03 crf450, should I buy this particular bike? Engine noise?

[popper357]

I am looking at all the used crf' around. I don't know what a healthy engine sounds like for this model. This bike is a 03' crf450. There was a loud high pitched, continuous sound from the top end while choked and running cold. Not a whine, sounded to me like piston hitting something. I'd hate to pay top dollar for a used bike and have to replace the valves or do other expensive mods I didn't expect. So I'd like to know if that is how these bikes sound? I rode a xr4 and the top end had a light valve sound, much quieter than this. This crf is supposed to have brand new oem valves and piston. Supposedly one valve was bowled and all four were replaced. Bikes in decent shape seemingly. Sprockets are toast, how many hours does it take to do that? I bet they are the stock stuff. Bikes supposedly ridden sixty hours, wondering if it's a can of worms. Thanks all

[bd450]

CRFs do make some clanking at idle. Not like the YZF's Iv'e heard. IMHO its due to the 4mm(?) offset of the crank from the bore centerline. The piston rocks more and the skirt slaps the cyl wall. But it give better mechanical advantage of the rod to the crank so a bit more torque. But it sounds more like a slap or clank not a continous sound. Some guys have had trouble with balancer shaft bearings that kinda squeal when they go bad.

Were the valve seats cut and new valve springs installed with the new stock Ti valves? If not its a job half done and the new valves won't last very long.

The valve seats should be cut by someone who knows how to cut seats in motorcycle heads and requires special machinery. Its not a do it your self job.

Thats one big difference between 2 and 4 strokes. A 2-stroke top end rebuild is usually a 100% DIY job. But ya gotta take the head somewhere and get the valve seats cut on a 4-stroke (especially with Ti valves).

Be a good idea to replace that cam chain tensioner with a 04/05 or manual tensioner asap.

[popper357]

Thanks alot, that's helpful. This bike had the updated tensioner. Clueless as to the valve seats so I'm contacting the seller to find out. I've gotten the impression that this bike was run hard and given mediocre maintenance, which means I have a bad deal. The seller is asking 3850 and his ads have run out so I'm considering an offer of much less.

Just talked to the seller, he installed the valves himself. When I mentioned the valve seat needed to be ground he had an excuse, said he made sure they were seating with a magic marker. This guy is an underhanded crook.

Do I buy a new one? Hmm