Seized 660cc motor : what happened ?

[hb7]

Seized 660cc motor : clutch side crankcase shows a huge crack around the balancer bearing and the primary gear is wedged up against the clutch basket.
Something made the crankcase want to get wider ....did the rod break/piston break ?
Curious as what happened, I know the crankcase is ruined.

This happened while someone else was riding it...
How did he manage to break it, with the rev limiter ?

[DAVID THOMPSON]

if the gear from the crank that drives the clutch basket is a bevel gear
it sound like some one down shifted and did it all wrong
the guy needs a slipper clutch in his next motor

or something locked up in the trans and stopped the motor in a micro second

if its a good chassis slap something in it from a Yamaha parts breaker that fits and ware it out
ar dave

[hb7]

Something interfered with the balancer....and I'm thinking it's a broken rod ?
Transmission is in neutral.....even if you over revved it from down shifting,
it's unlikely to seize up....like this. Something broke ? and got wedged between the crank counter weights and
the balancer which caused the clutch side balancer bearing to crack the crankcase.

I don't know....

[Bill Jurgenson]

I've never seen a broken rod in this engine - which is not to say that it won't happen.
What most probably did happen is, the Woodruff key in the crank for the balancer gear or the similar key in the balancer itself sheared of, leaving the balancer free to turn as it wanted. It met up with the crank: BANG!.

This one of Yamaha's best kept secrets: this happens far too often for it to be a freak happening. I have seen it three times in my limited geographic area,including once to me with my at that time completely stock Tour with 35000km. That is what prompted me to remove the balancer for good. back then, I did some online homework and found out that it happens much too often. Both MZ and Yamaha were trying to reassure me that it was a once in a million occurance for which they could take absolutely no responsibility.The guarantee was still in effect.

Demand that your shop check this when they do a big service job. Or do it yourself. You have, of course, to take off the right sidecover and to unscrew the primary drive on the crank so that you can actually check the key itself. With my engine, the nut on the crank was snugged up to the correct torque and could only be opened with an impact wrench, but the balancer gear could be turned on the crank nonetheless. This happens 'cause the threading is smaller than the cylindrical crank stub and the nut can snug up to the shoulder on the crank. This is the case when the sum of the parts on the crank's stub: steel washer/balancer gear/steelwasher/primary gear/lockwasher are less than the space alloted. This was the case on my bike by a couple of thou: the gears could be turned on the stub while the nut was still tight. Manufacturing tolerances, but also the fact that the 3 steel washers are stampings of soft steel and are compressed when the nut is tightened. The package is then actually only held by the key; both primary gear and balancer gear can turn a bit, slapping against the key in its race. the balancer gear has a recoil spring assembly as hub, so it has quite a bit of backlash and this aggrevates the slapping so the the key itself gets compressed from both sides. When the play increases, the slapping increases, too, etc etc etc until the key is sheared off. This can happen to the balancer gear as well. I have a balancer gear here, which was about to go.
http://www.zabernet.de:16080/bill/temp/balancer_damage.JPG

this donated to my collection by another "victim."

b

[hb7]

I believe this engine was driven hard....That explains it....Bill, thank you.
I will post the pictures showing the large fracture around the balancer drive bearing....
Did you think adding another steel washer to take up more space between the gear and the large nut helps ?
Do you think the right side crankcase can be welded back or is it probably dimensionally compromised ?
Or do I have to find a new case for that side or both sides ? What else is probably damaged ?

I am tooling up for the repair and found various YAMAHA 660 crankshaft tools and prices here :
http://www.motorcyclecarbs.com/kl/catalog/2003/090.pdf

CRANKCASE SEP. CENTER POINT
35-8498
Price: $26.16

CRANKCASE SEPARATOR TOOL
35-9642
Price: $144.09

CRANKCASE SPLITTING TOOL
35-9638
Price: $105.45

CRANKSHAFT ADAPTER SET
35-8512
Price: $253.13

CRANKSHAFT INSTALLATION SET
35-8509
Price: $176.26

CRANKSHAFT INSTALLER ADAPTER
35-8510
Price: $52.08

[Bill Jurgenson]

Not too sure what hard riding has to do with it. Did I write that? My blue bike was probably one the hardest ridden Skorpions in the world.

neither here no there.

Adding a shim washer is what you need to do when the tolerance is overstepped. They can be had in thicknesses starting with 0,1mm upwards and of course various thicknesses.

You need the right half of the crankcase. Without seeing the damage, I cannot say if welding is an option. Basically, the case can be welded, however.
Crank is of course damaged. Will need a new main journal and bearings, tho the conrod should probably be OK. Again, without seeing it, I can't say much. With my engine, the crank was pressed apart and rebuilt with a new main and bearings, retaining the original conrod. Piston and top bearing were not damaged and are still OK after over 80000km.
The case was not cracked, however.
What else?: balancer shaft, right bearing of same. Has the transmission mainshaft been damaged. i.e. does the clutch basket wobble when the shaft is turned?

