Condensor insulation melted (twice )

Caferacer
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Re: Condensor insulation melted (twice )

Post by Caferacer »

OK thinking this through a bit more, I have some other ideas
A condenser is not something you can test, all it does is prevent sparks from jumping the points as they open
when it works, the points last longer, when it is bad the points get pitted, and usually they are either good or bad, "USUALLY" that is
IF the heat is being transferred from the condenser to the isolator block via the mounting screw, the question is how is the condenser creating the excess heat?
now "IF" the condenser has a small internal short, not one big enough to ground the ignition and prevent the sparkplugs from firing, but just enough to draw off SOME of the power causing a weak spark AND heating up the condenser enough to melt the plastic isolator, that could explain things

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Dave Reina
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Re: Condensor insulation melted (twice )

Post by Dave Reina »

First thanks for all the hard thinking on this subject.

OK here are a few pictures. Today with the tank off I tested the new coils I bought from Moto. They both seem perfect, 1.3 ohms between 1 and 15 (the small terminals and about 6.1 between the spark plug wire hole and 1 or 15. The new plug wire has 5 ohm resistance. I double checked my wiring to the coils and I believe both coils are hooked up correctly. The only other wiring I messed with on the bike was the ignition switch. I had misplaced the key and the locksmith wanted me to remove the back part
( electrical) of the switch so he could remove the cylinder and make a new key. Something could be on the wrong terminal there but what else does the switch do except be off or connect power to various systems. I've read so much trying to get this bike running properly I'm overstuffed with information. I do remember Snowbum talking about it being not necessary to change a working coil and that there were batches of bad ones. However true or false I don't know but I have read condensers get "conditioned" to match a set of points and should always be changed along with new points. I may have a situation of too high a resistance with both 5 ohm spark plug wires and resister plugs. I'll check that tomorrow. It ran halfway decent when I drove home from my shop tonight.
Dave
Attachments
Old original condenser back in place
Old original condenser back in place
melted off insulation vs new condenser
melted off insulation vs new condenser
melted insulation mess
melted insulation mess
first melted mess
first melted mess
Dave Reina
Brooklyn, NY

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srankin
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Re: Condensor insulation melted (twice )

Post by srankin »

Hello Dave, I am still digging for a possible answer.

As to testing a condenser, yes, they can be tested. They can be tested for resistance in the micro ohm or micro farad scale, sorry, I am trying to dig out the specs as to values expected.

Generally condensers don't go bad so this is a novel thing for me and my friends at the airhead shop to discuss.

Dave, you may perhaps try to contact Snowbum in regard to this issue? I know Tom Cutter at Rubber Chicken Racing is asking for a donation in order to to answer questions. Perhaps Duane Asherman would help?

Snowbum might be your best bet he has written about more BMW technical information than anyone I have heard of except maybe the late Oak at the Airheads Club.

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

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srankin
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Re: Condensor insulation melted (twice )

Post by srankin »

So looking at the pictures, am I correct in assuming it is not the actual condenser itself that is melting but is the black insulating block going into the points can at the terminal end? That changes things a lot.

LOL, you have to understand Dave, no disrespect but I HATE points! In all honesty, I haven't dealt with points out of a bean can or in a bean can for a long time until just a few days ago, when helping a friend troubleshoot a misfiring R75/6.

I converted my 78 RS over to a Dyna system the day I bought it and as of this writing I have the new Wedgetail electronic ignition on its way from Rubber Chicken Racing to upgrade that system. Who knows, I may be opening a big can of worms doing that.

Anyway, sorry to divert the train, back to your problem, it could be just a simple short. If I turn up anything, I will of course share. St.
Owner of a 84, R80RT and 78, R100RS

Caferacer
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Re: Condensor insulation melted (twice )

Post by Caferacer »

sorry but no, you can not test a condenser, at least not in any practical sense,
a condenser is just a capacitor, and in order to test a capacitor you need a capacitor tester, not a common tool, and you would also need to know the value of the condenser, capacitors are marked in microfarads, condensers are not, yes you can check it with an ohm meter but that will only show if it is shorted, and if it is shorted you will have no spark,
as far as condensers being "matched" to a set of points, also not true, the reason to replace the condenser when replacing the points is they are a cheap part and replacing a good used condenser with a new one doesn't hurt anything,
the problem is, finding quality points and condensers is getting quite difficult, as most are now imported from China Taiwan or other places at the lowest price, with little to no regard for quality,
case in point, the magneto on one of my bikes does not like the $6 point condenser set, it is difficult to start and runs poorly, however if I use the quality $35 points and condenser set it starts easily and runs like a top
I have only found quality points and condensers for magnetos, not for anything else
as a result I agree 100% with the idea of converting to electronic ignition, and have done so on most of my vintage cars and bikes, that said my 1980 R65 still has points, for now at least,
if I can't find good quality replacement points and condenser I may install a DYNA III conversion, (if they make one? if I can find one?)

