So i just got back from a ride.... walking. As i was driving along in mid to higher 6th my engine bogged down and locked up... I'm tearing it apart in 2 days. Is there anything i should look for to see whether my bottem end went, or if it's just my topend?
When you get the piston off of the rod, take the rod in both hands and pull it up to tdc, (top dead center). When the rod is at tdc, try to move it up and down. It should not move up and down. If it has any movement that you can feel, your big end bearing is worn and should be replaced. It is ok for the rod to rock side to side a little bit, but not up and down. Also, look and the little copper washers on either side of the rod at the big end. If these are excessively worn or missing or have an indication of a lot of heat, the big end should be replaced.
If the piston was damaged to the point of pieces of the piston going down into the bottom end, you should remove the crank and clean everything. It is difficult to get all of the pieces out without disassembling the engine.
Is the engine still locked up, or can you kick it over? If it is still locked up then you want to pull the plug and spray some WD-40 or similar solvent/oil into the cylinder to get the ring/piston to let loose of the cylinder. You may need to put it in 6th gear and rock the bike back and forth to break it loose. Get the piston moving before you pull the head, otherwise getting the cylinder off can be a bitch.
As Ol'89er said, account for all the pieces. A small burn hole in the piston is probably okay, but if there are any jagged pieces that indicates something broke off then you need to find the missing piece.
thanks alot guys... feeling better already seeing as i can do that sort of stuff myself most likely... i was thinking if the cylinder walls are scored, i might look at getting the bike bored out to a 133, maybe 144!
OK... cylinder walls look fairly decent, nothing that needs machining... Piston is scratched up baaad on one side and the ring is worn down and sticks out on one side = s. Im not sure ol89er what exactly you meant by it shouldnt move up or down, but the connecting rod wiggles side to side maybe 1/8 of an inch... is that bad?
I just got done with a complete engine rebuild on my son's RM65.
It all started with a piston seizure. I replaced the piston had the cylinder cleaned up and replaced the top bearing. The rod had NO up and down movement, but seemed a little shaky on the side to side. Remembering what I'd heard about side to side being okay, I fired her up and let the little man have at it (after break in). Within an hour, maybe two, it seized again. This time the big end bearing flew apart and DESTROYED the entire power portion of the engine. Had I taken a really hard look at the big end, I'd have saved myself a piston, cylinder, and head, etc. :bang:
It's pretty difficult to get a good look at the big end and harder still to rationalize splitting the case unless it's absolutely necessary, but after a seizure you need to take a long hard look at things because of the stress and heat that accompany a seizure event. Make SURE the copper washers are intact and that lateral movement is within spec. Look for for signs of discoloration from overheating. Any little tic as you roll the rod around the crank. And don't be afraid to do the work BEFORE it's too late. It'll save you money and heart ache in the long run. :cool: