Fj Carb Sync Question.

[Lloyd Van Duzen]

Ok, so at some point down the road I plan on doing a carb sync on one of my 84 Fj 1100's. My question is can you, or is it a viable alternative to use the "pop sickle stick" method of syncing the four carbs on these bikes?  I have had success with this on 2 cycle, twin engine sled's. I'm wondering what other owners think.  I do have a manual describing the procedure to use ultimately. Thanks for any input.

[fj1289]

I'll probably regret this - but I'll bite: what is the popsicle stick method?

I have a feeling it is similar to how an old manual I had for a Honda twin said to feel the pulses from each muffler and adjust to make them even 
  

[Lloyd Van Duzen]

Ok here is how it works.... Some should know this I think.

In the intake side of each carb, without the engine running and with the breather box removed, you place a pop sickle stick so it is balanced with one end held under each carb barrel, heavy end of each stick hanging free.  As you turn the throttle you will see each stick move (drop) as the barrel rises and visually you will see the sticks either move in unison if in sync and if out of sync the sticks will move at different times or delayed to the rest. Hopefully you can see how it works.  I think any carbs with the barrels, this method should get you close to sync by means of adjustment and repeating until all four in a row drop at the same time.  Maybe I should have explained in depth, I thought people would know about this procedure.  I have used this with my sleds and twin tuned carbs (mikuni) and in synced time seem to work pretty well and perform as designed.

[fj1289]

Nice!  I like that idea!

But ...  I'm thinking this procedure probably doesn't work as well with CV carbs?  Since it is the butterfly valves (and the vacuum they cause) you are trying to sync. 

There are some DIY carb sync setups online if you want to keep it completely DIY.  Also common tools available for a reasonable price - especially if you compare it to how much you will have to pay a shop these days to do it!

[Pat Conlon]

Ok for carbs with cable raised flat slide or round slides,  don't see it working with FJ's vacuum operated slides.

Besides....the thought of having to remove the oem air box just to sync the carbs gives me heartburn, although it's  a great character building experience.
It will make investing in a carb sync tool seem like a wonderful idea.

Speaking of carb sync tools,  I have tried out my new a 4 channel DigiSync, and I love it!

https://thedigisync.com/

My trusty Morgan Carb Tune will soon be up for sale

Cheers

[Millietant]

That method won't work with the FJ's constant velocity carbs. You can't static synch CV carbs.

Without the engine running, opening the throttle just rotates the butterflies and with no vacuum to act on the diaphragms, the slides just sit in their bottom position.

It's so straightforward to synch the FJ carbs with vacuum gauges (no need to remove the airbox) it's worth the cost of buying a decent set of gauges 

[fj1289]

I finally remembered the bench synch technique for the CV carbs - to at least get them close.

Tuen the idle speed adjustment up fairly high and use a small drill bit shank as a feeler gauge.  Adjust the idle speed until the drill bit barely passes through the opening onbase carb.  Then adjust each successive carb to match the base carb. 

Not sure how close this gets you - I do t know if this is a "rough sync" to get the bike running on a set of rebuilt carbs so you can get them on the vacuum gauges, or if it will get you pretty close to what a set of gauges will yield. 

[twangin4u]

Ok, so at some point down the road I plan on doing a carb sync on one of my 84 Fj 1100's. My question is can you, or is it a viable alternative to use the "pop sickle stick" method of syncing the four carbs on these bikes?  I have had success with this on 2 cycle, twin engine sled's. I'm wondering what other owners think.  I do have a manual describing the procedure to use ultimately. Thanks for any input.

I've tried the cheap vacuum gages and their junk (needle bounce). The glycerin filled are $10/ea on Amazon.  They probably work well,  but haven't tried them.  For me,  the best way that I've found... again,  for me is simple 1/4" tubing and some pilot jets stuffed in each tube as a snubber. For me,  it gets it synced dead nuts. 

**I know I should have painted background of wood white...