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Timing Marks - Crank Shaft Sprocket/Cam Shaft Gear

b25bsaboy

b25bsaboy

New member
Good evening and New Year 🥳

I purchased a 1972 BMW R75/5 a year and half ago as a project to work on in the winter. The bike was put In to storage, covered in Vaseline till I bought it home.

Pretty much stripped and I am doing a mechanical restoration and thus far all is going as planned. In inspecting the timing chain, it needs to be replaced. This should be simple enough, but before I start stripping the chain off, I went looking for the timing mark on the crank shaft sprocket and the cam shaft gear. Either I am blind or there is none. can someone shed some light on this!

In looking at the crank shaft sprocket I will replace as it seems to have sone wear along with the ball bearing front crank. It was evident its been hitting the inner case on the right side facing forward.
 
Timing marks and TDC marks are on the flywheel visible through a viewing port at the back of the engine case. Remove the rubber plug to see them.
 
if you are using a master link replacement,just make a mark where the two gears are before you cut the old chain off
tensioner and spring should be replaced as well
 
Hi b25bsaboy,

The timing mark on the crankshaft timing gear is hidden by the timing chain.

Here is how I did this work on my 1975 R75/6. It's the same chain and procedure for your bike. I would advise using bolt cutters to break the continuous row chain and not try to grind off the pins on a link. That creates lots of sharapnel.

11 BMW 1975 R75/6 Replace Timing Chain, Crankshaft Sprocket, Nose Bearing


I used the bolt cutters on the 1977 RS project, which also has the dual-row timing chain. Much easier to clean up after :)


11 BMW 1977 R100RS Replace Timing Chain, Crankshaft Timing Gear & Nose Bearing



I hope that helps.

Best.
Brook Reams.
 
brook.reams said:
Hi b25bsaboy,

The timing mark on the crankshaft timing gear is hidden by the timing chain.

Here is how I did this work on my 1975 R75/6. It's the same chain and procedure for your bike. I would advise using bolt cutters to break the continuous row chain and not try to grind off the pins on a link. That creates lots of sharapnel.

11 BMW 1975 R75/6 Replace Timing Chain, Crankshaft Sprocket, Nose Bearing


I used the bolt cutters on the 1977 RS project, which also has the dual-row timing chain. Much easier to clean up after :)


11 BMW 1977 R100RS Replace Timing Chain, Crankshaft Timing Gear & Nose Bearing



I hope that helps.

Best.
Brook Reams.
Click to expand...

Evening Brook,

Follow your web site and appreciate that fact you are reaching out and sharing your knowledge and experiences!

https://www.flickr.com/photos/brook-reams/23947313970/in/album-72157660967429743/ - On this page with you showing the lower sprocket for the crankcase timing and you are marking it with white paint? I have closely inspected my sprockets and cannot visible see and marks which is my concern. Before I start pulling the sprockets off want to align at the lower sprocket at 12 o’clock and the upper at 6 o’clock.

It’s funny in all the British engines I’ve done the timing marks usually align with were the key way sits on the shaft, thus eliminates guessing. I will go into the shop tomorrow and remove the front bearing to give me a better look at the crank upper sprocket. When I removed the pressure slipper spring and shoe itself, the sloppiness of the chain is very noticeable, even with a low mileage R75/5.

Have a figure out how to make my photos smaller to attach so that you folks can see what in h#*l I am taking about!

Thank you all for your responses as I appreciate all thta has been mentioned.
 
20774 said:
Snowbum has a comment on the timing marks below a picture in the middle of this page:

https://bmwmotorcycletech.info/timingchain.htm

He indicates they are hard to find. In my Haynes, there's a picture which shows that the crank mark at 6:00 and the cam mark at 12:00...pointing at each other.
Click to expand...

Mr. Snowbum, Appreciate tour comments. My problem is that I cannot find any marks. Will look once I get the nose bearing off things will come to light! One only hopes.....
 
b25bsaboy said:
Evening Brook,

Follow your web site and appreciate that fact you are reaching out and sharing your knowledge and experiences!

https://www.flickr.com/photos/brook-reams/23947313970/in/album-72157660967429743/ - On this page with you showing the lower sprocket for the crankcase timing and you are marking it with white paint? I have closely inspected my sprockets and cannot visible see and marks which is my concern. Before I start pulling the sprockets off want to align at the lower sprocket at 12 o’clock and the upper at 6 o’clock.

It’s funny in all the British engines I’ve done the timing marks usually align with were the key way sits on the shaft, thus eliminates guessing. I will go into the shop tomorrow and remove the front bearing to give me a better look at the crank upper sprocket. When I removed the pressure slipper spring and shoe itself, the sloppiness of the chain is very noticeable, even with a low mileage R75/5.

Have a figure out how to make my photos smaller to attach so that you folks can see what in h#*l I am taking about!

Thank you all for your responses as I appreciate all thta has been mentioned.
Click to expand...

Rick,

The key way on the crankshaft nose is at 9:00 when the engine is at TDC. So, you can mark the 6:00 tooth of the crankshaft timing gear by looking at the key way slot in the gear, positioning it at 9:00.

I marked the camshaft sprocket and crankshaft sprocket with paint marks BEFORE I removed the timing chain, as described in the documents I posted the links to.

Hope that helps.

Best.
Brook.
 
The timing marks are often quit faint and also usually appear to have been etched by hand with a scribe of some sort. Make sure the flywheel TDC Mark is visible through the timing hole in the block and aligned with the mark there so both sprocket marks will be adjacent. The crank sprocket will have a visible mark scratched into the surface at or near the 6:00 tooth. With the chain in place the cam sprocket should have its corresponding mark near the 12:00 tooth. It will be more easily seen with the cam bearing out of the way but it can be viewed with the bearing in place. B843E327-846C-4AD3-B32A-00310069B156.jpeg
 
b25bsaboy said:
Good evening and New Year ��

I purchased a 1972 BMW R75/5 a year and half ago as a project to work on in the winter. The bike was put In to storage, covered in Vaseline till I bought it home.

Pretty much stripped and I am doing a mechanical restoration and thus far all is going as planned. In inspecting the timing chain, it needs to be replaced. This should be simple enough, but before I start stripping the chain off, I went looking for the timing mark on the crank shaft sprocket and the cam shaft gear. Either I am blind or there is none. can someone shed some light on this!

In looking at the crank shaft sprocket I will replace as it seems to have sone wear along with the ball bearing front crank. It was evident its been hitting the inner case on the right side facing forward.
Click to expand...

Thought I would update everyone about the timing chain and crank gear sprocket. I purchased the bearing/cam tool remover from Cycle Works and it worked perfectly both in removing and replacing the crank gear sprocket and outer bearing.

Everyone talks about the timing gear stretch or condition and I was surprised at the difference from the old chain verses the new chain. Huge difference in the new chain did not have the sloppiness as the old one did. If I do another project, that timing chain gets replaced! The chain can make a huge difference in the timing and will be anxious to see the difference.

I appreciated all of the responses to my questions and Brook’s site is a very good reference point for guidance!
 
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