Exhaust Seals

I installed my new set of after market exhaust header seals on my '81 XJ550; for about 30 miles it sounded as good as new ... then it sounded as it did with the old seals ...
I had taken off the header pipes to clean them, put the header pipes back on and the noise began; under acceleration it sounds as if the cam shafts are coming through any minute.
I ordered from chacal new seals; I installed the seals, hand tighted the bolts that hold the collars (didn't want to over tighten). Now every time the engine gets up to operating temerature under acceleration and some times under deccelaration the it sounds as if it didn't have any header pipes on.
Question: did I miss anything after installing the seals? what are some remedies other than putting new seals in?

Thank you all

8O

 

Did you inspect the headpipes for cracks when they were off? If you have the stock pipes they are double walled and do develop cracks in the inner tube. It makes a horrible buzzing of clanking sound, generally only after they are warmed up.

 

Thank you.
I'll have to take some time and redo the whole exhaust set up and look for and inspect for cracks

 

The seals are squash or crush gaskets. When torqued down they conform to the shape of the exhaust ports and header tubes. Hand tightening will give an initial seal, but with vibration and settling the pipes will become loose and will need re-torqued.

Anytime one installs parts, especially head/intake/exhaust, be it auto or motorcycle, the engine needs to be "run in" and then gone back over with a torque wrench and re-tighten all the fasteners. When I install new seals, I leave all the fasteners for the exhaust loose. I start with the ring clamps on the head tubes to head. Tighten them all finger tight while wiggling the tubes a bit. This gets them seated squarely with the head. Then with the torque wrench, I make 1/4 turns until I get them all torqued to spec. Then I move down to the tube to collector bolts and repeat. Then the collector to muffler crimp bolts, collector to block mounting bolt, then the muffler to footpeg mounting bolts.

I would check try this before getting new seals. My above process is for installing a completely disassembled exhaust. You do not need to loosen the collector to muffler clamps just to change the header seals, but you will need to loosen the head tube to collector bolts and make sure they move freely before before tightening the head tube to head nuts. The reason being, if the head tubes were in a bit of a bind and not seating squarely on the exhaust port when the collector crimp bolts were tightened, they they will hold the pipes in the off square position and will not seal well on the head. Then when the engine is ran, the exhaust gases will find the least point of resistance and burn out the seal making a leak.

 

You need to TORQUE them to spec; in stages as above.

If you don't have a torque wrench that has a low enough range to be accurate at 7.2 ft/lb; invest in one. You'll need it elsewhere on the bike. Once properly torqued, they shouldn't come loose.