2000 ST1100 refuses to fire on #2 cylinder.

[Gazbrown]

OK brains trust.
My 2000 ST1100 is being a right royal PITA. Cylinder 2 is refusing to light up!
New coils and leads. Good spark, have swapped from #4 which is firing, no luck.
Changed out plugs to known good ones, (I have a second bike 1999 model) so not plug problems.
Not fuel problem as far as I know, plug is wet with fuel. And I have swapped to another carburator with no change.
I can block the plenum to #2 (air cleaner removed) without any alteration in engine, however if I do this with any of the other pots it will try to stall the engine.
Compression test is 130psi, but is probably down because of the unburnt fuel washing oil from the bore.
I can get a vacuum from the vacuum line used to sync the carbs.When I ballanced the carbs the screw adjustment alters the vacuum.
One thing I have not checked and probably should have is the rubber connectors from carb to head.......pretty sure there are no cracks, leaks.
Ideas please if you have any.

[Brock]

Can you feel the suction on #2?? how does the compression compare to the other cylinders. Have you tried a shot of oil in each cylinder on the compression test ?? Was there s difference??

Have you pulled the rocker covers and checked the valves??  the valves could be sticking open or closed ( extremely rare to halve valve problems). Another rare occurrence is damaged valves &/or seats..

[Gazbrown]

Thanks Brock.....an update, this morning, decided to reverse the carbs! Strange as it sounds, but as I know right hand side are firing it would eliminate a carb problem........and it did, #2 still kaput. So as per your sugestion, some oil into the pot, and tested compression, and low and behold 175psi, so not a compression problem.
Next step take out the "new" coils and replace them and see what that does.
Will update following that step.
I might do a resistance measurement before I do.....

[Gazbrown]

Gremlins!
Swapped the coils as I know right bank is OK, rhs to lhs. Problem remains. No fire in # 2.
Swapped plug connectors. No fire in # 2.

Not sure where to go with this now.

Rocker cover off next and visual inspection of #2...........

[Gazbrown]

Rocker cover off and everything looks normal. Lobes look great.
Bike has only done 50k......

Maybe matches next!

[Brock]

How did the compression compare to the other cylinders?? A jump to 175 could indicate worn or stuck rings. Has the bike been sitting for a long period of time??

[Gazbrown]

Thanks Brock,
Oily comp test on #4 same side 155psi.
Checked valves from rocker cover side and both exhaust and inlet rebounding and working as far as can be seen from outside.
Strange as it may seem, when I just did the comp test on #4, I disconnected the plugs on the right side but left the problem #2 connected, so only that one had spark from the coil and it did fire or at least tried to? So that's got me even more confused.
I think it is possessed.

[STeveo]

Check your valve clearances.

[Brock]

The proper way to do a compression test, is to remove all plugs, connect the tester to each cylinder and note the readings. Then repeat with a shot of oil in each.  From the work shop manual, each cylinder should be 199PSI (+/- 28PSI) at 400 RPM (cranking speed)
  adding oil to the cylinder helps seal the rings..

[Gazbrown]

Stevie ,  will do that next, need to get a new set of feeler gauges.
Brock, will do exactly as you suggest regarding compression test when I get a bit more time during the week.

Thanks for the input, will keep you posted.

[Brock]

I really need to get off my arse, and do some work on my bike. If only tp allow Wombat to sell his spare engine..  I need to get rid of some coolant leaks, and replace the timing belt ( only about 60000Ks over due)

[mikan13]

Whats the expected life of a timing belt Brock?

[Brock]

Replacement is due at around 150000 I think, mine is at 200000 so far..