Timing without timing marks!

[Jem Wilton]

Hi all, '89 r100gs - runs ok, pops and bangs a bit on overrun, but got me to the Sahara and back in March. I want to get the ignition timing correct but I have no timing marks on the flywheel - I think it's been installed incorrectly... So the question is, how to find TDC (I used to put a pencil in the barrel on my '69 Triumph, but that doesn't work on the German. Is there a tool for finding TDC that you lads have used? After that, how many degrees round the flywheel is the advanced setting and how do I mark that on the flywheel? Any advice welcome.

 

[Gelandestrasse]

To find TDC. Put bike on centrestand. Take off LH rocker cover (have oil tray underneath), remove plugs (this makes engine easier to turn over). Using kickstart lever or rear wheel in gear turn the engine forwards (kickstart direction or rear wheel forwards not reverse), and watch the valve gear, especially the inlet valve. When it has opened and then closed you are on the induction cycle and the piston is returning to TDC on that cylinder's firing point. If all is normal (look at the picture now) you will see the 2 timing tabs (not highlighted, to demonstrate how difficult they are to see) go past the timing hole in the crankcase by the dipstick. Use your pencil technique down the plug hole to estimate the TDC point. The picture is for you to identify what you are looking for in the timing hole.

If all is not normal, and the flywheel (or clutch carrier, as BMW call it), these tabs are elsewhere on the 4-stroke cycle because the flywheel has been put on incorrectly. Although possible, I've never seen it/discovered that condition. You might be better off, in that case, to remove the rear wheel, swing arm, gearbox and dismantle the clutch, taking the flywheel bolts out, and rotating the clutch carrier whilst holding the engine at approximately TDC on the alternator bolt. When the tabs seem to be close, then refit the flywheel bolts and reassemble.

As for degrees, just do a google search, I'm sure Snowbum has written a few pages on it!

 

[monoi]

You can also use the alternator bolt to turn the engine. There should be a S mark with a dot above and below for the idle timing. I believe it is 6deg BTDC at idle, going to 30deg advance at 3500rpm.

 

[Bubb]

Popping on deceleration is rich mixture usually….

Mixture screw on bottom of carbs may need adjusting to get correct rich/lean mixture.
Turn screw out ( anti-clockwise) is leaner if I remember correctly

Someone with FAR more knowledge than me ( not difficult) will be along shortly to confirm ( or to advise thet I’ve got it arse-about-face again)

Good luck with the timing.

 

[Jem Wilton]

Popping on deceleration is rich mixture usually….

Mixture screw on bottom of carbs may need adjusting to get correct rich/lean mixture.
Turn screw out ( anti-clockwise) is leaner if I remember correctly

Someone with FAR more knowledge than me ( not difficult) will be along shortly to confirm ( or to advise thet I’ve got it arse-about-face again)

Good luck with the timing.

Cheers matey, yes, I have weakend the mixture and the pops and bangs have gone... Thank you. However the old German is still a little lumpy so I am going to carry on trying to find the timing marks, TDC, and better running....!!!

 

[mikeyboy]

Hardly a big job to remove the box and refit the flywheel in the correct place

 

[dogshome]

Hiya, My R65 also has a misplaced flywheel. Since 1984!

I used a dial gauge stuck down the spark plug hole. Stoppers and the little gauges with plungers that thread in also work. It is, a PITA, until you realise the flywheel can be 1/5th out, but not related to TDC. I forget the number of stupid degrees. I painted marks where I could on the swiss cheese piece of steel humerously called a flywheel on my 650 and then set it with a strobe.

Works with no issues, but god help a new owner

 

[Jem Wilton]

Hardly a big job to remove the box and refit the flywheel in the correct place

Ha ha ha, changed the clutch plates, crank seal and oil pump o ring when I got back from my March trip to Morocco...

 

[Jem Wilton]

Hiya, My R65 also has a misplaced flywheel. Since 1984!

I used a dial gauge stuck down the spark plug hole. Stoppers and the little gauges with plungers that thread in also work. It is, a PITA, until you realise the flywheel can be 1/5th out, but not related to TDC. I forget the number of stupid degrees. I painted marks where I could on the swiss cheese piece of steel humerously called a flywheel on my 650 and then set it with a strobe.

Works with no issues, but god help a new owner

Thanks for the advice, I'll have a look this weekend (I'm not going down the previous lad's suggestion of gearbox out etc)!

 

[Gelandestrasse]

Ha ha ha, changed the clutch plates, crank seal and oil pump o ring when I got back from my March trip to Morocco...

So you put you own flywheel on wrongly?

 

[Jem Wilton]

So you put you own flywheel on wrongly?

locked it up - presumed it was on the right way - looks like it wasn't ah well, the bikes running ok, next time I have the gearbox out I'll fit it up properly - thanks for the advice lads