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Old 10-04-2012, 02:22 PM   #1
bushyb OP
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Location: Rotorua, New Zealand
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Shoud I replace my diode board?

I am sure this has been asked before; I just couldn't find the answer that fits my situation. After setting up a 1982 R100RS that had been is storage for 8 or 9 years the job is complete and looks good and I am happy at the outcome. I have also asked some of this before. I have fitted a new battery, had the started serviced and new solenoid fitted, replace the relay, checked the float level etc. All is good. In the mornings I struggle to start the bike it is almost as if there is too much compression yet if I crank it a couple of times it as if the battery gets flat. I then put it on charge and go to work. When I am back from work its warmer ever so slightly then it starts. Once it starts its fine and will start again and again that afternoon and evening with prolonged brakes in-between. Once it starts it runs great so there are no issues with the float level or the fuel settings and tuning.
The generator light comes on when the ignition is turned on and once started goes out as it should and shows no sign that it is not charging. I do believe there is no short anywhere that will cause the battery to lose charge.
I am not to clued-up with electrical things but I did read somewhere that there might be a damaged diode that when the ignition is turned off the battery leaks back through the diode board creating a loss of battery power or charge. That is what I understand from the reading.
My thoughts are that this could be the situation, that the bike struggles to start and that the diode board needs replacing. There must be some simple tests to check the diodes but I think I will struggle with understanding the process and measurements.
This is the million dollar question: Will a bad or defective diode board create a situation that makes the bike difficult to start and having to top up the battery constantly?
I have just managed to start the bike and checked the volt metre its showing about 13 volts at about 2000 rpm, if I rev it a bit it goes a bit over that.
One other thing it sometimes starts with the choke 1/2 on and other time with the choke off. When I use the choke it is as if it struggles even more. I have made sure the choke start valve is in the right way round.
Any thought welcome.
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Old 10-04-2012, 06:08 PM   #2
Biebs
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Starting

1/2 choke works to start then use 1/2 choke. My 74 r75/6 starts at 1/2 choke.

Also test battery / for leak down by disconnecting battery at night reconnect in the morning see if it starts.

How old is the battery?? There is a way to test diode board.



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Old 10-04-2012, 06:56 PM   #3
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I'd second that suggestion - disconnect the negative battery lead (at the negative terminal) once it's parked at night. See how it does in the morning.

There are basically two sides to this equation - the battery and the starter - although the wiring and connections add a third. It's gotta be one of those three.

When the engine is cold it presents the heaviest load to the starter and battery. If connections and cables are good, then it's one of the two. Since the battery has been replaced, I'd check out the starter or the main battery positive lead. The starter grounds through its base and mounting bolts, so if it's loose and oily, there won't be much electricity flowing.

At this point I'd say it's either the starter or the connections. Especially if it still has the hard start symptoms tomorrow morning after disconnecting the negative lead tonight.
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Old 10-04-2012, 07:46 PM   #4
bushyb OP
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Quote:
Originally Posted by Wirespokes View Post
I'd second that suggestion - disconnect the negative battery lead (at the negative terminal) once it's parked at night. See how it does in the morning.

There are basically two sides to this equation - the battery and the starter - although the wiring and connections add a third. It's gotta be one of those three.

When the engine is cold it presents the heaviest load to the starter and battery. If connections and cables are good, then it's one of the two. Since the battery has been replaced, I'd check out the starter or the main battery positive lead. The starter grounds through its base and mounting bolts, so if it's loose and oily, there won't be much electricity flowing.

At this point I'd say it's either the starter or the connections. Especially if it still has the hard start symptoms tomorrow morning after disconnecting the negative lead tonight.
Thanks I have checked all the connections and believe them to be good, The battery is new (2 off) and the starter has been checked and is good. I am sure there must be an answer to it and its going to be something small maybe a connection that I have missed or something like that. I have also added a extra earth wire from the battery.
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Old 10-05-2012, 12:14 AM   #5
boxerboy81
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Are the float bowl gaskets in good condition? If the holes are very compressed, damaged or too rounded then they can let too much air into the "choke" aux starter system, making it too lean and difficult to start.

