rubberneck Posted September 29, 2009 Report Share Posted September 29, 2009 Ok, im trying to help out a friend who doesn't have a lot of money to spend on his bike. He broke a ring on the right piston, and we were planning on just doing a top end and putting her back into service. I checked the end play on the big end of the connecting rods to make sure the crank wasnt separated, and both were less than .029" so within spec. However when i check the small end side to side movement (measurement D in the clymers) im getting .045" on one and almost .050" on the other. Clymers calls for .039 max. Do i need to replace the crank? I have a feeling i know the answer, but i dont see the volume of these things that some of you guys do. I was wondering if they tend to be like that often, and i dont need to worry about it? Perhaps it will live a decent life as is. Both big ends of the rods look good , no discoloration, im just concerned about the side movement. He doesnt have the money to spend, but i dont really want to put it together only to have to rebuild in a trip or 2 because of a blown bottom end. Fyi, the bike is bone stock right now, but had planned on putting an old set of t5s i have on it when we reassemble. thanks Quote Link to comment Share on other sites More sharing options...
JMADD Posted September 30, 2009 Report Share Posted September 30, 2009 (edited) I don't have a clymers in front of me. Do you mean that the wrist pin is able to move that much on the rod???? Either way, I've never worried about side to side movement on those, just up and down. I'd run it. Edited September 30, 2009 by JMADD Quote Link to comment Share on other sites More sharing options...
blowit Posted September 30, 2009 Report Share Posted September 30, 2009 Ok, im trying to help out a friend who doesn't have a lot of money to spend on his bike. He broke a ring on the right piston, and we were planning on just doing a top end and putting her back into service. I checked the end play on the big end of the connecting rods to make sure the crank wasnt separated, and both were less than .029" so within spec. However when i check the small end side to side movement (measurement D in the clymers) im getting .045" on one and almost .050" on the other. Clymers calls for .039 max. Do i need to replace the crank? I have a feeling i know the answer, but i dont see the volume of these things that some of you guys do. I was wondering if they tend to be like that often, and i dont need to worry about it? Perhaps it will live a decent life as is. Both big ends of the rods look good , no discoloration, im just concerned about the side movement. He doesnt have the money to spend, but i dont really want to put it together only to have to rebuild in a trip or 2 because of a blown bottom end. Fyi, the bike is bone stock right now, but had planned on putting an old set of t5s i have on it when we reassemble. thanks Don't worry about your top side clearance. You are probably looking at the wiseco pistons anyway which is not directly relative to the OE pistons. The big end is what controls the rod centering. As long as there is not excessive side clearance on the big end, you are fine. Good to ask though..... Many engine failures could be avoided with a few questions I think B Quote Link to comment Share on other sites More sharing options...
rubberneck Posted October 2, 2009 Author Report Share Posted October 2, 2009 no i wasnt talking about the amount the small end can move inside the piston. In the clymers (and i believe yamaha manual) they tell you to check the big end clearance which is max .029 and we are good there, then they tell you to mount up a dial indicator and check how far the small end can rock back and forth. I am over on that, but just about everybody i have talked to agrees with you guys, dont worry about that spec as long as end play on big end is good. Also made sure bearings look good (well as much as i can see through the oiling slots on the big end and no signs of a broken cage. Thanks for the info. Were going to run it. I wanted to weld it, but he doesnt want to tear it down. Hopefully i wont be proven right on that one. At least not anytime soon Quote Link to comment Share on other sites More sharing options...
No Limit Powersports Posted October 2, 2009 Report Share Posted October 2, 2009 no i wasnt talking about the amount the small end can move inside the piston. In the clymers (and i believe yamaha manual) they tell you to check the big end clearance which is max .029 and we are good there, then they tell you to mount up a dial indicator and check how far the small end can rock back and forth. I am over on that, but just about everybody i have talked to agrees with you guys, dont worry about that spec as long as end play on big end is good. Also made sure bearings look good (well as much as i can see through the oiling slots on the big end and no signs of a broken cage. Thanks for the info. Were going to run it. I wanted to weld it, but he doesnt want to tear it down. Hopefully i wont be proven right on that one. At least not anytime soon If the crank is separating from the webings it can and will be a problem. As the crank seperates it can actually make contact with the case and lock the motor, the crank will become more and more out of true and cause the motor to vibrate and premature bearing failure. The good news is that we can press the cranks back together and weld them and as long as the bearings are good it will be fine. Putting a separating crank back in a bike is asking for problems. Quote Link to comment Share on other sites More sharing options...
rubberneck Posted October 2, 2009 Author Report Share Posted October 2, 2009 Yes i realize that, the crank is not separated. Big end clearance is within spec. if it were my bike i would weld it. I can lead the horse to water but... well you know the rest Quote Link to comment Share on other sites More sharing options...
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