Header construction question. Please help. Bad design?

[Snickare]

This is my first post here, but I've been lurking and soaking up info for a while now. I am in the midst of building up a great little brat style cafe racer from my CB750K it's a 1982 model. I'm putting a 900 cam in it, and a dynojet kit on the carbs with K&N pod filters...

In trying to get just the right exhaust, I found that a guy in SO CAL is making a nice looking header system. Carpy, or Steve Carpenter has sold me his header system for my DOHC, but here I am now on my second set of his pipes, and they seem to have a big leak in the middle of the collector. He's not being very friendly in working with me to get a set that does not leak... The collector seems to not be welded up in the center of the pipes...

Now, in doing more research I've come across other pipes that are much more expensive and made from SS and ceramic coated, but they all seem to be very expensive. But here's the kicker, those other pipes all have spring loaded unions at the collector. This means that they are not welded shut... isn't' that a pretty mean leak? Doesn't it create a soot leak there?

Does that decrease performance? Does it make for a bad exhaust leak noise like it does on cars?

If that's the case, could I or should I end up trying to weld the collector back together to get rid of the leak, or is it normal to have that leak? I don't have a mig welder myself, but I could cut the collector open at the back end of the union have a friend of mine weld the leak up and then reconnect the union with the remainder of the pipe... Is it even worth the effort? There isn't much else on the market for this bike that's not over $500.

Any info and input you guys could share with me would be greatly appreciated.

Thanks for the help.

 

[crazypj]

There shouldn't be a leak in the middle of collector, it wasn't made right if there is and needs fixing.
You shouldn't have to DIY it unless you bought a pipe kit to weld up
Sounds like they missed a bit during assembly?

 

[spotty]

usually sets of pipes that are slip/spring joined will have the (slightly larger) rear pipe slipping over the (slightly smaller) front one so that the gases are less likely to do a u-turn and flow back thru the gap, if they were the other way (rear pipe inside front one) then there would be more likelihood of gases naturally flowing thru the gap (does that make sense?)

also what happens in reality is that
A) the gap is so narrow it doesn't really make that much difference and
B) the gap fills up with carbon and seals itself up (as you'll find if you ever try to pull apart an old system)

it sounds like you've got bigger problems than that, it should be weldable from the outside but maybe you want to try brazing....try attaching a largish blob of braze near where you want to fill (but can't get to) and then heat the required area and the braze should run/bleed into the gap and fill it.....worth a try maybe

 

[Snickare]

Thank you. That's just what I was thinking of doing. I have discussed this option with a friend of mine who has a good collection of welding equipment. He suggested that we just use an oxy-acetylene torch and flow some braze into the small pin hole. This should close it up.

My only other worry here is the real attitude I seem to be getting from Carpy now. I really like the design of the pipe, and the fact that it's in the raw. But he is relentless with the 'send it back and f*@& off..' attitude.
Does anyone else know of some good exhausts out there for the DOHC CB750K?
I've heard really bad reviews of the MAC, and the CycleX. The others all seem to be running around twice as much as Carpy's after shipping and Tax. I'm really tempted to just keep the pipes and do the fix myself. Or go to my local muffler shop and get the guy there to weld me up a replica system like Carpy's.

What else is there that is worth the money? I'd really like to run the OEM flanges with the Heat syncs as well. Most of the systems I see have totally done away with that mounting style. SO much so that you can't even mod the pipe end as to use them. I was going to make new shims to mount Carpy's pipes using the OEM flanges.

 

[crazypj]

I though you had the 'square' (or diamond) piece in the center of 4 pipes missing?

 

[Snickare]

No turns out it's just bad welding. The guy is probably trying to save himself money by shorting Carpy on parts. He probably tried welding shut the diamond piece with fill welds, instead of adding in the diamond. Then just proceeded to do bad welds. I found the leak while washing the pipes before paint. Water was flowing out of a good 1/8" hole from the center of the collector.

 

[teazer]

Pictures would make this a whole lot easier....

 

[Rich Ard]

The others all seem to be running around twice as much as Carpy's after shipping and Tax.

There's a reason for that...he switched suppliers not that long ago because of terrible quality problems with the previous work, and I've not heard much positive about the newer stuff either.