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Exhaust manifold crack

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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There is a small crack (about 1mm wide) in one of the 4-1 manifold pipes. It is right where the manifold connects to the engine and it's goes about halfway around the pipe.. I can actually see the engine firing through the crack.

Is there a way to repair this? All the 4-1s that I've seen cost around $250, and I can't afford that. The bike is still rideable, but I can't imagine that riding it in this condition is good. How do I repair it?
 
I would think someone with a MIG welder and some skill could weld it right up. I think you will have to grind the chrome off around the crack, though. You should definitely stop-drill the crack right away, or it will keep running until the dang thing falls apart.

A cheap and dirty thought: maybe a hose clamp with wood stove sealant putty under it? Nasty.
 
Metal fatigue caused by vibration.
I managed to carefully repair mine with the arc welder ( don't have a mig.) Built up a seam right the way round the end of the header and ground it flat afterwards. That was 3000 miles ago and it's still fine.
 
Be careful riding it that way. Check the plug color for that cylinder and make sure you're not running lean. I've been told to be wary of piston damage when running lean.

Just for kicks, take it to a muffler shop and see if they'd be willing to weld it up for you. You'll probably want to remove the header first, though.

Brad tt
 
I've got a friend who welds and he's gonna help me do it. We'll see if it works...
 
Have your friend be careful with the heat input while welding. if you put too much heat into the metal, it will warp, then you will have an alignment problem. I would have him weld it while it's on the bike if possible.

Make sure you dill the ends of the crack with a 1/8" drill bit to stop the crack from migrating any further.
 
Katamaniac said:
Make sure you dill the ends of the crack with a 1/8" drill bit to stop the crack from migrating any further.
Click to expand...

How do I do that? Should I drill beyond the two ends of the crack?
 
Drill just beyond the ends of the crack. Do not drill into the crack, that will cause more stress. The reason for that is the stresses will be absobed by the rooundness of the drilled hole. A crack will continue to propagate until it either runs into a stop point (round area) or completely breaks.
 
Well, just from sitting in my driveway, and despite drilling a 1/8" hole just beyond each end of the crack, I went out this morning to check out the bike and the crack is now completely around, separating the header pipe almost at its connection to the engine.

Is it still possible to weld it? Is there any other option short of buying a whole new 4-1? Is there any reason I shouldn't keep riding until I can get it fixed, considering the bike still runs well?
 
I bought a Supertrapp 4-1 header section only on e-bay for $64 shipped to my door.

Jethro just bought a whole new exhaust for $75 from another site.

Just FYI. I know about shortage of cash too. :?

If it broke all the way thru, alignment might become an issue. However, if your friend is very experienced, he should be able to do it.

Good Luck.
 
Are headers year/model specific? If not, I have no idea what to look for other than that I know it's a Vance and Hines 4-1.

My bike is a 1979 GS850G. What exhaust systems will work with that? I'll certainly check e-bay... That would be the ideal.
 
The cylinder spacing on your bike is the same for LOTS of models. GS750/850/1000/1100... the only fly in the ointment is how they fit as far as changing oil, etc. Denniskirk.com has a "scratch and dent" store. They don't have an 800 number and you have to get their Minnesota number from the denniskirk.com operator. They generally have LOTS of pipes for sale and generally about 1/3 what a new set would cost. Most of the time, these pipes are in "as new" condition... returns and take offs where the bike wasn't run. The folks who work in the store are real good about detailing any issues or defects so there should be no surprises.
 
Well, my friend welded it last night, and he did a great job. There wasn't enough metal left on the manifold to weld that, so he bent some steel around the crack and then welded that on. I can tell the difference in the idle and throttle response.

I'm still looking for a new exhaust system, but at least this solves the short-term problem. Thanks for your help, guys.
 
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