Normal engine wear (noisy) on 99WR400

I have a 99 that has not seen been used too hard, been maintained well. I have though, as of late noticed some disturbing sounds coming from down-under. The disturbing noise is say when I´m loafing up a hill in say 4th gear and give it "a bit" of gas, I sometimes hear a bit of a "thrashing" noise, somewhat akin to "pinging" on steroids. Now whats weird is I think I can make the noise go away by giving it MORE gas. Anyone know what could be doing that? I was thinking piston slap, or a sloppy timing chain? I´m probably going to tear it down soon, what I´m I likely to find? What would be normal and what would be considered unusual wear for this bike? Also, is there an oversize piston available for this bike yet? Tacoma motor sports say they cant find ANY oversize piston for this ol girl, which sounds a bit wierd to me me :ride: I refuse to buy a new cylinder, so any chance the cyl bore just needs a hone and I can responsibly just do a new stock piston, pin, rings, valve adjust? The bottom end is pretty tough right? I donut plan on doing the crank bearing right now.

Oh, and 426 piston wont work.. right? Even if I make the hole REALLY REALLY BIG??? :banana:

K den...

Thanks much,


What if you went up the same hill at the same speed but only in 3rd gear, would it make the same thrashing noise you described? If not, your lugging the beast! The lugging in all probability is causing the pinging you hear. I think what yo are hearing is normal for what you are doing. But. from my expierence, the tear down in all probability will require a new piston kit. No need for an oversize piston. Its usually the rings that wear out, followed by the piston. Unless you did some damage, the cylinder should be in good shape. My original top end lasted 5 years. All I did was drop in a new piston and rings and gasgets. Even then, I wasn't so sure I needed to do that. Everything under the valve covers looked like new. I just replaced the piston and rings because I was already there and had the parts in hand. I think the bike will tell you when its ready. Poor starting, poor preformance, burning oil, down on powerand just a lack luster feel to it....

If there is no metal in the oil screen, I wouldn't worry too much about the noise. There all noisey :ride:

Yes, I know this is a noisy bike... but the sounds are changing... and that is a bad sign. This new noise never happened before and I know not to lug a machine. It´s something that shows up only under a very narrow range load condition, which happens to be just right off of, and into load from no load,(just off coasting in gear) in higher gears. It appears when I´m not really lugging it at all, but when I do lug it it loads the engine and the noise goes away... and I repeat... it´s new.

So what does a worn chain sound like on these bikes? This machine is 9 years old and has never had any work besides a valve lash adjust. Sounds like my chain is slapping around when its just loose enough to slap, then when you load it up it quiets down. Am I right huh huh?




Well, and I was so sure... but I adjusted my drive chain and lo and behold, the sound is LESS than it was, less frequent and less intense. For once it wasnt something BAD. Thing still runs like a champ and no smoke nor naughy habits, so I shal leave well enuf alone for a while.

thanks for the help ya' all. :applause:


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