[WesFourtrax300]

I've had a noise I believed to be the timing chain worn, a small light tick tap kinda sound. but yesterday on the way to the river (about an hour ride) not long in I notived I have a new sound. much more dominant and defined of a sound. I'm going to try and describe it best I can but might just add a video for better results. there is no sound during idle or at low rpm say 5th gear, 20 or so mph but during acceleration and holding a higher speed or higher rpm there is a constant very high speed knock. not extremely hard or painful almost sounds like a rattle. I believe it's from the top end area but didn't pin point it. I can also hear it in the crankcase vent on my snorkel but its faint which leads me to believe its not in the bottom end. I'm wondering if it could have jumped time and is slapping the piston on the valves or maybe the piston has too much play on it but I don't see that randomly happening. it rode fine the way there other than the sound but on the way home started to miss fire I believe. be riding trying to avoid the sound so low rpm but the bike would bog for blink then go for maybe 20-30 seconds another bog ect. any ideas where to start this diagnosis?

 

[SamUK]

Is start with the timing.

 

[WesFourtrax300]

fourtrax 300 engine noise: http://youtu.be/--spFPsq-_4

 

[WesFourtrax300]

what are your thoughts on this?

 

[SamUK]

From my experience (which isn't much) it's similar to timing chain but sounds more like valves to me. My 300 has a timing chain tick but said tick disappears at quarter throttle.
Your noise speeds up as the rpm get higher which would suggest to me something worn or in need of adjustment.
Try adjusting your valves and see how that goes.

I'm interested to hear others opinions on this, it's a learning curve for me too.

 

[fishfiles]

How much slack was on the timing chain , it sound like the chain throwing off the timing and the rockers flapping

 

[fishfiles]

oh when you take a pic of the piston turn it to the skirt side so we can see the marks on it ,

 

[misterclean59]

oh when you take a pic of the piston turn it to the skirt side so we can see the marks on it ,

Yes we need to see the wear on the piston skirt. Could be minor piston slap from a worn piston and cylinder. Could be rockers and or cam in addition to what others have said. I'd have some one with experience inspect the complete top end or else go thru the step by step process of photos and let us help.

 

[WesFourtrax300]

when I took the engine apart there were 2 one inch long pieces of cam chain guide broke off and flopping around... do you think that could be the noise?

 

[retro]

when I took the engine apart there were 2 one inch long pieces of cam chain guide broke off and flopping around... do you think that could be the noise?

Yep. You'll need new guides, chain and cam sprocket. Your piston doesn't look healthy either. Has that motor been sunk?

 

[WesFourtrax300]

yeah she got sunk awhile back

 

[SamUK]

yeah she got sunk awhile back

There's your problem then ^^^

The extent of your rebuild now depends on how deep your pockets are. In the ideal world every bearing and 'bit' that moves should be replaced.

 

[fishfiles]

the saying around here is , " if you are going to run with the big dogs you have to piss with them too , if not then stay your puppy ass on the porch and quit barking " , no disrespect , just telling the saying

 

[WesFourtrax300]

well it wasn't intentionally I wrecked into a huge ditch and it rolled over for just long enough. but my pockets are far from deep these days. just want her to run good and not die on me

 

[fishfiles]

chit happens , been dare and done dat , and didn't even get a tee shirt

 

[WesFourtrax300]

so deep pockets aside, just replacing what has to be is the way to go... I know the gasket kit comes with valve seals so ima do those and make sure the valves are good... I'll measure the cam but really hoping it is okay, retro mentioned the sprocket I'll give that a look as well but money is tight. I got a new chain coming already. I'll get better pictures of the piston and of the cylinder... hopefully I won't have to buy much. I can rebuild again later to a fuller extent if need be but for now gonna have to go minimal. I do appreciate all the help tho. what would cause the weird color (not black) and weird pattern on top the piston?

 

[retro]

so deep pockets aside, just replacing what has to be is the way to go... I know the gasket kit comes with valve seals so ima do those and make sure the valves are good... I'll measure the cam but really hoping it is okay, retro mentioned the sprocket I'll give that a look as well but money is tight. I got a new chain coming already. I'll get better pictures of the piston and of the cylinder... hopefully I won't have to buy much. I can rebuild again later to a fuller extent if need be but for now gonna have to go minimal. I do appreciate all the help tho. what would cause the weird color (not black) and weird pattern on top the piston?

The piston top & head photos show that a lot of water was being drawn in through the intake valve over time (possibly from a soaked airbox/air filter element?), washing the piston top & chamber down. The incoming water blasted away some carbon buildup and left some pitted looking erosion on the piston due to cavitating water implosions. Thats why I asked if it was sunk... I'm sorry to hear that it actually was though. :-(

If your cylinder is still OK (and the motor isn't smoking yet), you can probably run it for a while longer since funds are tight right now. Its your call though... check the rocker arms & cam lobes for heavy wear and definately replace those chain guides and chain. The cam sprocket might be OK, but you should wrap your new cam chain around it before making that decision, in case the chain won't lie down in a relaxed manner all the way around it.

Keep us updated if ya can...

 

[WesFourtrax300]

Is it normal for a cam to have wear marks like this?

 

[retro]

Yes, that cam looks normal to me. The story you are searching for will be better told by the rocker arms. Are either of them flat spotted or worn concave looking? Can you post up some pics of each rocker foot where it contacts the cam lobe?

How does the cylinder bore look? Thanks.

 

[WesFourtrax300]

This is the rockers here