crummycold starts

[dave Esch]

I have a 76 750k. The bike runs like a champ, but on a cold start she only fires on 2 cylinders. At least thats how it sounds. After a couple of minutes of throttle feathering one cylinder kicks in, then finally the fourth. Takes about 3 minutes for the bike to run smooth. I know bikes need a litttle idle time, but it just doesn't seem normal. I figure if it was a spark plug, it wouldn't run at all. Any ideas? It isn't a big deal really since the bike runs so well, but I am a little worried about cylinder wash.

[shadow06]

about the only thing i can suggest is that the next time you cold start it ,after a minute shut the unit down and pull all your plugs and see if they are dry or wet .if you have 2 wet ones your problem is electrical and if both plug wires run to the same coil and your points and connections are clean and voltage is 12v.,replace the coil .if they are dry then you have a fuel supply problem to those 2 cylinders .hope this helps .....shadow 06

[bobtacker]

Dirty carbs!!

[Re-run]

Maybe, maybe not. Could just be poorly tuned.

[craigwadsworth]

If there is an electrical problem why do they seem to come online?  My '80 Custom has the same symptom.....

[Re-run]

If the ignition is weak, the cool engine makes it harder to atomize the fuel so it does not mix or burn properly. Once the engine warms some, this process becomes easier.
Before I would ever tear the carbs apart, I would go through the ignition system completely and clean up the connections, make sure timing is spot on and check the plugwires and boots. The plugs themselves may be iffy or the wrong number. For example, the 78k takes a d8ea plug. If you put in a dr8ea, it will still run, just poorly.
If you can, test the coils too. Make sure they are not weak, weak coils do not send a strong spark and with then fail to burn the a/f properly.
All the carb tuning and cleaning in the world is worthless if your ignition is not working right.

[craigwadsworth]

Is that due to the lower temperatures meaning weaker intake vacuum because of greater space between engine components?

[Re-run]

Not so much, but coler fuel is harder to atomize. There is also more condensation inside the engine.

[OTTODOCTOR]

My 82 custom starts exactly the same way , but the time isn't nearly 3 minutes . Is it actually 3 minutes before it picks up the other 2 cylinders , or just a short time ??  -- Try this to see if it helps . -- Turn the fuel on a few minutes before you start it , and just let it sit there while you get dressed to ride . -- I've found that , on mine anyway , the carbs are just empty , and it takes a bit of time to fill them back up . -- Just an idea , which may or may not help . -- Otto