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R1100RT Disconnect O2 now it barely runs


Dave P

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I'd follow DR's advice and do all the usual things to reduce surging. Does the fuel you use have Ethanol in it? E10 fuel will reduce the effectiveness of pulling the Coding Plug.

 

A respected guy over on the BMWMOA board just installed an LC-1 on his 2000 R1100RT. After trying everything else imaginable, he beta tested the BMW-AF-XIED and it worked great for him, BMW-AF-XIED on R1100RT.

 

He's an electronics guy so once he found that lambda-shifting worked he decided to binstall an LC-1 (so he could log his AFR), which I helped him with. Here's a photo:

 

r1100rtlc1install.jpg

 

 

Once you've taken care of the basics on your tune, either will make a nice transformation of how your bike runs.

Edited by roger 04 rt
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Dirt / Roger- I think I'm going to clean up the TBs and maybe slide them off the intake and look / clean out the inside. I'll try pulling that CCP plug and seeing how she rides. Most fuel up here is Ethanol 10%, but There are places here that sell Ethanol free 91. I've been running 89 E10 or 91 ethanol free.

 

Think not that I'm over this hurdle with the bad running i think i'm ready to do my valve adjust... Dave

 

ps- any of you go to the Finger Lakes Rally in Watkins Glen, NY over Labor Day weekend? I'll be working in the swap shop tent most of the weekend. D

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ps- any of you go to the Finger Lakes Rally in Watkins Glen, NY over Labor Day weekend? I'll be working in the swap shop tent most of the weekend. D

 

 

Afternoon Dave

 

Yes, I usually go, didn't make it last year though as something came up last minute.

 

Sometimes I camp at the rally (usually on the far side of the walkover bridge (near the Canadians) & sometimes I stay at the state park if I am in a mood for peace & quiet camping.

 

That swap shop tent is nice-- If you offered some type of UPS shipping you would have had some of my money a few years ago.

 

Good thing about riding there is I can't buy or carry much home.

 

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Funny thing, surging decreases over time. Use extra thou or two on valves. Iridium plugs. See if idle stop screws still have factory paint seal; don't change. Edging throttle voltage a little bit higher might help enrichen, not certain, but not over .39 volts.

 

Playing Russian Roulette with the CCPs (which includes removing it) makes no sense at all. BMW spent a lot of time tuning different models and the CCP color is the key that identifies your tuning programming. Unless you think you'd like to play random luck games with your tuning, just leave it.

 

Ben

Edited by Peter Parts
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Funny thing, surging decreases over time. Use extra thou or two on valves. Iridium plugs. See if idle stop screws still have factory paint seal; don't change. Edging throttle voltage a little bit higher might help enrichen, not certain, but not over .39 volts.

 

Playing Russian Roulette with the CCPs (which includes removing it) makes no sense at all. BMW spent a lot of time tuning different models and the CCP color is the key that identifies your tuning programming. Unless you think you'd like to play random luck games with your tuning, just leave it.

 

 

Morning Ben

 

Actually the 1100RT bike WAS tuned to work with no CCP. That was a European release non U.S. emission compliant bike. No cat & no evap system.

 

The European version did have the idle trim pot but without that trim pot they just idle a little on the rich side.

 

Back in the 1100 days a lot of U.S. riders removed that CCP, didn't hurt a thing & never any Russian Roulette involved.

 

Those 1100RT's would regularly go well over 100K with no CCP, no engine damage, no cat damage, & no other oddities other than less light throttle light load surging.

 

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Hello Ben,

Agree 100% with D.R.'s assessment of what happens when you remove the CCP or cut the code jumper from an early 1100. I cut the jumper in my '94 RSL and installed a CO POT which I thought was necessary. If I had known the CO POT wasn't required I would have not bothered with it. Also disconnected the O2 sensor. This simple mod completely eliminated all detectable surging. Too bad you can't modify an 1150 this easily but an LC-1 takes care of that.

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Soon the whole question of no Coding Plug on an R1100 will be put to rest since an lc-1 was installed on a friend's last week.

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The CCP (including absence of CCP) is a means of selecting one of a number of ECU programs. All of these programs are similar - but different enough for BMW, after what is supposed to be extensive test track testing*, to want to cut a separate color key for each one they think is different enough.

