If you like our site, please consider joining our club!
By joining you will help ensure that we can continue to provide this service
JOIN HERE!

Timing Issue R 75/5; R 60/7

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Timing Issue R 75/5; R 60/7

Post by srankin »

Thanks Craig, so do you think the timing chain skipped a tooth? Oh yes, I seem to be blank in forgetting you are talking about two bikes not just one, sorry.

I understand exactly what you said, in your case, because the bike is not running, idle has no effect. It has been a long time since I messed with points.

Not to be a disbeliever but I know there is a double chain in these bikes and man, I find it hard to believe timing could have jumped a tooth. Unless they have tons of miles on them or god forbid something really bad happened I would have to see it to believe it.

Just out of curiosity has anyone ever had the timing chains off in order to repair anything, seals or what not? BMW didn't make the alignment marks very clear on some bike on the cam sprocket an crank sprocket. If they were apart, perhaps they were put back together one tooth off?

Kurt, a question, do the valves hit the pistons if the cam is out of time with the crank? I have not had it happen but I remember hearing I can happen. If the engine cranks over with an Allen wrench, and the gears are off, it may not be much off.

Craig, where are you at? LOL, it might be easier to go to your place to see if I can help than to write back and forth. St
Owner of a 84, R80RT and 78, R100RS

User avatar
schrader7032
Posts: 9016
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX
Has thanked: 2 times
Been thanked: 29 times

Re: Timing Issue R 75/5; R 60/7

Post by schrader7032 »

ST -

RE: valves hitting the piston. You know I don't think I've heard of this kind of interference with the Airhead engine. Certainly if a valve stem breaks and the valve drops into the chamber, then that will hit. But in all the discussions, I can't say as I've heard of valve-piston interference.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Timing Issue R 75/5; R 60/7

Post by srankin »

Well Kurt, you know how it is, a rumor about something gets out, or some tenuous thing gets mentioned by someone. I had heard the valve interference a while back, and filed it away in the brain box.

I sure as heck don't ever want to find out if it is true and thankfully I have never had a bike jump a tooth or teeth in the timing system to bear out the valve and piston interference issue. I hope I NEVER do.

I do however know in a lot of cars with timing belts, if the belt breaks pistons can hit valves while things are spinning and out of sync. Again, I have never had it happen to me, I have seen it happen to others. Prevention and following the company recommendations on replacement intervals keep me from the problem.

This problem is a real head scratcher, because if the cam and crank are in perfect alignment, then the points if gapped properly should open and close at the proper mark, lined up with the window.

It can be frustrating reading posts and trying to visualize things given only the written word. Maybe someone should start a jet set airhead repair business, LOL, Have wrench will travel. St.
Owner of a 84, R80RT and 78, R100RS

User avatar
cbclemmens
Posts: 216
Joined: Sun Apr 25, 2021 2:21 pm
Location: Apollo, PA
Been thanked: 4 times

Re: Timing Issue R 75/5; R 60/7

Post by cbclemmens »

Thank all you guys for your help. I reduced the point gap to 0.010 and the timing came right in line. I learned something new. I bought my first airhead in 1972 and have owned this particular bike over 10 years. I must have put new points in these things a couple of dozen times. I knew that the point gap affected the timing but I had no idea how much.

The R 75/5 is running just fine. I haven't dived into the R 60/7 yet but I am confident narrowing the point gap will work as well on it.

Thanks again.

Craig

User avatar
schrader7032
Posts: 9016
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX
Has thanked: 2 times
Been thanked: 29 times

Re: Timing Issue R 75/5; R 60/7

Post by schrader7032 »

So did you rotate the points plate back to the middle before you did that? A gap of 0.010" seems a little small...probably OK. Just note how the coil works. With the points closed, current is flowing through the coils saturating the field. As current flows, the wiring/coils will heat up. Just imagine if the points gap was 0.0 all the time...current would be flowing all the time. So, it's important that there be a gap, one to collapse the field, and two let the coils cool down a bit.

I'd be scratching my head as to why the gap had to be so small. Obviously BMW didn't design the bike that way, so something is off a bit. As you see, even a small thickness change makes a huge difference.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Timing Issue R 75/5; R 60/7

Post by srankin »

LOL, Now you know why I went to a pointless system. Try gaping points and messing with timing in a parking lot rather than a garage at home.

My R75/7 always had the habit of points getting out of whack and the timing advancing to where pinging started.

Since I put the Boyer system in the 78 RS, I have never had to adjust timing in the 30K miles I have ridden it.

On my electronic from the factory 84 RT, the only time I have adjusted timing was when the system was apart for timing chain changes, an oil seal change and two times the cover was off for cosmetic painting.

LOL a lot of guys talk about electronic ignition failing and getting stuck. To be honest, it is just as easy to carry a spare BMW ignition module as a set of points. Same goes for a bean can. Hey, that is just me.

I am very happy you have solved your problem, enjoy the ride. St.
Owner of a 84, R80RT and 78, R100RS

ECJ
Posts: 21
Joined: Fri Dec 15, 2017 9:50 am

Re: Timing Issue R 75/5; R 60/7

Post by ECJ »

cbclemmens-

I suppose it goes without saying that while you chase your timing issue, you have already checked/set valve clearances (maybe even re-torqued the heads), know that your air filters are good, have synched the carbs/set idle, checked your plugs and plug gaps, etc.

As I'm sure you know, having too tight valve clearances, for example, can certainly cause an engine to stumble and stall.....

Might also be worth checking coil resistance, and ensuring that your spark plug leads are in good condition as well.

Let us know!

ECJ

zeroreturnjim
Posts: 1
Joined: Mon May 03, 2021 8:29 pm

Re: Timing Issue R 75/5; R 60/7

Post by zeroreturnjim »

sorry to post a late suggestion on timing issues but i thought if this does not help you it may be of use to someone else.i had some issues with timing plate and solved it this way:
loosen spark advance and apply counter clock-wise force to advance unit and re-tighten.there is a little play in these things
when loose(cw and ccw) and when tightening all play is pushed clock-wise.it is easy to try and non-destructive to parts involved.it helped on both my /5 and/6.
hope i described process clear enough.

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Timing Issue R 75/5; R 60/7

Post by srankin »

It is never too late for good advice or data. So how are the bikes running now? I hope well, St.
Owner of a 84, R80RT and 78, R100RS

Post Reply