Topic: Help! Loss of power, exhaust is much louder, and noticed a gas leak after riding

[wildkarrde]

Hey guys,

I have a '77 CB550, and noticed a little problem when riding last week. I specifically remember a clunking sound coming from the left side of the bike, stopped to check it out, but couldn't find anything noticeable. I rode it home fine with no problems, and chalked it up as me just hearing things.

The next day I rode it for about 30 minutes, and I was noticing the exhaust seemed significantly louder at higher rpms and it also felt like it was lacking power. I originally suspected an exhaust leak, but after parking it and coming back about 2-3 hours later, I noticed a huge puddle of gas that originated from the overflow tube.

I'm not a mechanic by any means, but looking around it seems like this could be a stuck float? It seems like the leaking gas would make it seem that way, but does it make sense with the lack of power and louder exhaust as well?

[eigenvector]

It's all relative of course, but yeah a stuck float can screw with the power. 

The gas puddle would be the first clue.  As long as it isn't a habit, I wouldn't worry about it too much.  If it's something that is happening all the time now - then it's time to worry.  Make sure you have clean gas.  I find a lot of problems I have with my bike start with crummy gas - water, debris, stuff like that.

[Dunk]

Puddle of gas is likely stuck float running out the overflow tube. Could hurt power a bit from running rich or fouling a plug, would not make it louder just a bit eye burning maybe. Down on power and louder could be retarded timing. Engines get louder with retarded timing as the gas can still be combusting on the way out. Check timing and that it is advancing properly.

For leaky needle and seats pull the bowls and inspect or spray clean, check float height. Quick and dirty in a pinch pull the hose off the tank and put a can of carb clean in the hose, pinch hose tight around it, and spray a bit. Can dislodge and solve it if it's just one tiny grain of schmutz.

[wildkarrde]

It's all relative of course, but yeah a stuck float can screw with the power. 

The gas puddle would be the first clue.  As long as it isn't a habit, I wouldn't worry about it too much.  If it's something that is happening all the time now - then it's time to worry.  Make sure you have clean gas.  I find a lot of problems I have with my bike start with crummy gas - water, debris, stuff like that.

I'm just about to go to where I store the bike, I'll start it up and take it for a spin to see if the problem is still there. The exhaust is really loud, which is my primary concern at this point. Maybe I'll take a quick video as well.

[eigenvector]

If it's REALLY loud, then it's probably a loose exhaust header.  That would be pretty easy to suss out.  Of course you could have just blown a baffle, but it would be easy to check the exhaust connection.  Maybe the nuts vibrated loose on a cylinder or 2?  But I would think that a loose exhaust header would be loud all the time, not just at certain RPMs.

[Retro Rocket]

If you heard a noise then it got loud, check that you still have a baffle, wouldn't be the first one that went AWOL...

[ekpent]

If a bike is just running on three cylinders it will change the tone of the exhaust but not necessarily make it louder.  But you did mention its down on power so check the header temps on all 4 header pipes when you start it next paying especially good attention to the one with the leaking carb. A wet rag should give a nice hot sizzle on all four.

[cougar]

wildkarrde ; You mentioned gas coming out the overflow. Check your oil. A stuck float Can allow enough gas into the carb (depending on flow and angle) to also allow some of the extra gas to flow into the cylinder ! Not good, washing oil off cyl. walls and thinning your oil as well. Check your oil and make sure it doesn't have an gassy smell, you don't want gas-thinned oil in your motor when running or when sitting over the winter.   ...cougar...

[neurotoxin312]

Been having the same issue with my 76 cb550 and overflowing tubes. What helped was running the carbs dry by turning off the fuel valve and running engine until fuel bowls are empty then turning fuel valve on again. If this doesn't work could be that the tip of your float valves have some crap on them. Take them out and polish the tips (assuming you have metal tip floats). 

As for the exhaust. When was the last time you changed the gaskets? Torque the exhaust bolts. Could very much be the baffle as well.

[willis]

My vote would be for the stuck float valve; almost all of the symptoms you described happened to me. After a good carb. cleaning, voila, no more power loss/leaking gas. Have you noticed gas leaking out of the overflow tubes when you rev the engine?