[jakedearborn]

I'm new to bike maintenance and riding in general. I got my license this summer, bought a 1981 CM400E and took it on a 5000 mile trip around the country from Vermont and eventually landed in the bay area where I've settled for now. My interest in the motorsport has taken off rather quickly as you can probably tell. Since the bike is relatively easy to work on I've been trying to learn as much as I can and keep it running right until I'm ready to invest in another bike.

Thus far I've done carburetor and clutch rebuilds, a bit of wiring and other little things and gasket replacements. I've got two manuals for the bike and I've unfortunately recently made the stupid mistake of cracking the lower crankcase by over-tightening the oil drain nut. I've got a temporary fix for now (jb weld), but I've found a new engine bottom block and I'm preparing to start the rebuild this saturday. I've been using a penetrant to get my 30+ year old exhaust system ready for removal and I've noticed a small hole on the narrow end of each muffler near where they meet the common collector.

I intend to try to fix or replace the holes on the cheap and I'm wondering what my options are. I imagine there's probably quite a few aftermarket mufflers I could install or maybe some of the same mufflers on ebay. However this may be an opportunity to find something a bit lighter and shed some pounds. I'm wondering if there's a particular size I should be looking for or if I'll need something designed specifically for my bike? Also where to look and how much to expect to pay? Anyone have bright ideas on where to start?

 

[longdistancerider]

Welcome aboard. Which Bay Area are you referring to? San Francisco, San Diego, etc?
The only correct manual to use on these is the Honda FSM, PM sent about that.
The 2 small holes in the mufflers may be the normal drain holes, should be @1/8-3/16" at the lowest point on the bottom.
Mufflers? there are so many options out there for you. David Silver Spares does sell the originals. Any aftermarket muffler you buy will need the support bracket fabricated, easy to do with flat bar stock from a hardware store. The inlet ID is 1.5". I recommend using ones the have an internal volume of 2 liters or more for noise control. That will also allow you to not need to rejet the carbs. DSS also sells a 2-1 system that is for the CB400/250 but it does require some work to get the fit right. MAC makes 2-2 and 2-1 systems, I'm not a fan of those though.

 

[jakedearborn]

Thanks, I'm in San Francisco, seems like these holes are probably just the drain holes you talked about (phew...relief) so I'll probably hold off on getting new mufflers until after I've swapped the lower crankcase for the new one. Going to be quite the learning experience, I'm hoping I don't break anything in the process... I'm told I should be cautious when I disassemble the exhaust headers for fear of breaking the studs which connect them to engine head? I haven't been able to find a note about this in any of the manuals I've flipped through anyone know more specifically what I should watch out for?

 

[longdistancerider]

They sometimes break. Tighten them first to break them loose per se, then start loosening. If they bind/stick tighten and loosen repeatedly and they should come off clean.