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srankin
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Re: Condensor insulation melted (twice )

Post by srankin »

In order to test the resistance of a condenser, you have to have the right tool. I do, and I can read the resistance for what it is worth. I agree, this is not a main issue here, as I erroneously thought the condenser itself was melting but now see it is only the plastic or synthetic ground material on the terminals that is melting. So who cares what the value of resistance is in the condenser.

I fully agree with the difference in parts depending upon where they come from. BMW surprisingly has burned my friend a few times in the past with cheaply built or incorrectly made points sold from his BMW parts source under BMW name to the point (no pun intended) he will no longer buy points from BMW but buys Noris points.

So, yes, the problem could be cheap points and yes, the cheap points could have come from BMW. One other thing is to check the terminal plugs on both sides of the bean can to make sure there is not a tiny bit of metal touching the case or something it should not be touching. Other than that, I am at a loss. Further discussion today at my friend's shop came to the same conclusion. The suggestion again is check back on the last thing you did and double check the wiring. Sorry St.
Owner of a 84, R80RT and 78, R100RS

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Dave Reina
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Re: Condensor insulation melted (twice )

Post by Dave Reina »

I have put back the old condenser which was on the bike when I bought it and so far have enjoyed some good rides back and forth to work. Of course I am not yet trusting the motor for a longer drive and even locally I have not driven again in bumper to bumper traffic on a hot day.

I'd like to understand at what temperature the insulating block of the problem condenser melts. I saved the melted plastic which I chipped off the bean can and I am trying to think how to remelt it and measure the temperature. I have a temperature reading gun and am thinking to melt it in a double boiler. Under severe conditions I wonder how hot it gets under the front cover of the motor.

Electrically does anyone think that rather than shorting the condenser terminal, instead a bad ground somewhere else was causing the ground load to be going through the condenser body which clamps against the insulator block. The first time it happened I had not noticed how corroded the three terminals were on one of the coils. The second time I had new coils but I wonder if the single ground wire which goes to one of the coil brackets was not providing a good solid ground. After it happened the second time I went back to check the wiring to the coils (which were correct) and loosened and retightened the brackets on the coils perhaps improving the ground wire connection on the one coil ???

Thank you all for thinking so hard about this.
Dave
Dave Reina
Brooklyn, NY

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cbclemmens
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Re: Condensor insulation melted (twice )

Post by cbclemmens »

You can, in fact, test a condenser (electrolytic capacitor) with a standard ohm meter. Set the meter on the largest ohm setting (greater than 100k). Short the input to the case to discharge any stored charge in the condenser. Then hold the negative lead from the meter against the condenser case and touch positive lead to the condenser input. The meter should show a resistance that gets larger as the condenser takes a charge. Within a second or two the resistance will go to infinity. If the resistance value remains readable, the condenser is shorted internally and is bad, If it reads infinity at the initial touch, then it is open and also bad. Just remember to discharge the condenser before each test.

Craig

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srankin
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Re: Condensor insulation melted (twice )

Post by srankin »

I like the idea of a double boiler to melt the plastic. I imagine sitting in stop and go or very slow traffic could perhaps get hot enough to melt something. If you do the test I am looking forward to the results.

Dirty connections raises resistance so, perhaps it could be a problem.

Thanks for the follow up and information. St.
Owner of a 84, R80RT and 78, R100RS

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Dave Reina
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Re: Condensor insulation melted (twice )

Post by Dave Reina »

OK today I have tried to measure the melting temperature the spade insulating plastic on my Bosch condenser . I had scrapped off and saved the melted material the second time it happened. To measure I used my Fluke Thermometer gun.

I jerry rigged a double boiler using a tiny frying pan and a metal jar lid. The inside of the jar lid would not rise above 200 F when buffered by the water. I finally had to let the water boil off and measure quickly as the pan temperature almost instantly went over 300 F. However it looked like the material went liquid at as low a temp as 250F.

To try another way I set the jar cap with the material in the toaster oven and set the temp to 250 checking frequently. In this set up it seemed like the material went liquid at 235 F.

I'm not sure what the temperature gets up to under the front cover of the engine. I'll try to figure out how to read that next although the second time I had a meltdown it was bumper to bumper traffic on a hot day. I wonder if my bike might run extra hot due to something like restricted exhaust pipes. The bike had sat for over ten years under an open sided car port and perhaps critters put junk in the pipes to even that there are internal rust issues.
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Heating in toaster oven
Heating in toaster oven
Melting material
Melting material
Heating in double boiler
Heating in double boiler
Dave Reina
Brooklyn, NY

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