this is what the brand new piston looks like after running the engine for maybe 5 minutes.
Thank you for the advice. I did notice side to side play in the connecting rod. I just have no idea how much is normal. And I am also concerned the balancer could be broken or something because the woodruff Key on the magneto wheel was sheared off when I opened it up to replace the timing chain. Hopefully when I pull it apart it will be something obvious. I’ve got the engine out of the frame and I’ll be replacing the crank once I find a good manual and get some free time. I bought a factory service manual and it doesn’t really have any step by step process for rebuilding anything in the engine.I'd check the balance shaft is still timed right too.. It might have broken it's key, or gear, and the shaft might be hitting the crank.. You might be able to see marks on the crank, but they are hard to identify.. There won't be much to see.. but if you rotate it to where it might be going to hit, then inspect it carefully, you may see something. If the key or gear is broken the shaft can move once it's running and so the hit mark might be a bit off from where it looks like it would.
Yes they were all in. The light damage you see on the new piston was in the same place on the old piston only it was much worse. As far as I can tell I’m the first one to ever pull apart this motor. However there is a gasket that looks a lot like a rubber wedding ring that was not present when I took apart the top end. It goes between the head and cylinder around one of those dowels you mentioned.Also.. There are meant to be hollow dowels around some of the head bolts down on the crankcase.. Did you have them in ? They locate the barrel and if they are out it might make it noisy.
The sidewards movement is a bit of a vauge thing, but on that it's probably a good sign if the top of the rod only moves about three mills when you rock the rod. If it rocks six mills I'd be worried, but that's not the only thing to check. You need to try pulling the con-rod up and down looking for play that way as well, and it needs to be done where the crank pin is going to be the most worn, which is at the position it will be in when the piston's about three-quarters or a bit more up the cylinder. The press down hard on the rod and roll it over that place that gets the wear feeling for any roughness.
If that knocking was loud Im picking it will be the balance shaft.. I've heard it before. Big solid knock, but doesn't get much different with a load on. And no obvious damage.. the balance shaft just glances off the crank..
2003 Yamaha Kodiak 450 YFM450FAR Service ManualYamaha Kodiak 450 YFM450FAR Service Manual got it for free so i thought i would sharewww.quadcrazy.com
That discoloration near the rod is actually much much more blue once you get better light on it. But I read that the blue color can be on there even on a brand new crank so I don’t knowView attachment 4436
View attachment 4437 Other than what you see here I found that one of the crank bearings seems to have an extremely small hitch in it. I honestly can’t find any sort of issue that looks like it could cause this. I ordered a new crank/bearings from hot rods and I will throw it back together and hope it runs better. The inside of the motor really looks good other than some shredded plastic that was in one of the needle bearings from the timing chain guide that was shredded. Which has also been replaced. I really can’t imagine why this issue would persist with a brand new cylinder, piston, rings, and timing chain if it was not the crankshaft.
Both main crank bearings look like they may have spun in the housing a little bit but I don’t think so since they rotate just fine. The balancer looked good and the gears were matched up correctly. The only key on this balancer is for the gear that drives the oil pump and it was in good shape too. The dot on the timing chain gear is also still lined up with the keyhole on the crank. I’m at a loss at this point. If the new crank doesn’t do any good I’m not sure I know what else to tryThe blue colouring is common on new crank throws, but it looks like it's been rubbed off on the right side crank throw in that picture.. Is that where the balancer rubs ?.
How was the balance shaft key? And the gear ? Any rub marks on the shaft ?
And does that bearing shown, look like it's been turning in it's case/housing ?
Before replacing crankHey guys just figured I’d update. I replaced the crankshaft and main bearings with an aftermarket crank from hot rods. Spent all this money on a crank puller to install it. Didn’t fit tho so I had to hang it in with a hammer which I know is bad lol. Anyway got her back together with a cheap aftermarket carb. I still have the Mikuni but it leaks. So far it runs good. Hopefully this weekend I’ll be able to ride it and test it out. Thank you guys for all your help especially you mech.
I’ll put a couple video links of the engine running before I replaced the crank and then after
After replacing crankBefore replacing crank