If you get lucky, you may avoid lots of time and money via a quick inspection or change 'em if they're old anyhow.


Quote:
Originally Posted by Motobins tips and tricks
Found at Motobins home page.....Cold Starting Problems can often be cured by replacing your old float chamber gaskets unless they provide a really air-tight seal around the choke fuel pick-up tube, the fuel level in the auxiliary chamber will not be raised, and the cold start mixture will not be further enriched during initial operation. The Auxiliary Carburettor itself can often become loose, so being by-passed and ineffective; the resultant air leak will also promote 'surging' at about 40 mph on a small throttle opening change the gasket every few years, and make sure the screws are really tight.
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Old 10-05-2012, 03:36 AM   #6
spo123
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Cool2 warning.

Do NOT run the bike for more than a couple of minutes WITHOUT a LARGE BOX FAN blowing on the engine.

Do NOT remove the front engine cover WITHOUT FIRST DISCONNECTING THE GROUND CABLE.

Do NOT STRIP OUT THE SPECIAL HOLLOW BOLT AT THE TRANSMISSION, GROUNDING THE BATTERY!

Good Luck!
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Old 10-05-2012, 11:58 AM   #7
bushyb OP
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Quote:
Originally Posted by boxerboy81 View Post
Are the float bowl gaskets in good condition? If the holes are very compressed, damaged or too rounded then they can let too much air into the "choke" aux starter system, making it too lean and difficult to start.

If you get lucky, you may avoid lots of time and money via a quick inspection or change 'em if they're old anyhow.
Thanks I ordered and replace the float bowl gaskits with silicone real gaskits.
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Old 10-04-2012, 07:21 PM   #8
bushyb OP
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Quote:
Originally Posted by Biebs View Post
1/2 choke works to start then use 1/2 choke. My 74 r75/6 starts at 1/2 choke.

Also test battery / for leak down by disconnecting battery at night reconnect in the morning see if it starts.

How old is the battery?? There is a way to test diode board.



Don't throw money at it fix it!!!
Thanks. Great ideaI will start it this evening and run it for a while with the charger connnected so it is as full as possible. Then disconnect the battery and charger and then reconnect it tomorrow morning and try it and will let you know.
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Old 10-05-2012, 12:38 PM   #9
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Quote:
Originally Posted by bushyb View Post
Thanks. Great ideaI will start it this evening and run it for a while with the charger connnected so it is as full as possible. Then disconnect the battery and charger and then reconnect it tomorrow morning and try it and will let you know.

Hey I am bad man! I did not do what I said and disconnect the battery and reconnect it this morning!!!!!!
I ended up replacing the new battery with the first new battery I had and started it up before I went to bed and just switched it off and left it. I was up early this morning, opened the fuel tapes, gave it half choke, no throttle and she just dragged a fraction and fired right up, so will check it without charging through the day and give a feedback.
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Old 10-05-2012, 06:07 PM   #10
BALSEY
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for what it's worth... I jump started my bike from a running car battery and fried my diode board. When I need a jump now I would try from a non- running car.
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Old 10-06-2012, 11:55 AM   #11
disston
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Quote:
Originally Posted by BALSEY View Post
for what it's worth... I jump started my bike from a running car battery and fried my diode board. When I need a jump now I would try from a non- running car.
Why would a running car be any different than a car that's not running. Something else is wrong here. Either somebody hooked the cables up backwards or the running car did not have a properly functioning alternator system, in which case this should have been known.
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Old 10-10-2012, 04:01 AM   #12
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It sounds like the timing is advanced too far.
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Old 10-11-2012, 02:08 AM   #13
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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!
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Old 10-13-2012, 01:50 PM   #14
disston
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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.
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Old 10-13-2012, 04:21 PM   #15
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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.

What now?
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