XJ650 Stalls When Syncing Carb 2 to Carb 3

Hey Guys/Gals,

I'm currently debugging why my XJ650 dies when the choke is off (bike is warm, replaced the petcock, carb aren't too out sync...) - there is plenty posts already on this topic so I can figure that out. When I try Syncing my Carburetor 2 to the Carburetor 3 the bike dies.

As you can see in this pic Carb. 1 & 2 needles are pointing higher than the Carb 3. needle (needle is a bit jumpy Carb 1 & 2 are point just a bit higher than what is shown). Lowering Carb 2 below the "red area" kills the bike.



Any idea why this would happen? Should I leave adjust the Carb. 2 to the point where it's closest to the Carb. 3 but it doesn't dies?

Thanks!

 

What have you done to the bike so far?

Stalling when warm and the enrichment circuits closed usually points directly to plugged idle jets or low fuel levels in the float bowls.

What are the idle-air screws set at?

 

^^ what he said first

read this link it will give you a better understanding of what a "carb Sync" is actually doing
TALKIN' TECH: Various thoughts on various issues

have you done a compression test? checked the valve clearances?

do you have restrictors in your hoses to reduce the needle jump?

carb 4 does not look to be synced to carb 3 , could be just the needle jump

and to be sure you have synced 3 and 4 as well as 1 and 2 before syncing 2 and 3?

 

I've replaced the air filter box with air pods. That's the most obvious mod that would affect the air/fuel mixture.
Took the carburetor out and I am in the process of cleaning in it.

Also, just checked the spark plugs and they seem carbon fouled.

 

Carbon fouled spark lpugs could be a result of a too lean mixture. What are your mixture screws settings?

 

Checked the valve clearance. I haven't done a compression test. I'll do one!

Yep got restrictors on the hoses. My manual said to sync Carb 1 to Carb 2, Carb 4 to Carb 3 and then Carb 2 to Carb 3. Which is the order I followed.
Carb 3 & 4 looks synced to me (2 gauges on the right). They are both jumping inside the same "box".

 

Agreed. Pods, lean, carbon fouling, fuel starvation.

 

Pods, huh? Well..... Here we go AGAIN

 

After cleaning up the carbs which were really dirty I was able to sync the carbs. My guess is the carbs got dirty from debris created by a misapplied tank sealer:




The bike is now running without any issue when the choke is off .
Thanks for the help!

 

Are those stock jets? Still running pods? Are you positive that there are no issues; for example, a flat spot in the midrange?

Be sure to fit an inline fuel filter so you don't get any more crap from the tank into the carbs.

 

Holy Crap, there's a lot of crap there!!!