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bustersat

DEAD 2002 426 Help!!!!!!!!!!!!!!

11 posts in this topic

OK Here is the deal. I am at the track on my forth lap starting the day. Hit a jump just before the end of my forth lap, when my wheels touch the dirt from the jump, it dies. I went to kick it over and NO compression. Nothing! I can now push the kick start with my hand. Zero chance of it firing. When I got home (early) pulled the drain plug and my heart sank. There is metal shavings everywhere! Real fine in the oil and bigger shavings stuck to the flywheel. Pulled the clutch all looks good. Pulled the head and found two cam bolts on the right side exhaust cam with stripped threads. Piston looks good and everything is lose/ turns easy. I removed the head and did solvent leak check and valves are a bit leaky, but not pouring through. I knew I needed to get those done any way Before I removed the cams I cranked it over and all seemed well. Am I missing something? The bike pulled real hard right up to that landing. Any help would be appreciated!

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Did you:

> Check cam timing as you disassembled it?

> Check for damage at the cam saddles?

> Pull the cylinder and check the condition of the crank bearings?

> Check the crank sprocket?

You may need to go deeper if none of that turns up the source of your metal debris.

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yes to all but the crank sprocket. Got cold and frustrated in the garage so quite for the night. Would a blown head gasket do this? The lack of compression? Mine seemed fine on disassembly. Or is it the valves? NO warnings, no noises just stopped. I am planning on pulling the flywheel and replacing the can chain during the rebuild. Also what would be the best way to flush the cases to ensure all metal is removed? Thanks for your help, Gray!

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The best way is a complete tear down, but short of that, dismantle the entire right side, and with both side crankcase covers and the cylinder off, wash through everywhere that you can get to with a mixture of ATF and mineral spirits (solvent).

A head gasket that isn't missing a chunk wouldn't have done this. A sheared flywheel key would have stopped it suddenly, but would not have accounted for the compression loss.

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I just thought of something on this. I just put a auto decomp cam in a year and a half ago. Could the auto decompression mechanism get stuck with all the metal shavings in there? the top end did not have any shavings in it that I could see. My oil screen, oil filter , and magnetic drain plugs all were stuffed the stuff. Both ferrous and aluminum as far as I can tell. I bought this bike to figure out how to work on them as much as ride it, but this almost seems catastrophic at this point. I am seriously thinking of parting it out and scratching money together for an 06 or 07 450. Unfortunately some of the big money parts are more then likely damaged. Just in case anyone was wondering, this thing never went more then two trips to the track without an oil change. And I don't ride that hard cause I am not that good!

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The auto decomp system could have gotten stuck, but not as you describe. First, you would have needed to stop the engine in order for it to reset to the starting (active) mode, and even if it did stick there, the bike would still have had enough compression to run. It would have been impossible for the AD mechanism to become active at speed like that.

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That makes perfect sense, Gray. So, with a good piston, rings and cylinder the only other place to lose compression is the valves and head, right? The solvent leakage test revealed some seepage, but not like it was pouring out. If the decomp is not enough to keep it from building pressure then I doubt the amount of seepage would either. I am going to buy a parts washer today and tear the cases apart to determine if it is even worth saving. Any friendly advice for a complete tear down?

it would be a great victory for me to figure this out. All the guys I ride with ride Honda. After Reed's Daytona race, and my four laps, followed by "THE PUSH", I am taking serious heavies over here. I want to assure you, though, if I do buy a new bike it will still be a YAMAHA!

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Any ideas on the best place to get my valves and head work done in the San Diego area? Thanks!

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Fly wheel key is fine a bit of damage from the cam chain rubbing the back side of the stator. Clutch plates and fibers are new. Just two rides on them. Crank shaft gear is fine. I am beginning to think I tore this down for nothing. Now I gotta wait for gaskets to start re assembly. All the gears look great no damage. No rough sounding bearings. I am losing my mind trying to figure this out. How much leaking is necessary at the valves to give a no compression situation? Are they that finicky? Thanks in advance for any help!

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I think I found the source of my problems. While reading other posts, I started thinking I never checked the timing correctly. My Cam chain was stretched and had a bunch of kinks in it. Found that while running it over my finger. The intake valves touched the piston either before or shortly after the timing jumped. The machine shop also discovered I had Steel valves not titanium. Not a big deal really considering I was leaning that way for the rebuild. So now with a fresh valve job and a 444 big bore kit coming, I am hoping to be ripping it up in a week or two. Just wanted to say thanks to everyone here. I have learned so much already and now seek the forums to maybe even help others out!

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Just a quick update. Gray you were right on with my timing issues. New cam chain, a couple new valve shims, a lukes 444 big bore (13.5 to 1), fresh valve job and seats re cut. Put 6 hours into the the rebuild and about $600. While I had it down I re-greased EVERYTHING. Took care of a few cosmetic issues and brought it to milestone ranch last Thursday. Holy Crap! For an older bike this thing is riping like new. I am glad I rebuilt instead of giving up! And the Lukes racing big bore is simply awesome!

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