The warnings about this was found after the damage was done: While attempting to fix an oil leaking right hand head gasket we found the cam sprocket bolt frozen and used a air impact wrench to remove it. That succeeded in destroying both upper and lower plastic cam chain guides. We finally did get enough force to break the bolt loose but now it's damage recovery mode. It looks like the engine has to come out and have the cases split to replace the cam chain guides due to the pins that pivot on inside the engine case. We've read about some people slotting the guides to enable replacement without the pain of the case splitting. I looks like for the lower one replacement might be possible by removing the pivot bolt on the outside of the case, but there is some concern about the one for the left cylinder coming out of position if this was tried. We saw some info about this technique, but the info. was old and we're interested to know if the method is reliable for the long haul. Is there any guidance on the size and location of the slots out there? Moe, Curly and Larry BMW repair... BTW, this 1996 R1100GS is scheduled to leave for a 12,000 mile plus trip to Central America December 30!
Departing Dec 30th? You better get busy. I cannot comment on replacing the chain rails...maybe Anton the Expert has some insight here...and if he isn't too grouchy, maybe Sir Steptoe will chime in....or even Dr. JVB. I'll be waiting and watching as to the path you take for repairs. 73
Steptoe has a method he posted, with photos, on how the change them without removing the motor or splitting the case. You cut the old ones out, then notch the hole where the pin goes and snap them in place. Do a search. I will see if I can find it. Jim
Given your time frame, unless you have about a full week of free time dedicated to do a rebuild I would suggest the "split the rails" method. I know several technicians who have done this method with much success and have had bikes run at least 20k+ with no signs of failure. I would imagine if they will go that far they should last without a problem. In regards to splitting the case method and why it takes so long: It's not the motor rebuild... its getting the motor separated. You do not drop the motor on this bike... You disassemble the entire bike from the motor... in sections, and without the frame jig its a REALLY big project. figure minimum 10-12 hours apart and 10-12 hours assembly thats 20-24 hours just to swap a motor provided everything goes smoothly. All said and done I had 40+ hours in mine due to a severe near untraceable oil leak in the clutch area (but I can now do a clutch swap on my bike in about 5 hours...lol). When I did mine, I split the case largely due to my bike having 132k on it at the time I did it. As it's a bike I intend on riding for a long time to come, I wanted to be sure of the condition of the entire motor. I'm pleased to say even at 132K miles everything measured well within spec range. Although I did discover the timing chain tensioner rail was shot, which I never would have known without having removed the timing chain cover to do the motor tear down. In summary, unless you just want a huge project or you have really high mileage on your bike and want to KNOW everything is right in the motor, and especially considering your time constraints... split the rails On a side note if you do decide to split the case MAKE SURE all the necessary parts are available IN THE USA! the engine gasket kit when I did mine was not available in the states, and took almost a month to get Rush delivered from germany. Good luck and let us know how it goes!
Here is the lower rail. It can be replaced without splitting the cases. See the bolt head to the right of the screwdriver tip. Here is the upper rail. It is secured in the left case.
Leave it to Anorak who has been everywhere in the boxer engine. I wonder what those rails are made of, ABS? Delrin? Kel-F?
There was nothing under his "threads started"! I would still like to see a rail that has been slotted!
Yo dude! I'll search a little harder next time I'm up to the computer. The search feature sucks on the phone.
Here's a thread on UKGSER that has some good photos http://65.38.186.190/forums/showthread.php?t=282821 I've seen something similar here but can't find it now.
That thread will tell you all you need to know. A couple of engines i've replaced the cam chain guides on have now done more than 40K miles without any problems. Have a good trip.
It looks like on the parts diagram shows a washer and snap ring for the side on the lower bolt the rail pivots on and that unscrewing the pivot bolt might cause those to fall out and drop down into the crankcase. How does that interact with replacing the lower guide?
