Cylinder Missing!!

[TheMuffinMan]

So I'm on a 7000 mile trip with 6000m miles down and an issue has come up. One of my cylinders has started misfiring when the bike is over 68 mph, but then it'll miss and idle on one cylinder for a few minutes (or the engine dies alltogether) If i keep it at 65 indicated (about 60 actual) it seems to happen much much less frequently. When giving it gas I get backfiring on acelleration/throttle after an episode.

I'm thinking it might be vapor lock, it doesn't seem fuel pump related, put a dr beans kit on a brand new pump 12,000 miles ago. Front carb throat is a little oily but not out of the ordinary. Carbs are securely clamped into the boots. The front head ticks a little at startup but it's always done that.

I'll see if it reoccurs tomorrow when the bike is cool. But figured i would ask for input since I'm about 1000the miles away from home.

[Katoom119]

At that speed any jets should be fully active, I would imagine. So a stopped up jet is unlikely.

The backfiring means that there is fuel being ignited, so you have flow. Supporting the jet theory.

I know that there is an occurrence called "heat soak" that wreaks havoc on the Isle of Man TT bikes. When they cut the engine in the pits, the heat from the engine literally soaks the entire bike, making it very difficult to start. With the heat wave that we're having right now, super heated air in the air box means less air density. Possibly enough to not allow ignition within the cylinder? Going by this theory the faster you go the worse it gets.

[MAXVERT]

Balance the carbs they could be out of sync.

I've had a 950 and a 990 exhibiting these characteristics before.

Some TPS tuning and a Carb Balance worked.

Max

[TheMuffinMan]

Originally Posted by MAXVERT

Balance the carbs they could be out of sync.

I've had a 950 and a 990 exhibiting these characteristics before.

Some TPS tuning and a Carb Balance worked.

Max

Hrm, this is possible. I didn't have a flowmeter to sync the carbs at the last valve check 1200 miles ago. I stupidly removed the vacuum hose nipples and blocked the ports. Because I bought a flowmeter, but forgot to bring it on my trip.

Could definitely be heat soak, I had been running the bike all day with no stops except gas really. And it didnt start until I came down into a hot valley.

[corndog67]

Mine is missing on one hole when idling or putting around on the pilot circuit. My mechanic buddies are about 99% sure the pilot is plugged or there is some crap in the float bowl causing an obstruction. Off the pilots, it runs real good. It's coming apart very soon, and I'll post up.

[DSM8]

How about telling us WHERE you are.

There is someone sure to be close by who might be able to lend a hand with tools and a place to work on the bike.

Just my .02

[TheMuffinMan]

I'm near Seely Lake, Montana along Highway 83.

[TcRulz]

What about one of your coil sticks or spark plugs breaking down when they get real hot. You could pull the plugs and read them to see if there wet (from unburnt fuel) or dry (from no fuel). Might have to do this while it's happening which could be a pain (pun intended)

[mousitsas]

Originally Posted by TheMuffinMan

So I'm on a 7000 mile trip with 6000m miles down and an issue has come up. One of my cylinders has started misfiring when the bike is over 68 mph, but then it'll miss and idle on one cylinder for a few minutes (or the engine dies alltogether) If i keep it at 65 indicated (about 60 actual) it seems to happen much much less frequently. When giving it gas I get backfiring on acelleration/throttle after an episode.

I'm thinking it might be vapor lock, it doesn't seem fuel pump related, put a dr beans kit on a brand new pump 12,000 miles ago. Front carb throat is a little oily but not out of the ordinary. Carbs are securely clamped into the boots. The front head ticks a little at startup but it's always done that.

I'll see if it reoccurs tomorrow when the bike is cool. But figured i would ask for input since I'm about 1000the miles away from home.

Is it speed related or rpm related? If it is rpm related, chances are it is electrical. If speed related then a fueling issue.

[68deluxe]

Originally Posted by tcrulz

what about one of your coil sticks or spark plugs breaking down when they get real hot. You could pull the plugs and read them to see if there wet (from unburnt fuel) or dry (from no fuel). Might have to do this while it's happening which could be a pain (pun intended)

+1