This is a "How-To" on bench-synching carburetors. I've noticed quite a people (me being one of them) searching for clear instructions on how to do this. At some point recently I came upon them, but I can't seem to find them anymore. So, I decided to add my own 'How-To' with the hope that future XJ'ers will find this guide an asset.

The carburetors we'll be working on today are a "junk" set that came on my wife's 1982 XJ650J Maxim. They may look okay on the outside, but they've got cancer on the inside. We'll need two Paperclips and a Phillips-Headed Screwdriver for this tutorial. Let's get started.

Here are the steps...
1. Turn all the Synchronization Screws clockwise until they bottom out on their springs.


2. Take two Paperclips of the same gauge and bend them to match the illustration.


3. Rock the Throttle Lever open with your right hand and slide the paperclip (the one with the short bend) between the Venturi and the Butterfly of Carburetor No. 3 (see first picture above for Carburetor positions) with your left hand. Gently let loose of the Throttle Lever so that it pinches the Paperclip. You will want the Paperclip positioned as close as possible to bottom dead center of the Venturi.

Note: if the Butterfly does not pinch the Paperclip securely, you will need to turn the Idle Adjustment Screw counterclockwise until it does. Refer to Step 9 for the location of the Idle Adjustment Screw.


4. With your Phillips-Headed Screwdriver, turn the No. 4 synchronizing screw counter-clockwise while sliding the other paperclip in and out between the venturi and the butterfly. Do this until the paperclip is "grabbed" by the butterfly. This butterfly should now match the butterfly of carburetor No. 3.


5. Moving to the No. 2 synchronizing screw, repeat Step 4 on carburetor No. 2's butterfly.


6. Lastly, adjust the last synchronizing screw (No. 1) so that carburetor No. 1's butterfly matches carburetor No. 3's butterfly.


7. Once you're satisfied that all four butterflies are set approximately the same, hold them up to a light source and compare with your eye. Adjust as needed.


8. Again, with your right hand, rock the throttle lever open and remove the paperclip from carburetor No. 3.
9. From the backside of the carburetor set, turn the idle adjustment screw so that a sliver of light can be seen between the venturi and the butterfly of carburetor No. 3. If you've set everything up correctly, the same amount of light should be visible looking through the other three carburetors.




That's it! It's time to re-install your carburetors and finish fine-tuning... But that's a whole other "How-To".


(Written by Don Bangert Author of several How-To's and the blog, The Path Less Traveled.)