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Discussion in 'Airheads' started by bushyb, Oct 4, 2012.
It sounds like the timing is advanced too far.
Thanks for the replies. Sorry in advance if I sound a bit frustrated as this has been a thorn in my side for a while now. It seems there is some consensus that the timing is out.
Now I can almost set a 59 Bonnevilles timing blindfolded because the process is set out step by step and I have done it a few hundred times.I have searched and found a lot of stuff with a gazillion pages a million other issues and models and part etc. I just get totally lost in all the jargon, I am the worlds worst reader I need pictures. I have not done this on a BMW or VW before. What I am looking for a simple step by step instruction to check the timing on my bike a 1982 R100RS. Hope someone can help with some photos and a step by step instruction. Thanks
Timing your bike is very easy,
Buy a strobe timing light
Connect it to the engine
Look at the timing marks with the strobe. They should be at the S mark at idle revs. And stop advancing on the F mark at about 3000-3500 revs. (some bike will have a Z mark instead of an F}
Loosen the 2 bolts securing the bean can and rotate to adjust the timing, (use a kitchen glove so you don't get burnt by the hot exhaust.
Tighten the bean can.
If the timing on the S mark is wrong, but it is right on the F mark, then go with the F mark.
If you don't have a strobe you can very roughly time the bike at idle by rotating the bean can and fixing it where the engine sounds happiest. Usually setting the bean can in the middle of its adjustment range will get the bike started. Ignore all the stuff in the manuals about using special BMW timing tools for setting the initial timing.
Sorry, but no pics!
Thanks for the reply. 1982 R100RS. It seems the timing was out quite a bit. But I am not sure its spot on now. Marks on the fly wheel are from the bottom upwards “---“, “S” and ”01” and about 2 inches on there is a “Z”. Note this is an electronic system (no point). Battled to start the bike once it was started we checked the timing with the strobe light which was showing the “Z” mark in line with the crank mark. Loosened and adjusted the bean can clockwise and got the “---” about 3mm above the casing mark, I had to fully rotate the bean can all the way clockwise so it could not go any more to get the “---“ close to the casing mark. When the bike was revved up to 3500 rpm we couldn’t see the “Z” mark but the “---” mark just moved up just a bit. I must say that it idled much better. It started this morning with a touch of the button. I actually couldn’t believe how easy it was.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
I am just wondering if this is correct or ”good enough”. My thoughts are that the advance springs (if any) are a bit seized so that there is not a big difference when revving up the motor.<o></o>
The other though was just like one replaces the distributor on the car and you got to slot it in exactly right to get an equal amount of movement either way on the distributor. Is it possible to remove the bean can and rotate it slightly anti clockwise to centralize it better and replace it without too much difficulty? <o></o>
I hope this makes sense <o></o>
I usually start my bike with the choke on full but unlike the rest of you I give her some gas while cranking. About 1/3 throttle. If warm out I turn choke off immediately and if cold only turn it half way down for a minute.
My bike does not sound anything like yours. Crank, pause, crank, pause. I also think that is a symptom of too much advance but never sure of this until I check the timing. Do you have an electronic ignition? I guess you do since it is an '82 bike. Be very careful to not crank the engine unless the plug wires are hooked up to installed plugs or the plugs are well grounded. These electronic ignitions fry parts if the coils fire into a blank hole.
You have a good battery and the starter motor is cranking good. It's not either of those.
I am a bit confussed. I went back and loosened the bean can and started the bike again then rotated it anti clockwize with the strobe light on it checked it again at all the way back the the ideling was higher and the "Z" was in line with the grove on the casting.
On turning the bean can clockwize again the "Z" moved downwards but the "S or ---" could not be seen and the ideling dropped.
Remenber when I first looked at it the bike was difficult to start and the "Z" was lined with the mark.
So with the bean can fully rotated clockwize the bike starts easy and the ideling is lower.
There are different letters on different bikes unfortunately. My 81 RS has OT and Z
OT in the timing window at idle ~1050 rpm
Z in the window @ 3000 rpm
There is always the possibility of the flywheel/clutch carrier being incorrectly placed on the crank, as in 'one hole out'
Can I give you my advice ? As I own an R65 RT (special offer in 1982 from French importer based on an RT fairing added to a plain R65).
This bike was heavily used up to 160 000 km then let aside for 10 years, been run on and off since today.
I decided to remove the fairing this year and put it back into use.
As on you bike, the battery, even if new, had big difficulties starting the bike. I was allowed only one stroke of the starter. So if I did not succeed to start it on the first stroke, I had to go to work by foot... I complained to the battery seller and he offered a new one. Same behavior. I tester all the charging circuit but to no avail. Then I removed the fairing and saw that the big positive lead going out of the motor casing had been destroyed by the bar which hold the two fairing sides to the frame !!! I had been lucky because the fairing is plastic, and the frame is well painted so earthing was not good. Otherwise...... Now with the new cable in place, the battery charges very well and keep it. I have a lot of starting strokes available and all is well. I suggest you remove your tank and have a peek... you may get an horror view...
Last but not least, I was quite unable to tune the engine. Even after thoroughsly cleaning the carbs and replacing all O-rings and diaphragms. I asked a competent BMW dealer and he told me to check the advance timing. bingo, it was at full. And could not adjust it properly. so I opened the can to see that the advance mechanism was seized at full stroke. A cleaning and lubricating later, the bike ran very fine.... Bear in mind that the advance springs are very delicate and difficult to source... so do not use your biggest hammer to dismantle the bean can....
Hope this helps !
P.S. I will spend some holidays next April near Rotorua...
OT means TDC so you should have the timing at idle set around 6° BEFORE this. If you do not have an S mark you have to use a timing light with advance settings. The Z mark means full advance and should only show around 3000 RPM. The start of advance (moving from S to Z) occurs at around 1500 RPM. As the bean can is the same for quite every bike using it, advance settings should be the same. Check either the user manual or the maintenance manual or Clymer or Haynes for the exact settings for your bike.
Yes, what George said. S in the window at idle, not OT.
Thanks, Correction I stated "01 it should have been 0T".
I will have to look again. I can get the "Z" at idel and at 3000 rpm. Would this be a problem? I will have to check again. To the best of my knowlge the bike has never been striped or a part.
Thanks you must make a turn. No problem with the wiring as soon as the timing was changed there was a marked difference in the ease of starting, so its got to be the timing. I must just understand it and get it right.