Noticed it this morning while on the highway. It's like the vibration out of the muffler is going slower. Instead of just that "roar," I can perceive individual "puts," but the RPMs haven't dropped any. Bike seemed to be performing fine, and the noise was only slightly different.

When taking it back home later on, the noise was MUCH deeper, almost cruiser-ish. Sounds maybe like an old-school lawn mower with the choke off. I kinda liked it, except that I noticed the bike wasn't taking off from the line like it used to. I could also feel the deeper vibrations in my feet through the rearsets, where I normally don't feel anything. I just got home, and my feet are tingly from it.

Other than that, nothing odd is going on. It doesn't sputter at any speeds, and it accelerates smoothly (just slow at first). I smelled gas just as I turned the bike off, even with my helmet still on, so maybe that's a clue. I thought I had been smelling gas in the exhaust in recent past, but this was substantial, and I was still in the seat, not behind the bike. I gave the rear half of the manifold and exhaust a quick inspection to see if I had a hole or something, but it all looks great. It's 3 AM here, so I didn't really get under there with a magnifying glass.

The only other possible clue I can think of is the bike got tipped over a few days ago while parked. It landed in the grass, on the exhaust side. I have the woodcraft rearsets that stick out farther than the exhaust, so the fairing and peg took the brunt of the hit. I inspected the exhaust immediately anyway, and it wasn't dented or bent or anything. Bike started right up afterwards.


Ideas?

I just did a carb partial rebuild and full cleaning in April, and changed the oil and plugs, so we can rule that out. Bike only has 11k miles on it.

 

Check the exhaust manifolds & the bracket under the right pillion foot rest, could have moved the exhaust enough to let air in. Check your plugs to see if they a burning ok (yeah I know it a bugger of a job) & check your oil. Tipping the bike may have upset the works a bit, but petrol smell usually means that unburnt fuel is going out the exhaust (could just be from the tip over though), but wot your referring to is often called the "Death Rattle" meaning that an underlying problem may be going to cause greater damage.

 

Yeah it really feels / sounds like an exhaust issue.

I forgot to mention that after the tip, I rode the bike for about 15 miles with no issues whatsoever, so any fluids that got out of place should have settled by then.

 

BC Rich Mockingbird?

 

I had the same problem on my 250 Ninja. Turned out the plugs weren't the right kind and they weren't very tight. Just like pacemaker said.. When i was at lights it would try to die and i'd give it some throttle and it would take a few seconds to catch up and it sounded just like you described. I'd #1 check exhaust & #2 check plugs like pacemaker said.. Sorry for repeating but that's just my Good luck!

 

**** Yes.
http://www.bcrich.com/Mockingbird_specialx.asp


Mockingbird Special X
Construction: neck through body
Wood: mahogany
Top style: deep arched
Top wood: ½” maple cap with AAA quilted maple veneer
Body binding: multi-ply / back = taper cut Body side thickness: 39.48mm
Body side thickness: 39.48mm
Body center thickness: 51.57mm
Headstock style: traditional 3 to a side
Headstock colorwhite
Headstock binding: black multi-ply
Headstock tilt: 14 degrees
Tuners: Grover Rotomatic
Neck wood: mahogany
Neck radius: 12”
Back of neck: painted to match
Neck binding: one ply black
Nut width: 43mm
Neck width at 12th fret: 2.062”
Fretboard: ebony
Inlay: white pearloid cloud
Frets: 22 jumbo 2.7mm
Scale: 24 ¾”
Bridge type: Tone Pros Tune-o-matic
Tailpiece type: Tone Pros stop bar
Pickups: 2 chrome covered Rockfield SWV vintage humbuckers
Controls: 2 CTS volume pots, 2 CTS 500k tone pots and 1 top bout three-way toggle
Hardware: black and chrome
Finish: painted glossy
Color: White

 

I took a better look at it today. Exhaust is FINE. You can hear the noise even up front by the engine, so I gathered a cylinder was missing. I pulled the plugs, and one of them was fouled and wet. I cleaned them all and threw the previously fouled one into a different cylinder, but I had the exact same problem. I did notice that I didn't have the boots pushed all the way down from the last time I changed the plugs, but they were still making contact. I made sure it was all good this time, but the bike is still doing the exact same thing. Thinking I'm gonna have to crack it open :/

I drove it around about a mile, but nothing cleared up. I noticed the RPMs are about 1500-2000 higher than normal just to maintain speed. I have to give it way more throttle than usual under all conditions.


I've got NGK R's in there now. Are those the right kind? Also, I never sync'd the carbs when I cleaned them, because I never separated them. I know I've been smelling gas in the exhaust for a few weeks now. Could it just be a sync issue?

Could it be that I'm running rich and that's what's CAUSING the misses?

 

I have a '96 also and was getting the same noise. I know that the bike is due to get the valves done but the A.P.E. Cam Chain Tensioner took away the noise a brought some life back to the bike. http://cbrzone.com/sprockets.html It starts better, gets better milage, and put some zip back in the bike. Easy fix for $50 or so. I had a one of the shop guys here listen to it to make sure it was not to tight or loose.

 

My valves aren't due, and I'm familiar with the CCT noise, and this definitely isn't it. Plus, I've already confirmed cylinder 4 is missing.

 

You are definitely running on 3 cylinders. Are you 100% sure that you are getting full pull out of upper RPMs? If you are then it is probably a carb thing, if you are not sure then it could be many things. Do you hear this noise at all times or just low RPMs?

Check spark on that cylinder. Check compression. If you don't have a compression tester then go straight to carb 4 before you spend money. Check the pilot jet to be sure it isn't clogged, hell check the slider to make sure it moves properly and even check the main jet though, so far it sounds like pilot. you may have just done a cleaning but trust me, random stuff can get in there if you aren't careful. I found rubber glue in my main jets one time lol.
As for spark plugs, use stock #. Not sure what F3 is but you never need hotter or colder or different plugs... just get the cheapest plugs you can buy at advanced auto, make sure they are the proper # and make sure they are gapped correctly.