2004 CRF450R Unknown bottom end noise?

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7/2/2018 9:24 AM

Hi guys, on Sunday i picked myself up a crf450r. I was hoping i can have some light shed on what to do with it.

This bike had been used as run just riding down country lanes etc. But, i was told that a noise was coming from the clutch push rod. However i'm thinking to myself that it could be faulty main bearings (due to the close proximity) I've opened up the clutch already and the push rod looks fine. Does anyone have any experience with main bearings or suggestions for what else it could be, engine turns over, with lots of compression; but the last bike i rode was a kx100 bored to a 120, so easy to kick. I'm thinking of replacing everything? (e.g airfilter, oils, coolent etc)

it's also it's been over-bored to a 510 w00t

So like i said, i'm hesitant to run it as is, just in case of blowing the engine to bits. I'll see if i can get a video of me kicking it over (if anyone is interested) might help?



7/2/2018 11:19 AM

Harbor freight sells a mechanics stethoscope for like $3. Id get that and use it to find the problem. It has a probe you can touch on things and listen. A bad bearing will be really obvious. It sounds really rattly.

Alternatively you would need to tear down the top end and actually feel for play in the crank.


7/2/2018 11:31 AM
Edited Date/Time: 7/2/2018 11:32 AM

The clutch basket was known to make a lot of noise when the bearing is worn. The basket will have up and down play in it if worn. The noise will also change with the engine running and you pull in the clutch lever.
Also the cam chain when worn will do the same thing. This can be checked by checking the cam timing marks to be sure they line up and making sure the chain has good tension on it.
The crank bearings were fairly bullet proof, but like everything they will wear also. They can be checked for wear by grabbing each end of the crank and attempting to wiggle it to see if there is any play.
If the piston is worn it will also make noise.
The best bet is to check it all out prior to venturing out on it.
Any idea on how many hours on the engine?

Paw Paw


7/2/2018 11:44 AM

Paw Paw 271 wrote:

The clutch basket was known to make a lot of noise when the bearing is worn. The basket will have up and down play in it if ...more

I have no idea how many hours, the engine looks very clean in comparison to the rest of the bike, and i know that it was the owner before the one i got it off who over-bored it, so maybe 80+ hours being conservative. I've since gone and kicked it over a few times and seems smooth towards the end of the kick but quite a brunt force is needed to start it off, not sure if that is normal, two strokes are normally consistent throughout. I'll go out and buy a mechanics stethoscope to be safe, but i'll give everything a good going through.


7/2/2018 1:49 PM

80 hours on a big bore 4 stroke is a lot and could be in need of a fresh top end. Remember that the bore kits put a lot of extra stress on the bottom end as well.

Paw Paw


7/2/2018 1:56 PM

Yeah, gunna take off the top end when I get the chance just to see what’s going on, if all loooks good, I’ll do a rebuild in 10-20hr or so just to be safe. Still debating wether to run the engine to see it I can hear anything wrong with it, can’t see any physical damage, and feels pretty tight


7/5/2018 12:00 PM


Video of the bike, anyone got any ideas

7/5/2018 2:16 PM
Edited Date/Time: 7/5/2018 2:17 PM

Could either be the basket bearing or the trans shaft bearing in the case.

Paw Paw


7/5/2018 2:20 PM

Yeah, well time to rip out the engine! :D gotta do some explorative surgery on this thing.