Bench Syncing

I am ready to bench sync - paper clip method:

All sync screws are currently backed off......

Observations:

Butterflys #1 & #4 are fully closed.......however I am noticing that # 2 & #3 are open quite a bit ( at least I think so )....#3 opened more than #2....is this normal before I even get started per the paper clip method....

Also, idle adjustment screw.....when fully screwed in ...it will barely reach the sync screw stop with not much left for adjustment after I finally get these bench sync'ed....doesn't seem right.....

Anyone's advice is greatly appreciated....

Thanks in advance....

 

** Disclaimer - I am not a Wizard! :lol: But here's what I know..

Are you using this as a guide: http://xjbikes.com/Forums/viewtopic/t=6 ... ching.html?

Great write-up but rather than using the paper clip I prefer the 1/4" wide strip of business card (or other thick paper). It sounds like what you've got there is pretty normal (but way out of wack & DEFINITELY in need of a bench-synch). Use your idle adjustment screw to get #3 open pretty wide then slowly turn it in until it starts to "drag" on the strip of paper when you move it in & out at the bottom of the port. Then use the carb synch adjustment screws to get the same amount of "drag" on carbs 4, 2, and 1 (in that order). After that I would go back and check them all again. Done!

Hope that helps! 8)

 

there is another way that does not use a paperclip, i think it's a little easier.
look at the top of the butterfly, your going to see a little hole that the butterfly closes off when it's fully closed. now turn the screws till that hole is just open and at the edge of the butterfly on all 4 carbs. snap the throttle a few times, check again and then turn the idle knob and all 4 should open and close that little hole the same. set the idle till all 4 holes are just fully clear.
your done

 

Teddy... I was going to use that write-up but I like Polock's method better....his method makes much more practical sense....

Polock....you are referring to the 2 holes that the butterfly will cover..... the other hole ( the single hole is the idle mixture hole which never gets covered by the butterflys )...the butterflys should only cover the other 2 holes that are close together.....

I believe your method is much easier.....I will give it a try......

but how can I be this far off before I even start...( see photo above )

 

I have also turned my idle adjustment screw all the way in ( where the spring is fully compressed )....and it is not even hitting the #2 sync screw stop.....what is that about.....???? stumped ??? something must not be put back together right....

Any thoughts ????

Thanks in advance....

 

I am also not a wizard and I may be completely off seeing how I've only done carbs once, but is it possible your springs are not right. There is a tight coil and a loose one and I believe it makes a difference which one is where. Again, better wait for a wizard to confirm or shoot me out of the sky.

 

Make sure your butterflies are not in backward.

Dave F

 

pictures are easier. here's 2 butterflys, set #3 with the idle knob and the 3/4 screw to split the holes(when the right hole is fully open the left hole should just be visible) now tweek the 3/4 screw till 4 looks like 3. now using the holes as a reference, using the 1/2 screw make them equal (equal to each other, not necessarily the same as 3/4 that's next) now with the 12/34 (center screw) make 1 and 2 equal 3 and 4, tweek as necessary.
snap the throttle a few times, check it, tweek, that's it
also a picture of the idle linkage. those BF's are set for 0 idle and pictures

 

I know my butterflies are definitely not in backwards...just not sure why idle adjustment screw is not reaching the the 2/3 sync screw stop.....odd

 

If you are recovering from a PO's "Hack-job"

Possibles include:

• Wrong Idle Adj Rod
• Right Rod / Wrong Spring
• Sync-screw stop Bent/Misaligned

 

Rick,

Previous owner is the only owner - ME, It is not the wrong idle Adj Rod with the incorrect spring, & the sync-screw stop is not bent nor misaligned.....

I broke this rack for the first time....& I believe it is put back together correctly...but maybe I am missing something here.....don't know what thou.....

 

@fiveofakind

I compared your rack with my spare rack and every part seems to be at the right place. The only thing that looks odd on your picture is that all of your adjustment screws seem to be completely backed out, so there is very little if any adjustment possible in one direction (you can't back up any more).

 

Quebec,

I just broke the rack again to adjust the butterfly's on #3 & #2....( not that I had to ) but thought one more good look over everything....before aligning & putting on the bottom bracket & top bracket again......

I presumed that backing off all sync screws was the way to start just prior to bench sync'ing......I am probably wrong on that assumption....

Thanks for the observation.....any other advice is greatly appreciated.....

I Know..I know...wet-set the carbs - fuel level & fuel height measurement....

I am in no hurry... I have had this bike for 30 years.....it is not leaving my presence any time soon....

 

looking at your picture, 4 is closed tight and 3 is open past where the idle screw can reach. if you turn the idle knob all the way in then turn the 3/4 sync screw, 4 will open as 3 closes until it hits the idle screw. now your in the ball park. now use the 3/4 and idle knob to split the holes, then move to 1/2 and your on your way

 

Polock, Thank you for the great advice.....I just broke the rack again tonight for one last look & adjustment to the butterfly's.......I will re-assemble tomorrow....following your direction.....

Thanks,

I probably didnt need to break the rack again but did.

I like your approach....

GO PENN STATE......alumni.....class of '78.....