I don't have any of the tools listed, never needed them, either. You absolutely do need a crank end protrector,tho, when removing the flywheel and a really good wheel puller specifically for THAT job.

You'll have to dismantle the thing to ascertain what is needed. It could rapidly become more expensive than another used motor.

[hb7]

I will put some pictures ASAP....Used 660 motors are not common over here.
I appreciate the advice. What did you use for a crankshaft protector ?

XT 600 crankcase assy # 3DS-15100-00 95mm x 84mm bore x stroke
XTZ660 crankcase assy # 3YF-15100-00 100mm x 84mm

Are these the same ? If you know...

[hb7]

Yes, balancer woodruff key is at 4 o'clock and the slot where it belongs is at 12 o'clock.
Balancer bearing behind it broken through the case.

http://home.roadrunner.com/~hb7/images/mz%20case.JPG

[Bill Jurgenson]

yup
Pretty out of focus but I think I can see what you are describing.
usually is one of the two keys. 20¢ part that causes hundreds of $ of trouble. Of course, it isn't the key that is at fault...
And then there are those actually marketing hardened woodruff keys that can't be sheared off. As if that was the answer.
If you look at the photo I posted yesterday, you can see that the key is plenty hard enuf as it is.
This is the correct crankcase:

XTZ660 crankcase assy # 3YF-15100-00 100mm x 84mm

The other does not fit.

The protector is just a cup turned from a piece of steel rod, drilled out to pass over the threading and reach to just short of the shoulder, outside diameter slightly smaller than the crank itself behind the threading - the part must pass thru the flywheel - and with a center for the wheel puller on the end.

I'll make a photo or two an take the exact measurements this morning; it is so long since I made it I don't remember. Once you have removed the nut from the flywheel end, you can take your own measurements, of course.

For the wheel puller, if you cannot borrow from your favorite shop, or do this:
in the flywheel you can see 6 holes for 8mm screws, three with the bolts holding the freewheel to the flywheel, and three that are threaded.
Measure this pattern, i.e. the diameter of this circle. Take a cut of of round steel as large as the flywheel at least 1/2" thick, mark the center and then scribe that measured diameter around that center, using the radius to construct the hexagon the way you learned in junior high. Center punch those three holes and the center and drill those three holes slightly larger than 8mm. Drill and tap the center to accept a large diameter with fine thread. NF or metric fine, it doesn't matter; tap to fit the bolt available, but it should be at least 1/2". The easiest way is to buy one such as this M16x1,5 (I use one like this)
http://www.sportingforless.com/flywheel-puller-kawasak-yamaha-xj650-suzuki-gs550-p-120.html?cPath=43
or cop the bolt from another wheel puller. This job is beyond the means of most household shops, but it should be easily possible to find a machinist to do it.
el cheapo wheel pullers are not up to the job, believe me, and top-quality pro tools or OEM Yamaha tools are very expensive. I have seen my share of bent and twisted one-size-fits-all wheel pullers - that f---in flywheel still wouldn't budge.
I'll come back to this thread later...

[Bill Jurgenson]

yup
Pretty out of focus but I think I can see what you are describing.
usually is one of the two keys. 20¢ part that causes hundreds of $ of trouble. Of course, it isn't the key that is at fault...
And then there are those actually marketing hardened woodruff keys that can't be sheared off. As if that was the answer.
If you look at the photo I posted yesterday, you can see that the key is plenty hard enuf as it is.
This is the correct crankcase:

XTZ660 crankcase assy # 3YF-15100-00 100mm x 84mm

The other does not fit.

The protector is just a cup turned from a piece of steel rod, drilled out to pass over the threading and reach to just short of the shoulder, outside diameter slightly smaller than the crank itself behind the threading - the part must pass thru the flywheel - and with a center for the wheel puller on the end.

I'll make a photo or two an take the exact measurements this morning; it is so long since I made it I don't remember. Once you have removed the nut from the flywheel end, you can take your own measurements, of course.

For the wheel puller, if you cannot borrow from your favorite shop, or do this:
in the flywheel you can see 6 holes for 8mm screws, three with the bolts holding the freewheel to the flywheel, and three that are threaded.
Measure this pattern, i.e. the diameter of this circle. Take a cut of of round steel as large as the flywheel at least 1/2" thick, mark the center and then scribe that measured diameter around that center, using the radius to construct the hexagon the way you learned in junior high. Center punch those three holes and the center and drill those three holes slightly larger than 8mm. Drill and tap the center to accept a large diameter with fine thread. NF or metric fine, it doesn't matter; tap to fit the bolt available, but it should be at least 1/2". The easiest way is to buy one such as this M16x1,5 (I use one like this)
http://www.sportingforless.com/flywheel-puller-kawasak-yamaha-xj650-suzuki-gs550-p-120.html?cPath=43
or cop the bolt from another wheel puller. This job is beyond the means of most household shops, but it should be easily possible to find a machinist to do it.
el cheapo wheel pullers are not up to the job, believe me, and top-quality pro tools or OEM Yamaha tools are very expensive. I have seen my share of bent and twisted one-size-fits-all wheel pullers - that f---in flywheel still wouldn't budge.
I'll come back to this thread later...

