1100RT High RPM/High Load Hiccup - Need Assistance with Diagnosis

[bharvey60]

My 1998 1100RT has developed a curious condition that I'm trying to narrow down. Symptoms...

- Engine misses abruptly; similar to what happens when I hit the rev limiter
- This occurs at 4,000 to 5,000 RPM, under load and full throttle, typically in 2 or 3 gear
- It's one, quick miss, and the engine returns to normal
- The miss is very noticeable; the result is significant enough to unsettle the suspension
- The symptom will occasionally repeat itself in a few seconds if I hold the throttle open, but it is somewhat intermittent
- No change in RPM
- I can't completely rule out some sort of abrupt slip in the drive train, but there is no RPM increase
- Bike has a slow leak into the driveshaft housing from the final drive; approx 15 cc leak in 2,500 miles; not making metal and no side-to-side play in rear wheel
- Bike runs normally under low to moderate load conditions
- No other changes to bike performance - starting, running, etc.
- Bike has 31,000 miles
- At 27,000 miles, spark plugs replaced (Bosch Platinum +4 4418), valves adjusted, throttle body sync

Since the onset is so sudden, I'm thinking this is electrical. I'm a reasonably competent home garage mechanic who performs my own maintenance. My first step is to replace the plugs, then the spark plug wires. I believe the wires are the originals, so they are 18 years old.. After that, I'm looking for suggestions. HES seem to fail around 70,000 miles or so and I'm not aware of these symptoms being associated with the HES.

Thanks for any suggestions you may have.

 

[gsaddict]

In your case I don't think it's the HES although PM replacement would be a good idea. (I have seen failures at much lower milages)

BMW had issues with coils in years around yours.
Start with plugs and wires as planned and go from there.

 

[pauls1150]

First thought is a stick coil.
Examine the wires too - I seen some mounting clips (routing the wires along the engine) that were clamping down on the wire so tightly that they damaged the insulation.
Second thought would be an interruption to the fuel delivery.

Side note - many of us strongly prefer the Autolite AP3923 spark plugs (but let's not deviate into a "plugs" thread...)

 

[dieselyoda]

First thought is a stick coil.
Examine the wires too - I seen some mounting clips (routing the wires along the engine) that were clamping down on the wire so tightly that they damaged the insulation.
Second thought would be an interruption to the fuel delivery.

Side note - many of us strongly prefer the Autolite AP3923 spark plugs (but let's not deviate into a "plugs" thread...)

I don't think stick coil can be an issue, if it is, WOW, big problem as I don't think it has any.

I like the plugs and plug wires route. It certainly will eliminate some basics and plug wire diagnosis is tough on these bikes as so much of them are buried. My next thought was if you are going as far as pulling the tank to the plug wires, I would do the fuel filter. It's not likely the cause but you can rule out another simple solution.

Best as well as has been mentioned, check the wiring harness for rub through but more importantly, make sure battery cables and grounds are in good shape. Look closely at the wiring on the HES going in that deep. Mine cooked the wiring at the connector under the tank. The wiring on the HES at the front was fine.

If it is the HES, best tool will be a credit card and cell phone when you go riding in the rain. It will show up pretty quickly.

 

[pauls1150]

Good catch, Yoda - kick me; did the 98s have sticks??? Not if it's a "single-spark" (one plug per cylinder).

 

[cycleman2]

1100's didn't have stick coils, just conventional coil under the tank. Normally would cause problems when engine was hot, let it cool down and then engine would start, then when it got hot engine would die, let it cool then it would start and so on.

The Autolite 3923's work well in the oilheads, well worth a try, but it does sound like a dead short or break in the ignition system. Do the simple stuff first, change out the spark plugs, then move on. Possible that it could be a cracked coil or the HES is acting up, especially if it happens during a rain or when it is damp outside. SF gets a bit of fog from time to time.

When I had my 2000 R1100R it did what you describe once, and then never did it again. I'm now riding a R1100s, but touch wood haven't had any issues, other than it runs too lean, so I'm trying to sort that out.

 

[m_stock10506]

I'll also lean with the coil as the culprit. There are plenty of 1100 Oilhead coils available used online. My high mileage RT wouldn't restart near the end of a ride last year. Prior to that it died on me while running a few times and would restart before I had to pull over to the side of the road. Replaced the coil and it is fixed.

A friend with a 1996 RT (60k miles) was also having issues with bike just losing spark during his rides. Replacement coil fixed his issue too.

 

[pglaves]

Face cam on the input shaft in the transmission is my guess.

 

[BC1100S]

1100's didn't have stick coils, just conventional coil under the tank.

The early 1100s didn't have stick coils. The later ones did - 'cause I just replaced two on mine.

 

[m_stock10506]

The early 1100s didn't have stick coils. The later ones did - 'cause I just replaced two on mine.

Maybe the R1100S had stick coils, but the OP has an R1100RT - the 1100RT has a central coil all the way to the end of the 1100RT production.