Dropping a cylinder after bikes warms up

[Colonel Nikolai]

1996 Triumph Sprint 900

After riding for about 45 minutes in warm weather, one cylinder drops. All three spark plugs look fine: slight grayish-brown tint on the ignition site except cylinder 2, which is wet with oil, but not burnt oil:



This is likely because valve 2 shim is too tall allowing oil to drip into an open valve. This is likely unrelated to the problem? Could my pickup coil be going bad?

Runs like a champ when cold.

[Mustang]

dropping a cylinder after warming up is generally one of two things

1. valves are tight on intakes

2 . coil going bad  (need nologys )

[Colonel Nikolai]

dropping a cylinder after warming up is generally one of two things

1. valves are tight on intakes

2 . coil going bad  (need nologys )

They've got PVLs right now I just switched them last night along with new plug wires. I have a valve adjustment planned this winter. Tight intakes could also coat the plug like this eh?

[blacktiger]

Tight intakes could also coat the plug like this eh?

Unlikely. IMO it's simply that you're not getting a spark on that cylinder.

[Colonel Nikolai]

Unlikely. IMO it's simply that you're not getting a spark on that cylinder.

Thanks blacktiger.

I changed the plugs, wires and coils and it hasn't happened since (put on about 200 miles since). In fact the bike runs better than ever: a little faster startup and seems to behave better when cold. Maybe I had a bad wire?

The bike is still overdue for a valve adjustment, so that's still on the schedule this winter.

[Bixxer Bob]

Just a thought, since the oil is all the way up the threads,  you've not got a seal gone allowing oil to seep into the plug tube have you?  A small amount of oil lying in the bottom would coat the threads as you remove the plug.  Something to check when you do the valve clearances maybe...  

Bear in mind we're not talking 2-strokes here, there shouldn't be oil in the cylinder, burnt or not.  Petrol, yes; carbon, yes; but not oil.

[Colonel Nikolai]

Just a thought, since the oil is all the way up the threads,  you've not got a seal gone allowing oil to seep into the plug tube have you?

I hope not.  :roll:

It's the second time this has happened. I will check it out when I opener' This is the bike that came back from the dead. Sure wouldn't want her to go down after all she's been though. She's my Millennium Falcon.

[Bixxer Bob]

All it would take is to nip the "o" ring when you put the cover back after a valve check - nothing serious!!!

[daveb]

I know nothing about the Sprint 900, however when my previous bike would suddenly drop a cylinder when riding was due to the starter solenoid / relay failing. it was a bit un-nerving as theYamaha  TDM850 only has 2 cylinders.

it would also cut back in with out any warning.

Don't know if this helps with your Sprint.

[Colonel Nikolai]

I will have to watch it daveb. I have done the valves now and I replaced 2 shims on the exhaust side a little tight and replaced the plugs. It never did it again all summer. That was the first time the bike ever acted up on me and it was after riding around in the heat going really slow. It's been really steady all year.