crankcase joint sealant recomendations

[lms6201]

 what,s good for yamaha case joints please ,the compound i have been using musn,t be as good as i thought, also has anyone experienced an out of alignment crank or had one bend somehow ? i haven,t put the dial on it yet but am getting some massive shaking   

[mx250]

Yamabond.

Although I can't see how it would lead to out-of-alignment .

[Marc.com]

Yamabond

even other makers use it, Japan has some very good jointing compounds made by a company called 3 Bond, Yamabond is one of them.

I doubt you could misalign the cases with the jointing compound unless you were using something really thick and lots of it.

[Lozza]

Yamabond and Threebond are the same substance, but strangely the yamaha branded box is more expensive Crank issues are worthy of another 4 page thread.

[zorroz]

Loctite 515 is great stuff too.

[evo550]

Ims,
Although I'm no crank expert here are a couple of possible prob's to the vibrations. I'm assuming it's a fresh rebuilt crank,

Reassembled not balanced.

Reassembled balanced, but if crank halves pin holes worn, pin is allowed to move putting crank out of balance (Have heard a backfire or Kick back could do this) Should require approx 20 tons pressure to press pin in.

Crank bearings worn, if new, housing in cases worn allowing crank and bearing to move up/down.

engine mounts loose.

Clutch shaft bearing could be worn. Would be a "Low Pitch" vibration as it's rotating slower than crank.

Guess what, you have to split the cases tyo check all but one of these.

Over to the crank EXPERTS.

[Lozza]

Alignment and balance are separate issues, but I suspect evo's suggestion of loose engine ounts to be the more likely cause of vibrations.

[magoo]

Have you tried using a gasket?

[holeshot buddy]

come on magoo its not a red bike
yamaha dont use a centre gasket
threebond i find is the best

[lms6201]

ok fella,s thanks , 3 bond it is (same as yamabond ) there,s two seperate issues thank,s marc , it has had a massive backfire , it is an original crankshaft , splitting cases is the whole idea of wanting to find the best sealant ,on closer inspection with the engine out , turning the shaft with the rod i,m seeing run out on the flywheel ,sometime in the last 29 years  the flywheel may have needed a big hit on the end of the puller to remove it from the shaft , will set  it between crs and  put the dial on it , i have got some cranks with bad bigends  but may be able to salvage the half needed perhaps ?

[gorby]

would not advise to trust centre to centre as most cranks have had the threaded end on the flywheel side
bent out of shape by rough handling or removal.
better to check on v blocks as far out on the crank as possible.

[lms6201]

i don,t have  v blocks , what about a 3 point steady ? should achieve the same thing ?

[Lozza]

I do all my cranks between centres, all you need to do is check each half separately between centres(the web will normaly have a centre from the original machining).That will tell you if the (usually the one) threaded end on the crank taper is bent. Remember to ALWAYS use a dead centre never a live centre.

[torm92]

Yes Lozza, between 2 dead centres is the most accurate. I usually have a turned centre in  the chuck and move it around until the very start of the rotor taper runs true.Then check the primary drive journal runs true at the tailstock end .Then see how the webs are going.
Thank gawd motorcrossers are single crank as twins are a bit more complicated , lol.

[brent j]

I’ve taken to setting my cranks up in a lathe with a large and very heavy 4 jaw chuck. Like Lozza says you should check both sides before you start.
I generally hold the primary drive side (using copper pads) and true that side with a dial gauge. The lathe I use has bushes in the head stock rather than bearings and I can tap the ignition side around to suit. I clock on the od and face of both crank halves and both bearing surfaces.
I agree with Gorby about damage to the crank ends, especially as some of the things we fix have had 30 or so years of abuse

If there’s less than 0.001” total run-out (0.0005” misalignment) I’m happy

Brent