RM 125, Piston died and need advice

[Gripit'n'ripit]

I have a 95 Suzuki RM 125, and while in 3rd gear , suddenly died, and the back wheel locked (scary moment). Anyway, took the bike apart and the piston is smashed around the diameter and shattered around the bottom. The cylinder and head have no damage. Some one told me that the piston was hitting the head, but with no visable damage to the head, i think there might be another reason. I'd like to figure out the cause of the problem before i put the bike back together.

Any thoughts or advice would be helpful.

http://s203.photobucket.com/albums/aa235/adrokamin/?action=view&current=Piston025.jpg

http://s203.photobucket.com/albums/aa235/adrokamin/?action=view&current=Piston026.jpg

http://s203.photobucket.com/albums/aa235/adrokamin/?action=view&current=Piston027.jpg

[tripod]

I cant view the pics you posted.From the detailed info you gave im gonna say you grenaded the crank.There is no way the piston should hit the head with out a major probem from the crank.

[RedRider_AK]

Yeah I agree. I'd check the cases and cylinder/head for damage and begin rebuilding that whole engine from the ground up, new crank bearings, new crank, new piston, etc. Just to be safe I'd also get it bored to the next size and buy a corresponding piston.

[Gripit'n'ripit]

The wrist pin bearings are good, so i'm thinking it was the crank bearings. I've got most of the motor apart but i need a tool to split the transmission case. Anyone know where to buy one cheap, local motor shop said the tool's about $140. THanks for the advice guys, keep it coming.

[Nightbiker07]

lol i used screwdrivers and gently pried it apart at the motor-mount areas. option 2 is take it to the shop and see if they will pull it apart for ya real quick for like 20 bux.

[Gripit'n'ripit]

Could using screwdrivers dammage the case bad? the Parts manual says that the whole motor is shot because the halves are specially machined to go together and you can buy just one half cus they won't fit? I think i may just go and take it to the shop. Quoted me $25 to pull it apart, and $35 for the needle bearings (ouch). Again, thanks for the advice guys.

[Nightbiker07]

yes, screwdrivers CAN screw your case up. you have to know where to pry, there are spots that dont seal anything (arounf the motor mount bolts, toward the outside)

but for 25 for them to pull it apart, definitely have it done for you. it takes quite a bit of skill to split a case with screwdrivers and not damage the case.

[Gripit'n'ripit]

Here's what's going on: pulled the case apart for $25, pulled the crank apart for $45, and the needle bearings are shot to hell.
got new bearings for the crank, and the connecting rod coming in the next couple days for $120 (all four sets of bearings).
I just got a couple O ring seals, and a full motor gasket kit coming.
Any advice for when i try getting this thing back together?
thanks for the help

[RedRider_AK]

The crank bearings will need to be frozen in your freezer overnight when you go to put em in the cases, and the cases will need to be heated up in the oven/with a torch.

[jason 32]

you got a cheep job bud- ++++ lol

oh freezing isn't worth crap guy- use a press - or heat the cases in a oven- drip water on them to see if there warm enough--- prob with this way is i dont like chancing it with new seals-
best is a press
i have also used a hammer soft 2x4 under them- and a socket to fit the outer ring of the bearing, or something to fit it- oil it so they slide in easy

they don't warp as easy as people think, the motors get hot and they withstand it-
take your time-

you can make a crankcase separator from a steering wheel puller, or make one from metal strips 1/4 inch or so thick,and a variety of metric bolts ,
all probly from the hardware store-
the motion pro separator is not worth 150 dollars---- they do not keep the cases level as they com apart, this is a problem if the cases are sealed ,and have dowel pins in them - most do

i always seal the center case gasket- i don't like yamabond or those style sealers- they have gotten hard and didnt seal right-
its nothing like a crush style /paper board gasket the kwis dont have 1 on most
i make one from thin material-(so it doesnt affect the tolerances with the shifting forks or tranny)- and a exacto knife

[seddon]

my buddy just had the same thing happen to him same bike same year look at *Edited**Edited* power valve it came un done and it hit the piston and borke it