1998 xr 100 NEED HELP

Hey there Markey Mark,
Stick to posting the same question to one forum only.
... and when you do, provid some information. :silly:

and Blaa, blaa, bla, .... everything is like its suppsoed to be, what is wrong?

Click to expand...

If everything is as it is supposed to be, ... then nothing is wrong. :think:

lets try this:
does it run?
if not when did it last run?
between then (when it ran) and now what did you do?
do you have spark at the plug?
is the gas fresh?
is the gas on?
is the filter clean? (yes, there is an air filter)
what modifications have been done to the bike?

If you want an answer, you need to pose a question other than 'what is wrong?' as well as providing just a wee bit-o information so someone can give ya a hand.

get ready Pred...

check the cam timing, adust the valve lash, then have a leak-down test done on it.

Valves wear over time. They slam into the valve seat thousands of times and over time the "margin" gets smaller and smaller. In a severe case they can even start to pull through the valve seat. Exhaust valve faces are often stelite coated and it makes them very hard. It's unlikely that you have this problem but it's possible.
How hard was your buddy riding the bike? Did he have it pinned when it died?
Valve float is another possibility. Weak springs and high R'sPM can cause the valve to "float" and lose contact with the rocker arm. When a valve floats it stays open longer than what it is supposed to and contact with the piston is a likely outcome.
I recommend you have a leak-down test performed on it.
If you can't do it yourself then take i to a shop.
They will adjust the valve lash.
Put the motor at TDC, pressurize the combustion chamber and listen for air leaks.
This will tell you if you have a bent exhaust valve.
Good luck

I failed to mention that the shop will also check your cam timing.