 

There are a good number of comments on playing switcheroo with CCPs by riders intending to give them the fairest kind of testing. Based on these posts, a reader would conclude there are differences but testing of this sort of tuning is not too reliable.

 

In practice, switching CCPs from what color is meant for your model is unlikely to produce much of a benefit and likely to produce a loss and either way, no two riders would agree anyway.

 

I'm still waiting to see anybody publish information on the different tunings inside the Motronic ECU. We are all (except for BMW engineers) completely clueless about what the CPPs actually control. So switching them around is mindless.

 

Personally speaking, playing Russian Roulette with unknown tuning - a purely random exercise - seems as unwholesome an enterprise as I can imagine. Take a die grinder and smooth out the crummy welds inside the exhaust system. On some models, open up the baffle in the front exhaust crossover pipe - badly needs opening.

 

But if mindless playing with CCPs seems like fun to you....

 

Ben

*and I say this as someone with occasional disrespect for BMW engineers

Edited by Peter Parts
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Afternoon Ben

 

Actually on the 110RT there has been lots & lots of testing with the different CCP's carried out by countless riders, under actual riding conditions, at their common riding altitudes, using the gasoline available in their area, on the roads they usually ride on, carrying the weight they usually ride with. Most end up with the (NO) CCP configuration but a few seem to like the tan (30/87A). Both are open loop fueling maps on the 1100.

 

 

I have a friend that has been testing the NO CCP iteration his 1996 1100RT for over 180,000 miles. So far not one sign of an issue as far as engine reliability is concerned. In fact the engine is about the only thing that hasn't been replaced or repaired drivetrain wise.

 

BMW engineering tested the 1100 final drives & they failed, tested the 1100 transmissions & they failed, tested the ABS-2 system & those failed, tested the evap system & those failed. All those mentioned have failed in everyday usage in the hands or riders.

 

So what would any CCP testing that was published by BMW mean to the BMW rider?

 

BMW's main concern was the emission output so that the BMW 1100 would meet U.S. emission import restrictions so the bikes could be sold here.

It's always been obvious to us engineers that work in this field that BMW didn't put a lot of effort into light throttle ridability as long as it was lean enough to meet U.S. emission requirements & protect the cat long enough to get it through the warranty period.

 

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snip

 

So what would any CCP testing that was published by BMW mean to the BMW rider?

 

BMW's main concern was the emission output so that the BMW 1100 would meet U.S. emission import restrictions so the bikes could be sold here.

It's always been obvious to us engineers that work in this field that BMW didn't put a lot of effort into light throttle ridability as long as it was lean enough to meet U.S. emission requirements & protect the cat long enough to get it through the warranty period.

Good to see we agree on the CCP: some folks like it one way and some another and maybe there are three or four other ways too.

 

Good to see we also agree that BMW engineers make lots of mistakes. But pre-release test-track tuning is a bit different. There are a dozen or more kinds of running that need to be sorted out. Fortunately, the engines on the different models are pretty similar but BMW still thought there were differences worth fussing over.

 

The matter of fake-lean is a bit too much of a "conspiracy theory" for my taste but there may well be some truth to it. On the opposite hand, shouldn't BMW be releasing models that the magazine reviewers (and early adopters) praise? Either theory, switching colors randomly when you have no idea what each changes does, doesn't seem a rational approach.

 

We also seem to agree on something I've been saying for a long time: there can't be any cat converters working for long on a sporty bike.

 

Ben

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Afternoon Ben

 

It's not "fake lean", It's needed (02 sensor) lean to make the cat work. No cat working = no pass U.S. emission standards.

 

No pass U.S. emission standards = no selling bike in U.S. or Canada.

 

I really don't think BMW cares what the magazines or forums are saying as they (BMW) are selling everything they send over here at fairly inflated prices.

 

I'm not sure I would blame the BMW development & test engineers either. I'd be willing to bet a bucket of money the development & test engineers didn't want to send the bike out with a known surge. More than likely corporate management, or bean counters (or both) put the brakes on spending the extra money to add dual spark cylinder heads, twin 02 sensors, & duel fueling control fueling computer, etc.

 

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Afternoon Ben

 

It's not "fake lean", It's needed (02 sensor) lean to make the cat work. No cat working = no pass U.S. emission standards.

