Timmay#678
Member
- Aug 29, 2007
- 48
- 0
Hi, a kid with a 150 asked me to have a look at his bike after it locked up on him. I'm more of a 2stroke man and have done plenty of top end and bottem end rebuilds on them but never opened a 4stroke before (those yzfs just dont give any trouble :cool: ).
Anyways, after pulling off the head, the valves have certainly met the piston a few times before the bike seized, there are clear marks on the 2 exhaust valve and one of the intake valves. also one of the lifters has broke the camshaft holder, and the camshaft lobe above that valve has been deformed a good bit. Other than that everything looks good, piston and barrel are good and rod isnt bent or anything. Seems like the kid got off very lightely!!!
The valves dont seem to be bent or anything, but when you rotate the cam around, at one point the inlet and exhaust valves are definatly both open (only a small bit though) at the same time, which I dont think is right, as i thought the valve opening didnt overlap. I'm thinking that I'll escape with just new valves, camshaft, camshaft holder and lifters. However i've never installed valves before, and am not too sure about the whole process.
Am I better off leaving it all to a proper bike mechanic?
I'm not really sure of what caused the valves to hit the piston in the 1st place also! the bike was a little low on coolant and oil, it was the kids 1st 4stroke bike and i dont think he did much maintaince on it. Having said that he couldnt have rode the bike for more than 4/5hours after buying it before this happened! the timing chain was well tensioned, yourman is a beginner rider and I'd be very surprised if he managed to float the valves. Also the bike was starting grand before this happened, so I'd be surprised if the valve clearance had gone.
Anyways, after pulling off the head, the valves have certainly met the piston a few times before the bike seized, there are clear marks on the 2 exhaust valve and one of the intake valves. also one of the lifters has broke the camshaft holder, and the camshaft lobe above that valve has been deformed a good bit. Other than that everything looks good, piston and barrel are good and rod isnt bent or anything. Seems like the kid got off very lightely!!!
The valves dont seem to be bent or anything, but when you rotate the cam around, at one point the inlet and exhaust valves are definatly both open (only a small bit though) at the same time, which I dont think is right, as i thought the valve opening didnt overlap. I'm thinking that I'll escape with just new valves, camshaft, camshaft holder and lifters. However i've never installed valves before, and am not too sure about the whole process.
Am I better off leaving it all to a proper bike mechanic?
I'm not really sure of what caused the valves to hit the piston in the 1st place also! the bike was a little low on coolant and oil, it was the kids 1st 4stroke bike and i dont think he did much maintaince on it. Having said that he couldnt have rode the bike for more than 4/5hours after buying it before this happened! the timing chain was well tensioned, yourman is a beginner rider and I'd be very surprised if he managed to float the valves. Also the bike was starting grand before this happened, so I'd be surprised if the valve clearance had gone.