Hey all this is my first post here. I have a 97 blaster that the piston skirt broke and fell down and sandwiched between the crank and the case and just barely cracked the case. I welded up the case and had to put a new crank in it. I bolted the cases back up and it went together fine. I rotated the crank to check and make sure it was spinning free and the crank feels a bit tight. I turned the counterweight and it would spin free except when the weight was on the top side, then it got really tight. I can turn through it but it is tough. I am splitting the cases again, just trying to see if anyone has ran into this before. Thanks
engine rebuild
- Thread starter kirch86
- Start date
welding the case was not a very wise decision. You should have spent the money to get a new case. Which case broke? was it the left or right if you were sitting on the bike?
Did you use the correct pullers to assemble the bottom end? If not, set a soft punch on the clutch side of the crank and give it a moderate smack with a hammer. Should free up the bearings. If that doesn't work, you have other problems.
Lots of folks with broken cases have them repaired and continue to use them just fine.
Like Brandon said, nothing wrong with a fix as long as it was done right.
The main concern would be sealing between the two case halves and making sure that it isn't bent slightly anywhere else. It sounds like the latter may have been of some concern to you...
The balancer shaft actually does not turn inside the crankcase, rather it turns with the transmission assembly. If the balancer shaft is dragging (and Ken's "re-alignment" doesn't free it up) your crankcase is probably bent inwards toward the balancer shaft cavity. The only way to know for sure is to split the cases again and turn the entire rotating mass without one of the side cases on to be able to see if something is dragging on a case, or just simply dragging.
Like Brandon said, nothing wrong with a fix as long as it was done right.
The main concern would be sealing between the two case halves and making sure that it isn't bent slightly anywhere else. It sounds like the latter may have been of some concern to you...
The balancer shaft actually does not turn inside the crankcase, rather it turns with the transmission assembly. If the balancer shaft is dragging (and Ken's "re-alignment" doesn't free it up) your crankcase is probably bent inwards toward the balancer shaft cavity. The only way to know for sure is to split the cases again and turn the entire rotating mass without one of the side cases on to be able to see if something is dragging on a case, or just simply dragging.
There is nothing wrong with welding a cracked case. it was done right. good penetration and I machined the sealing surface with a mill. I understand that you want it to be as true as it can get, but you are using sillicone for your seal there. I am not too worried about it. I took the cases back apart. When I pulled the crankshaft through the case I was using some large washers stacked up to the threads. The largest washer was on the bottom. it was just barely too small. I am guessing 1/32 or something. I punched out a bigger hole in the bottom couple washers, pulled the crank through the rest of the way and that took care of it. now the balancer. When the case cracked i am guessing it tweaked the other suface around just slightly. The silicone looked like it made good contact all around the crankcase chamber though. I am just going to grind out the case a little bit and throw her back together. Justed wanted to let you guys know what I found. Thanks for the help!!!!
How much did you mill off the case? I lapped a set the other day and had a similar problem. The cases had been hit by pieces of the piston and were distorted pretty bad so I had to take about .005 off each case. When I assembled the bottom end, the crank was binding. I took the bolts out of the case and the crank turned fine. I ended up pressing the crank together an additional .008 and now it turns fine. If this is the case with what your working on, make sure you have a minimum of .012 between the rod and thrust washer after you press the crank.
Blaner
Your Friendly South African Ambassador
ive had this issue before...i changed the crank bearings but didnt get genuine yamaha parts and the compatible bearing (just the one) had the exact same number as original but i later discovered that it was 1mm thicker than it should have been, thus it held the casings apart and made them tight when bolted together. So i just forked out and got the genuine one. If youve got the correct bearing, make sure they are seated well in the case.... Just a thought here, welding the cases could cause the cases to warp? perhaps its a bit outta shape from the heat??