 

No pass U.S. emission standards = no selling bike in U.S. or Canada.

 

I really don't think BMW cares what the magazines or forums are saying as they (BMW) are selling everything they send over here at fairly inflated prices.

 

I'm not sure I would blame the BMW development & test engineers either. I'd be willing to bet a bucket of money the development & test engineers didn't want to send the bike out with a known surge. More than likely corporate management, or bean counters (or both) put the brakes on spending the extra money to add dual spark cylinder heads, twin 02 sensors, & duel fueling control fueling computer, etc.

Always a privilege to hear thoughts from DR beyond the usual fix-it advice he generously provides. But, I respectfully must ask why a bike living with a closed-loop stoich mixture shouldn't ride fine and past emissions tests OK too? The same O2 sensor works great on millions of cars. And the open-loop status is not lean.

 

To answer my own question, the boxer heads need improvement to work with leanish mixtures that other engines take in their stride. Adding a second plug, as DR mentions, was a big embarrassing hindsight gesture - as those of us who added plugs to our Airheads can tell you. But I can't answer why BMW was so lazy in fixing.

 

So my guess is that it shouldn't have been much trouble passing standards "back then" and having an engine that does not surge too.

 

About reviewers, I think you are quite wrong. I think BMW is sadly faulty in producing an engine with high-speed HP but at the cost of low speed flexibility - which advertizes well and impresses test track reviewers. But it is not what sports/tourers like the folks at this forum should be demanding.

 

Ben

Edited by Peter Parts
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Evening Ben

 

Cars of that era did have a lot of lean operational problems.

 

Modern pulse width modulated torque converters, EGR systems that change mode at light throttle, cam timing/profile that helps low end engine smoothness, some have multi spark plugs per cylinder, etc, all to help low throttle opening operation came about because of the light throttle operational issues.

 

BMW could have greatly improved the light throttle operation on the 1100 & 1150 with cam timing & lobe profile designed to help that operational region (at the expense of power & torque at higher RPM's) , using much smaller throttle bodies that increased air speed at low throttle openings ( again, at the expense of power & torque at higher RPM's), lowering the compression ratio & using smaller combustion chambers, (again, at the expense of power & torque at higher RPM's).

 

Probably the best change they could have made was to make it a 4 or 6 cylinder with very small pistons & smaller high turbulence combustion chambers (like cars)

 

None of those options would be acceptable to most BMW 1100 or 1150 boxer owners.

 

Not working for BMW or knowing what was going through their minds when the 1100 engine development was taking place all I can do is guess.

 

My educated guess is that the 1100 was primarily designed & devolved for the European market. At that time it would have needed only to meet the European IDLE Co. emission compliance. (therefore the non cat with idle Co. trim pot configuration for Europe)

 

At the time of the 1100 release that bike might very well have been imported into the U.S. with the European emission compliance (no cat) but not to the large market area of California.

 

So the simple (inexpensive) fix would have been to make all the U.S. imports the same & for all to meet California emission requirements (and that they did as there was no Ca specific import) .

 

To meet Ca emissions would mean that the bike would need to have either a required cat or a much leaner yet fueling, cam change, valve size change, lower compression, etc at a very reduced engine performance.

 

Simple way was to just offer the same base European bike/engine with a cat. Then to make the cat operate correctly the dreaded o2 sensor was needed.

 

It (the 1100RT/1100R) might have died quickly in the U.S. market with BMW making expensive changes to make the light throttle runabilty of the 1100 better. EXCEPT, they sold all they could import as it was so what incentive to increase cost in extra development time or other changes-- like different cyl heads, or dual plugs, & different fueling computer.

 

Riders liked the 1100 bike, they were terrific high speed long distance bikes, got great fuel economy for the engine power, held a lot of fuel, great air management, were easy to work on, and overall the bike was well liked.

 

A little bitching about surging & a little bitching about failing final drives but still all that were imported sold at a very profitable price.

 

THEN-- the U.S. pretty well went to 10 alcohol fuel across the board. That single handily made the surge noticeable by every rider. I doubt BMW even considered that at original vehicle development.

 

I know of MANY early BMW 1100RT buyers that bitched about the light throttle surge but went right out & bought another one the next model year. (couldn't have bothered them that much)

 

The thing is-- with a little work from the rider/owner the surge could be reduced to a very acceptable level. For others they never even noticed the surge, & others yet just changed their riding habits & kept the RPM's up so were happy as clams.

