Carb Synch

Help!
I just don't get the idea of carb synchronization. I've read my shop manual I Cleaned out my carbs but i just can't get them to run together. They don't have a synch gauge at my Yahama dealer, they also don't have that special tool needed to bypass the YCIS assembly. By the way what does the YCIS assembly look like? Here are my problems
Idles at 4000 rpm or not at all
backfire like crazy
on the highway she runs fine, but in towm it's a total nightmare
I am willing to build the tools I need
Does anyone have any advice

 

Oh wow.. I think you dont need to ride her until you get it right.. personally...
Did you Bench Sync?
Did you check your valves?
Syncing is easy! You can do it with two glass bottles, two rubber stoppers fitted into the tops, and extra fuel line.
Theres a post with pics on how to build one around here. Cost me less than 10 bucks.
The YICS tool is........ well... Useful for the first time i think... Gets you at your syncing destination faster... the first time. I have one I'd be willing to sell you. PM me if you want it.
After you get your valves, your sync, you need to Colortune. Which is setting the mixtures correctly at Idle. It help a weee bit above 3-4k rpms too. ANd while you've got the colortune in, you can see what your mixtures look like at higher RPMS. Which is useful.
Anyway
Valves
Sync
Colortune
THAT ORDER
And THAT will give you a FANTASTIC starting point for diagnosing any more probs you have
-Chris

 

Buy the YICS tool from the forum vendor XJ4ever.... easy and cheap it'll be there in a week... Go to crappy tire and buy a 20 buck vacuum gage...

 

Checking Valves
http://www.xjbikes.com/Forums/viewtopic ... art=0.html

Bench Sync
http://xjbikes.com/Forums/viewtopic/t=6366/

How to make a SYNC tool
http://www.xjbikes.com/Forums/viewtopic ... +sync.html

Seriously. Look at these and take the information in. It'll save your bike

 

Um... quick question, so I don't have to remove tank or airbox. If I want to close butterfly valves more, pilot screw in or our (tighten or loosen)??

 

No, the butterfly valves are located at the "front" for th carbs. Pilot screws affect the mixture, those are at the "back" of the carbs. The three screws in the middle of the carbs in the front controls how open or closed the butterflys are. Read the Bench Sync Post

 

Things seem top be getting "Lost in Translation"

Close Butterflys.
Locate Idle Adjustment Rod with Thumb Knurl
Below Carbs
Between Middle two Carbs.

Turn Idle Adjustment Rod Counter-clockwise to CLOSE Throttles and reduce RPM's.

 

Okay... lemme think, I have a screw between 1&2 that opens/closes the butterfly valves and a screw between 3&4 that does the same but for valves 3&4. I have a large screw between 2&3 that changes idle speed. I have the idle adjustment screw backed all the way out cause when I bench synced, I left the idle adjustment screw almost all the way out so when I used a paper clip to set butterfly valves, I didn't ave enough space on the idle adjustment screw to back down to 1050.

(I have a 92)
|
|
|

 

That bench sync post has some good pics to help figure out what is what. Gamuru did a great job putting that together.

 

You'll have to bench sync again, start with the thumb screw mid way on the thread, then sync, that way you can always back that screw off & close the butterflys.

 

I can do this with carbs on the bike, right Wizard? I will take the idle adjusting screw and put it halfway on threads, then screw the valve adjusting screws out until they leave butterflies closed and use idle adjusting screw to fine tune it, correct?

 

No to bench sync them you will need to take them off the bike. If you follow this thread: http://xjbikes.com/Forums/viewtopic/t=6366/ it will walk you through the steps to bench syncing your carbs. Just take a look at it and relax... It is not as hard as it seems. Then after you do that you may need to turn idle down a bit after your bike warms up. That is done by adjusting the knob that is in the middle of your carbs by the airbox. Check out the link and after you get going on it you will do fine!

 

OK, So I did the bench synch on my carbs. Then I built the two bottle tool to synch my carbs. I connected my tubes to the vacume inlets. But I still can't get things to run right. Question, should I touch the #3 carb during the final synch. I get the feeling that since everything is benched to the #3 I sholud not touch it. Any opinions? Thanx.

 

YO! One more question. What is colourtune?

 

It is a special spark plug that has a window in it that allows you to see into the combustion chamber and see the color of the flame that is produced. Thus allowing you to set your air fuel mixture to the corrrect amount.

 

Your feeling is correct. #3 has no adjustment other than the big main idle knob. It is the "base" you synch the others to; #1 syncs to #2, and then the pair to #3, and #4 to #3.

And even though this is going to start a firestorm, you are blocking off the YICS when trying to sync, correct?

 

When you Sync you carbs, best thing to do to get it to run right is to take a 5-10 min ride and warm your baby up. I tried it cold and could barely get her to start. Make sure when you put the Hoses on the Vac ports that it fits snugly. No loss of air. And fitz is right I think. The first couple syncs I think you should use the YICS. After you arrive at your sync destination I dont think there is much need for the YICS tool after that
Every riding season the carbs should be cleaned, and then re-assembled and synced and colortuned. Feel me ma'hn?
-Chris

 

I've just been using a 3/8ths rod (not 100% sure of the dimension though it is an easy one to measure) with some engine oil on it as my blank off tool (it is a tight fit so I suspect that it renders the YCIS passage useless).

If I were you I would also conduct other general checks like the gas tank and lines, battery and air filter just to eleminate any odd ball problems that might being making your life hard than it needs to be.

 

This is starting to make sense. I was trying to tune #3 to #4 . No wonder I couldn't get it right. I'm going to bench the carbs again and try to set them.
My YICS passage seems to have been sealed, there is no access to this feature on my carbs. It looks like it was done at the factory as it is very clean and permanent. Any thoughts?

 

look on the head not the carbs - Just forward of the carbs you should see a small bolt - one on each side