number 2 carb wont sync

[OrlinEngh]

On my 84 Venture I have 1,3,and 4 synced but number 2 will not, It also when warmed up will go from 1000 rpm to 2000 rpm up and down and have noticed a small back fire when running down the road. And at a idle you can hear it miss and then smooth out.

I have good fire to number 2 spark plug.

I checked the slide when runing and moves the same as the rest and checked the diaphragm and it looks good cant find any holes.

Orlin

[Yammer Dan]

Sea-Foam??

[MiCarl]

They sync in pairs. It's not that two isn't synced, it's that 1-2 aren't synced.

 

The way you sync is to get 1-2 matched. Then match 3-4. Finally you match the left (1-2) to the right (3-4).

 

What makes it extra fun is until you get pretty close changing one changes the others. It's quite likely as you sync 1-2 the other pairs will go out, don't worry about it.

[Yammer Dan]

What Carl said!!

 

Then Sea-Foam!!

[Venturous Randy]

Also, check for vacuum leaks.

RandyA

[Flyinfool]

Also check for binding linkage.

 

When I did Bills at your MD I had to turn the 1-2 screw at least 10 turns before anything moved on the carb tune. It was just that far out. Earl had the same issue with mine at Dons MD.

[OrlinEngh]

I have to think that this a fule problem I pulled the spark plug wires when runing and on 1and2 no change and on 3 it will die out and 4 a small change I can hear it ark to the plugs

I had my gauges on for syncing the carbs and when I choked it a quarter of the way open number 2 and the rest of the carbs were close to the same.

This spring I got a bad tank of gas and I changed the tank, carbs, filter and lines I am wondering if my fule pump is not pumping enough fule or if there was still some gunk in the pump and it has made it to the carbs I am going to check the filter to see if it has gotten pluged.

Orlin

[Marcarl]

Just to be sure: #2 doesn't sync! You need to sync #1 to #2. Then # 4 to #3 and then #3 to #2.

#2 is adjustable only by the idle set screw.

#2 is your base to which you set #2 and #3.

 

If you can't adjust #2 with the idle screw, then you have another carb that has it's butterfly closed too far, preventing #2 from closing.

 

Make sure you keep the idle around the 900 mark as you go around. The amount of vacuum drawn at 900 is different than what is drawn @1200, so if you notice that the rpm's change, reset the idle screw.

The idle screw is not the sync screw, although the sync screws will change the idle, the idle screw is located on the left side, between the carbs, hidden behind the bracket that holds the carbs together. It's a thumb screw, not a Phillips or slot.

[spitfire9]

Bookmarkig this one... thats my next project after electrical issue figured out. Good luck, Orlin.

[OrlinEngh]

I got it after pulling the air cleaner box and pulling the number 2 slide and getting in there and spraying some carb cleaner in all of the holes I could find and the same from up on top and draining the float and then putting some air threw it. And then I was able to do a sync on the carbs. Sets and idles great and starts as soon as I hit the button.

Must have got what ever was in there flushed out.

Orlin

[OrlinEngh]

now I have this surgeing going on when going down the road at highyway speeds. If I choke it about a quarter of the way it smooths out. we had it out for a 4 hour ride the other day and had never run that smooth untill about 20 miles from home. I took it for a ride today and it started doing it about a mile or so down the road.

Orlin

[jasonm.]

you likely have an intake leak''. somewhere....Or the bike is simply running WAY lean from carbs improperly set low speed screws. If you find your idle increases when adjusting a low speed screw and you are at 4+ turns CCW. That's a leaking manifold o-ring. BUT Since you say you removed the air box...ALSO Need look at the 2 hoses that work as PCV for the engine. They connect @airbox between 1 and 3 and the odd ball is almost behind #2 carb. Then go to the center of the "V" by the oil pipes. If all these are solidly connected. I suspect an intake o-ring is bad under one of the manifolds. You can spray WD40 at the mate of the maniford and head while it idles to see which is the leaker. Typically the engine will slow down...WD40 won't ignite. It happened to me. And carb removal is required. It's not fun nor easy...the 1st time

Edited July 18, 2012 by jasonm.

[Condor]

If #2 won't sync it's because all the rest are too tight and are really not sync'd, even thought you think they are..... #2 carb is the bench mark carb. All other's sync to it....

Back off all the other sync screws and set the engine to idle at 1000rpm using just the idle knob. Then turn in the #1 sync screw until the rpm just starts to increase and back it off a tad. #1 should be sync'd or dam close to #2. Then hook up your sync tool and get #1 perfect. Then work on 3 and 4. They'll probably be way out but keep at it. The closer they get ballanced the rpm's will start to climb. Reach over and set the idle back down to 1000. You may have to do this a couple of times. Once you get 4 and 3 ballanced, bring the left side and right side together. It should run like a raped ape.....

[OrlinEngh]

I checked for leaks and didnt have any by the heads or around the carbs I tryed it a couple of times to be sure, rechecked all of the clamps to make sure they are tight, re synced and they were still even. I am going to richen it up just a bit and see how that works.

Orlin