Topic: Muffler Question...75 CB750F...

[weasel897]

I bought my bike back in March and it had a small hole in the muffler then.  Bike had just had a complete tune-up and was running really good. (Too good to believe)

I first noticed (about 1 month after purchase) that it was running rich and had black sooty plugs, but it still ran fine. 

Now the hole in the muffler is larger and the bike is not running so well.  It gives me the good ole running way too rich signs: hesitation at takeoff, black plugs after a few miles, smell of gas, random idle speeds, won't idle at low rpms, etc.

My question is, Can just the muffler cause this?-----or------Is it possible for it to start acting up after only a few hundred miles after a complete tune-up?

I've cleaned the carbs and made sure all the passages are clear.

As far as I know, everything is stock.  I do know it has 110 mains in it which are getting replaced as soon as they come in! It has new plugs, air filter, stock air filter box, stock exhaust (minus the growing hole)

Thanks in advance for any help!

Brian

[fatmatt650]

I replaced the muffler on 76 cb750f and it made a world of difference. I had no rust through, I thought I was just doing it for cosmetic reasons. It had been about 1500 miles since a tune-up so i figured that's why it was running like crap. Installed the muffler and it felt like a new bike. My set-up is also stock.

[weasel897]

I could see if the muffler had a restricted flow, but does it work the other way around?  Less pressure on the engine or something like that. 

I speak computer, not physics!

Brian