Exhaust collector leak

[Formula51]

Took my exhaust off to repaint. Reinstalled with new gaskets and locking nuts but still sounds like I have an exhaust leak. Any tricks to getting them to seal?

[CutterBill]

You didn't give us much information...

Where is it leaking: head, collector or mufflers? Stock exhaust or after-market? Did you get all of the old gasket out of the heads? New gaskets and seals everywhere? Did you wire-brush and scotchbright all of the sealing surfaces squeaky clean? Did you coat the slip joints with Permatex high-temp anti-seize?  Are all of the clamps and clamp bolts clean and tight?  You used the anti-seize on all of the nuts and bolts, yes?

Take photos so that we may judge the quality of your workmanship, Newbie.  Yes, this is a tough crowd.     Report back...
Bill

[PaulG]

Take a close look at the collector as you can start to get pin holes or cracks that will coalesce into larger holes due to corrosion. The collector is also a condensation sink as it is the low point in the exhaust system. It's lifespan can depend on your local climate, storage, riding frequency, and if you have a belly pan.  Humid conditions and infrequent use is a worst case scenario.

The metal at the gasket surfaces is already pretty thin. My original box developed holes at the transition point after the gaskets into the box.  I was able to purchase another OEM box from another member. I still have it and am thinking of trying to seal it just to see if something works. Just haven't bothered to investigate what product to use yet.

If you end up needing a replacement I have a few OEM ones that are still useable. Or you can go all out for a SS one from Delkvic.

[Formula51]

You didn't give us much information...

Where is it leaking: head, collector or mufflers? Stock exhaust or after-market? Did you get all of the old gasket out of the heads? New gaskets and seals everywhere? Did you wire-brush and scotchbright all of the sealing surfaces squeaky clean? Did you coat the slip joints with Permatex high-temp anti-seize?  Are all of the clamps and clamp bolts clean and tight?  You used the anti-seize on all of the nuts and bolts, yes?

Take photos so that we may judge the quality of your workmanship, Newbie.  Yes, this is a tough crowd.     Report back...
Bill

320 grit paper on head and face of collectors, squeaky clean. The leak is at the collector to head on drivers side, can't say exactly which pipe.

It is a Kerker exhaust. The previous owner had used some high temp silicone on the collector gaskets, which I assumed was a no no, but thought I would ask. I put the new gaskets in dry.

I might be a newbie to motorcycles, but I have been turning a wrench a long time

[rlucas]

Take photos so that we may judge the quality of your workmanship, Newbie.  Yes, this is a tough crowd.     Report back...
Bill

I might be a newbie to motorcycles, but I have been turning a wrench a long time

Doesn't matter. We'll be judgemental anyway. 

rossi

[racerrad8]

Some aftermarket pipes do not fit into the head very well. There is also a shoulder in the cast of the head. If the header pipe catches on the shoulder it will tighten up, but you will have an exhaust leak.

I'm away from the shop today to take a photo of the shoulder.

Randy - RPM

[CutterBill]

... The leak is at the collector to head on drivers side, can't say exactly which pipe....
The previous owner had used some high temp silicone...

The 4 Down Tubes (or Exhaust Pipes) run from the head down to the Collector.   The Collector is the box under the engine that "collects" the exhaust gases from the 4 pipes and distributes them to the 2 mufflers.  Got it, Newbie?   
As Randy said, you may have caught one of the exhaust pipes on the shoulder in the exhaust port.  Or maybe an exhaust gasket slipped out of place; you can glue them in place with the aforementioned anti-seize.  Or it could be that you have a crap exhaust system where the ends of the pipes (where they go into the head) are not flat and square.

Silicone seal, whether hi-temp or not, is always a bad idea.  Yes, it does work but only long enough to sell the bike to the next Newbie.

Attach photos, so that you may be scolded or praised.  Depending....
Bill

[Formula51]

Even though I apparently misspoke, your expert brain should have put two and two together when I said new gaskets and locking nuts.