 

There are still a lot of 1100RT owners that have had their bikes for many years & ride them across the U.S. yearly many still stock with the factory fresh surge.

 

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Guys- To leave CCP plugged or to not leave CCP plugged. That is the question!

 

I've been talking / emailing with Matt at Dobeck (Techlusion) about this surging thing, he was the one who suggested disconnecting the O2 to begin with.

 

He does not recommend unplugging the CCP plug, says it makes the fuel mapping very unstable and erratic. He said the best way is to just unplug the O2 sensor.

 

Still haven't unplugged anything, still planning to do my valves etc. But I rode it to work yesterday (no lower bodywork)! Dave

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Matt at Dobeck has it wrong on the R1100. Unplugging the O2 and leaving the coding plug in leads to unstable (Limp Home actually) fueling. Removing the plug on an R1100 results in stable Open Loop fueling that most feel is less lean.

 

If you can be patient a while, we have an LC-1 on a R1100RT and will soon, sometime within the month I would think, publish how the R1100 fuels with no Coding Plug.

RB

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Guys- To leave CCP plugged or to not leave CCP plugged. That is the question!

 

I've been talking / emailing with Matt at Dobeck (Techlusion) about this surging thing, he was the one who suggested disconnecting the O2 to begin with.

 

He does not recommend unplugging the CCP plug, says it makes the fuel mapping very unstable and erratic. He said the best way is to just unplug the O2 sensor.

 

Still haven't unplugged anything, still planning to do my valves etc. But I rode it to work yesterday (no lower bodywork)! Dave

 

Brother, you are WAY overthinking this one. Pull it. Ride the bike. If you like the way it rides, leave the CCP on the sehlf. If not, put it back. It's that simple.

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Afternoon Dave

 

First off, when researching do not confuse the 1150 Ma 2.4 system with the 1100 Ma 2.2 system (two completely different fueling systems).

 

On your 1100 Ma 2.2 system you can basically try a few things to reduce or remove the surge, some seem to work better on some bikes than on others.

 

First, simply try removing the CCP. (see how you like that)

 

Next, try the tan (light brown) CCP or just jumper terminal 30 to 87A in the CCP socket (terminal locations are on the bottom of your old CCP (see how you like that).

 

Keep the one you like best-- If you like it well enough stop there.

 

That is your new baseline to work from.

 

If you want to keep playing then try the 02 disconnect with the stock CCP in place (must use stock CCP or no workie)

 

Once you have found the iteration you like best in the above then move on to the TPS adjustment.

 

Warm engine, good high impedance voltmeter, NO CHOKE ON set the TPS voltage (between term 1 & 4 ) to .385 volts. Maybe even .390 v but .385v is safer setting so it ALWAYS returns to under .400 volts at hot engine idle.

 

You might try doing a good TB balance at idle & above idle 2000-3000 RPMs.

 

If something in the above makes you happy with less surging & good mid range runability then you are good to go.

 

 

If still surging or you still aren't happy with the fueling then it's time to try something to modify that like Rogers LC-1.

 

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Guys- To leave CCP plugged or to not leave CCP plugged. That is the question!

 

I've been talking / emailing with Matt at Dobeck (Techlusion) about this surging thing, he was the one who suggested disconnecting the O2 to begin with.

 

He does not recommend unplugging the CCP plug, says it makes the fuel mapping very unstable and erratic. He said the best way is to just unplug the O2 sensor.

 

Still haven't unplugged anything, still planning to do my valves etc. But I rode it to work yesterday (no lower bodywork)! Dave

 

First, many thanks again to DR for much "insider" information. Appreciated.

 

I've chatted with Dobeck a few times and I think nobody could have as much dirt-under-the-fingernails grasp of Oilhead fueling and dyno testing as does Matt at Dobeck.

 

Enriching using the Techlusion is a sure-fire good fix for surging and nobody is going to say otherwise. It adds fuel and maybe you object to that for some reason. But it will make your engine really nice (AKA flexible). Simple. Long-since debugged. Not expensive. Install in a few minutes and go for a trip with a small screwdriver in your pocket. That's it.

