1998 xr 100 NEED HELP

[marky522]

I recently pikced up a 1998 xr 100, i was told it needed rings, but when i checked it out it has great compression its just putting it all out the tailpipe, i pulled the top cover off the enggine and everything is like its suppsoed to be, what is wrong?

Thanks for any help,
Mark

 

[whyzee]

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?

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

 

[marky522]

well, i found the site signed up to try and fix my bike, didnt see the repair section and posted in the main section. What i meant by everything looked fine was everything looked fine... The cam was spinning if i kicked the bike and opening and closing vavles, for some reason i believe that the exhaust valve is not closing so all my compression is going out the exhaust? Does this make sence? What woudl cause this on a good running bike, my friend was riding it and it quit??? Make sence now????

Thanks,Mark

 

[whyzee]

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...

 

[yzbluebeast]

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

 

[marky522]

it has great compression its just putting it all out the tailpipe [/B]

I'll expand on this, It has good compression, it just isnt able to compress because i believe there is something wrong with the exhaust valve, the bike ran till end of last summer, my friend was riding it down the road and it died, he kicks it over and it kicks real easy, he assumes he blew the rings, i bought it wit hteh intention of replacing rings and was told to look further cause there were other possibilites, i start playing with it today and relize if i cover the exhaust port on the head while kicking it over i have compression. What causes a valve on a bike to just go bad? I pulled the top cover off the engine, the one that goes over the valve train assy, then rolled the engine over and everything is working as it should, i did see a adjust ment that would affect the seating of a valve but wanted to get some advice on what i was doing first. Thanks for any help,

MArk

 

[yzbluebeast]

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

 

[yzbluebeast]

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

 

[marky522]

Thanks for the replys, that was exactly what i needed to know, i am going to talk to the guy across the street, he works at my local honda dealership. :)

Mark