Super Jet Why/How do base gaskets fail.

[SXIPro]

Pulled my motor yesterday, destroying 3 motor mounts, but that's a story for another day. Went to leak down test the motor and could feel air coming out between the cylinders and the lower end right behind where the pulse fitting is. Looking at this, it appears I am missing about a 1" long chunk of base gasket in that spot. Gasket is 3 yrs old. How/why did this happen?

 

[snowxr]

Could be a few things. Loss of tension from loosened hardware would be my first choice. Could be that your cases are warped, too.

 

[RivMan]

I believe mine failed due to installation error. The thin part of the gasket was pushed into the crank area, and allowed air to leak there. The witness marks on the case and cylinder appear to show that it's been that way since installation.

-Rob

 

[Quinc]

Are you following your Super jet manual and re-torquing the bolts every 10hrs or whatever it is? Or at least the first couple rides after assembly.

I dont think anyone else does either.

 

[SXIPro]

I did that initially a couple times after I did the top end. I think this time I will follow Chuckie's torque specs instead of ADA's.

 

[txsuperjetfreak96]

Whats his torque specs


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[SXIPro]

Whats his torque specs


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He goes to 20 on the head bolts and 36 on the girdle nuts, as opposed to 18 and 23 per ADA's instructions.

 

[txsuperjetfreak96]

Awe ok thanks cpt chuck?


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[Quinc]

He goes to 20 on the head bolts and 36 on the girdle nuts, as opposed to 18 and 23 per ADA's instructions.

Why are ada torque numbers so low?

Manual has:
cylinder head 26
Cylinder Body: 29

 

[SXIPro]

Why are ada torque numbers so low?

Manual has:
cylinder head 26
Cylinder Body: 29

No idea. I've got the ADA Racing Yami 701/760 Billet Head Instructions right in front of me though. Maybe because it's an O Ring head versus a stock gasketed head? Honestly, I have no clue, but I'll trust Chuckie going forward.

 

[Quinc]

You would think at least the cylinders to cases would need to be at least 29lbs... I am going to redo mine to 34 now too. Thanks! =)

 

[augustaf]

These base gaskets fail sometimes. Ever notice that "print-o-seal" on oem gaskets? A/M gaskets don't have that, so a gasket adhesive like " High Tack" - Napa dealer maybe- would be indicated. Since noticing this issue, I've always used Cometic copper base gaskets- you can use them over and over by annealing them. A light coating of sealer applied to the copper helps. They don't "suck in" like paper.

 

[restosud]

ada studs are long and don't pinch the cylinder to the case like oem do.instead the ada setup pinches the cylinder between the head and cases and the head holes overhang the cylinder with not much support so ada lessened the torque setting to limit bending the head shell.

 

[Vumad]

Too much treble.