yz 85 crank sticking

[adamd]

ok i have been helping the neibor kid with his yz85 it set for a few months his dad had him runing it with 50;1 mix (i still argue this is way to rich ?) and then was ran hard for a couple hrs and then it sorta locked up he had me looking at it and i messed with the crank for about 20 mins and got some dirty grime out of the rod bearing then it started moveing with just a couple sticks in it so i got some motor oil and put a bit on it and it freed up fine and has no sticky spots and turns like a new one it has no up or down play and just a wiggle side to side everthing else is fine should it be runable?

also the kids dad thinks he knows everything about a 2 stroke but i had to bring my flywheel puller over becuse he was gona tryin pry it off.
i convinced him to just let me reasemble the motor the cases r back togther now with the crank and it seems fine

[Macs]

Sounds like rod bearing is bad. If any junk got in it, then it likely damaged the bearing. Why you have it apart you should go ahead and rebuild the lower end. It doesnt cost much and you will know that there isnt a problem.

[adamd]

if it was my bike it would get a new crank. he dosnt have much money hes geting the cylinder bored .5mm over and new piston/ring. with the crank out i checked as much of the rodbearing as i could threw the lil gap in the middle of the bigend and it seems to turn fine and the bearings has no play i think the cylinder was a bit out of round its never been apart bfor and it a 03 and been rode perty hard.

also i think he was runing the wrong kinda of bottom end oil. he was useing yamalube 4stroke 20w40 could this have something to do with it ? and he was mixing the gas 50:1 or more with weedeater oil cas thts what his dad mixed him and said that what he used in his old bikes like in the 70's-80's

[Macs]

If it binded, it was most likely damaged. I wouldnt buy a new crank though, that is over kill. Just buy a new bearing for like $20. that way, you know it is good and inspect the crank bearings really good. This is the minium i would do.

[adamd]

he would proly do that im doing the work for him for free just to help out a friend

i havent eer changed a rod bearing is this hard to do?

usly i need a rod also on my bikes so i just get a crank

[Macs]

I have never changed a crank. Unless the bearing crashes so bad that it leaves grooves. you will need to press the pin out of the crank. Also put a mark exactly were it sits so you can get it lined up upon reassembly. Use a bit of heat and a vice and the crank will be in two separate pieces. Then the rod just slides off. Replace the bearing and press it back together with heat and a vice just like it came apart. whoa la, just saved you $200. It is much easier if you have a shop press but i dont so i use this method. When i was a kid KX80's were known to throw this bearing. I couldnt afford one but sure made some side bucks doing this. I will recomend changing the crank bearings out even though they are a bit more expensive. Also check every journal for some grooves. If they have them then you can buy a slightly larger bearing from mogul and get the crank turned. This is about 10 minutes extra work then replacing the whole crank assembly.

[adamd]

just talked to a friend of mine that runs a business i think hes gona rebuild the crank for us


if inyone else is intrested in my buddies business its MrCrankshaft.com his shops bout 15 mins from my house him and my dad have been friends for a long time

[Macs]

just out of curiousity, how much is he charging? Most shops around here that do it charge $75 and hour with a minium of 1 hour charge for there minute of work.

[adamd]

not sure exactly but he has prices on his site but thts for a rod and everything im just gona get the bearing swaped proly run me bout 50 bucks

[Macs]

If you can get it for $50 including the price of the bearing, go for it. I just priced the bearing at $33, so $17 to press the pin out and back in is a fair deal. of course you will spend more time getting it to the shop and back then it will take, but it is only 17 bucks. go for it.

[MTS]

The pressing part isnt hard, its the getting it perfectly true again, The halves can be outa phase. or V on you, Dial ind works good