Topic: Carb sync.......kill me now.

[dylboss]

Ok, so I've been battling a carb sync for about 4 hours today.  I did a valve adjustment, points adjustment, made sure the spark plugs were gapped correctly.  Everything checks outs, and carbs have already been cleaned.  Now, go to fire her up and she is running worse than before i started.  I just can't seem to get the carb sync right.  Seems like i'm going in circles.  Now it is all screwed up.  Is there a way to start from zero with a carb sync?  I'm getting backfires like crazy at idle, engine is clanking, and just can't seem to sync this blasted thing.

Anyone have some advice?

Thanks.

[OldSchool_IsCool]

Bench sync, but you have to pull the carbs out.

[fmctm1sw]

If you did any work on the carbs beforehand, make sure the linkage is all tightened.  Ask me how I know... 

[vance]

First of all if you're getting frustrated take a break and come back to it later. Second of all, don't worry I guarantee you that these guys will help you figure it out.

You need to state the year and model bike and what modifications if any. Then exactly what you did in what order and how you did it. There's a mistake in there somewhere and the more specific you are the sooner the forum guys will figure it out for you.

Good luck!

[benjamin550]

I was in you position about a week ago and created a post on the topic. DYSKORD responded with some advice that really saved my ass and made the whole job a lot easier. Here is the link, read the whole post and follow his instructions perfectly and you should be good to go.

http://forums.sohc4.net/index.php?topic=87117.0

[dave500]

you are vacuum syncing?

[xedge4lifex]

Bench sync, but you have to pull the carbs out.

ive been running my carbs on a bench sync for over 5k and 8 months. all its really going to help with is a solid idle, and return to idle. i wouldnt touch vacuum sync gauges unless you have some serious carbs going on the bike or a billy bad ass engine that needs to run perfect.

[dave500]

bench sync gets the motor running,then you need to vacuum sync them,full stop,you are balancing the vacuum between the carbs more than equal throttle positions.

[DYSKORD]

Ok, so I've been battling a carb sync for about 4 hours today.  I did a valve adjustment, points adjustment, made sure the spark plugs were gapped correctly.  Everything checks outs, and carbs have already been cleaned.  Now, go to fire her up and she is running worse than before i started.  I just can't seem to get the carb sync right.  Seems like i'm going in circles.  Now it is all screwed up.  Is there a way to start from zero with a carb sync?  I'm getting backfires like crazy at idle, engine is clanking, and just can't seem to sync this blasted thing.

Anyone have some advice?

Thanks.

Yeah you can start from "zero." Just follow the link Benjamin550 posted. If you follow those instructions you should be golden. Just remember to have all other adjustments (valves, cam chain etc.) done prior and follow the sequence outlined in the posted link. If you dont follow the sequence it is most likely you will chase yourself in circles until you run out of adjustment, like myself and Benjamin550. Good luck and dont hesitate to ask any questions.
DYSKORD

[dylboss]

Guys, thanks a lot for all the advice.   I will follow the instructions from Benji and post an update.

[dylboss]

Well, thanks to those that offered advice.  I did the valves, timing, points gap, cam chain adjust, air mixture screw adjust, then the carb sync (vacuum).  I have to admit, it didn't quite go as smoothly as Dyskord describes, but nevertheless I think I got it finally, and thanks Dyskord for the help.  It gave me somewhere to start.  Kept wrestling with no more idle to play with because it was screwed all the way in, and when I adjusted the sync screws the bike wanted to stall.  Back and forth, back and forth, but in any case carbs appear to be synced, and she is running a steady idle.  Still seems to be slow to settle down to idle (about 4-5 seconds) if I rev it up into the 2500-3000 RPM range.  If I stay under 2k, she comes right down to idle.

Also, I'm trying to make sure I have the right expectations about how this motor should sound.  Are these generally noisy engines?  Seems like even with the carb sync, I didn't lose the clutch noise.  Clutch is very rattly.  Pull it in and it goes away.  Are the clutches on the CBs generally loud?

