cylinder pinging

i have a cylinder that gives me a tap tap tap tap tap tap when under acceleration when at full running temp. when i let her cool down it goes away. i pulled the plug from the suspected cylinder and it is completely black . others are a bit black but nothing even close. i suspect she is running a bit rich anyway so the others im not worried about. i ran a bunch of seafoam through it today but no luck as of yet. any ideas of what would cause the tapping or pinging . what confuses me is how it gets worse the hotter it gets. i am running ethanol free premium as of the current tank

 

What are your compression numbers? That might give us a clue as to what might be going on.

MN

 

When it cools down, ... it goes away.

If you are running real rich on good High-test you shouldn't ping.
Unless the Piston Crown and Combustion Chamber is excessively covered in a Carbon Deposits.

You might be hearing valve Train noise.
And, ... because it goes-away when cool ... an exhaust leak.

 

Might be nice if we knew what bike, and a little more about it;

but without any more to go on, I vote exhaust gasket leak at the head.

 

ill do a compression test today . its a 82 xj1100 with 42k on it . ive only owned the bike for 6 months. i am leaning towards excess carbon but what way can i seafoam though the intake

 

i dont think its an exhaust leak because the sound also is heard out of the exhaust as well. i figure if it was drivetrain i wouldnt hear it in the back side of the muffler. something isnt going boom like it should i suspect something in the carb isnt right. with this bike can i do a simple swap with a carb to see if the problem follows it to the new cylinder ?

 

a carb swap, i don't think so cause of the fuel inlet rails

 

well i dumped a bit of seafoam directly into the cylinder to try and get rid of some carbon to see if that would change the issue. when i started off in my neighborhood my clutch cable broke so i no i have that also to fix. i need to fix my transmission anyway so hell maybe this is a sign its time to start tearing her apart .

 

is there any oil coming from the gasket area where the head meets the cylinder? moisture, anything to indicate the seal blew?

 

i do have oil leaking out of the valve cover pretty bad. if there is a leak anywhere else its hidden by whats comming from up above

 

i feel its time to go ahead and start collecting parts and tear her down. i have too many other issues as well. if there is a good thread that is helpful with a teardown rebuild let me know. ive rebuilt a car but never messed with a bike so ill need all the direction i can get

 

Start by tracking down a service manual. There are a lot of little details and "intracacies" in the XJ series motors; some you won't even think of without a book.

 

i have the shop manuals . what about the xj cd i see people talking about.

 

Before you yank it apart, DIAGNOSE.

Run dry and wet compression tests, at the very least. Maybe even a leakdown test.

BEFORE you rip into it; so you'll know what you're doing.