1983 R80 G/S hard start

G/s

yup, I have a crack in mine (it's brownish red). Can anyone explain what "resistance" is? Looks like on Motorrad Elektrik, there are three DYNA coils, green, brown/red and blue. Looks liker the red is 1.5 ohms and the blue is .7 ohms (but is indicated for heavy duty ignition, maybe like the Omega?). What do the different ohms do? Seems like although I have the brown/red, I might need a blue since I upgraded my ignition. Is that true?

happy wanderer said:

Ooooh yeah it was a scary one. But I must have had a recent Karma top up because a guy just behind me in the next lane must have realized what was happening as I sped up and slowed down repeatedly. He was catching up and falling a bit behind and I bet the exhaust was popping pretty good too. I was too busy evaluating my options to notice.

He actually slowed down while waving me over and stayed behind me all the while changing lanes until he got me to the rightmost lane and off the bridge where I could pull over. The guy stayed behind me to protect me from a rear ender. I wish he had stopped so I could thank him for his presence of mind and kindness in action.

The bike fired up again and I rode a lot slower to my local bike shop and diagnosed a failing coil. I had a good spare at home so I rode back on side roads at slow speeds and made it to my tools and parts stash at home and made the repair.

This is my coil and the photo shows a classic Crack O' Matic failure. Hairline crack or cracks and signs of arcing on the outer casing.
View attachment 73947

Click to expand...

The problem might be on one side only. After a couple of failed starts from cold check the temperature at either exhaust pipe. If careful you can check the temperature by hand or with one of these remote temperature gauges.

/Guenther

Resistance is basically the opposition to current flow - the lower the resistance, the more current flows (up to whatever the power source can supply).

On some bikes, not typical BMWs set up for "normal" use, it may be beneficial to use a coil with a lower primary [input side of the coil, which is actually a transformer] resistance, to hopefully produce a bigger spark on the secondary [output] side. This has several potential drawbacks if the situation has not been thoroughly examined; the first is greater wear of the points' contact surfaces (in a bike so equipped), or if it has solid-state ignition (doesn't matter whether it's stock or after-market), the output stage of that ignition system may not be able to "source" the new current draw and may self-destruct. "Hotter" spark may also require a different ignition timing and/or carb readjustment. I've witnessed a case where the (admittedly ignorant) owner of an older Sporty installed a "hot" coil and wound up with melted metal on the plugs.

Another issue is that the inductance (another techie term) of the coil should be compatible with the capacitance (ditto) of the condenser; an incorrect match here can also result in burned points.

Bottom line is - use the coil that the specific ignition manufacturer says to use, unless one Really Knows what they're doing.

GTRider said:

This sounds like your carb enricheners are not functioning correctly and you have a lean condition at startup.

Click to expand...

It does, but the lean condition can also be caused by a vacuum leak.

If the rubber "hoses" that connect carb to manifold are old, they can become porous. The manifold screws into the head and can be loose. The vacuum ports feeding the hoses to the air injestion system ...

These bikes do not have any provision to automatically or mechanically provide the fast idle required for a cold engine running on choke to ... run. You do this yourself by holding throttle open a bit until it all warms up. It's not going to start with throttle at idle.

G/s

Got it. How do you choose which coils to use (3ohms .7ohms or 1.5 ohms? Particularly because I installed an OMEGA ignition setup. Does this change the coils needed? https://www.euromotoelectrics.com/category-s/1689.htm

lkchris said:

It does, but the lean condition can also be caused by a vacuum leak.

If the rubber "hoses" that connect carb to manifold are old, they can become porous. The manifold screws into the head and can be loose. The vacuum ports feeding the hoses to the air injestion system ...

These bikes do not have any provision to automatically or mechanically provide the fast idle required for a cold engine running on choke to ... run. You do this yourself by holding throttle open a bit until it all warms up. It's not going to start with throttle at idle.

Click to expand...

If you click on the three coils, it helps a bit. The 3.0 ohm coil is for older bikes than yours. If I had to guess, it would be the 1.5 ohm coil. You could call them and ask specific questions. The BMW part number appears to be 12131244426. You might need a mounting plate, so worth calling.

-- later on --

I looked at Ted Porter's site and specified the '81-84 R80G/S and it seems that he show only the 0.7 ohm coil. So at this point, I really I have no clue. So much easier with the dual coil set up!!

G/s

Yup, that's exactly what happened to me. Looks like either the brown or the blue will work, but I'll email Ted and ask him. I'll report back in case it will help anyone else.

20774 said:

If you click on the three coils, it helps a bit. The 3.0 ohm coil is for older bikes than yours. If I had to guess, it would be the 1.5 ohm coil. You could call them and ask specific questions. The BMW part number appears to be 12131244426. You might need a mounting plate, so worth calling.

