01 CR80+No Air Filter+Dusty Track=Big Trouble!

Joined
May 8, 2000
Messages
5
Likes
0
#1
My friend just bought his sons brand new bikes a 01CR125 and a 01 CR80. His youngest son(11) forgot to put the air filter back in his CR80 and rode the bike for two days on a dusty track until the bike started to spit and sputter a high RPM's then we discovered that the air filter was missing. The bike still runs with good lowend response it hits in the midrange then it starts to spit and sputter. So far we've cleaned the airboot and the carb(main jet was pretty clogged,float bowl had some dirt in the bottom,airboot had a layer of slime on the bottom)then we took the pipe off and looked in the exhaust port the piston looked fine no scratches on it or the cylinder walls.Still no topend power though.Could the bearings in the crank be bad?Or should we replace the piston?I don't know what to do next. I need someone who has experienced this before.
 
Joined
Dec 10, 2000
Messages
1,490
Likes
1
#2
It sounds like the powervalve has seized. To check the top-end condition, do a compression check. There will certainly be some damage to the bearings, piston, cylinder, and rings, it is just a question of how much. The only way to really determine the extent is to tear it down and measure. The chances are it will be fine, just check the powervalve, and clean the carb thoroughly.
 

KawieKX125

Subscriber
Joined
Oct 9, 2000
Messages
948
Likes
0
#3
Spanky, are you all right? A cr80 has no powervalves. I am surprised that the bike still runs. The best scenario is that somehow by a grace of god, all you need is a top end. Worst case and sorry to say that after 2 days the bike is most likely pretty ruined is that it needs a cylinder, top end, crank, and crank bearings. From the way you describe "slime" in the airboot, I would not be looking forward to finding out the results of this 11 year olds folly.
Moral of this story, never let 11 year olds do work on bikes without checking that they did it right!
Also, whenever I hear a bike run without an air filter, it makes a deep intake noise. I am surprised the bike sounded normal!
 
Joined
Dec 10, 2000
Messages
1,490
Likes
1
#4
Originally posted by KawieKX125
Spanky, are you all right? A cr80 has no powervalves.
Oops! you are right about the powervalves, I'm not used to minis.:confused: I would still tear it down and measure everything before just throwing money at it. A very worn cylinder and piston/ring can certainly cause it to run very poorly. Clean the carb very thoroughly, and measure the piston and bore. Check the runnout for the crank and rod bearings, if they are still within spec I wouldn't tear into the bottom until it needs it. If they are questionable, rebuild the bottom end as well. A worn bottom end can quickly trash a new top-end, especially a worn big-end rod bearing. This can wear the cylinder on the exhaust side very quickly. You may get lucky, and only need a piston and replating.
 
Joined
Aug 21, 2001
Messages
14
Likes
0
#5
Chances are all you need is a new set of rings. It sounds as if your losing compression on the top when its reved out high. If you would have smoked the crank bearings it would have scattered the piston first and you would definately know where the problem is. Pull the head off and ring it and it should be good to go.:)
 
Joined
Feb 20, 2001
Messages
95
Likes
0
#6
Poor kid... he probably feels terrible. Talk him through it and explain the best lessons are sometimes the hardest to learn. Don't stop him from working on the bike - I bet he never forgets an air filter again :)