as you will need to remove the flywheel and magneto, then look at the crank teeth there too
If you go this far, you might aswell replace the cam chains
Another chance with the gap on valve;
Front
0,03 (IN) 0,12
0,24 (EX) 0,26
Rear
0,11 (IN) 0,11
0,25 (EX) 0,16
I’m crying right now…
Front intake is too tight. Try to aim for 0.13-0.15 as perfect mark.
Rear = It will need re-doing as both EX & IN are on the tight side , if the engine gets hot, you will get problems and possibly cylinder head damage as hot heat reduces the clearances even more, so it is like we are “chocking” the bike’s neck and it can’t breath like it used to.