-- later on --

I looked at Ted Porter's site and specified the '81-84 R80G/S and it seems that he show only the 0.7 ohm coil. So at this point, I really I have no clue. So much easier with the dual coil set up!!

Click to expand...

Just looked at the EME site, and it shows two modules for your bike... but neither one specifies which coil to use with it.
As posted earlier... Contact the manufacturer (and/or vendor) of your Omega system for their recommendation.
http://www.omegaignitions.com/
They have instructions and a decent FAQ page, especially toward the bottom...

Udpated

Few updates here. Coil was cracked and I replaced it with a blue Dyna (.7 ohms). I also replaced the plugs. I was having a bit of hesitation at take off and that's now gone. The cold start issue, however, is still present. It's absolutely perplexing and I'm not exactly sure where to go from here. As I mentioned, I replaced the coils, plugs, starter, charging system, changed all the fluid, adjusted the valves and rebuilt the carbs. Anyone have anything I should be looking at? Seems like I'm getting a good enough spark, must be an issue with the carbs (or maybe one carb?)?

Sounds like the electrics are sorted out. Have you checked the enricheners as mentioned in post #10?

Best,
DG

You mentioned back in the first post that you set the valves...
What's your "feel" for the drag on the leaf gauges? It's pretty easy to set the clearances a little too tight, and this will cause hard starting.

There are some on this forum who absolutely refuse to deviate from factory spec, some who chase that teeny bit of extra horsepower, but I've ALWAYS found - on many bikes of several different brands - that setting the valves a hair on the loose side - and accepting a little bit more clatter - makes starting easier.

armartel said:

Few updates here. Coil was cracked and I replaced it with a blue Dyna (.7 ohms). I also replaced the plugs. I was having a bit of hesitation at take off and that's now gone. The cold start issue, however, is still present. It's absolutely perplexing and I'm not exactly sure where to go from here. As I mentioned, I replaced the coils, plugs, starter, charging system, changed all the fluid, adjusted the valves and rebuilt the carbs. Anyone have anything I should be looking at? Seems like I'm getting a good enough spark, must be an issue with the carbs (or maybe one carb?)?

Click to expand...

Hi Armartel,

A couple of things to consider, come to mind that can cause hard starting and not idling well. I listed them in order of most to least likely.

1. The throttle butterfly plate:
- Can be reversed
- Isn't flush at the bottom with the bore of the carburetor.

The butterfly plate has a sharp edge that has to touch the bottom of the carburetor intake. The bevel on the edge of the plate has to be facing the right direction so the plate can touch the bore at the bottom. Then, when the butterfly is barely open, as is the case when the carbs are adjusted properly, the plate creates a set of low pressure vortices right over the tiny holes in the bottom of the carburetor intake. These holes lead to the little fuel well in the corner of the float bowl. Without the very low pressure from the vortex, the carburetor can't pull sufficient fuel into the intake at idle. Result is hard starting and you can't keep it idling since it is running lean.

It is very easy to NOT get the butterfly plate to touch the bottom of the carburetor intake. It is easy to verify it touches using a light on the intake side and look through the engine side of the intake. NO LIGHT should be visible at the bottom of the plate. It's okay to have some light visible on the sides and top of the plate.

2. Air leaks:
- at throttle shaft
There is an oring on the throttle shaft. If you didn't replace it, it maybe leaking. If you did replace it, it could be damaged (not likely). This will create a lean condition as the leak is down stream of the venturi.

- at engine-to-carburetor rubber tube
Same problem, too lean a condition

Both can be checked with the engine running. Spray a bit of carb cleaner at the end of the throttle shaft where it attaches to the throttle linkage and spray a bit at the edges of the rubber tube between the carburetor and the engine. Any change in engine RPM indicates an air leak.

- at float bowl
If the float bowl gasket is damaged, it affects the vacuum inside the float bowl and will reduce fuel flow from the small idle fuel well. This results in a lean condition at idle.

3. Plugged passage from idle fuel well into carburetor intake.
Look carefully at the bottom of the carburetor intake near where the butterfly plate is when the throttle is closed. There are tiny holes. If they are plugged, no, or limited fuel comes up from the small fuel well in the float bowl. Result is hard starting and you can't keep it idling since it is running lean.

There is also a tiny hole at the bottom of the idle fuel well inside the float bowl. If plugged it won't let fuel into the idle circuit

Use one strand of copper wire from a piece of stranded copper wire to check the passages. This should be small enough to fit and soft enough not to damage the passages.

4. Idle jet not screwed in tight, or o-ring damaged.

5. Incorrect size idle jet.

6. Idle mixture screw tip broken or bent.

I hope this helps.

Other's suggestions below may also lead you to the cause.

Best.
Brook Reams.