Anyhow, I was curious if there was any particular torque sequence or something similar that I may not have known. No worries.

[CutterBill]

Even though I apparently misspoke, your expert brain should have put two and two together when I said new gaskets and locking nuts.

I'm an engineer.  I don't assume anything.     And realize that it's always fun to beat up on the new kid in town.  In our own perverse way, we are actually trying to help you.

Now post some pics of your bike, ya newbie...
Bill

[Pat Conlon]

I was curious if there was any particular torque sequence or something similar that I may not have known. No worries.

I had a Kroaker 4 into 1 header on my previous '92 and I had that header off many times thru the years.
A couple of things I noticed:
1) when tightening the lock nuts, count the exposed threads on the head studs. Try to get all of them the same, or very close.
2) after the initial tightening and a day ride, plan on resnuging the lock nuts.
3) the collar flange on the header tubes worked fine however the plates which hold the flange against the gaskets can bend if tightened unevenly.

Hope this helps. Pat

[ribbert]

Anyhow, I was curious if there was any particular torque sequence or something similar that I may not have known. No worries.

You are on the right track, there is definitely an order for fitting engine pipes.

Loose fit the engine pipes with the nuts and bolts but don't tighten them up. If properly engaged into the collector, they should be sitting on or just off the head and a slight push with your hand will feel them seat. If they are not snug against the seat at this point, knock them into the collector until they are.

Give everything a bit of thump with your hand (or rubber mallet if your a surgeon) to take any strain off the joints, hit each engine pipe with your hand and the sound of them hitting the seat should all be the same and visually they should all line up perfectly.

Now the important part, tighten the flanges up first, alternating sides half a turn at a time once you feel the nuts taking up, this drawers them in evenly. Your engine pipes are now seated tightly with perfect alignment without any pulling or tugging from other components.

Now tighten the collector collars. Alignment on the slip joints on the collector are not as critical as where the pipes seat against the head and will accommodate the pipes at whatever angle they are at.

The golden rule for fitting any parts to an engine is to offer it up by hand first, if it doesn't go all the way home, you have a problem, remove it and find out why. NEVER EVER pull any part in with nuts and bolts if you can't seat it fully by hand.

The easiest way to get those gaskets to stay in there is to squash them slightly out of round (and I mean slightly) until they are a push fit.

Eyeballing (or counting) protruding threads is not reliable, particularly on old engines, there is no guarantee the studs are all engaged to an identical depth, feel is a far better gauge.

Engine pipes that are under strain can leak, cause vibration, crack at the flange or strip threads. The same applies to the entire exhaust to a lesser extent. A well fitting system should have everything perfectly lined up before you bolt it up.

As Pat said, tighten them up after a couple of rides.

IMO

Noel

[X-Ray]

Lol, gees you guys crack me up

[Formula51]

Even though I apparently misspoke, your expert brain should have put two and two together when I said new gaskets and locking nuts.

I'm an engineer.  I don't assume anything.    And realize that it's always fun to beat up on the new kid in town.  In our own perverse way, we are actually trying to help you.

Now post some pics of your bike, ya newbie...
Bill

BS, we assume all the time, we just list them to cover our arse.  MS in ME here.  You know pesky little things like exhaust leaks drive us anal engineers nuts!

Pics here: http://www.fjowners.com/index.php?topic=16354.0

[Country Joe]

Oh no......Two engineers in one thread. Nothing good will ever come of this

[CutterBill]

BS, we assume all the time, we just list them to cover our arse.  MS in ME here.  You know pesky little things like exhaust leaks drive us anal engineers nuts!

Pics here: http://www.fjowners.com/index.php?topic=16354.0

Very nice ambulance, ya got there.  Very nice indeed.  You will have many happy rides on that bike.

Just a lowly BSME here, but I've been lucky enough to do some cool stuff.  I helped test the radar altimeter for the Curiosity Rover (Mars) back when I worked at NASA.  Fun times...
Bill