Topic: Idle Problems? - 73 CB350

[matt s]

Does this sound like a carb issue?

- Bike starts and idles fine at 1200 rpm to start with
- After riding for about 10 minutes, the idle speeds up to around 2500-3000 rpm
- I adjusted the idle speed while stopped to slow it back down to 1200 rpm
- After riding for about 10 more minutes, when I stop, the bike dies
- After dying it is nearly impossible to start up again
- After starting up, I have to keep rpm's high to keep running, otherwise it dies

I have new plugs, too

Thanks!

[bender01]

Being cold blooded and using the idle screw isnt abnormal. As it warms up things settle in and the idle climbs. It does sound carb related . Have you done a tune-up? Points /timing?

[matt s]

Thanks for the reply.

I have done a tune-up.  Points, timing, cam chain, tappets.  Haven't moved on to the carb sync yet, that is next on my list.  Could out-of-sync carbs be to blame?  Or something like running rich/lean?

[fmctm1sw]

Does this sound like a carb issue?

- Bike starts and idles fine at 1200 rpm to start with
- After riding for about 10 minutes, the idle speeds up to around 2500-3000 rpm
- I adjusted the idle speed while stopped to slow it back down to 1200 rpm
- After riding for about 10 more minutes, when I stop, the bike dies
- After dying it is nearly impossible to start up again
- After starting up, I have to keep rpm's high to keep running, otherwise it dies

I have new plugs, too

Thanks!

My bike acted a lot like that when the idle jets were clogged...

[Gordon]

Haven't moved on to the carb sync yet, that is next on my list.  Could out-of-sync carbs be to blame?  

Yes, they could be.  

[matt s]

Being cold blooded and using the idle screw isnt abnormal.

So is it okay to adjust the idle screw when it gets warm?  Or should I just let it run faster.  Will adjusting the idle screw mess up cold starts?

My bike acted a lot like that when the idle jets were clogged...

I think my next step is to tune the carbs then...

[Gordon]

So is it okay to adjust the idle screw when it gets warm?  Or should I just let it run faster.  Will adjusting the idle screw mess up cold starts?

Of course it's okay to adjust the idle stop screw, unless you want it to idle at 3000rpm.  When starting cold you will probably need to turn it back up in addition to closing the choke.  Later models of sohc4's have a fast idle cam on the choke linkage that automatically raises the idle speed when the choke is engaged, earlier models don't. 

Some people prefer to set the idle stop screw for full operating temperature and then never touch it again.  If you do this you still have to find a way to keep the carb slides open slightly more until the engine warms up.  Some do this with the large screw on the bottom of the throttle grip that some bikes have, others just hold the throttle open by hand with the throttle grip.  I'm one of the ones who just turns up the idle stop screw when I start the bike, and then turns it back down when the engine warms up.