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!

R60/7 backfiring after warm up... help!

BMW37
Posts: 9
Joined: Sun Jun 28, 2020 9:00 pm

Re: R60/7 backfiring after warm up... help!

Post by BMW37 »

Makes sense as well to me. The over-voltage would be fed back to the plugs instead of going to ground at the critical time. BMW made a strong bike. In the process of adjusting my Static timing plate with my Ohm meter I can get close to the timing marks but can't get it right on the "S". I am a few inches short in the window. The plate can only moves a few millimeters either way. Is there a another way to readjust or is this the best I can do? I'm going from one problem to another lately. :evil: :cry: Thanks for all the feedback so far.

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: R60/7 backfiring after warm up... help!

Post by schrader7032 »

I would certainly investigate why the backing plate only turns a small amount. I don't recall how much it moves, but it's certainly more than "a few millimeters".

Remember, you can adjust the points gap over a reasonable range and not affect the way the bike runs. If you're stuck with the limited plate movement, adjust the gap to bring the S-mark into the window, and more importantly, the F-mark in the window at around 3000 RPM.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

BMW37
Posts: 9
Joined: Sun Jun 28, 2020 9:00 pm

Re: R60/7 backfiring after warm up... help!

Post by BMW37 »

Thanks for all the input and help everyone that chimed in. It seems I have a greater problem. :roll: Now when I engage the start switch I get an instant cutout and all lights go black. I am cleaning the switch now, and it I kicked over once. Is this a starter motor going bad? Any thoughts? The lights come back on if I wait 30-40 minutes when I put in the key. I'm researching again while everyone is out on the road this weekend... :shock: :cry:

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: R60/7 backfiring after warm up... help!

Post by schrader7032 »

What happens at the battery when you hit the starter switch and things go dark? I might think that if the voltage doesn't really change, then the starter relay might be at fault...it should click when the starter button is pushed. If the voltage on the battery goes well below 8v, then I might wonder if the battery is toast or something is wrong at the starter in which it demands too much for the battery to handle. There is a way of using a screwdriver to short the starter to see if it will turn over...I don't really know the exact procedure. Certainly, if the starter were pulled about out of the bike, it could be tested to for operation.
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: R60/7 backfiring after warm up... help!

Post by srankin »

Kurt has the idea for the starting problem. A dead battery will not help things in many areas. A battery with an internal short can cause all kinds of problems.

A bad relay can cause a problem.

If you have not had problems in the past with the starter, I kind of doubt it is the starter motor, they are pretty robust and last a long time.

If the battery is good, and the relay is good, the next step would be to get out a schematic and start checking things out for loose or corroded contacts. Start with the simple things like you have with the starter switch.

Good luck. St.
Owner of a 84, R80RT and 78, R100RS

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

Re: R60/7 backfiring after warm up... help!

Post by srankin »

Sadly, even cleaned switches sometimes are bad. You made a good choice on trying to clean the switch first before replacing it. Now, Is it working properly?

If you have to jiggle it, or repeatedly push it to get anything to happen, it might be bad.

Wish I could be there to give you a hand. St.
Owner of a 84, R80RT and 78, R100RS

BMW37
Posts: 9
Joined: Sun Jun 28, 2020 9:00 pm

Re: R60/7 backfiring after warm up... help!

Post by BMW37 »

Again an update, but this is good and bad. I found a disconnected wire in the headlight assembly. :o Something in my troubleshooting review, long and methodical. I see two green wires coming out of the harness, along with a few others, from the bottom inlet hole of the headlight. One green wire goes to terminal #15 of the switch plate and the other which goes to and through a fuse is the one disconnected. I'm looking at a few schematics but not clear where this wire should be. All the switch plate connectors are tight so not sure where this terminates. Anyone knows from there headlight where this wire connects would be greatly appreciated. The fuse is aftermarket but probably a replacement for the original as I only see two fuses in the /5 electrical schematic. One step closer and I truly appreciate all the help.

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: R60/7 backfiring after warm up... help!

Post by schrader7032 »

Is this a '77 or '78 R60/7? Probably doesn't make that much difference.

I'm a little confused by the term "switch plate". Are you talking about the board that is in the back of the headlight assembly with a bunch of terminals on it? Also, I don't know why you're referring to a /5 diagram.

At any rate, I see a green wire going from the ignition switch (terminal 15) to terminal 15 on the terminal board. This should have a fuse associated with it. From the same side of this terminal, a green wire goes to the kill switch on the handlebar. On the other side of the fuse at terminal 15, a green wire goes to the turn signal relay. Green wires are usually power on while green with black stripe is switched power...power is only on that wire when something switches it on.

On the '78 model, there does appear to be another green wire that joins the other two I mentioned and it goes to the light dip switch. I think this gives constant power to be able to hit the high beams.

At the kill switch, a green-black wire leaves and goes to input side of the coil, left coil I believe.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

BMW37
Posts: 9
Joined: Sun Jun 28, 2020 9:00 pm

Re: R60/7 backfiring after warm up... help!

Post by BMW37 »

Hi again, the model is two in one. The electrics are for a /5. I put a /7 engine and frame with a /5 front end. I should have mentioned this in the beginning. I am so use to the bike it slipped my mind completely. :oops: So the headlight and electrics are from 1970 app. It's a mix but has been running fine for years. I really like the fifth gear and don't miss the kick start. Sorry for the confusion. Yes, the headlight ignition switch on terminal #15. If you look at the plate from the front after you open the headlight it is on the right corner farthest to the back. I have the other green wire which came undone and has caused a total loss of electrics and lights. This green wire is the obvious culprit and will continue searching where I need to go with it. I have no loose connections or connectors so I do not see where it could have been just yet.

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: R60/7 backfiring after warm up... help!

Post by schrader7032 »

OK, more info! From the /5 wiring diagrams for no fuse (or even with a fuse for that matter), one of the green wires from the #15 terminal on the board goes to the input side of the ignition coil...I would say that is the left side coil...should be terminal 15 there as well. The other green wire from the headlight board goes to the horn...the second wire from the horn (black wire) goes to ground. But the diagram also seems to show that from that point where the green wire connects to the horn, it also connects to the start-prevention relay. It gets pretty complicated after that.

Snowbum has some wiring diagrams for the /5 with and without fuses here:

https://bmwmotorcycletech.info/Slash5Schematic.jpg
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Post Reply