Cylinder not firing/ white plug.

Hi Folks.
First off I'd like to apologize if I am posting incorrectly. I'v never been on a forum before.

Alright now for the bike.
I have a 1980 yamaha maxim 650.
I did a valve clearance adjustment because well they were out of spec (tight) and I had a noticeable lack of power and hesitation when on full throttle. After doing so. I did a vaccum gauge sync and adjusted my idle accordingly. I also rebuilt and cleaned my carbs( many times mind you) "church of clean was very helpful) . After all the work and adjustments, I still have the same results. All plugs read a nice brown color except for carb #1 all the way to the left bike being forward. It's a dry white, like it's running lean and pilot screw has no effect when I turn it in or out. I did a pressure test on all cylinders, all read 115-125.
I have checked for all air leaks around boots and exhaust gaskets.
I have spark
I have fuel flowing to my float bowl on #1 so that must mean the needle and needle valve must be working. I don't understand why that plug is white/lean. And I Still have that hesitation and slight backfire at idle.
Any help or Insight is greatly appreciated. Thanks!

 

Have you swapped plugs between cylinders? If it's a bad plug, the condition would follow the bad plug, same with a bad plug lead.

 

I have tried different plugs

 

I would focus on the passages there. Make sure you don't have remnants of an old o-ring jammed in there.

 

BTW the correct order for the pilot goes screw, spring and then o-ring correct?

 

there is also a washer there to protect the o-ring from the spring.

 

As is often the case, there is good documentation in the xj4ever catalog.

https://www.xjbikes.com/forums/threads/xj-parts-catalog-section-c-fuel-system.44642/
The order of things is:
a) HCP895 o-ring
b) HCP896 spring seat washer
c) HCP6573 tension spring
d) the idle mixture screw
e) the anti-tamper cap.

What is mostly confusing is the order of the o-ring versus the spring seat washer....which goes in the hole first? The answer is that the HCP895 O-ring does. The HCP896 washer primarily acts as the lower "seat" for the HCP6573 tension spring, while also keeping the o-ring firmly and securely in place.

 

Have a 1982 Yamaha XJ 750J Maxim. The number one cylinder (far left while sitting on the bike) is not running at idle. While riding I can reach a certain RPM and notice it kick in. Have checked the plugs and swapped them around. Have also checked the compression, coils and carburetor. It will idle, but backfires and can tell it is not running. Any suggestions?

 

Could be the mixture screw position or spark plug cap making and breaking where it joins the high tension lead. I would check the lead first.

 

The carbs have been synced and have also swapped the number 1 and 4 cylinder spark plug wires and still have a miss. Have also swapped the coil around.

 

At idle give it a little choke and see if the cylinder fires. If so, your pilot circuit is probably blocked. If the pilot circuit is blocked there is almost no fuel getting to the cylinder. As the throttle is opened the main jet becomes more prominent and will provide enough fuel to fire the cylinder. I assume that you have verified that the plug is firing.

 

..start a new thread next time.

 

Will try giving it a little choke. Not sure how to start a new thread.

 

Click the 'Post New Thread' Button - either top right or scroll down bottom right.