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Strange miss, looking for possible causes


eddd

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'96 R1100RT...just under 77,000 miles

 

OK, here is what I've experienced. Twice recently I have had what appears to be a miss in one cylinder after riding for about 10 minutes. It will miss...but not continually...for about 10-15 seconds...never to return for the rest of the day. In each case the bike had been sitting for about a week. This has never happened before, including during a recent 4,500 mile trip.

 

Plugs replaced at 70k along with valve adjustment. Throttle sync at 72.5k

 

Any ideas?

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If I had to place a bet, I would go for the coil though it could be symptomatic of an incipient HES loom failure.

 

Andy

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Does a pending HES failure typically affect only one cylinder? I was always under the impression that it was a total loss of power.

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That's why I would plump for the coil. It is however, possible that what feels like a miss on one pot is poor running on two.

 

Andy

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If I had to place a bet, I would go for the coil though it could be symptomatic of an incipient HES loom failure.

 

Andy

The coil fires to both sides at the same time too. I'm not clear how a coil could cause a one side only miss.
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'96 R1100RT...just under 77,000 miles

 

OK, here is what I've experienced. Twice recently I have had what appears to be a miss in one cylinder after riding for about 10 minutes. It will miss...but not continually...for about 10-15 seconds...never to return for the rest of the day. In each case the bike had been sitting for about a week. This has never happened before, including during a recent 4,500 mile trip.

 

Plugs replaced at 70k along with valve adjustment. Throttle sync at 72.5k

 

Any ideas?

 

Ed, could be many things but start with the easy things first..

 

Start with a fresh set of spark plugs (you just never know)..

 

If you still have the evap canister installed try plugging the purge line running from the evap can to the TBI units.. If that evap can is partially plugged it could be fuel logged from the bike sitting & venting through that canister so when it enters closed loop it could be purging pure fuel into the TBI’s.. Possibly one side can fire it & the other can’t.. (worth a try anyhow)

 

Make sure the R/H throttle TBI cam isn’t rubbing on the spark plug wire on that side (I have seen a few with that problem).. Hard to believe it would only act up for a few seconds but again you never know)

 

You could even have a fuel injector acting up as it goes from cool to hot (will be difficult to find if you do) ..

 

Could be the Hall Effect sensor but doubtful only one side (but possible)

 

Could be the ign coil but again highly unlikely if only one side,, but the side that fires reverse polarity would take more KV to spark under load so theoretically possible..

 

Could even be the 02 sensor as the system goes into closed loop (shouldn’t take 10 minutes of riding to get into closed loop though)..

 

For just a SWAG guess my money is on either a bad spark plug or the evap canister..

 

Twisty

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OK, here is what I've experienced. Twice recently I have had what appears to be a miss in one cylinder after riding for about 10 minutes. It will miss...but not continually...for about 10-15 seconds...never to return for the rest of the day. In each case the bike had been sitting for about a week. This has never happened before, including during a recent 4,500 mile trip.

 

Ed:

One side only? Could it be a sparkplug wire? Maybe pull the connectors and put some dielectric grease on them and reinstall.

Tipover Bob

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Here is an update:

 

Rode it today, about 100 miles. No miss. I am focusing on what happens when it sits for a week or so. That seems to be the key clue at this time.

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