Syncronization....again...

Hi, i am new to the XJs and bought myself a -83 XJ550 who hasnt been running since 1991. I have done the typical theings like brakes, oil and of course new tires. The carbs has been at a workshop and has been totally rebuilt and cleaned in a ultasonic cleaner. I only sent him the carbs so i have put them back on the bike a week ago. The workshop has adjusted the a/f-mixture to 2,5 turns out but the engine runs like crap. I have spoken to the former owner andhe said they had adjusted the syncronization screws in and out so they are possibly way out of adjustment. I have the Clymer manual and the procedure for adjusting them but i wonder if anyone knows if the syncro screws as a "starting point" like the a/f screws ? Maybe someone knows ? It is possible to adjust them 7-8 turns so it would be nice to know where to start. I have checked the compression and valve clearance and the spark plugs are new. Any good tip would be highly appreciated carbs,

 

Welcome to the group! You will need to bench sync the carbs initially to get it close, then follow up with the running/vacuum sync and mixture adjustment. Here is a good write up on the process:

https://xjbikes.com/forums/threads/how-to-bench-synch-your-carbs.6366/

 

tidbits of advice.
Don't trust what someone else did to rebuild your carbs, double check as much as you can.
Check float levels (dry level pulling bowls and measuring hieight of the floats) Check both sides to make sure they match closely. Floats can be bent
While you have the bowls off, check the fuel enrichment path that is on the bottom of the float bowls, use flashlight to look for light. Mezmo engineering carb video shows that on youtube.
Wet level set the carbs per the manual, 3mm from the edge.
When you use your quad vacuum sync gauge, make sure the gauges all match.
Get the bike idling and then get 2 carbs to sync. Then swap those 2 gauge hoses and make sure they still match. if they don't start adjusting the gauges with the screws on the dial (remove gauge clear cover). Then swap in the other 2 gauges to make sure they agree.
My failure the first time I synced was the guages did not match. You don't really care if the value on the gauge is correct, just that they all match.
Although the A/F mix may be set to factory default 2.5, you will want to see if turning them out increases RPMS or not. You want an idle on the rich side of things.
Good Luck

 

Just to answer my own question…took the carbs out and did a bench sync. Then after reassembly ordered myself a Carbtune pro and adjusted as described. First 3 and 4, then 1 and 2 and finally 1/2 to 3/4. Worked perfect and now it runs supernice with a/f-screw adjusted to 2 and 3/4 out. Tried with a chinese vacuum set first and it was way out my experience is that if you are working on carbs, use proper tools.

 

Today's big winner of the truth-telling award!