this is what the brand new piston looks like after running the engine for maybe 5 minutes.
Knocking/piston slap?
Hey guys. Just wanting some advice before i go into this headfirst. I have a 2003 kodiak 450. I love this era of yamaha machines. i bought one that wasnt running from a guy who said it had been sunk. 900 hours on it. he said it needed a top end. Well the cylinder and piston were scored (mainly intake side) and the camshaft/rocker arms were completely ruined. all of that got replaced as well as the timing chain and guide. the engine rotated freely and smoothly even when using the electric starter. However i got her put together last night and it fired right up. Once i got the muffler on i could clearly hear a loud knock. the knock increases with engine rpm. it also does not like to shift all that well but if you rotate the axle back and forth some it does it okay. this knock also persists with the cvt belt removed completely. it sounds like the crankshaft hitting something to me but i am no expert. after running it for maybe 30 seconds a few times i checked timing and timing did not skip. any advice on what to look for/ what to do first? the service manual is not so great for step by step instruction.
i will say this atv was not worth the money i already have in it but i like these machines and i enjoy this type of work, my goal is to get it back to being a reliable machine*
i will say this atv was not worth the money i already have in it but i like these machines and i enjoy this type of work, my goal is to get it back to being a reliable machine*
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this is what the brand new piston looks like after running the engine for maybe 5 minutes.
Have you checked the conrod for play on it's big end bearing ? Try rocking the rod sideways...
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.
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.
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..
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 Manual
Yamaha Kodiak 450 YFM450FAR Service Manual got it for free so i thought i would share
www.quadcrazy.com
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 Manual
Yamaha Kodiak 450 YFM450FAR Service Manual got it for free so i thought i would share
Sensitive content, not recommended for those under 18
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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.
When I opened the post the second pic was hidden as sensitive. Crazy computer stuff.
The 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 ?
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 ?
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 ?
Just throwing this out there, have you ruled out the clutch. Can't figure how it would sound like a knock but...
Hey 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
I’ll put a couple video links of the engine running before I replaced the crank and then after
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
2003 Kodiak engine knock
youtube.com
The clutches do have shock absorbing springs in the hub I think, and they would allow the hub to chatter as the crank pulsed if the springs were broken, or worn into their seats.. I wouldn't expect that to make knocking sound like a crook crank though.
I've heard other things with the hub shock pads or springs worn, and they never made a real metal to metal sound. I think it would probably be irregular, and quieter too. Hard to tell since I wasn't there and we didn't get to suggest any tests to confirm where the noise came from..
I've heard other things with the hub shock pads or springs worn, and they never made a real metal to metal sound. I think it would probably be irregular, and quieter too. Hard to tell since I wasn't there and we didn't get to suggest any tests to confirm where the noise came from..
After replacing crankBefore replacing crank
2003 Kodiak engine knock
May 4, 2023
youtube.com
Oh good stuff Brock. You posted while I was typing.
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