Cutting out at low RPM '98 RT

My '98 R1100RT recently developed a problem with cutting out at lower RPMs. I had noticed a little hiccup occasionally when accelerating from a stop or slowing to make a turn. Yesterday that little hiccup developed into a consistent low RPM miss. At first I was able to overcome it by keeping revs above 3000, then as the day went by, I had to keeep it above 4k. By the time I made it home, I had to drive the last 35 miles in 3rd gear at 5500 to keep the miss out.

Just to help any would-be advisers on diagnosis; I have installed GS tubes, use Auto-lite 3923 plugs (for 3 years), KN filter, set valves about 6k ago and total mileage on bike right now is 68K.

Don't normally abuse a bike by pushing it with problems but was a couple hundred miles from home with no cell phone and alone. Besides it ran perfectly at higher RPM and higher and higher...etc. Just had to keep using a lower gear to stay within the speed limit.

Thanks in advance
klc

Just to help any would-be advisers on diagnosis; I have installed GS tubes, use Auto-lite 3923 plugs (for 3 years), KN filter, set valves about 6k ago and total mileage on bike right now is 68K.


K,
First I would put in new plugs (this sounds a lot like a failed plug) and then proceed to check the secondary wires and then the coil. You are not firing the cylinder when under load and that is typically an electrical fault.
PS I'd ditch the K&N too.

bmwmick said:

PS I'd ditch the K&N too.

Click to expand...

Thanks for the quick response, but just curious. You are the first person I have encoutered to say anything negative about a K & N filter. Is there something I have missed over the past few years? Everyone else I have talked to loves them and I have had no other problems with mine in either the RT or the C.

Here is one of the best reasons for NOT using the K&N:

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

There is a lot of data that indicates the K&N allows way more dirt to pass through than a high quality paper filter. Our bikes are NOT starved for air in any way so why risk the higher cylinder wear with a porous filter.

Verrry interesting

That's good information to have Mick, thanks. I will have to re-think my use of K & N filters. For now though since it is Sunday and our nearest BMW dealer is 250 miles away, I will simply have to clean and re-oil the K & N.

Anyone else with any thoughts on my problem? I just installed new plugs, (the old ones looked perfect) and will take her out for a quick test drive. Hoping I don't have to push it back home.

For some, using a K&N air filter in a BMW, is about as blasphemous as using a non-BMW oil filter.

BTW: I do both.....and have never had any problem or issues crop up. A BMW service tech (manager) told me about a non-BMW oil filter.

Well got time to do about a ten mile test drive with the new plugs. She never missed a beat so I went back home to do some more general maint. type stuff. By the time I finished, it was too late to do any more testing and we are now recovering from 10" of snow. Maybe I will get a longer test ride in this coming Sat. Possibly make the St Patty's Day event in Shamrock, Texas about 80 miles away.

As for the filters, I have been using the K&N in both beemers for five years now without a problem and the Fram 6063 oil filter without a problem. That's not to discount the info from the link above just to say hey it has worked for 120K over the past five years--ride on.

P.S. Thanks to all for the responses, advice and good info.

K,
First I would put in new plugs (this sounds a lot like a failed plug) and then proceed to check the secondary wires and then the coil. You are not firing the cylinder when under load and that is typically an electrical fault.


Glad you found your problem.

premature celebration

Well after more extensive testing, it seems that the problem has returned. It apparently only happens after the engine is up to full operating temperature.

Here is a more precise description of what happens. When cold everything seems fine, great acceleration in all gears from all RPMs. Once up to full temp. it wants to cut out from around 3800 to 4500 RPM in all gears. From 4500 up it runs like a scalded dog. When holding steady RPM the problem seems minimal but is still noticable.

I am suspecting a few possibilities: old/bad plug wires, O2 sensor fouled or failing, fouled injectors, clogged fuel filter, wrong CCP for current tune specs.

Anyone have any other ideas?

I read on one of the internet sites a while back about an O2 sensor available at Auto Zone or O'Reilly's that was an exact match to the OEM. Does anyone here recall where that was or what part number it was and from what vehicle. I thought that might be a good place to start since I am so far from the nearest BMW dealer (250 miles).

I may have a glass of wine this evening to contemplate this delima.

Thanks in advance for your input.

Pull the CCP and go for a test ride. I've seen several bikes
that act like that normally. The roughness occurrs right when
it goes 'closed loop'. Mine did that too back in 1995 when it was
new. I've been running with no CCP, Staintune exhaust and a good
0=0 for 35K miles.

Mick

Throttle bodys

You might be sucking air through old weather checked rubber connectors connecting your throttle bodys to the intake manifolds. Or one may be even lose.

bmwmick said:

Pull the CCP and go for a test ride. I've seen several bikes
that act like that normally. The roughness occurrs right when
it goes 'closed loop'. Mine did that too back in 1995 when it was
new. I've been running with no CCP, Staintune exhaust and a good
0=0 for 35K miles.

Click to expand...

Actually the problem started when I pulled the CCP about 6 months ago and gradually worsened over time until I reported it here. I tried putting the pink CCP in this AM and the result was slightly better performance but still not what I wanted, even after 50 mile test ride. Then I let it cool down for about 5 hours while I did some wiring work on the custom cruiser. I put the original yellow/mustard CCP in and went for about a 130 mile ride. She ran perfectly from the get-go and all the way through the ride. All RPMs in all gears were thoroughly tested, never missed a beat. I should have changed back to the original CCP when I first noticed the low RPM miss.


Appreciate your input though.

Stan said:

You might be sucking air through old weather checked rubber connectors connecting your throttle bodys to the intake manifolds. Or one may be even lose.

Click to expand...

That was one of the first things I did when I got it home last weekend. All connections seems pliable and tight. Thanks.

I'm gonna hold off on the celebration until I have a few hundred more miles without problems. Will be in touch if/when anything else develops. Thanks to all for you help.