different camshaft sprocket

[Plumbvp]

Hi To start with, this is my first post, so if I get something wrong a. don't be suprised and b. tell me nicely and I won't do it again. Greetings from Canberra.
I've recently been doing a replacement of a left side head gasket on my 06/94 manufacture date R1100RS (after reading the post by Steptoe on the subject){very helpful}. In particular, I read the bit on ensuring that the tab on the camshaft sprocket fits properly into the slot in the camshaft and that it can be damaged if put on incorrectly. When I looked at my sprocket about one third of it was missing, either worn off or mangled during a previous replacement. I headed off to my local BMW dealer who ordered in a new one Part no 11317 677 680 However, when I compared it to my existing (worn/damaged) one I noticed that if you aligned them using the tab on the camshaft side, the sprocket teeth were half a tooth wrong. I've asked the dealer why this is so but he hasn't supplied me with an answer yet (over a week).


As I understand it, if I fitted the new BMW part the camshaft timing would be about 10degrees from where it was.

So either the sprocket that was fitted to my bike or the new BMW part is not correct for my bike. The only other info I have is that the above part number superceded a camshaft sprocket with a part number of 11317 677 670 however my informant (Stefan, the BMW parts guru in Melbourne) said that there was no indication in the parts fiche that any other parts had to be changed when replacing the 670 part with the 680 part.

How possible is it that my bike has been fitted with a wrong camshaft sprocket (by some dumbkopf during a previous job)? I've only owned it for the last 2 years. However, the spark plugs have always been sooty and the inside of the head was also sooty when I took it off.

Can anyone shed any light on this? If I can be assured that fitting the 680 part is the way to go I will have to turn the engine over very carefully and check that there is no piston/valve clash. Even so I 'm not sure how I will know which sprocket tooth to sit the chain in because, if I'm right, it won't be possible to line the timing marks up to where they were. Thanks in anticipation of help

By the way It's 37 degrees in the shade today and about 60 in the shed where my bike is patiently waiting for me to sort this out!

 

[Stewart H]

Hi and welcome to the forum, you have an interesting problem, I suggest that you build up your motor observing all timing index marks, then turn it over several revolutions using a spanner on the crankshaft bolt, then re-check all timing marks before attempting to start it, sorry I cant be more help.

Stewart

 

[MattW]

You're right - that is a strange problem.

I might be inclined to whip the rocker cover and sprocket inspection cover off the other head, remove the sprocket bolt (for safety, cable tie it as if you were going to remove the head) and take a look at the sprocket. If the damaged sprocket shares the same timing with the other head's sprocket (keyway to sprocket teeth), I'd be thinking that the original (damaged sprocket) may be the correct item after all?

I could imagine the RS having a different cam grind / timing

A question for Steppers I think....

 

[Steptoe]

A question for Steppers I think....

Haven't a clue.

 

[MattW]

Haven't a clue.

We're doomed.

I can't find any on-line sources of part information for the RS, so I can't work out if the sprockets are different - it wouldn't be the first time dealer's have missinterpreted parts fiches....

 

[ebbo]

I've only owned it for the last 2 years. However, the spark plugs have always been sooty and the inside of the head was also sooty when I took it off.

It’s just possible you might have an incorrect sprocket fitted because my mates 1100RS had the right side cam sprocket fitted incorrectly, half the sprocket tab was crushed due to misalignment during reassembly (not Patto I hasten to add) That sides plug sooted up, compression was low and there was some vibration. Carefully re fitting the sprocket sorted it completely. Maybe, fitting a new correct sprocket might just fix it?

Good luck with it,

 

[Pukmeister]

Plumbvp, the online parts fiche at A&S Motorcycles (USA) shows two in number cam sprockets ending 670 with a suffix AE (component number two) and also two in number sprockets ending 680 with no suffix (also component number two).

It doesn't state which sprocket relates to which year of bike, or whether you might need a different part number of sprocket for each side of the engine?

Hopefully your dealer will be able to find an 1100 guru within BMWs organisation who knows your answer. When you get it, please post for the benefit of future 1100 owners.

 

[Trullion]

If I remember correctly the Haynes manual points out that on the bike they were working on the mark on the sprocket did not align with a tooth (as BMW claim is the case), but with the gap between two teeth on the sprocket. (Mine are the same). I reckon that you should put the new sprocket on. It sounds to me like whoever last had the sprocket off did the not unheard of ham-fisted trick of 'squashing' the sprocket on because it wasn't properly aligned. It's not difficult to do properly.

Good luck.

 

[Plumbvp]

Thanks for comments so far guys! Yes the BMW dealer is now sending the bike's details off to Germany. I'm coming to the view that the sprocket on my bike may not be the correct one. (although how it got on the bike is anyone's guess).I agree with Mat W that taking the sprocket off on the other side and seeing whether it's the same will be worthwhile, as soon as BMW come back with some info. Trullion's comment about the Hayes manual is useful too - I have one myself but its not clear which model they pulled apart. In the long run if I don't get any definitive answers I intend to put the new (680) sprocket on and as you say turn it over with a spanner and see what happens. If its Ok I'll then put it back together. It's just possible the bike will suddenly have a new lease on life and go like stink (compared to how it has been)
Re pukmiester's comment:- The AE marking after the 670 number could be the superceded indication that Stefan from BMW Melbourne was talking about. The BMW people assure me that the 680 part is what the fische says is correct. I've also been assured that the sprockets on right and left sides are the same. The indication that two are fitted is presumably just one right and one left.

I'll be happy to report back on the full story when(/if) I get some progress.