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Chasing down rough running on R69S

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schrader7032
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Chasing down rough running on R69S

Post by schrader7032 »

A couple of rides ago, on the way home, the bike started to lose power and run a little rough. I was near home, so just throttled back. My first thought was that there might be a fuel flow problem, so I cracked the gas tank cap but that didn't help. Also switched to reserve that didn't help either. So later on, I thought I'd check the easy stuff first before ending up with timing. Plugs looked OK and the floats were still OK...I have the plastic floats from Vech and have had some take on fuel in the past. So all good there. Not much changed, but I took the bike out again a few weeks later. Seemed sort of OK but I guess it was still bugging me.

I thought I'd recheck the valve clearances, but it wasn't that long ago that I did that. They turned out to be fine. OK, so maybe it is timing! I had the idea that I would pull the plugs and put them back into the leads and tie them to the engine. Then I'd put the transmission in 4th gear with ignition on and spin the rear wheel and try and hear the snap of the plugs to get some general idea of the spark timing. Hmmm...no spark. I think my assumption was wrong. I forget that the magneto system doesn't really do spark well at low speeds...it seems to do OK at kicking speeds as the bike will start. So my easy method of checking timing wasn't going to work! Doh!

So this was turning out to take longer than I had hoped. Guess I'd better remove the front cover and check things out. I only go into this area once in a blue moon, so I really forget things! I could see that I had a gap and it was opening and closing. I tried to put a 0.016" feeler gage in there and it wouldn't go...so gap is wrong...how wrong? I did remember that with the standard setup (with Emerald Isle coil), I have to disconnect the condenser lead and other wire that comes off the coil. That's always difficult because it's such a tiny screw/nut. Got those off and hooked up the ohmmeter...but to the wrong side of the points!! OK, move to the other side and move the engine with the rear wheel.

Whaaaat! It appeared that the points open when the TDC is past the window!! Wow, really retarded ignition. So, I'm thinking that the points rubbing block has worn down, closing the gap, and making it run bad. It's a testament to the engine design that it even ran!! So, continued down this path and opened up the gap...I really didn't measure but just knew that it was bigger. Rechecked points opening...around the F-mark...too big on the gap. Closed the gap up a bit and rechecked...was getting opening on one side around the S-mark and the other side with the S-mark lower in the window...I know I have some differential timing. I called that good and buttoned things up. Oh, and also put some cam lube on to help with the rubbing block.

I haven't started yet...next ride. I will listen to the engine to be sure I'm not pinging and will also be prepared with my timing light once I get the bike warmed up. If I'm having troubles with it, I might call Vech up and purchase that "buzz" box they have to help with timing. I believe you don't have to take all that stuff off to check timing...their system uses inductance to monitor points opening.

Here's hoping the bike runs better next time! Man I had that learning curve!!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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wa1nca
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Re: Chasing down rough running on R69S

Post by wa1nca »

Buz box
Best tool ever
no need to disconnect the points wires or even have to take off front cover to check timing
you can remove headlight and connect it to #2 terminal on switch board and push key in to see when points open
So time consuming taking off the point wire then loosing the nut ect. then you have to reconnect it
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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Re: Chasing down rough running on R69S

Post by schrader7032 »

Nice endorsement, Tommy!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: Chasing down rough running on R69S

Post by schrader7032 »

First chance to try the adjustments out. Bike started well, but not long after leaving the neighborhood, I could hear pinging. So ride aborted. Seems I've encountered this before. If I set the timing statically with the S-mark around the window, I get too much advance. I suppose that speaks to a worn out advance unit. I came back, parked the bike, and put the timing light on it. I could find one F-mark from left cylinder and it seemed to go below the window a bit...I didn't find an F-mark when I switch the lead to the other side...it probably was already past...that was the right side and that was where I heard the pinging.

I'll call Vech tomorrow and talk about this issue...probably get the "buzz" box anyway.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: Chasing down rough running on R69S

Post by schrader7032 »

The magneto timing device arrived last week, so I thought I'd get down to using it. In the end, it seems to be useful, but using an ohm meter to monitor for points opening does the same thing. The benefit to the timing device is that you don't have to remove the small wire from the coil. That wire makes a connection to ground, so if you're going to use a DVM then you have to deal with that really tiny nut/screw. So, this is faster and easier.

I hooked things up...instructions say to have the ignition on but for the DVM method, that's not required so another difference. I did a check of my current situation and could easily see that one cylinder was firing more advanced than the other. I've known I had differential timing. Richard at Bench Mark Works gave me pointers to correct that. I rotated the engine until the one rotation that resulted in the more advanced condition was just opening the points. I got out a small steel flat tipped punch and set it against the bolt holding the advance unit in place. Richard said to give it a "love tap" from the right side towards the left side of the bike...I did give it a couple of very small taps. I went back and checked...the points now opened at almost the same time for each cylinder! Pretty amazing! The theory here is that for the cylinder too advanced, the points were running up on the cam too soon. By tapping the bolt from the right to the left, I'm driving the cam away from the points rubbing block, thus retarding the ignition.

