Misfire after warmup

[Scotty]

Hi Guys:

 

I searched the archives and have not been able to find anyone who has posted with a problem similar to mine. My 97 RT began to misfire and spit small clouds of black smoke after the temperature reached four bars. I suspected that it was a fuel delivery problem. Since I had 40K on the clock, I replaced all throttle/choke cables and replaced the fuel filter. After reassembly, I did a TB synch. The bike runs flawlessly until it has reached full operating temperature. I have no idea what I could have missed. Any ideas? Thanks in advance!

[Stan Walker]

I have no idea what I could have missed. Any ideas? Thanks in advance!

 

You mean like spark plugs, coils, HES???? Or maybe adjusting the valves? How about checking the timing? Or even air leaks?

 

Stan

[chrisx]

well we all know it can't be plugs because they are firing when cold.

 

not sure of the motronic but generally a FI engine will have an NTC ( neg temp compensation to make the engine rich when cold) i would start there and look for vacuum leaks too. spark is also an issue as a rich mixture fires easier and the A/F ratio is leaned out when warmed up.

[T__]

Hi Guys:

 

I searched the archives and have not been able to find anyone who has posted with a problem similar to mine. My 97 RT began to misfire and spit small clouds of black smoke after the temperature reached four bars. I suspected that it was a fuel delivery problem. Since I had 40K on the clock, I replaced all throttle/choke cables and replaced the fuel filter. After reassembly, I did a TB synch. The bike runs flawlessly until it has reached full operating temperature. I have no idea what I could have missed. Any ideas? Thanks in advance!

 

Scotty, other than the above mentioned ignition components I would suggest you look at your carbon canister (if that is plugged off it could purge pure gasoline into your intake),, it could also effect your fuel tank vent & that could cause high pressure in teh fuel tank..

Maybe also give your engine oil a sniff,, if your engine oil has gasoline it it from a dripping injector it could allow gasoline to wick up past the piston rings when the oil gets hot enough to crack off gas fumes..

 

Twisty

[duckbubbles]

Hi, Scotty-

 

Just helped my cousin with his R11RT and this exact problem. He checked the normal things, valve adjustment, wires, etc. But when he installed new spark plugs, the problem went away.

 

Frank

[Scotty]

Thanks for the suggestions. I have done most of the things suggested, such as check coil, adjust valves and check for vacuum leaks. Tomorrow, I'll throw in some new plugs and see what happens. This place rocks.

[Scotty]

Gave up and took the bike to the shop. Turned out to be a bad plug wire. Thanks for all of your suggestions!

[Green RT]

Interesting. Thanks for posting the resolution.

[BFish]

Gave up and took the bike to the shop. Turned out to be a bad plug wire. Thanks for all of your suggestions!

 

since the problem has been solved i have a related question. what's the average lifespan of plug wires?

[Scotty]

The guys at the dealer told me that coils/wires rarely need replacing during the lifespan of the bike. This, of course, is based on conditions. I have no idea why my plug wire failed. While the bike was apart, I decided to replace both wires. Oh yeah: BMW plug wires are about $75 a piece.