[Duke McDukiedook]

Shouldn't be if it (The clutch) is adjusted properly.

Sounds like you have your carbs kinda balanced but it sounds like one or two has more vacuum if it wants to hang.

You might want to start from scratch, pull the carbs, clean thoroughly again (with compressed air in all orifices),  bench synch then synch with manometer according to the manual.

[DYSKORD]

Well, thanks to those that offered advice.  I did the valves, timing, points gap, cam chain adjust, air mixture screw adjust, then the carb sync (vacuum).  I have to admit, it didn't quite go as smoothly as Dyskord describes, but nevertheless I think I got it finally, and thanks Dyskord for the help.  It gave me somewhere to start.  Kept wrestling with no more idle to play with because it was screwed all the way in, and when I adjusted the sync screws the bike wanted to stall.  Back and forth, back and forth, but in any case carbs appear to be synced, and she is running a steady idle.  Still seems to be slow to settle down to idle (about 4-5 seconds) if I rev it up into the 2500-3000 RPM range.  If I stay under 2k, she comes right down to idle.

Also, I'm trying to make sure I have the right expectations about how this motor should sound.  Are these generally noisy engines?  Seems like even with the carb sync, I didn't lose the clutch noise.  Clutch is very rattly.  Pull it in and it goes away.  Are the clutches on the CBs generally loud?

The clutches are notoriously loud!

[dylboss]

Shouldn't be if it (The clutch) is adjusted properly.

Sounds like you have your carbs kinda balanced but it sounds like one or two has more vacuum if it wants to hang.

You might want to start from scratch, pull the carbs, clean thoroughly again (with compressed air in all orifices),  bench synch then synch with manometer according to the manual.

According to the gauges, they are all spot on with each other at idle and also when I bring the RPMs up to about 3k.  Gauges were also calibrated prior to sync.

[Duanob]

I had the same problem. Did you use the inline valves when doing the sync? If not, when you install the guages you're introducing air into the carb system and leaning the settings out. Use the valves, close them off and slowly open them after you start the bike until you start to see the gauge respond.

[flybox1]

if your rpms hang with a blip of the throttle, check your carb to engine boots for a vac leak.  make sure all your clamps are in their grooves and tightened properly.

[dylboss]

I had the same problem. Did you use the inline valves when doing the sync? If not, when you install the guages you're introducing air into the carb system and leaning the settings out. Use the valves, close them off and slowly open them after you start the bike until you start to see the gauge respond.

I am using the inline valves, but I didn't close them before starting the bike.  I guess I'm confused as to how that would make a difference.

[DanielB]

sub'd for later.

[dylboss]

Well, I removed the carb sync tubes from the intake holes, and replaced the screws.  Everything seems to run great now.  Idles smooth, no hang up on the RPMs when reving to 3k.  Can't complain at this point after 2 weeks of wrestling with engine tuning. 

Definitely difficult to start and remain at idle when cold, but I'm guessing that is normal?  When warm, the bike runs like a top.  Haven't ridden it yet, so I guess that will be the tell tale.

[dave500]

straight up cold it wont idle like a fuel injected engine,i use the throttle lock screw to hold a smooth idle as i gear up,many people have never had a car without fuel injection so are less learned in the art of the cold start procedure and limitations of a carby engine,,your bike wont idle straight from cold very well,i live in a climate like your florida or new orleans.

[Duanob]

I had the same problem. Did you use the inline valves when doing the sync? If not, when you install the guages you're introducing air into the carb system and leaning the settings out. Use the valves, close them off and slowly open them after you start the bike until you start to see the gauge respond.

I am using the inline valves, but I didn't close them before starting the bike.  I guess I'm confused as to how that would make a difference.

I think you answered your own question. With the gauges attached, your carbs act like vacuum leaking into the system. They won't run or idle correctly with too much vacuum. Closing the valve is like getting rid of the vacuum leak. Only open the valve enough to get a reading. trust me I only know through my own experiences.