Seized 2002 YZ125

[MLK]

I'm thinking about buying a '02 YZ125 with a seized engine(don't know why or how it seized). He's selling at a pretty good price and I can probably afford to put another $300-400 into after buying it. Is this a bad idea? I've worked on 2 strokes in the past but never taken on anything this involved. Does anyone have any advice for me?

Thanks,
MLK

 

[RocketRaccoon]

Depends on what the rest of the bike looks like, how much you are paying for it and how extensive the damage is. If you are getting it for $500.00 and the rest of the bike is mint...go for it. If its a rat and he wants $1500.00....pass.

 

[mxmoto19]

it is not that hard to fix .last year my yz125 siezed up while jumping a 50ft tabletop owch . dont try to force the piston down .take the bolts off the jug and see if the piston slides in cylinder .if it does the crank bearings may be locked up thats what was wrong with mine forcing the piston may do more damage good luck

 

[KX250Dad]

You can do a crank, top end, cylinder work for around 8-$900. Downside is should the trans gears be trashed cost obviously go up. Figure a top end and cylinder work regardless... you'll need a baseline for the upcoming season. Buyer beware... and I'd be curious as to history of the siezure, this may give you some clues.

 

[rmc_olderthandirt]

A lot will also depend on the type of cylinder it has and how many times it has been bored out before.

The standard remedy for a seizure is to rebuild the top end. Prior to a seizure a top end rebuild is a new ring(s) and some gaskets, probably no more than $50. After a seizure the cylinder usually has to be bored out oversize, which means you need to buy an oversize piston. Bore job can be $50 to $100, piston around $90.

Some engines have a plated cylinder, so in addition to boring (or sometimes in place of) you have to have it re-plated. I haven't done this myself so I can't speak from experience, but a quick look tells me it is around $200.

The past history of the bike is important because you can only bore the cylinder out a few times before there isn't any more room to bore. At this point you can have a new sleeve inserted (couple hundred $$) or buy another cylinder from someone's part bike. So if the seller tells you that it has never been bored before then it is probably good. If he tells you that it is already at the fourth overbore, the cylinder is toast.

As long as the bottom end is okay, and you don't drop any parts down into the crankcase, rebuilding the top end is pretty easy. Take off the tank to get room to work. Remove the radiator hoses, carburetor, top engine mount. 5 nuts hold the cylinder head on. Four nuts hold the cylinder down to the crankcase, remove them and the cylinder should just slide off the top. If the piston is still stuck spray some WD-40 into the cylinder and let it soak for a day or two to get the piston to break loose.

Take your cylinder and piston down to the bike shop and ask them: How much?

They will either refer you to another bike shop or send the cylinder out to a machine shop to have it bored out. You can bypass the bike shop and go directly to the machine shop if you know of one.

It will probably take you a couple of hours to tear the bike down, a week to get the cylinder bored and the parts you need, and then a few hours to put it back together. Oh, before you put it back together, be sure that you check the end gap on the ring(s)! If the gap is too tight you will seize the engine again right away!

Rod

 

[CRazy250]

do it if its in your price range, they are good bikes and i love my yz125!

 

[MLK]

Thanks, for all your help!

 

[lynch racing]

Pass it, He knows what the problem is and if he thinks that fixing it and selling will not be profitable then why buy his problems? Tell him to restore it first and then give a him a fair price after you have test ridden it and everyone will be happy

 

[rmc_olderthandirt]

Pass it, He knows what the problem is and if he thinks that fixing it and selling will not be profitable then why buy his problems?

I know a lot of people that ride who wouldn't know what to do with a wrench! When their bike breaks, if they can't get a buddy to help out they take it to the shop.

Such a person might sell a bike at a really good price in order to avoid paying the shop to rebuild the top end.

Rod

 

[lynch racing]

Just a thought...If such a person neglected the most important part of the bike( motor) then just think of what the remaining bike looks like? A motor does not just "seize" without warning signs, and if these warning signs were not looked after or if regular maintanence and upkeep and teardowns were not followed to prevent such breakdowns then I would walk away from a very neglected piece of scrap metal. You seem to assume that this is only a top end problem(ONLY). It will just be a can of worms when opened up, A 5 yr old neglected motor...Don`t walk away



RUN!!!!!!

 

[2strokerfun]

While I agree that every motor I had gave enough warning that I've been able to avoid a seizure, I've heard many people say theirs did seize without warning. I really wonder though.
Personally, I'd talk the guy into letting me take off the top end to look at it before making a decision to purchase it. If it's the crank, I'd probably put it back together and say "no thanks."