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Help with yamaha R6 engine repairs

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Brrrap82

Brrrap82

Joined
Aug 7, 2022
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Hello all , I am new to forum and seeking some help/advice from someone on my yamaha r6 engine. I got the bike which is a 2012 model with a locked up enigine. I cracked the cases and found a spun rod bearing. it was stuck on the crank but popped right off with no visible damage to the crank itself. Ordered a new rod and bearing which i am going to replace. My question is how do i know if i really need to change out all my pistons and what actually caused the damage to begin with. three of the four pistons look a little gummed up on the top but no visible skirt damage or cylinder damage. I however am having issues getting the pistons to go back in even with the compression tool. Do i need new rings and pistons possibly? Could a valve have caused this? the valves look ok upon inspecting them through the side but we have not pulled the valve buckets or anything as we know little about the valve assembly. This is my sons bike and im just trying to helo him get it running again. I just dont know if i should just replace all the pistons and wrist pins anyway while im this far into the engine already. Any help and knowledge from anyone out there that knows more than me is greatly appreciated. Oh, also pics to follow soon. im currently at work on work computer.
 
I can’t give a definitive answer without seeing the engine, but usually a seized crank bearing will not damage the pistons on the other con rods, so unless your engine has a high mileage, or was run without oil (this may of been the case and caused the spun bearing) it is highly unlikely that the other pistons needs changing. Try removing the rings and clean the pistons with a gentle wire brush (be gentle, you don’t want to mark them, just remove the carbon buildup). Pistons and rings on modern engines are notoriously difficult to get back in their bores (even with ring compressors), I suspect the problems you are having are completely normal, you just have to keep trying.. do make sure the oil scraper rings have been assembled in the correct order, there are 3 parts to the scraper ring and if not fitted to the piston in the correct order, will cause many issues getting the piston in the bore and could lead to smoking (burning oil) once the engine is assembled and running.
best of luck,
 
Thrasherg said:
I can’t give a definitive answer without seeing the engine, but usually a seized crank bearing will not damage the pistons on the other con rods, so unless your engine has a high mileage, or was run without oil (this may of been the case and caused the spun bearing) it is highly unlikely that the other pistons needs changing. Try removing the rings and clean the pistons with a gentle wire brush (be gentle, you don’t want to mark them, just remove the carbon buildup). Pistons and rings on modern engines are notoriously difficult to get back in their bores (even with ring compressors), I suspect the problems you are having are completely normal, you just have to keep trying.. do make sure the oil scraper rings have been assembled in the correct order, there are 3 parts to the scraper ring and if not fitted to the piston in the correct order, will cause many issues getting the piston in the bore and could lead to smoking (burning oil) once the engine is assembled and running.
best of luck,
Click to expand...
Thank you for your reply! You are correct. We finally were able to get the rod bearing replaced and all the pistons back in there cylinders. We now have smooth rotation on the crank and got everything back together on the engine itself minus the stator cover and clutch cover. Tonight we're going to do all that and try and get the engine back in the bike. We're crossing our fingers that it cranks when we get it back together. Just hope we get the timing set correctly. Other than the rod bearing the transmission and everything else inside engine look excellent. Thanks again!
 
Update:
I tried laying the cans in and they're not quite sitting down all the way in their journals. I pulled some docs offline and it tells me to rotate the crank until piston one is a TDC. Which I did but when I do this they won't sit down straight. So I tried rotating the crank a bit and it moves the valve buckets I'm guessing allowing it to sit down a little better. However my sprocket at this point is not aligned where it says it should be. ( It's about 45° out from lining up with the mark) attached is the document I'm working with. Anyone have any suggestions? I don't want to force the cams down and mess this up. We're so close to being ready to put this engine back in the bike. Thanks in advance,
 

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Update:
I got the cams aligned and at TDC I believe. Cam caps are on and torqued down and crank spins all the way around, ending up at tdc after full rotation again. Motor is now bolted back into the bike just need to hook up throttle body and all the wiring harness us exaust.
 
Update: We got all wiring reconnected and fuel tank back on to test fire. We in fact did test fire around 2am and she cranked up quick. We killed it bc we need to fill the coolant level to required level and put exaust back on the bike. So far , so good! Just nervous about start up and letting it idle for a while. I know they're lubrication point on the oil ring inside cylinder and a couple I think on the crank journals. U guys think it will be ok and not starve upon start-up? Thanks
 
Just don't want to end up starving a bearing and be right back where we started.
 
So I ran the bike for a few heat cycles today. Not long. Maybe 2-3 minutes each time. Sounded ok and was idling well. I noticed upon the fourth startup a bit of white smoke but nothing too major coming from back side of head. (Intake side) I killed the bike immediately and began inspecting further. I did look at the exaust side right where it bolts to the motor and noticed a little bit of coolant which to means head gasket possibly. We did not remove a gasket from this when we originally disassembled the motor. However I did put some high temp gasket maker on this before assembly bc it was odd to me it had no gasket before especially since it appeared to never had been opened. Anyways, I used the gasket maker and got it on there well. Does anyone care to respond with ideas? I'm thinking I need to take the head off again and put a new real head gasket on it so it doesn't sieze something if the coolant mixes with the oil. Thanks in advance
 
> Does anyone care to respond with ideas?
Sorry - my only idea is for you to take and post photos! You're WAY beyond my wrenching abilities, but I love following along...
 
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