Adjusting the Needle Height

Is there a good tutorial out there on adjusting the needles on a 1976 KZ900? I have never had a bike that had the carbs linked together in the manner that these are. It acts like I need to raise them up a notch to richen up the midrange a bit. Any help would be appreciated as the factory shop manual doesn't help much in this aspect.

The bike is 1976 KZ900A4.

Thanks again for any assistance.

Raising the needles a notch will richen the mixture across the entire range. That is not always a good thing. It could cause cold blooded starting and a rough idle. What modifications have been made to this bike? Pods? Exhaust? Which jets?

The jet needles have grooves in which a circllip is placed. The clip can be moved to a different groove to either raise or lower the needles. I'm not familiar with your carbs, but I guess access is by removing the carb tops, then removing the throttle slide assys. Removal of the throttle slide shaft & other stuff may be necessary. not sure.

Some jet needles don't have the grooves. In those cases small washers can be used to raise the needles. I guess for precision tuning, washers could be used on the type w grooves to obtain a needle setting between two grooves.

Groove numbers. There is a table in the 81 650 manual, which shows a Jet Needle number of 5CN15-4. The "4" is the groove number for the stock placement of the clip. The groove numbers are counted from the topmost groove, 5 being the lowest groove.

OutsiderKZ900A4 wrote: Is there a good tutorial out there on adjusting the needles on a 1976 KZ900? I have never had a bike that had the carbs linked together in the manner that these are. It acts like I need to raise them up a notch to richen up the midrange a bit. Any help would be appreciated as the factory shop manual doesn't help much in this aspect.

The bike is 1976 KZ900A4.

Thanks again for any assistance.

Before attempting any carb adjustment, and if not already done, would assure that the carbs are as-new clean, especially the pilot circuit.



Perform a proper bench-sync, being sure to allow ability to further drop the throttle slides when performing the later running-sync.

Adjust valves. Install new spark plugs. Assure ignition timing is spot-on.

Install a new aftermarket in-line fuel filter in each fuel line. And don't let any gasoline enter the freshly cleaned carbs without first passing through the in-line filters.

Then, after all the above, perform the running-sync. And set pilot air screws for best idle.

Test ride to decide whether or not any further carb adjustment might be indicated.

Good Fortune!

The needles are set at the factory. The adjustment is for minor changes not to compensate for jetting. The slide cutaway, nossle and needle are a matched set. Minor changes in altitude can be compensated with the needle and air screw. It's best to leave them in the center position if possible.
Steve

For each change in the needle placement (up or down) there will be a difference in the mixture strength as follows:

At low throttle opening 3 to 6%
At mid throttle opening 5 to 8%
At wide open throttle 1 to 2%

Maybe I should rephrase my question... How does remove the needles/sliders from the carburetors on the KZ when they are linked by a shaft that connects all 4 of them?

Take the tops off, on yours three screws. Inside you will see the shaft. There is a small bolt holding the arm. Be careful not to shear the bolt loosening or tightening it. There are two screws at the bottom inside if the slides. Take them out. Rotate the arm and linkage up and out of the way. Pull the slide out.
If you had a manual you wouldn't be asking this. I suggest you get one. Sometimes the carbs are switched. It helps to show pics of what you have.
Steve

I have a factory shop manual but it was not much help in this instance, unless I am not looking in the right spot...

And swest, thanks again for your post, it was exactly what I was looking for. I appreciate it.

I hope I'm not forgetting anything....I've done it many times so take this worth a grain of salt, but I find it much easier to pull carbs off the bike, remove the return spring, take the tops of the carb bodies, remove all four of the lock screw/bolts from each carb slide arm, remove the shaft clamp and and then slide the entire shaft out of the carb holder block.
Then you can just pull the arms with the slide all the way out. Easy to remove the two little screws that hold the arm assembly cap to the slide and pull the needle out.

I've never done it like that or knew anyone else to do it. What if you want to go the other way?
This way you can do it in the bike. The carbs need to be synced anyway but one at a time isn't as drastic.
Steve