Someone Please Tell Me Why Bike Runs Only With Full Choke?

[iSack1L]

Can someone enlighten me as to why I cannot get my 72cb350k4 to idle/run w/ the choke anywhere near closed, even after getting engine up to temp and speed? Just had carbs cleaned and rebuilt by Honda, etc. Thought I had the stop screws and mixture screws right already but guess not. Ideas?

 

[iSack1L]

Full Open is down, Full closed is up. Right now we're dealing with all the way down, or it won't start (understandable), idle (semi understandable) or run consistently. It likes to stall, even at full speed/temp it won't run.

 

[killerdwarf]

Either you have a big air leak somewhere , or the carbs were not done properly, and the pilot circuit is plugged.

 

[chrisf]

I agree. Are these CV carbs? If so, I suspect an air leak--possibly in the diaphragm. Other than that, it sounds like your pilot circuit is out of whack.

--Chris

 

[iSack1L]

Weird, the guy at honda seemed very knowledgeable and confident that he had fixed my original problem by properly cleaning and rebuilding the carbs. I was idling high then the RPMs would crash. He noted in my cleaning that I missed the smallest jet when I removed and soaked them myself. Are their any other possibilities where there would be an air leak? Or other problems attributable to these symptoms? Could it just be that I haven't taken sufficient time/care in tuning/syncing? B/c I'm new and suck at it.

 

[Flugtechnik]

crazypj is trying to give you a hint. The choke should be fully open to run. If it is closed, no air is going into the carbs. I had the same problem when I first got my bike. I was used to my previous bike that had a plunger to set the choke. I would put the choke "ON" to start it (pull the plunger out). It would decrease the airflow, but would also increase the idle speed.

These older bikes are a bit more primitive. The choke is simply a butterfly valve that restricts air going into the carb. I rarely ever use mine. It is almost always "Open" (lever down). You only need to use it when it is cold, and then, you probably only need to close it half way. If you close it all the way, no air can get into your carbs. No air, no run.

 

[iSack1L]

crazypj is trying to give you a hint. The choke should be fully open to run. If it is closed, no air is going into the carbs. I had the same problem when I first got my bike. I was used to my previous bike that had a plunger to set the choke. I would put the choke "ON" to start it (pull the plunger out). It would decrease the airflow, but would also increase the idle speed.

These older bikes are a bit more primitive. The choke is simply a butterfly valve that restricts air going into the carb. I rarely ever use mine. It is almost always "Open" (lever down). You only need to use it when it is cold, and then, you probably only need to close it half way. If you close it all the way, no air can get into your carbs. No air, no run.

Thanks, I just wanted to be sure it wasn't necessary to have it fully closed while riding or something. Thanks to Crazypj as well.

 

[VonYinzer]

Just a thought, but on my 71 cb350, when the choke is full on, there is still air getting into the jugs. If you look on the butterfly vaves at the carb intakes theres a little flapper that should open. Mine were all gummed up, but after a little cleaning they open now. There spring loaded to only open when the bikes running and there is a vacuum created. Even if your choke is full on, you should be getting enough air into the cylinders to start / run the bike, though your not going to get the engine response of a warm motor with the choke open.