2001 CR 250 Cylinder Plating coming off

Mar 25, 2008
69
0
what would happen if I ran a cylinder that looks like the plating is worn off in an area? I have a race I want to ride this weekend and Im out of money, I just bought a complete top and bottom crank piston etc and want to race but i am afraid to after closely looking at the cylinder because i dont want pieces of piston going places. What do yall think?
 

Tom68

Member
Oct 1, 2007
407
0
Risky but anybody thats stripped a few 2 strokes will confirm they can run OK with a fair bit of bore wear (plating completely worn through at top of bore) the biggest concern is braking a piston because of the piston to bore clearance. If it does that on an up ramp you're gunna wish you sat it out.
 
Mar 25, 2008
69
0
Thanks for the encourgment TOM68, I dont mean that with any sarcasm either. im not sure if the problem i have is piston material or plating wearing off now that I have looked at it CLOSER. It does sorta seem like piston material clung to the plating as much as it looks like plating being worn off. Its hard to tell. either way tho i think the cylinder needs rebuilt its just not gonna happen by the race 10/19/08, I do have a question, This damage im refering to is on the right side of the cylinder just above the ports and going upward yet is really pretty light, being that the damage is to the right its not on a thrust side. what do you think? ya think itll hold together for a race or TWO?
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Take a green or purple skotch brite pad and some wd40 and lightly match the crosshatch. Oven cleaner applied with a q tip may help also. Do not get any on the aluminum. The thrust side of the cylinder? Ain't touching that one? The mark is above the right transfer? You live in good old sandy Florida woud be better speculation. Are you putting new rings in? Is the piston rubbed also? What is the skirt clearance?
 

Tom68

Member
Oct 1, 2007
407
0
whenfoxforks-ruled said:
Take a green or purple skotch brite pad and some wd40 and lightly match the crosshatch. Oven cleaner applied with a q tip may help also. Do not get any on the aluminum. The thrust side of the cylinder? Ain't touching that one? The mark is above the right transfer? You live in good old sandy Florida woud be better speculation. Are you putting new rings in? Is the piston rubbed also? What is the skirt clearance?
Like he said
 
Mar 25, 2008
69
0
Thrust side of the cylinder (The side that the piston would rub the worst on its way up or down/ The front or rear) I have a brush hone that I bought from wiseco that they reccomend I use on the cylinder between reringing. Should I still use scotchbrite on the spot in question? what kinda clearance should I hope for? and should I measure clearance with a feeler gauge from the top of the piston or should I turn the piston upside down and measure because its always been my understanding that the very top / crown of a piston is larger than the skirt. Thanks for your help on this, Stuart
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
If you know how to properly use the hone, then by all means use the hone! The skirt is wider than the top of the piston, put the piston upside down and measure with the feeler gauge. Bigger than a .003" is too much, I am pretty sure? You usually ride in the sand, the harshest environment for a dirtbike. Sure hope you are running a pro seal filter! An '01, look very carefully at your airbox seal, any sign of light or deteriorated caulk, at least reseal it.
 

John.Jr

Member
Jan 5, 2009
32
0
Hey brother I got a 01 KX500 with the same problem about a $200.00 cylinder fix and a $150.00 top end kit with gaskets doing the work myself. Rather do it right or maybe spliting the engine ,you must have deep pockets,Peace
 
Top Bottom