 

It is the view at Dobeck (and mine too) that the closed-loop performance of the Oilheads is not good. But the open-loop performance, like for decades of bikes before, is pretty good. So just disconnect the O2 and sweeten the mixture, as Matt recommends.

 

Of course, I also think he is quite right about not randomly fooling around with CCP.

 

Footnote: I used a Techlusion for a year beneficially. Still sitting on the bike (doesn't weigh much, easy to connect and disconnect). Haven't felt I needed it for last 5 yrs)

 

Ben

Edited by Peter Parts
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Jim- You know I hear one person say "pull it" and another say "you'll ruin it". Thought I took care of the second one last week. :-)

 

But I think I will clean my plugs well, pull the CCP (remove that #5) and see how it goes, check the plugs after some mileage, see what they look like.

 

Then I will replace it and try the O2 disconnect like Matt at Dobeck suggests with my stock yellow cube in there. See which scenario I like best for acceptable performance and economy.

 

Dave

 

Edited by Dave P
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Afternoon Dave

 

Don't discount trying that tan (light brown) CCP (or jumper terminal 30 to 87A). That is a non-cat European open loop calibration. It automatically deactivates the 02 sensor input signal usgae just like the no CCP configuration does.

 

On the nay-sayers that say removing the CCP or other CCP configuration will plug your cat or ruin your engine. Just have them show you, or provide you one incidence of, ANYBODY having a cat plug or engine damaged from running any or no CCP.

 

Riders have been using the no CCP or the tan CCP in the BMW 1100 for well over 15 years & countless of millions of miles, one up, two up, loaded with camping gear, 100mph+cruising, high altitudes, etc. You would certainly think that if any inherent problems it would be all over the internet & BMW forums by now.

 

On the spark plug readings-- They will all look white after a good (long) high speed run (no matter the CCP or 02 sensor configuration used. Modern unleaded gasoline makes spark plug reading really really difficult.

 

If you are really worried about the possibility of one of the CCPs or 02 disconnection harming your engine then simply remove & inspect your spark plug electrodes every 1000 miles. Early sparkplug electrode degradation is an early warning of impending lean fueling engine damage.

 

In any case, it surges now so if you mistakenly make it leaner that thing will surge even worse at light throttle & be flat as can be, power wise, at higher speed roll on's. Trust me, if you make it leaner you won't keep that configuration long enough to hurt your engine.

 

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Dirt- Good morning! Chilly, rainy August morning up here, drove the Volvo in today and turned the heat on!

 

I disconnected the O2 last night and also (carefully) turned in the Brass screws (counted turns in) and removed. Boy they were black! Did notice I was 5 turns in to seat on the left, 3 1/4 turn in to seat on the right. That seems kinda strange. Cleaned them off and replaced. Next parts order I'll get a couple of new rubber rings.

 

As far as the CCP, I'm learning that different color cubes are simply different jumpers between terminals. Is that correct? So to do the jumper thing, I simply pull the cube and make a short wire with spades to go between slot #30 and slot #87A. Theoretically I could try all of the different CCP configs just with the jumper trick.

 

But today I'm going to try just that O2 disconnect, see what happens. Dave

 

 

 

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Morning Dave

 

Yes, all those CCPs are just jumper wires in a fancy box.

 

For the 30 -87A just a 2 terminal jumper wire is needed for something like 30-87-87A a 3 terminal jumper will be needed.

 

Put your stock CCP back in before riding the o2 disconnect iteration.

 

Back in the 1100 days when I was playing with the different CCP configurations I made up an extension harness to the different terminal pins in the CCP socket, then ran them remotely out from under the seat, then terminated them in a small plastic handy box with 4 toggle switches installed. That way with the flip of a switch (or two) I could change CCP configurations.

 

Just a quick stop & engine re-start to assure the Motronic accessed the correct CCP map & I was off again.

Later on I added a second extension to fuse 5 so I could remotely clear the Motronic adaptives when changing to or from a closed loop CCP configuration.

 

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Dirt- Sounds like you did some serious evaluation of the CCP device! Right now the O2 is disconnected and CCP plug has not been touched. at lunch today seemed a little less surge-y but I need to give it a little more time. I did have 5 bars when I gave it a try.

