Topic: CB750 Exhaust Removal

[Weatherman]

Hello everyone,

I just received a new set of HM341's for my '74 CB750 today. I began the process of removing the existing exhaust (original downpipes with slip-on mufflers) and the downpipes will not come off of the flanges....will not budge. I tried banging on them with a hammer and block of wood, prying with a broomhandle, and even tapping on the pipes where they fit over the flanges with a ball peen hammer. No luck. It is as though they are welded on. 

Does anyone with experience in this procedure have any tips? I thought about trying to remove the flat head screws and pulling the flanges off with them. Don't know if they would come off any easier.

Thanks,
Dennis

[Patrick]

When I took off my ancient exhaust last year I pulled the flanges off with the pipes. It was eaier to separate the flanges from the pipes when they were off the bike. You can soak the joint between the flange and the pipe with separating oil and get a much better angle for rapping them off with a rubber hammer. It's really fun.

[turtle]

I had this problem with the CX. My better half eventually got the header out of the collector box but the header (which was pretty much toast anyway) was fairly well destroyed. Someone has suggested using heat (oxy gun). Haven't tried it but it could work.

[mbrock307]

In my experience (diesel mechanic)....when u have metal rusted to metal, heat is best

[jsaab2748]

Judicious use of heat is the way to go Those phillips head screws for the flanges are usually
stuck in the head and must be destroyed in a lot of cases. Penatrating oil overnight might work
as well. One last thing might to be to saw the headpipes off to a point where they're short
enough to be able to "twist" them back and forth. A good way to keep the new ones from
becoming discolored is make sure your engine is in reasonably good tune, and running in
its proper mixture range. If your bike is all stock, as an obvious side benefit, it'll run it's best that way too    Now if someone could just find a way to keep chain lube off tne inside of #2 muffler...

[don76]

I don't know about anyone else, but when I had to remove mine, someone had riveted the header pipes to the flanges.  I just took the smallest bit I could and drilled out the rivets.  I left the flanges right on the bike.  As soon as I drilled them out, the headers came right off.  Good luck
Don

[Weatherman]

Thanks for the tips. I would feel much more comfortable applying heat to them off of the bike. Typically will the flanges come out out of the heads easily one the screws are removed? Would using an impact screwdriver on the mounting screws be dangerous?

Thanks,
Dennis

[jaknight]

Weatherman,

     I would try several night/day cycles of penetrating fluid before trying other methods.

     If after the fluid liquid wrench (or whatever, I have heard that brake fluid is a very good penetrant)  night/day cycles and they will not loosen, then I would try a very judicious use of heat from a butane/propane torch with perhaps the use of an impact wrench.  Possible use of a rubber/plastic hammer or a good dead blow hammer that is rubber coated might be in order.

     I wish you good fortune and freedom from any mishaps........

     ~ ~ ~ jaknight ~ ~ ~