Bubble test

[jerryd]

I am going to bubble test the manifold again. If bubbles show should i loosen the clamp the n retighten? Is there any advantage to putting a little light oil on the o ring or keep it dry?
Thanks
jerry

[awander]

Couldn't hurt to loosen it first-but do whatever works!

I don't think the oil would do any good, but again, if it works-go for it!

Best solution I ever found was the oversize O rings I use.

[awander]

And whatever you do, use Viton (FKM) O-rings, so once you get it sealed, it stays sealed.

[Excalibur]

Only tighten the clamps until bubbles stop, then perhaps very slightly more. This stops the o-ring being forced through any gap plus doesn't overstress the seal. Seems to work.

[Mongrel505558]

Make sure the manifold and heads are aligned. The time to do that really is when you're putting the heads back on. Leave the head bolts loose and turn the heads so the intake ports are parallel with the manifold. Have the manifold on its mounting bracket (i.e., where it will be when everything is together). Clamp the manifold and even bubble test then before tightening the head bolts if you want. It's a lot easier to get it all to seal this way. If you have done this the last time the top end was reassembled the alignment should still be good even if you've removed the manifold.

[jerryd]

Thanks for the advice. The cylinders and heads went on before I had the bike and I hesitate to disturb them because the joints are dry. I did notice four years ago when the present orings went on the alignment was slightly off. Having inconsistent starts so checking that first.
jerry

[Mongrel505558]

Thanks for the advice. The cylinders and heads went on before I had the bike and I hesitate to disturb them because the joints are dry. I did notice four years ago when the present orings went on the alignment was slightly off. Having inconsistent starts so checking that first.
jerry

You can only get a little wiggle room with the heads - just the head bolt clearance. The large O-rings as mentioned above do the job - I have them on my pan. They are BIG. I can't get the clamps to contact the manifold evenly with them in there. I have V-Twin head on the motor right now and the gaps between the head ports and the manifold are pretty large. These o-rings easily took care of that problem.