 

Maybe I'll put a few more miles on it this way and try the 30-87A jumper (after I rehook the O2) over the weekend. Or maybe remove the CCP altogether, see how it goes.

 

Dave

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Dave,

I have some charts below that show the typical fueling patterns of R1150, F800 and R1200 motorcycles that I've measured with LC-1 Wideband sensors. I fully expect that the R1100 will show the same pattern when the measurements come in later this month. I've already measured R1100 Closed Loop and it is nearly identical to the others Closed Loop.

 

 

Here is the pattern of fueling with the O2 sensor connected. (I use a 13.8 target AFR but the chart below would have the same tight fueling pattern if I used a stock sensor.) The key thing is that the fueling is tightly mananged.

afrresetadapt1.jpg

 

Here is what happens when you leave the Coding Plug in and disconnect the O2 sensor (or do that and also add a BoosterPlug). The top chart is the open loop AFR and the bottom is open with the BoosterPlug added (AFR improves from about 15:1 to about 14:1).The key thing to note is that in response to the disconnected O2 sensor the Motronic moves the fueling around a lot. It doesn't make it richer (in fact if you run E10 fuel it goes leaner), it just goes higher and lower with the AFR in an attempt to make the catalytic converter partially function.

afropenbp.jpg

 

DR's suggestion that you start your testing by removing the Coding Plug is a good one. Although I haven't yet measured it yet, I expect that on the R1100 no Coding Plug will be stable as with O2 connected, not unstable as with the O2 disconnected.

 

RB

Edited by roger 04 rt
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Afternoon Dave

 

You can just leave the o2 disconnected for either the (No CCP) or (30-87A) evaluation as both of those disregard the o2 input anyway.

 

With the either the (NO CCP) or (30-87A) iteration you might end up with a higher base idle speed as both richen the idle as they were meant to be used in conjunction with an Idle Co. trim pot.

 

Not a biggie but if you like the no CCP or 30-87A iteration you can always lower the idle speed later using those BBS screws. (or buy/build a Co. trim pot)

 

I see you mentioned removing & cleaning those BBS (brass idle screws) in an earlier post & also mentioned new "O" rings.

Those "O" rings were never available separately from BMW (need to buy the entire "expensive" bass screw) so unless things have changed just match those "O" rings up form general stock at your local auto parts store.

 

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Now you guys have me scratching my head again. Matt at Dobeck said pulling the CCP gives an unstable fuel map and I should just disconnect the O2.

 

Roger- what you are saying is disconnecting the O2 gives the unstable fuel map and pulling the CCP keeps it stable.

 

So I don't know which way to go here. I rode today with O2 disconnected, still felt some surging. So I think I'm going to try the CCP 30-87a jumper, ride it then CCP out, ride it. See what I've got.

 

Dirt- any opinions on those brass screws? 5 turns out on left, 3 1/4 on the right? sounds a little wacked to me- i thought they were supposed to be 1 1/2 turns out.

 

Dave

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....

 

Roger- what you are saying is disconnecting the O2 gives the unstable fuel map and pulling the CCP keeps it stable.

 

So I don't know which way to go here. I rode today with O2 disconnected, still felt some surging. So I think I'm going to try the CCP 30-87a jumper, ride it then CCP out, ride it. See what I've got.

 

...

 

Dave

 

Yes, that's what I'm saying, based on careful measurements of three BMW models. Also, I feel there is good reason for the Limp Home ( unstable) pattern shown by the O2 disconnected graphs. Also I've measured the R1100RT with Yellow plug so I don't believe I'm making a big leap by saying the R1100RT will show the same pattern when O2 is disconnected.

 

The no Coding Plug config per the document I posted earlier is a BMW config for the European R1100RT. 30-87a is for the R1100GS, but if no Coding Plug doesn't give you relief, why not try 30-87a.

 

As DR said, if his recommended step don't bring surging relief, a BMW-AF-XIED will. Two veteran riders have beta-tested. One liked it so much he removed a PC III, the other liked the XIED so much he installed an LC-1, which is where I'm getting the R1100 data.

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Clip--

 

Dirt- any opinions on those brass screws? 5 turns out on left, 3 1/4 on the right? sounds a little wacked to me- i thought they were supposed to be 1 1/2 turns out.

 

 

Morning Dave

 

 

Those brass screws being different side to side can mean a few different things.

