Dee Duble Yuh
02-07-2004, 10:23 AM
This text is taken verbatim from from TrevorW's site:
---------------------------------------------------
"Surging" is the major issue for owners of the R1150RS and R1150RT. It is a phenomenon that usually appears at about 2500-3500 rpm under light loads or when cruising with a steady throttle (i.e., around town). It feels like the bike is continually speeding up and slowing down, as if the rider were making tiny throttle adjustments, and it can be very annoying.
It has always been a problem to some extent on oilhead twins, but the larger the engine and the higher the state of tune, the worse it seems to be in practice. Hence the 1150 is worse than the 1100, and the RS/RT are worse than the R/GS and the cruisers.
Some bikes suffer more than others, and it's impossible to predict whether the one you buy will have the problem before you hand over the cash. I would strongly suggest raising the issue with the dealer before purchase, so that you have good grounds for complaint if your bike does it. There's nothing the dealers like more than to say "Sorry, they all do that, Sir". The good news is that there are solutions available if you're unlucky. The links I've included in this section are to what I believe to be pretty definitive information about solutions. There's a lot of less informed speculation around, unfortunately.
Steve Makohin has a good writeup about the possible causes here (http://www.interlog.com/~wateredg/Bike/PurgeTheSurge.html), although most of the cures are only related to the 1100s (Motronic 2.2).
The BMWRT pages, especially their Forum, have more information than you could possibly want on surging - but in the forums, not all of it is accurate. The usual advice is to perform the valve clearance adjustment and throttle synchronisation extremely carefully, which helps on most bikes, but does not cure all of them. Their FAQ (http://www.bmwrt.com/faq/surge.htm) has a lot good information, mainly for 1100s.
In some countries, BMW have approved a different Motronic 2.4 Catalyst Code Plug (CCP) for the 1150RT/RS, which for many people has reduced the surging to an acceptable level. It doesn't seem to completely remove it. You will often see this referred to on the net as the Olive Green CCP. The stock CCP is pink. The effect is to change the mapping of the fuel injection, presumably to run a richer mixture.
You should be able to get your dealer to do this plug swap for you. If not, you can buy the plug and swap it yourself, or just make up a jumper and connect it as shown here (http://www.smugmug.com/gallery/308/6). This is what the green CCP looks like on my bike (http://www.krakar.co.uk/rrs/sofar.htm#remus). The procedure for swapping is to remove the old plug, install the new one, and remove fuse #5 for 30 seconds to clear the memory in the Moronic unit (which will also delete any fault codes it happens to have stored).
One important thing to note: The coding plugs used, and the effect they have (even the effect of not fitting one) is different between the 1100 and the 1150. So be very careful when following advice on the net about this problem, that the solution you're reading about applies to your bike. Also note that the R, GS, S and cruisers, which have engines in varying different states of tune, use different coloured plugs, and it is unlikely to be safe to use these plugs in the RS or RT.
For a further twist, it appears from reading various French and Belgian riders contributions to the RT forums, that BMW dealers in those countries supply some or all 1150 RS/RTs with the CCP removed altogether. There's no definitive evidence I can find about what this setting actually does, but it's probably safe to assume that it's a different, but richer, setting to that given by the pink plug. In the UK at least, the green CCP is now also approved by BMW to be fitted in the 1150RS. I've got this on my bike, and it does what other RS and RT owners have reported. The surging is still present, but a lot less noticeable, and rarely enough to be annoying.
---------------------------------------------------
"Surging" is the major issue for owners of the R1150RS and R1150RT. It is a phenomenon that usually appears at about 2500-3500 rpm under light loads or when cruising with a steady throttle (i.e., around town). It feels like the bike is continually speeding up and slowing down, as if the rider were making tiny throttle adjustments, and it can be very annoying.
It has always been a problem to some extent on oilhead twins, but the larger the engine and the higher the state of tune, the worse it seems to be in practice. Hence the 1150 is worse than the 1100, and the RS/RT are worse than the R/GS and the cruisers.
Some bikes suffer more than others, and it's impossible to predict whether the one you buy will have the problem before you hand over the cash. I would strongly suggest raising the issue with the dealer before purchase, so that you have good grounds for complaint if your bike does it. There's nothing the dealers like more than to say "Sorry, they all do that, Sir". The good news is that there are solutions available if you're unlucky. The links I've included in this section are to what I believe to be pretty definitive information about solutions. There's a lot of less informed speculation around, unfortunately.
Steve Makohin has a good writeup about the possible causes here (http://www.interlog.com/~wateredg/Bike/PurgeTheSurge.html), although most of the cures are only related to the 1100s (Motronic 2.2).
The BMWRT pages, especially their Forum, have more information than you could possibly want on surging - but in the forums, not all of it is accurate. The usual advice is to perform the valve clearance adjustment and throttle synchronisation extremely carefully, which helps on most bikes, but does not cure all of them. Their FAQ (http://www.bmwrt.com/faq/surge.htm) has a lot good information, mainly for 1100s.
In some countries, BMW have approved a different Motronic 2.4 Catalyst Code Plug (CCP) for the 1150RT/RS, which for many people has reduced the surging to an acceptable level. It doesn't seem to completely remove it. You will often see this referred to on the net as the Olive Green CCP. The stock CCP is pink. The effect is to change the mapping of the fuel injection, presumably to run a richer mixture.
You should be able to get your dealer to do this plug swap for you. If not, you can buy the plug and swap it yourself, or just make up a jumper and connect it as shown here (http://www.smugmug.com/gallery/308/6). This is what the green CCP looks like on my bike (http://www.krakar.co.uk/rrs/sofar.htm#remus). The procedure for swapping is to remove the old plug, install the new one, and remove fuse #5 for 30 seconds to clear the memory in the Moronic unit (which will also delete any fault codes it happens to have stored).
One important thing to note: The coding plugs used, and the effect they have (even the effect of not fitting one) is different between the 1100 and the 1150. So be very careful when following advice on the net about this problem, that the solution you're reading about applies to your bike. Also note that the R, GS, S and cruisers, which have engines in varying different states of tune, use different coloured plugs, and it is unlikely to be safe to use these plugs in the RS or RT.
For a further twist, it appears from reading various French and Belgian riders contributions to the RT forums, that BMW dealers in those countries supply some or all 1150 RS/RTs with the CCP removed altogether. There's no definitive evidence I can find about what this setting actually does, but it's probably safe to assume that it's a different, but richer, setting to that given by the pink plug. In the UK at least, the green CCP is now also approved by BMW to be fitted in the 1150RS. I've got this on my bike, and it does what other RS and RT owners have reported. The surging is still present, but a lot less noticeable, and rarely enough to be annoying.