| Author | Message | ||
     Buell82 |
Hi there...I recently have had some trouble with my 97 Buell S3. I took my bike on its first hard ride, and lost power on an uphill climb. Once I was able to inspect the cause I saw thick smoke coming from my crankcase vent system. Specifically from the rear cylinder. I tried a compression test and found hardly any psi when cranking.:-( Although when I added oil to the cylinder I found no change. This leads me to belive a valve, or head gasket problem?.... Could this be happening?! The bike has only 15k on it? Any info you guys can give me help me fix this problem will be greatly appreciated. I have a bit of mechanical ability, but I need all the help I can get. Also do any of you know of a good parts resource? Thanks, Mike | ||
| Blake |
My guess is that you have holed rear piston. Not good news. The cause of that is usually an engine that is running exceedingly lean. The excessive leanness may be caused by poor carburetion and/or an intake tract air leak between the carburetor and cylinder head, usually at one of the two intake manifold to cylinder head seals. Any of the performance shops that sponsor BadWeB will be happy to talk you through a diagnosis and rebuilding effort. The first step will be removal of the rear rocker box and cylinder head. Take some good photos. They are valuable in helping others diagnose and resolve such issues. I sure hope it turns out to be something else than a holed piston, a bad/bent valve or valve-guide or head gasket as you mentioned would be a much easier issue to resolve. Let us know. | ||
| Buell82 |
Any good testing tips or ideas to rule out bent/broken valve or blown head gasket? Thanks, Mike | ||
| Pammy |
Blow air into the cylinder...listen where it comes out. Did you do the compression test with the throttle wide open? If not, do it again. | ||
| Pammy |
It won't be just a head gasket problem. Sorry, I hate to be the one to tell you, but once you let the smoke out it usually means trouble. Sounds like a siezed piston to me. | ||
| Panic |
When you put air into the plug thread: 1. comes out the timing hole - piston crown failure 2. comes out the intake manifold: stuck/bent intake valve 3. comes out the exhaust pipe: stuck/bent exhaust valve | ||
| Buell82 |
Thanks for all the helpful input! Here is one more question I have that hopefully someone can help make reason of...The smoke that is coming from my engine is only from the crank case breather system (the little hole tapped into the top of the rocker box) But not a bit of smoke comes from my exhaust...Now all my mechanical knowledge tells me that if my ring is shot then I should have smoke coming from the exhaust as well? Any input on this? Thanks, Mike | ||
| Blake |
If you have a hole in the rear piston or broken the piston in some way such that it has lost its ability to maintain pressure in the combustion chamber, there is no exhaust left to exit the exhaust pipe; any exhaust from the rear cylinder (there would be little) is escaping out the breather during the power stroke before the exhaust valve ever opens. Pistons don't work very well when they have holes in them; they won't allow much fuel/air charge to enter the combustion chamber and they won't allow much if any exhaust to exit via the exhaust tract. Think of it as though basically your rear cylinder no longer has a piston. | ||
| Blake |
though I think it is unnecessary since the symptoms you describe are extreme and point to a holed or broken piston... One additional comment to Panic's advice should you choose to try the pressurized air testing: Before doing the air pressure test, be sure the rear cylinder is at top dead center of the power stroke where both the intake and exhaust valves are expected to be fully closed and well-sealed. Also be sure to hold the throttle open to best note if the air is escaping out past the intake valve. | ||
| Fulgur |
Have you also had a look down into the cylinder while your plug is out. If there is a big hole in your crown you might see it with a torch (and maybe a mirror). .....Fulgur. | ||
| Buell82 |
Just thought I would post an update for this thread. I ended finding out upon doing a leak down test, that all the air was coming out through the crank case. So I torn down my cylinder and found a holed piston. :-( I have the cylinders and heads in the shop getting machined, and I should have her back together and running within no time. I am still a little puzzled why I had such a bad detonation. I check my intake gaskets and they all looked good, and my timing should have been good. I guess I will have to really look into that before I start riding again. Thanks everyone for all your help, Mike |
