Looking for answers on why this happened so it doesn't happen again. It is a 3mm sleeved big bore to 72mm full ported that turned 20 to 30 hours before this. I was in Halsey for a three day ride and noticed it didn't seem like itself the last day and I also lost headlight sometime out there. Didn't think much of it as it still ran pretty dam good. Got home cleaned filter replaced plug cleaned carb and it lost spark on wide open run down the road messing around. I post more pics after I tear into this more. Looks like crank, flywheel, stator are all toast...hopefully not anything else as it still had plenty of compression after this. Anyone gots thoughts??
Why Crankshaft torched and sheared
- Thread starter Neblasker
- Start date
The flywheel was still attached to the end of crank shaft that broke from main shaft. I had to take a air hammer to separated them and the woodruff key was still intact. The crankshaft was the only 3mm stroker available for these blasters so if you know blasters, then you know who makes these crankshafts. I really don't want to mention their name on this deal, but I will say I called Paul sent him pictures and they did warranty their crank but nothing else. If they didn't I will say I would have boat anchored this engine and started over. And I will have the main bearings out before the weekend is through but at this point I believe they are tight.
Did you use a impact wrench on the crankshaft when installing the nut that holds the flywheel on?
Well sure there is wear marks on the magnets and also on the coils but whos to say that came before or after the flywheel went free spinning at full throttle. I'm going with the small crack theory that led to even more flexing and heating in that area that eventually became a split. I did get to the main bearing and see nothing wrong with them, but the crank seals are not as both appear to be over heated. They must have went from all the heat as I believe the motor got super hot. Piston and bore are in good shape. Quick hone and new rings.
Oh I know to much to lose lose for the few coins I'd save. I got new main bearing, new crank, quality used flywheel and stator, all new oil seals, new oem gaskets, couple new circlips and lock tab washers, new rings, new big bore bore head gaskets, and couple things I'm forgetting. No expense spared on rebuild of premature failure and hopefully I can actually wear the next crank out...time will tell.
Oh and one more thing, would a lightened flywheel be something I should consider here.
So motor is together and air tight. I'm gonna send flywheel out to be lightened before I run this and I might switch oil too. Can anyone look at these pictures and tell me I shouldn't. The rings were extremely sticky and the sh*t on bottom of piston was like cooked rubber
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That oil was klotz super techniplate sh*t on premix @ 32:1. Air filter was clean and jetting was spot on I believe. I used to run the yamalube 2r stuff but this build I decided to try something different and my builder or machinist said everyone uses klotz techniplate, but I really think it was oil that made the sticky mess. Any recommendations on what to change to or back to yamalube 2r.
