My 426 needs help

I need your expertise on a few questions iv got.I had my 2000 426 out for a ride last week. I hit the rev limiter 2 times on a stretch of trail in 5th gear and after that the bike was noisier than usual. I thought mabey the valves needed adjustment so I parked it. Last night I finally got a chance to check it out, it had 1 loose exhaust valve and 1 tight intake valve. The intake cam seemed a bit tight in its bore. I also took the jug off and found the piston is scored on the back skirt from the oil rings down. The jug is trashed because of this. the top of the piston is fine and so are the compression rings. The piston to pin was also tight and the pin bore in the piston is galled. It lookes like mabey it was low on oil, but I know the oil level was good. Do the oil pumps go bad? I need to redo the jug so is worth it to get a bigbore kit? How can you tell if the crank is good? It clunks just abit when you turn the flywheel back and forth but the rod seems tight up and down. Any suggestions will be helpfull. Thanks!

A bike of that vintage is definately due for a rod kit. I'd put new main bearings on when I had it apart if I were you. Don't risk trashing the top end for the sake of saving a few $$$. I don't know of any oil pump problems. Obviously check the filter and change the oil on a regular basis. You can check the oil pressure at the rear of the head, that will test the lube pump. If you have more than a few 100ml of oil in the sump after shutting the engine down the scavenge pump could have a problem.

Before you toss that cylinder, is the cylinder actually scored or does it have bits of melted piston stuck to it? If it's got bits of piston stuck to it, then you can get an acid and eat the piston off of it and odds are good that your cylinder will be fine. If the cylinder is actualy scored then that's another story.. I forgot what kind of acid to use, but do a google for it and you should find some good information.

I believe its muratic acid; you can find it at a pool supply store. Be careful, and have water ready to rinse the jug and dilute any acid that gets where it doesn't belong.

My cylinder does not look scored from what I can see, but the piston is melted to it. I'll give the acid a try, I know where to get muriatic acid. As far as the rod job, I'v never split cases so I guess I gotta have somebody do it for me. While the crank is out, should I just get a 2001 and eliminate the key problem? Thanks guys!

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