Locked Up Temporarily?

[biglong350]

So i have this 96 rm 125. i was riding home from my buddys the other day and it died i pulled over to start it and it was locked up. so i pushed it a mile home. got some time and put a little oil down the cylinder and kicked it and broke it free. so i pulled the head off it to check things out. the cylinder wall is missing some of the plating but the piston looks intact. i am going to pull the whole jug off but i was just curious id anyone knew exactly what i should do. i was hoping a piston rings and some replating would do the trick. i am hoping the piston skirt is all together and didnt get in the case. can anyone lead me in the right direction as im a certed auto mechanic but have never really dealt with bikes?!?! email at or just reply on here thanks a lot!

 

[zarak]

i had the same problem with my sx 125, i had to get a sleeve put it. i took it to the local shop and they ordered a sleeve for 109 and sent it to a machine shop to get bored and installed. i personally had called la sleeve and for 275 including the sleeve they would bore it and evertthing. but then you have to get the new piston and gasket set. ive had mine in for over a month and still not done
hope this helps

 

[Ol'89r]

Have it re-plated. Do a search on Eric Gore, US Chrome, Millinnium plating and a few other places that can re-plate your cylinder back to original. Although it is one way to repair it, you will lose performance if you re-sleeve it with a cast iron sleeve.

 

[biglong350]

yeah but do you think all i need is a replate and piston rings etc? do i have to time anything or is it just unbolt send in get back and re install?

 

[mxbrian199]

get it replated and get a new piston and rings. get it nickle plated it cost more but its worth it.

 

[biglong350]

but does that sound like thats what happened? the rings just dug into the cylinder wall and finally it just stopped runing cause it lost compression? i am confused. also with the powervalve do i have to do anything special with it?

 

[mxbrian199]

no i dont thinkso just take it out slow and is the crank still good??

 

[Ol'89r]

yeah but do you think all i need is a replate and piston rings etc? do i have to time anything or is it just unbolt send in get back and re install?

You will also need a piston. Just send the whole cylinder to Eric and he will supply you with the proper piston and ring set. You will have to remove the power valve first. Your manual will show you how to do that. when you get the cylinder back it will be ready to bolt on. You may have to reinstall the head studs since Eric will remove these to have the cylinder plated. Just doublenut the studs and screw them back in. Your manual will show you how to reinstall and set-up your power valve.

 

[rmc_olderthandirt]

but does that sound like thats what happened?

Your description sounds exactly like the classic "engine sieze" situation.

For one of several reasons piston overheated, expanded due to the heat and then no longer fit in the bore of the cylinder. When this happens the piston jams into the cylinder and it locks up.

The reasons this could happen include:

) the lubrication between the piston and cylinder broke down. On a two stroke this could be from not using enough oil in the gas.

) The rings could have simply worn out and the hot gases slipping past the rings caused the piston skirts to over heat. This is why it is recommended to rebuild the top end on a preventative maintanence basis.

) The engine could have overheated. As the engine heats up the piston gets larger and the hole it is operating in gets smaller. There wasn't a lot of clearance to start with so when the engine overheats it can go to zero and then things go bad in a hurry. This will often happen if you are operating at WOT for an extended period. (were you holding it wide open on your ride home?)

) detonation: If your gas didn't have a high enough octane rating the resulting detonation will focus heat onto the piston and the "knock" can hammer away at it.

It is easy to get a combination of the above. Running cheap gas without enough oil in a worn out engine on a hot day and holding it at WOT for a few minutes is very likely to result in a blown engine.

There is a very good chance that all you need is a "top end" rebuild, which will be whatever repair to the cylinder (sleeve, bore, plate, etc.) and a new piston/rings. It is also a very good idea to change the wrist pin bearing. Throw in a set of gaskets and you should be good to go.

On the other hand, if the piston has a big hole in it or has pieces missing then there is a good chance that the missing material is down in the bottom end and you need to clean it out, which generally means splitting the case.

Rod

 

[biglong350]

alright thanks a lot. yeah i have talked to a couple guys and they send to check my crank seals to make sure it didnt lean it out from leaking in air. yeah ill probably re do the top end and put one step up richer jet in it. i dont think it was cheap or old gas maybe not enough oil but usually i put a little extra in it. but yeah ill get it going! i drained the clutch/crank oil and it was clean with no metal in it so once i pull the top end off ill look at the piston and see if its missing anythign lets hope not

 

[TimberPig]

The oil in the transmission case only lubes the clutch, tranny, and related bearings. The oil mixed in your gas lubes your crank. Not finding metal in your tranny oil simply means you did not grenade the tranny or clutch, not that your engine is fine.

 

[DieselX]

Same thing happened to my bike a few days ago, but it's my fault...

I was racing my friend (Husqy 410) and topping my bike out in 6th gear when it just turned off and seized. Could even kick start it, so had him pull me with a rope to the truck.

Looks like I'll be getting my top-end rebuilt this weekend. Hopefully I didn't do any major damage.

 

[Dylan19302]

i had the same thing happen to my cr 80 seized up on me. The bike was running 2 lean and melted the piston. You probally need a hone or bore on the cylinder and new piston and rings.