 

Could simply mean that the last person that did a TB balance didn't know what he/she was doing & messed the adjustment up.

 

Or, the last TB balance was done without cleaning the BBS screws or air passages under them so "more open" on one side was needed to compensate.

 

Or, one or both side TB throttle shafts or bushings are worn therefore allowing more air in at curb idle on one side.

 

Or, that the TB throttle bores are coked up.

 

Or, that the valves are not set correctly on one side so the BBS are offset to even the curb idle air flow.

 

Or, some engine wear (in something) has altered the engine pumping at curb idle so the BBS were set differently to compensate.

 

Or, a combination of some of the above.

 

At some point in your future you REALLY need to check your TB throttle shafts/bushings for excess wear, fully clean the BBS screws & the air passages under them, do a quality valve adjustment, then set the idle & above idle cross side balance.

 

Try not to combine too many things at once so settle on a CCP or no CCP before trying to do the BBS & TB balance.

 

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OK Dave my two bits worth. If, after you look into all the things specified by D.R. and you still have a surge problem you might try tweaking the TPS (throttle position sensor) and see what you get. You can find a procedure for this at the IBMWR web sight. I had occasion to do this on a '96RT that had very low miles and it made all the difference. I have an early built in 06/93 R1100RS that is absolutely surge free after disconnecting the O2 sensor and cutting the yellow CCP jumper in the wiring harness and installing a home made CO POT which essentially made it a EURO version 1100RS with no need to experiment with the TPS. Oh, I also wonder if the previous owner maybe diddled with the throttle stop screws which might explain why the brass screws were set so different from one another.

 

Just my opinion but I think BMW made or Bosch made changes to the 2.2 Motronic in '96 when the RT was introduced. Of course my actual experience with a '96RT is limited to just one motorcycle so take my opinion for what little it's worth but that is what I would do if it t'wer my bike.

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What's the starting point on those brass screws? I seem to remember reading 1 turn out from seated on both sides, then hook up the twinmax and dial the right side (in or out) to get a balance at idle. Dave

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What's the starting point on those brass screws? I seem to remember reading 1 turn out from seated on both sides, then hook up the twinmax and dial the right side (in or out) to get a balance at idle. Dave

 

Dave, I don't think there's a set number. They need to be out far enough so that your bike will idle. Could be anywhere from 1 to several turns. Make sure that the throttle plates are solidly touching down on the stop screws.

 

In order to do the job, start with wherever they were, get it idling, and turn them both in or out until you 1) Have the correct idle speed and 2) Have the Twinmax in balance. That's the rough idea. After that's done, turn the throttle until rpm=2500 and then use the right handle cable adjuster above the TB to rebalance.

 

If you look around, you can find detailed instructions either here, on advrider.com hall of wisdom or ibmwr.com.

 

Edited by roger 04 rt
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Roger- OK, that sounds good. I think I'll see if anyone in my club has a Twinmax I could borrow. I seem to remember a couple of nice understandable write-ups on the sync. Gonna set my (cold) valves first.

 

I tried the RT last night with the O2 disconnected, yellow CCP in place, 5 bars- Surge city! So last night I reconnected the O2 and pulled the CCP, (fuse 5 out for 10 seconds). Rode in today but it was all at highway speed, will try a slower route home later today, see what it feels like. Dave

Edited by Dave P
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  • 7 years later...
Mark Davisson

mY 1998 R1100RT has been operating at half power for the past month and halk.  I have removed and replaced the spark plugs, checked the throttle cables, adjusted the air intake for the injectors to a reasonable idle, changed oil, and removed the leaking exhaust system to no avail.  It still runs at half power....Please help/

 

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5 minutes ago, Mark Davisson said:

mY 1998 R1100RT has been operating at half power for the past month and halk.  I have removed and replaced the spark plugs, checked the throttle cables, adjusted the air intake for the injectors to a reasonable idle, changed oil, and removed the leaking exhaust system to no avail.  It still runs at half power....Please help/

 

 

 

In order to get the proper assistance from The Oracle, please start your own thread with that question.  Also, it may help to have all the info of what it is doing, when, how much has been done to it, when, etc.    You may to go back and take a look at what you did to see if something was disturbed or is amiss.

 

Cheers, 

  • Like 1
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