carb tuning

hi all , when tuning the carbs on a xj700 air cooled after a major clean is it best to do thr air mixture first with a colortune spark plug and then sinc the carbs or the other way roumd ??????? can someone please advise thanks john

 

1. Valves in spec
2. Set float levels
3. Bench Sync Carbs
4. Set pilot circuit to previous value, or to some initial value
--Install---
5. Make coarse adjustment to idle, and/or pilot circuit to get a consistent idle in the appropriate RPM range.

Now to your question:
Each adjustment to the pilot circuit will change your sync. So I'd try to get a consistent sync first, then colortune 1, sync, colortune 2 sync,...etc. You might have to go over it more than once to get everything set up right.

FINE adjustments (too rich to too lean is about the width of a nickle on the pilot, and sync should be adjusted in the same increments). Blip the throttle between adjustments to make sure the setting "takes" (your throttle shaft is just a bunch of linkages).

And make sure your engine is warmed up before making adjustments, or you'll be all over the place. A fan on the engine can keep it from over heating, and consider hooking the battery up to a tender between tests.

 

I find that after I sync then colortune that I need to re sync and then colortune that keeps on for at least several times before I'm really happy.

 

what do u mean pilot circut ??????

 

Mixture screws.

Sync first;

adjust mixtures (ColorTune.)

Re-sync.

Repeat until it idles like a sewing machine, responds instantly to throttle and returns to idle immediately when the throttle is released.

 

What you initially called an "air adjustment" is the Pilot or Idle circuit adjustment. A circuit is a separate fuel/air path, isolated from other paths in the carb body.

 

i have installed the carbs today but i am waiting on a yics tool . is there any point in trying to tune the bike untill i get this tool . thanks for all the info so far guys . this is a project but have to say the most comfortable bike i ever sat on . long live the xj

 

You really do need the YICS tool.
I made my own, there are instructions on this site.
The YICS tool seperates the carbs so that when you are tuning you are getting a true tune on each carb/cylinder.

 

do u leave the yics tool in when doing cokortune or do u remove it when the carbs are synced ? realy gratfull for all the info

 

do u leave the yics tool in when doing cokortune or do u remove it when the carbs are synced ? realy gratfull for all the info

 

You can use the "cram-it with strips of oil-soaked cotton TEE shirt" method for now - what are you using for a Sync devise??

Yes, you plug the YICS while sync-ing and tuning.

However, there are those who tune in the "natural" state, unplugged.

 

You pull it out after the sync is done
You can leave it in there when you colortune between syncs
after sync you take it out and return the bike to the way it was.
The purpose is to be able to sync each cylinder independently otherwise the yics ports tend to equalize the intake system so you really cant tell what the real vacuum is in each intake unless you use the YICS tool
Or the oil rag...

 

noy using anything at the moment but have a yics tool ordered . im in northern ireland and most parts have to b sourced in the states . i have this bike 8 years now . i bought it ready for the scrap heap but have restored it till its like new . would love to get it running well but where i am if i need something it takes 6 weeks to get it ,

 

my bike has a k&n air filter . would i be better to get the original filter ?

 

It would eliminate one more "variable."

 

do u no where i could get a original air filter ?

 

The K&N one is fine.

I would bet that there is not much difference between a K&N and a stock filter. Now if you were talking K&N pods, then it would be a different story. I would keep the standard box filter. Its as good as any.

-Kaya

 

And FYI.

Ive read tons of posts about people skipping the YICS tool all together like timetoride stated.

-Kaya

 

its not pods just the box filter , just want it to be right

 

It will be fine.


Ive been digging for a bit now to find who made the OEM ones. In all honesty, If the company was still around, (Hitachi for example) the would have forgotten about our bikes long ago.

I mean, Yamaha cant even get many of the parts.

Try calling Hitachi and ask for parts for 1982 carburators. If they speak English and can understand you, they will probably tell you your SOL. I just saw a set of new old stock hitachi carbs on Ebay. Know how much they wanted for them? $1200.

I get the need to run stock on these bikes. As someone told me. They screamed as stock off the showroom. However, such a minor thing as a different brand air filter or non NGK plugs, I find, make little difference.

-Kaya