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I have a very strong Odyssey battery, plenty of cranking power. Heavy gauge second ground and connection between diode board and starter. Cranks with some fire but no start - takes between 5 and 20 short cranks, no matter position of choke. I've checked the float levels and choke operation. Bike starts immediately when hot. Runs strong and smooth once running, through all RPMs. When sitting at idle when the engine is not yet completely up to temp, the engine sometimes suddenly dies. Starts back up with no problem.

Curious.

Any ideas?

A friend of mine had the same issues with his 1982 RS. I'm not sure he ever solved the problem, but I think it's in moth balls by now.

Anyway, take off you float bowl's. With the bowl upright in your hand look at it's interior. You should see a small channel / port on the edge of one of the corners. If I understand it right this feature plays a roll in the cold running / starting process. Make sure it's clean out. Let us know what you find.

Ken

Thanks for the reply. I should have mentioned that as well - I had read about that and, when I had the carbs apart, I blew carb cleaner through those holes, from the inside. No sign of blockage. Found out today, that if I move choke from full to none and back, quickly, while cranking the engine that she starts up much quicker. Will have to investigate.

I am having the exact same problem with my '74 R75. Very frustrating. It will sart grudgingly on the left cylinder and then, with a little revving, pick up on the right. After that, it runs and starts like a champ ... til it is stone cold again.

The choke trick works sometimes and other not. I can find nothing out of whack or adjustment - valves or spot on, choke gaskets and orientation are good, carb diaphragms are ok, strong battery, ohmed spark plug wires and caps, all connections at the dual coils are clean and tight, grounds are clean, even changed the starter, good clean plugs.

An old guru here in STL suggested that when the bike gets hard to sart cold, a weak or failing coil is indicated. I have not ohmed the coils yet bit I did verify the spark would jump about 3/8" from a nail in the cap to the head - seems pretty strong and consistent on all 4 wires.

Teo

I go along with Teo on thinking about ignition. I have no hands on experience with post 70s bikes, but the few I have ridden where much more cold blooded than the early airheads. I have put that down to carbs set up for lower emissions.

If you know anyone with a similar bike, an afternoon of parts swapping and telling stories could be in order.

A few years back I had a problem with some used carbs I rebuilt. I spent a huge amount of time including a complete valve job trying to get to the bottom. I finaly went to another airhead owner's shop and swapped carbs and found out that all my problems where in the ignition.

Bing bmws start better with choke and a closed throttle, you just' pick the' engine up on the throttle as it starts to start.

Other wise on the carbs, make sure that the choke gasket and the float bowl gaskets are good and that the 3 screws that hold the choke onto the carb are nice and tight.
Twinplugging will help but is a fairly expensive solution!

When I crank her with the choke fully engaged, I get no spark. Seems that the choke is too effective. I get spark with no choke, but need some choke to get 'er lit.

My plugs are relatively new (4 months) and the plug wires & caps were new a year ago.

Have you taken a good look at the coil? Mine sat for 16 years or so. Cleaned it up and it ran fine until the day it didn't at all. Coil failure. It had a big crack in it that was not new and had been running fine. I tripped over a deal on the newest style factory coil, swapped them out and it fired right back up. Started better than it had in a long time. According to the warnings, the coil has enough zip to kill you. It should make a spark with the choke engaged.

chasbmw wrote:Bing bmws start better with choke and a closed throttle, you just' pick the' engine up on the throttle as it starts to start.

Other wise on the carbs, make sure that the choke gasket and the float bowl gaskets are good and that the 3 screws that hold the choke onto the carb are nice and tight.

Common reason for poor cold starts is a faulty bowl basket. More air is allowed to dilute the "choke", hence too lean when cold. Replace them and try again.
Ensure the jet in the corner of the bowl is clear while you're there.

Steve,

THANKS for the post. What you say makes mucho sense and the pix are a big help. I would not be surprised if that's a big part - if not all of - my problem.