[Bill Jurgenson]

yup
Pretty out of focus but I think I can see what you are describing.
usually is one of the two keys. 20¢ part that causes hundreds of $ of trouble. Of course, it isn't the key that is at fault...
And then there are those actually marketing hardened woodruff keys that can't be sheared off. As if that was the answer.
If you look at the photo I posted yesterday, you can see that the key is plenty hard enuf as it is.
This is the correct crankcase:

XTZ660 crankcase assy # 3YF-15100-00 100mm x 84mm

The other does not fit.

The protector is just a cup turned from a piece of steel rod, drilled out to pass over the threading and reach to just short of the shoulder, outside diameter slightly smaller than the crank itself behind the threading - the part must pass thru the flywheel - and with a center for the wheel puller on the end.

I'll make a photo or two an take the exact measurements this morning; it is so long since I made it I don't remember. Once you have removed the nut from the flywheel end, you can take your own measurements, of course.

For the wheel puller, if you cannot borrow from your favorite shop, or do this:
in the flywheel you can see 6 holes for 8mm screws, three with the bolts holding the freewheel to the flywheel, and three that are threaded.
Measure this pattern, i.e. the diameter of this circle. Take a cut of of round steel as large as the flywheel at least 1/2" thick, mark the center and then scribe that measured diameter around that center, using the radius to construct the hexagon the way you learned in junior high. Center punch those three holes and the center and drill those three holes slightly larger than 8mm. Drill and tap the center to accept a large diameter with fine thread. NF or metric fine, it doesn't matter; tap to fit the bolt available, but it should be at least 1/2". The easiest way is to buy one such as this M16x1,5 (I use one like this)
http://www.sportingforless.com/flywheel-puller-kawasak-yamaha-xj650-suzuki-gs550-p-120.html?cPath=43
or cop the bolt from another wheel puller. This job is beyond the means of most household shops, but it should be easily possible to find a machinist to do it.
el cheapo wheel pullers are not up to the job, believe me, and top-quality pro tools or OEM Yamaha tools are very expensive. I have seen my share of bent and twisted one-size-fits-all wheel pullers - that f---in flywheel still wouldn't budge.
I'll come back to this thread later...

[hb7]

Sheared off the woodruff key...... Balancer Gear looks fine ! Keyway slightly damaged...
Used slap hammer gear puller to get it off. Here's better pictures....
Crack goes to base of the cylinder. Is it worth welding....? or trying ?
New case is about $500 USD....+ shipping.

http://home.roadrunner.com/~hb7/images/IMAG0089.JPG
http://home.roadrunner.com/~hb7/images/IMAG0090.JPG
http://home.roadrunner.com/~hb7/images/IMAG0092.JPG
http://home.roadrunner.com/~hb7/images/IMAG0097.JPG
http://home.roadrunner.com/~hb7/images/IMAG0098.JPG

When you say fly wheel puller : do mean this ? Scroll down....it's at the bottom.
http://www.raptorstarterclutch.com/index.htm

[Bill Jurgenson]

Yes, that sort of thing, altho I do not like the one-size-fits-all kind at all. It doesn't cost much, however, so it might be worth a try.

the protector for the crank is 29mm long, and 20mm Ø, drilled 14mmØ inside 23mm deep.

DSC_1615.JPG (56.33 KiB) Viewed 8001 times

DSC_1616.JPG (55.6 KiB) Viewed 8000 times

I have also attached a photo of my wheel puller. It is of highest grade aircraft aluminum and 30mm thick.

DSC_1614.JPG (65.86 KiB) Viewed 7996 times

Once to have the case apart, you can see how extensive the damage is. To weld what I can see, you'll need to steam clean the case side as it must be oil free to weld. If that is all there is to weld, it is worth the effort, but you'll also need someone to mill the bearing seat from the inside once it is welded. No big deal and it is not rocket science.
So once apart and clean check out both the welder and the machine shop for pricing - and competence.

b
b

[hb7]

Thanks for the tool pics and measurements. The flywheel puller I found for $54 is for Raptor specifically.
One further disassembly note : the retaining nut on the balancer gear 60Nm/80ft lbs and primary gear
120Nm /160ft lbs appeared to be significantly *under* torqued....

I appreciate the invaluable help and enthusiasm Bill.

[edec]

hb7 I might be able to help. I sent you a pm
Ed