Manifold and exhaust question from a Newbie

[newfiedoo]

Hi all. Really enjoying this site. Great to be on here. A couple questions from a new owner of a 1999 Speedster SK.

Shortly after buying I noticed one of the inside bolts on the exhaust manifold was loose. I've tightened it, and after one ride it came loose again. Would this produce any symptoms in the running of the engine? I've also noticed that on the other manifold, there is a stud with a nut, instead of a bolt. What's the reason for the stud, and should I order one for the side that now has a bolt?

Second, I noticed one of the hose clamps fastening the sealing ring between the exhaust cone and the pipe was missing. I've replaced it, but noticed today on my maiden voyage that the engine didn't seem to accelerate smoothly. Is that consistent with a leak around that sealing ring.

Many thanks for your help!

 

[Sportster-2001-951C-Stock]

In all my years of wrenching I've learned a stud and nut system as opposed to a bolt is usually superior. Can't say that's true 100% for your particular instance, b/c I'm not familiar with the circumstances of your particular struggle.

A few ideas/comments:

Spring washers really are only intended to be used once, may as well replace all those exhaust manifold fasteners once they've been removed, also lock-tite is spec'd for the threads, no? Fasteners stretch when torqued, critical applications such as exhaust manifolds most often perform much better when replaced.

Not only is Lock-tight often spec'd, there are torque specs as well on those, too tight and the manifolds may warp or crack, too lose they may leak? Probably should use new gaskets as well, and clean the mating surfaces thoroughly.

I think I would reference the BRP shop manual procedures and attempt to duplicate those assembly instructions. The shop manuals are a "must-have" and generally easily obtainable, IMO

 

[newfiedoo]

Thanks! Anyone know why BRP used the stud and nut on 1 out of 4 manifold bolts?

 

[Sportster-2001-951C-Stock]

Thanks! Anyone know why BRP used the stud and nut on 1 out of 4 manifold bolts?

I would bet someone has disassembled the one manifold and during reassembly, used the nut/stud system, which is my personal preference, but most likely not a factory original piece.

These manifolds are notoriously hard to reseal if not done to the letter of the assembly procedure. I have used the nut and stud approach many times on many applications and have always experienced excellent results, I have never tried it on a seadoo manifold.

Well, if BRP did use the nut and stud, then I applaud the decision.

And if you have leaks around there, your hull can fill with carbon monoxide and starve your engine's oxygen source, or water can spray out from the sealing area and be ingested into the engine intake, causing problems with the combustion process. Also, perhaps it's possible for water to run down into your cylinder while the engine is shut down, but that doesn't seem to occur very often on these seadoos.

 

[Coastiejoe]

Thanks! Anyone know why BRP used the stud and nut on 1 out of 4 manifold bolts?

In many cases a stud/nut setup is used to aid in assembly. Once you have one on, it is just a matter of twisting to get the rest. It allows for installing it even when you can see the holes.

 

[Coastiejoe]

Sportster,,

It would seem you are a faster pecker than me...

 

[newfiedoo]

Ah, that's helpful. I see in the parts diagrams that 1 out of 4 fasteners for each manifold was the stud and nut. Mine has it on one side but not the other. Just wanted to be sure that I didn't need to replace the bolt that is currently serving its purpose very well.

 

[Sportster-2001-951C-Stock]

Well, sealing those manifolds properly so they don't leak at high throttle loads can be challenging, so it's a good idea to replace the hardware and gaskets, and I would say, at least the spring washers. The correct Loc-tite, the specified torque, and the whole nine yards.

 

[Sportster-2001-951C-Stock]

Sportster,,

It would seem you are a faster pecker than me...

Ha, just trying to help someone achieve something b/c I think I can.

 

[newfiedoo]

Will do. Also took me several tries to get the hose clamp on the sealing ring btwn the pipe and the exhaust cone to seat properly. When it comes loose the engine runs like crap. But, strangely to me, neither engine works properly when it lets go. They'll both fall to around 4000 rpm max. I can understand this affecting one, but can't figure out why it happened to both. Are they synced in any way?

 

[racerxxx]

On the 717's (720's) You have to make sure the lower pipe mount is securely fastened to the side of the engine. Verify the rubber grommets, washers and spacers are ALL there. If that lower pipe mount has movement it will put undo stress on the upper 4 manifold screws/stud. The one is supposed to be a stud and the rest are screws.

The following is my repair of my 720 manifold on my HX, someone cobbled up studs in all 4 locations. They were not even metric threads! If you want it to last and not come back and haunt you you need to do a solid repair. Most guys will tell you to replace the manifold with a good used one--do what you like, mine is just as strong as a new or used one and a ton less work. It also helps if you're confident in hand drilling and tapping, it's part of my daily job so it's second nature to me.

http://www.seadooforum.com/showthre...eliCoil&highlight=720+exhaust+manifold+repair

 

[Sportster-2001-951C-Stock]

Will do. Also took me several tries to get the hose clamp on the sealing ring btwn the pipe and the exhaust cone to seat properly. When it comes loose the engine runs like crap. But, strangely to me, neither engine works properly when it lets go. They'll both fall to around 4000 rpm max. I can understand this affecting one, but can't figure out why it happened to both. Are they synced in any way?

They're both breathing the same air source, see post #4 of your thread.

 

[Coastiejoe]

Ha, just trying to help someone achieve something b/c I think I can.

By all means, peck away.. LOL

 

[newfiedoo]

On the 717's (720's) You have to make sure the lower pipe mount is securely fastened to the side of the engine. Verify the rubber grommets, washers and spacers are ALL there. If that lower pipe mount has movement it will put undo stress on the upper 4 manifold screws/stud. The one is supposed to be a stud and the rest are screws.

The following is my repair of my 720 manifold on my HX, someone cobbled up studs in all 4 locations. They were not even metric threads! If you want it to last and not come back and haunt you you need to do a solid repair. Most guys will tell you to replace the manifold with a good used one--do what you like, mine is just as strong as a new or used one and a ton less work. It also helps if you're confident in hand drilling and tapping, it's part of my daily job so it's second nature to me.

http://www.seadooforum.com/showthre...eliCoil&highlight=720+exhaust+manifold+repair

Excellent. Very helpful!

 

[martin18152]

I just installed my exhaust header, and used high temp sealer on both end, its been good for about 10 hours. If they did not have that stud and bolt, I'm not sure how you would get a wrench in there.

Just a word of warning, the reason I had to remove my header is that it sprung a leak. The exhaust header, or tuned pipe as its called, is water cooled, so it is double walled, there is a welded plug on the bottom side, its probably left over from the casting process, you cannot see it, but you can feel it. Its notorious for corroding through, and filling you bilge full of water, your bilge pump can barely keep up with it. I had mine repaired, then replaced it. I can feel the other header plug going also, probably pull the header and have it repaired before it goes. Your may have already been repaired.