Post carb rebiuld shakedown run...thoughts please.

I set the idle/mix screws at 2.5 turns out. The carbs are bench synced only because my vaccum guage has no filter/damper.

I let it warm up enough to need to back off the choke to about half way. At first, it ran poorly. It was very thready with poor throttle response. At this point, I was only a block from the house and decided to turn around and go back. As I let off the throttle, POP!, massive backfire and the engine died right away. I dropped it into 1st and popped the clutch for a rolling start and it fired right back up. After that, it ran quite good. I rode for a further 10 minutes or so with no further issues until I turned the last corner leading to my house. Right after I came out of the turn, it sputtered and died. After stopping, it fired right back up.

For the second issue, I have the feeling that my carb floats are set to keep the fuel level too low and I sucked air in the turn. What was the deal with the backfire though?

Next question. When the bike is fully warmed up, should the choke lever be fully off or should it be say, 1/3 open while the bike is running? I suspect I need turn the idle screw in a bit more so that I can back off the choke all the way without stalling.

Chris

 

Choke should be fully off when fully warm and yes it sounds like the idle screw needs to be turned it a bit so it can maintain its idle.

Pop and backfire through exhaust sounds like a lean mixture, i would use 3 turns out as a starting point. Once its running not to bad you can use your plugs as a guide on mixture settings.

Have a read of this link, you should be able to check float levels with carbs on bike, can be tricky but if you think they are set low this will tell you.

http://www.xjbikes.com/Forums/viewtopic ... level.html

 

Bring the Mixture Screws out closer to 3-Turns and begin a close monitoring of the Plugs.

As you get it running better ... read the Plugs and only adjust the Mixturue Screws for holes that need a tweak.

Tweak is the rule.
Once you get it going good ... you adjust the Screws turning them a minuscule amount ... a couple of degrees ... NOT quarter-turns.

Shoot for Tan to Med. Brown.
Idling nice with enough extra to support ignition when the throttles are opened until the Main Jet Fuel Supply arrives.

 

On a 82 550xj, I started at 3 turns out and it ran great once sync. I started to clean the pilot jets but ended buying and replacing all four. That was $15 well spent. Have looked at the plugs and they don't look bad. Left it at 3 turns. I will look at the plugs again every couple of hundred miles.