KZ650 Idles great runs like #$*! on the road

I have a 1980 kz 650 that I have Bobbered out, pod filters insted of air box and no exaust- pipes off the head into the collector then a 4" streight pipe. It will idle great but when I get it out on the road and the RPM's come up it starts to sputter and it sounds like the carb is popping and it stumbles. I have tried adjusting the air screw on each carb to see if this will help but no dice. Anyone have suggestions?

I would check for vacuum leaks around the manifolds first and if you are running an open exhaust the carbs will need to be rejetted as well.

Any Idea what size jets? I have stock air screw type carbs.

No idea on the jets but some of the 650 owners would have a better idea. I had to do a fair amount of trial and error on mine to get it right though.

Thanks, I keep tinkering and see if I can get it right.

Capt806dfd wrote:

I have a 1980 kz 650 that I have Bobbered out, pod filters insted of air box and no exaust- pipes off the head into the collector then a 4" streight pipe. It will idle great but when I get it out on the road and the RPM's come up it starts to sputter and it sounds like the carb is popping and it stumbles. I have tried adjusting the air screw on each carb to see if this will help but no dice. Anyone have suggestions?

pics please
sounds like the exhaust is the major problem
and the pods are contributing to it also
with what you have done jetting is totally outof whack

If you have the stock vm24ss carbs a good starting point for jets with pods and good flowing pipe is 17.5 pilot 110 or 112.5 mains - needle either on 3rd or 4th clip

Should have also said check the spark advance and make sure it is working correctly as when they do not move like there are ment to you will have issues somewhat like you are having.

Is there rust in the tank?

Would help if you can feed us some more info such as what carbs you're speaking of... Assumption would be stock but being bobbed who knows....

Also, any head P&P work done?

Stock of performance cam?

Condition of spark plugs (White, carboned, speckled etc...)

When it stutters, what rpm?
If mid range, if carbs are good sounds as though your running lean....

@ 65mph, let the throttle snap shut... Backfire/Popping?

@ steady hold of 65mph, seem as though the bike surges back and forth as starving for fuel?

If YES to either of the 2 questions then you're running lean... Try a different Needle clip position for RICHER operations....

Of course assumption is all other variables (timing, ignition, spark etc) are to spec....

Follow the link, whole slew of good crap in there on tuning and T-shooting Carbs..... Especially "How to Read Spark Plugs"... That was the bomb in understanding Tuning/Jetting turned onto me by Larry....

kzrider.com/index.php?option=com_docman&...d&gid=461&Itemid=108

Pods will create performance problems unless you are willing to fiddle with the carbs long enough to find the magic combination of ingredients to compensate for the additional airflow. Even then, you may experience issues with rain, high wind, etc. I respectfully suggest you use the search function on this site and review any of the hundreds of postings describing the pros & cons of pods and tuning tips. Nearly everyone who switched to pods is thrilled with the way they perform, and nearly everyone that uses pods on this site knows the secret of making them work as well as the stock airbox. However, you may receive slightly different recommendations as to which jets / needles / clip positions, pods, carb supports, shields, etc. to use. But don’t give up; just keep trying the various combinations that are recommended until you find the perfect setup. Good luck, and be sure to provide feedback on which setup works best as there may be new folks in the future that your feedback will help. Ed