Do I need a CR85 engine rebuild?

Question

i do not use this bike a lot at all. i have a 2006 yz125. i bought this bike because a friend was moving and i had some extra cash and thought a little bike would be fun.

this bike is a 2005 model, expert. it was raced for probably 2 seasons by him, and if i had to guess i would say he didn't rebuild it once. it's now 2008; do you think it needs a new engine rebuild, or what are the signs of needing one? thanks

i tried to start it on saturday, it was VERY VERY hard to start, it almost didn't.

and the smoke it lets out is unbelievable. it floods the entire driveway practically when i run it.

how much does it cost?

Answer 1

you might just need a new top end since it is a 2 stroke

Answer 2

i don't race bikes, but i can almost garuntee not rebuilding the engine after even one season is bad.... let alone two...

as for prices, depends on how detailed you get into it... there are rebuild kits online, just look for one.

Answer 3

If you don't know what you're doing, don't do it, but if you do, piece of cake!  just rip that head off, pull the case and your two rings and a piston from a new motor rebuild!

Answer 4

It sound to me as if your burning oil. this is probably just the fuel mixture. the mix was probably correct when put in but the petrol will have gone stale. giving a stronger oil mix. drain the old fuel and replace the air filter. it might be OK. if not you wont have lost anything.

Answer 5

lol if its still running and working fine it doesent need a rebuild (i just bought a 2002 yz 125) for 850 bucks all its needs done is a new piston and a ring so the most common thing you have to ever replace on 2 strokes are pistons and rings becuz if you mix the gas wrong it screws up the piston and ring and you will know if you piston isent working cuz the bike wont start

oh and prices pistons and rings arent to cheap a full on kit is  about 100-200 dollars

Answer 6

When was the last time it was rebuilt? Never? If so then yes.

If it was rebuilt then raced for two seasons, then it might not need one. It does lose some horsepower the more its ridden. You could take off the head and check the barrel and piston for wear. If you can definitely tell they are worn out then yes rebuild.

Two strokes are easier to start than 4, so you will need to investigate that. Make sure the spark plug is in good condition and your gas mixture is 32:1. Start with that mix and see if it runs too rich or lean and then make the next mix better suited for your bike.