I know the bolts are one time use, the tightening torques and sequence is outlined in the service manual. We are on the 3rd season (about 12 race weekends total) on this engine and it's still making power like a champ- but we started getting a little oil weep at the last round. Coming from one of the crankcase bolts on the bottom. 2-3 drops over the course of a week sitting in the garage. I gave it a 1/4 turn and it was fairly loose- Final tightening torque is a little confusing- 18 ft lb, then 13 ft lb, then 60 degrees. Is it ok to retorque these bolts? or just give them a little snug up?
Gino, is it one of the 6 big boys that supports the crank, or one of the smaller bolts toward the back that have an o-ring under it? Either way, it's Yamaha junk so tighten it up and let it rip.... Its probably leaking from the frame flexing so much the cases are warping....
Yes it's one of the "big 6". I actually fully believe it's because the engine is part of the frame- putting alot of force into these things over what they are designed for. Also, this is what I get for being easy on engines- all the fast guys blow theirs up before this becomes a problem- so maybe I need to start banging downshifts harder and hitting the rev limiter more often.
Hopefully your case is ok. Seen them where the case is cracked at the main bearing and the bolt is holding everything together.
This is actually what I was worried about, a cracked case. I cleaned the crap out of everything with contact cleaner and was looking for weeping oil. That's when I discovered the bolt. Would be nice to know if it's cracked before I haul it to Laguna.
well, I tried putting some torque on that bolt and it just didn't feel right. So I pulled it all the way out, and it looked fine, no metal came out. But again when I re-installed it, it won't torque down and I feel like it's gonna strip. So........
It won't torque properly because the hardware has been torqued once already and now it's stretched. That feeling like it's going to strip is very likely a result of the bolt itself being fatigued from the first installation.
I know the bolts are one time use, many of the Yamaha bolts are and that was a reason for alot of the blown head gaskets around the paddock early on. Are you thinking it's just the fastener that's the problem? I know the bolts stretch, but the threads look fine and 18 ft lb isn't much for an M8 bolt- I'm thinking it's something in the case that's messed up. However If the threads were stripped, I should have gotten some aluminum coils coming out on the threads of the bolt, right?? The backup engine is going in today, but I will need a plan going forward with this one. right now I plan to take off the side covers and oil pan and inspect the cases for cracking. Would really love not to have to split the cases on a great running engine if I don't have to.
I can only comment on the hardware itself as I'm not fully knowledgeable on this particular engine. I do agree that if the engine side of things were about to be stripped out, there'd be some indication on the bolt threads but I've also tried to reuse one-time hardware and it felt exactly as you described just before it broke and I learned my lesson. If I'm in your shoes I'd try torquing a new bolt while keeping in mind that I may end up splitting the cases anyway. Any chance of sneaking a borescope in there to inspect the threads?
Same (FZ07) symptoms, great running motor until it pulled the case threads and started weeping, time-sert fixed.
So I guess splitting the cases is the only way to do that correctly? Or is it possible to just turn the engine upside down and pull the bottom cases off ? If I have to fully disassemble the engine it probably pays to do rings, bearings, etc. I suppose. Forgive my ignorance, Sensei! We did have a good run with this thing, it's making great power still.
Not familiar with FZ07s specifically, but no way 18ft lb is stretching an M8 steel bolt that's clamping two pieces of cast aluminum together. If anything is failing in that scenario it's the aluminum unfortunately.
Gino, Yes you can do the procedure without dismantling the top if you're careful. Flip it and remove just the bottom, then build a dam with tape and masking isolating the 6 main bolt openings to protect the top from shavings falling in. Have a second person operate a vacuum while drilling/tapping. The threaded portion is recessed and you need to bore with the timesert tool to accept the sert at the proper depth.
Gino, I think you are on to something here, the motor being stressed member on a weak frame puts a lot of force on the engine. I have seen several heads that crack or strip at the frame mounting point after crashes.
No, sorry for the poor description, you have to remove the bottom half of the case exposing the crank etc. It sounds like a lot but it is not too bad of a job. There are a few bolts that hold the cases together that need to be removed from the top before you flip it. If I recall correctly you need to remove the shift shaft assembly to relieve the bottom case. After removing all the bottom fasteners it should lift off like a clam shell, all the insides stay in place. Clean surfaces, tape and mask the inside off from shavings falling in.
Well, the disassembly was not bad at all. Shift shaft doesn't need to be removed, only the oil pump and strainer. The cases look good, and I have all of the timesert materials so I'll hopefully bore tomorrow. @Randy Sullinger you mentioned boring to the correct depth- the timesert tool probably countersinks approx 3-5mm- the hole in the cases is 35mm deep and the longest timesert insert available is 22mm. so there will be 7-10mm at the bottom of the hole with no threads. I understand this is necessary for the timesert to be inserted correctly. Just making sure I'm not missing something critical.