Ididn't seize the engine but.........

I was racing in a harescramble in Berthoud this weekend when the bike just died. If I hadnt just pitted I would have thought I was out of gas.

Here is what I know. I lost the lower drain plug in the bike. When I checked the oil in the top I still had a little touching the dipstick. The bike had compression until I used the decomp lever to move past TDC. While the bike still kicks through, there is no longer any compression. The bike had died 10 minutes earlier, but started right back up so I thought I had killed it on the back side of a jump. Last there wasn't any smoke or excess heat before or after the shut down in both cases.

I think I seized as valve. any other sugestions?


Pull the cylinder head and have a look, usually the piston and barrel will be damaged first.

big bummer! I think you will need to take the entire engine apart and inspect it.

Take the plug out and check it for any signs of piston damage,you may see some bits of the piston on the plug!,maybe a piece of it got in between the electrodes of the plug and caused it to cut out,then bring it to tdc and put a rod or some thing long enough down the plug hole to see if you can find o hole in the top of the piston,i think it may be more likely that it chewed a ring due to lack of oil,but what ever it is will mean an engine strip down.I hope it won`t turn out to be to bad,good luck i hope you get it sorted with out too much hassle!

Your right. I have faced the in-evitable. I will need to bring this all the way down.

On the upside, this will probably be a good time to order a 450 cam and YZ time the scoot.

silly drain plug!!!! :):D :D


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