I was still advance generally, so I closed the points just a bit. The static timing was pretty good at that point. But my concern is mostly with where the timing is at full advance. So, I got a toothpick and propped out the advance weights to simulate full advance. I can do this because I have removed the small spring that was originally connected to soften the rate of advance. I have the later advance unit with the spring on its side, not the breakage prone "question mark" spring. In place of this spring, I installed what has been deemed the Caro stop screw. I don't have a good picture of it, but it acts as a hard stop for the advance unit weight movement. Years ago, I bought this screw from Bench Mark Works...not real sure of the size or dimensions of the screw. If you don't have this configuration, then this way of setting the timing won't work. It looks like this configuration but in my case, I removed the spring.

https://www.snafu.org/restore/service/g ... 7-2106.jpg

With the advance unit propped into full advance, I turned the engine again for each cylinder and noted where the F-mark showed up. Because I had "love tapped" the advance unit bolt, the marks were in the same place but I was still advanced. I closed the points a little bit more and ended up with the F-mark slightly low in the window when the points open. This is 2-3 degrees of retardation. I can live with that...I'm more concerned about getting too advanced on the R69S plus being slightly retarded in timing gives me some room to move if I'm a little bit off. I removed the toothpicks and rechecked static timing...it was retarded as well, but the S-mark was near the bottom of the window. Shouldn't be a problem...I'm sure the bike will still start fine.

I won't know if this has been helpful until the next ride...this weekend sometime.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: Chasing down rough running on R69S

Post by schrader7032 »

Well, a bit of a follow up. I was able to get out on the bike. I was going through my start routine and did not have the key pushed home. I was priming the engine when the bike rumbled to life. I pushed the key down and began coaxing the throttle. So, it started rather easy. I'm going to have to follow up on that. It's the situation explaining by Tommy in Micha's thread regarding the coil and the switchplate.

As for running, I'm not sure what to think. I was getting mixed info and even had some hesitations right as I was getting to my shift points. I was a little unsure about things, so kept it close to home. I was only out for about 15-16 miles and the engine was beginning to get warmer and maybe running a bit better. Towards the end, I was running in 4th gear and had a bit of a headwind...that's when I heard the right side pinging again. OK, back to home.

I quickly set up to use the timing light. I have to park my bike in front of my car in order to use the 12v battery to power the light. I liked what I saw. I could see the S-mark in the window...maybe a bit low...at idle. I ran the throttle up to a higher RPM and there came the F-mark in the window and stayed there...it did not advance past the window. Hmmm...why is it pinging? I may have to retard the ignition a few degrees. And maybe recheck the timing with the buzz box.

One other issue I was seeing was the generator light come on whenever I would step on the brake, but go out as soon as I was off it. Plus, I remember when I started and was at idle, the generator light was on and there wasn't a neutral light. I recall having this issue before and the problem was an old battery...I got a new one and it went away back...that was 3 years ago and that's the battery in the bike now. I measured the battery voltage with the bike not started and got about 6.5v...I really expected a bit higher. Started the bike and tried to measure the voltage...I forgot you can't check it that way with a cheap digital voltmeter...I have a simple panel analog meter that I will have to use. But I did discover that the negative lead to the battery was not solidly in place. I pushed it down firmly and the issue with the generator light went away. That might be the issue with that. I had pulled the negative lead to the battery when I was removing the front cover...I must not have pushed it home when I was finishing up.

So, I'll have to regroup and check it again when I have a change. :?:
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: Chasing down rough running on R69S

Post by wa1nca »

Timing seems good
Bad gas,tight exhaust valve right side ?
R69s needs high test gas
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
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Re: Chasing down rough running on R69S

Post by schrader7032 »

I've checked valve clearances several times in the past couple of months. I also run the highest test octane I can get. So I'm scratching my head. Thanks for the ideas!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: Chasing down rough running on R69S

Post by jwonder »

Kurt,

Maybe I missed it, but the pinging sounds like a lean condition when the motorcycle is hot. I would look at the carbs and sonic clean them. Pay attention to the jets and spray through them with carb cleaner.

If you have done that, and I missed it, try the higher octane gas. I have run a mix of race fuel and high octane pump fuel in my R69S in the past, now I just use high test pump fuel.

If all of that fails your could raise the needle one hole to richen up the mid to top range (as I am fairly sure you are not revving it as high as it was made for).

Let me know if any of this helps.
James Wonder
Vice President, Vintage BMW Motorcycle Owners
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Re: Chasing down rough running on R69S

Post by schrader7032 »

Thanks, James. No I have not touched the carbs in a long time. I did wonder about running lean, but I've had the plugs out several times in the past few months and nothing jumped out at me as being unusual. Certainly worth a look, though. I get between 45 and 50 mpg and have been getting that for many years. Doesn't seem overly lean.

It's been about 10K miles since I had the engine overhauled...slinger cleaning, new bearings, heads redone, etc...and I wondered if I might have some carbon build up which increases compression.

Easy stuff first, so carbs is on the menu!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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