Carb sync. trouble

My 1100 Maxim was running fine but I hadn't sync'ed the carbs for years. They where close, just a tweak here and there. Then I realized that I had not inserted the YICS blocking tool. I blushed out the chamber and inserted the blocking tool. The 2nd cylinder vacuum jumped up to double the level before, the other 3 remained the same, and would not move while the adjustment screw was turned. Any ideas what I am doing wrong? I have used the blocking tool before and everything worked fine.

 

I don’t know YICS, I believe the general consensus here is to sync without the Tool in place. Under normal operating conditions the bike doesn’t have the passages blocked off so why synch/ tune with it in?

Hopefully someone with a YICS will chime in with their real world experience.

When is the last time your carbs have had a deep clean and refurbishment done to them?

 

Seems odd. Maybe the problem is with the tool. Can you insert it from the other side of the engine to see if you get the same results?

 

could be his internal passages are blocked in 3 cylinders.

as far as the other cylinders becoming non adjustable no Idea

 

Supposedly you get a more accurate sync with the tool in place -
The blocking tool only inserts form one side, pretty straight forward, or so I thought. Possibly the other ports are blocked. There are 3 adjustment screws. The left screw syncs #1 to #2, the right screw syncs #3 to #4, the center screw syncs 1+2 to 3+4. With the tool in place I was unable to sync 1 to 2. Always worked before, should have left will enough alone. Anyways I will try a friends sync tool. If that doesn't work I will sync without the tool.

 

On my XJ700 the blocking tool can be inserted from either side. In fact, when I remove the tool I always remove the bolt plug from the other side which makes it easier to remove. My tool fits tight, especially when it's hot, and unless I remove the opposite plug I'm pulling against a vacuum which makes it difficult to remove sometimes.

As XJ550 H said, maybe some to the passages are blocked. Have you tried to run a gun cleaning brush through the passage? Also, I think I saw where someone used a small probe with a 90% bend in the tip to try to clean out the passages. I've used the brush with some carb cleaner, but never tried the probe.

 

Waka waka waka!

 

I knew someone would play with that statement, but at 73 — well it ain’t what you think.

 

Now Mati keep it clean lol ....I did not use the blocking took on my seca and synched just fine and runs great. I synch my carbs using the 4 vacuum gauge manifold.

 

I don't use a YICS blocking tool when synching my xj550 using a homemade 4 tube manometer. Runs fine.

 

I agree that a lot of folks don't use one, but I'm still curious as to why using one changed the reading so much on one cylinder. I'm thinking that the YICS passages may be clogged to various degrees. Maybe I'm missing something, but without the blocking tool it seems to me that the carbs could be synced even if one or more of the passages are blocked since they all share the same YICs chamber. Maybe the use of the blocking tool is intended to show condition of the YICS passages. I admit that I don't know much about the YICS system, so I may be way out in left field.

 

Thanks for the ideas guys. I did brush out the passage several times with a .375 cal rifle brush and carb cleaner. The brush came out relatively clean. Even if the ports were blocked I don't understand how that would double the vacuum on one cylinder. When I say double I am referring to the mercury height in the sync tool. The #2 vacuum port is the port the fuel shut off is normally attached to but that tube is obviously removed to attach the sync tool. This all started last fall as I was about to put the bike into storage. I hope to pull it out this weekend and resolve the issue one way or the other.

 

Surely if you don't block off all yics passages the vac signal will be shared, at least to some degree - the fluid dynamics issues come into play here, blurring the lines depending on how far open/how much difference between carbs/how much rpms.
Block the passage and try adjusting, it has to work.

 

My thought process regarding the Yics passage is this: will the engine be running with the passage blocked? Then why optimize the carbs for that condition?

On the other hand, I have a Honda....