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Howdy all,

Was going to start working on my 1973 cb350 again soon. A couple of years ago, I bought I really nice set of scrambler pipes (HM318's) from Carnivorous Chicken. The only thing wrong with them was the little drain tube on the right muffler was broke off. The hole is the size of the base of the tube and not rusting out, it just looks like a small outlet hole. The hole looks just like this one, sans rust:

Auto part Muffler Vehicle

My curiosity is this: will that affect back pressure/performance at all? I have a spare set of CL mufflers off my old bike, I could take a drain tube off and weld or braze it on. Wondering if I will have to I guess...
 

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There is a small amount of exhaust gas that comes out while running, doesn't affect anything. I used a short piece of SS tubing and had it welded on.
 

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You want a drain hole, so water gets out on a cold start. Without it, the exhausts will rust considerably faster... If I even install some aftermarket muffler, I always drill one on the bottom side. Also, sometimes it is good to drill one small hole on the top, on the end. The heated water evaporates and goes up, and on some muffler designs, it gets trapped in that area. I know the CB360 exhausts (and many others) have such a hole originally too.
 
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