Doesnt look to bad to me but I cant really see it to well with the red outline distracting me. Like mentioned a TIG welder can fix that up nice and quick if they know what their doing. If not use the auction site for some cases and have fun learning more than you wanted to tearing the motor apart. Not to hard once you get going.
I'm still a little concerned why it cracked there and its only a small crack and not a severe blowout.
You might want to split your cases anyays to replace the main bearings. If they are worn, that would seem to me as the most likely cause of the cracking.
On another note, the casting process used by most manufactuers for cases leaves some spiderwebby ridges all over the inside of the casting that look exactly like cracks. I suggest getting the cases dye penetrant tested before doing any welding to see if the case really is cracked and the extent of the cracking. This is something you can do yourself if you can get the dye and developer.
I know there is the main crack, first picture to the left of the red line, sorry for all the lines, the welder wanted to knokow what he was up against. I did a leak down myself, pulled carb and exp chamber, plugged both holes and put a few lbs of pressure where the sparkplug was, worked like a charm.
The others may not be cracks, they just look like them.
I'm guessing the reason the case cracked is because the engine siezed at a high rpm and there could have been a huge jolt cracking it.
As for the bearings and internals, EVERYTHING is new from top to bottom, when we put the engine back in it was blowing tons of oil out the exhaust.
I'm sure the welder is going to do, he fabricates racing chassis for porsches and one that actually won the Lemans.
I'd lean towards improper install of the bearings also. Those bearings aren't a press fit in the case, they're an interference fit which is a couple thou tighter. I froze my bearings and oven heated my cases and they were still pretty tight going in. The cases are very thin to reduce weight and are easily cracked. Seizure at high speed would make the bearing spin, and even then the crank would normally spin in the bearing, not the bearing in the case due to the interference fit. In order to produce the crack(s), an outward force would have been required and I can't see any mode of bearing failure capable of producing the axial force required to break the casting.
Didn't want to wait, so JB Weld to the rescue. Cleaned with ether, sanded, cleaned with ether again and a wire brush and put the weld on. So far its holding fine and I don't think i'll have any problems. now just need to tune the carb, andyone got any pointers? Thanks for all the help!
Having a serious problem trying to get the nut off !
I’ve tried a penny in the gears after heating it up
Tried hitting it with air ratchet
How do I know if that seal is junk??
I was told from person I bout the bike from
It blew out a whole quart of oil at top off casing but think that was from faulty gasket
New piston n rings were installed recently