VAC SYNK SUX, SCREW IT UP AND BACK TO BENCH SYNC. T or F?

My bike was running pretty darn good when I put the carbs on. I drove about 50 miles of city driving and had very little flogging except when it got hot it bogged sometimeg when I goosed it. I got out the colortune and my popular Ebay $25 vac sync with the two hoses with the BBs in it. The instructions were really hard to figure out. It said to keep one hose on the base cylinder and use the other 3 with the hose or something like that. But I started out doing it the other way where you do 1 and 2 then 3 and 4 then 2 and 3. I couldn't get it all togher. I wasted 2-4 hours messing with it. I had the whole works going on with the batt charger, fan, YRICS blockooo tool,etc. Now I am totally lost and can make it run alright but I don't think the butterflys open or close together properly. Looks like I have to bench sync to get it right again.

 

your mixture adjustments (colortune) and vac sync are 2 seperate processes. get your bench sync first, which will get you close, then do your running vac sync (1/2, 3/4 2/3)

 

Re: VAC SYNK SUX, SCREW IT UP AND BACK TO BENCH SYNC. T or F

I've seen those bb sync things before and truthfully, they look like a bunch of voo-doo to me.

Get a Carbtune or something similar where you can watch all 4 carbs at the same time, adjusting one carb can change the other carbs....then sync as jm said above.

And to answer your question....false! There's no days a bench sync will be superior to a vacuum sync.

 

I don't completely agree with that. Sometimes, if you get too far out on the vacuum sync by making large adjustments, and not blipping the throttle in between adjustments, it is definitely beneficial to just take them off and get your starting point back by re-bench syncing.

Remember: small adjustments and blip the throttle in between.

 

I hear ya on that funky BB tune thing. I been at it 12 straight hours. I forgot to stop to eat or drink after breakfast. One fail after another and then when I finally started to think I was going to make an acomplishment, I'm back to square one. I ruined the blanking tool maybe by purtting some oil on it. I ended up pulling out peices of the rubber out of the YICS port cause of it. I used a fan. It was a cool day here in Portland, Oregon and rained most of the day. Pulled carbs and bench synced. Set the idle mix screws to 2.5 turns out. I skipped the blanking tool, it was wasted. Vac synced, it looked like it was already close to being set alreadyand made minor adjustments. Colortuned and they were all blue and it sounded great. Took it for a test ride and it got all loco on me and quit running. That was it. Tommorrow..

 

Hopefully you weren't running the plant a majority of those 12 hours.

If the engine gets too hot, she'll race independently. Adjusting will be pointless. Let her cool off a bit. Also, make sure your carbs are good and synced before messing with the mixtures. Ride it around a bit. Feel her out. Do some plug chops.

Then when you are confident the sync is good, do your colortune.

 

Also, define "all loco"

Could be a separate issue...

 

Have you got an in-line fuel filter fitted ? sound like you might have the 'C W Moss' syndrome.

 

What is a plug chop.
I also did not mention #1 spark plug has a serious short but doesn't affect anything except delivering a powerful shock when I get too close to the wire. I hope that doesn't mean I will need to replace the coil soon. Hope it's just a wire.

 

I ran out of gas and also forgot to turn the petcock on a couple of times. Maybe I should go and check to see if I simply left the gas off again! Thanks!!

 

Gas was on. Forget that hope.

 

I used a Chacol 3" clear srtaight filter.

 

First thing was the idle hanging like a slide was slow to close. Rich running, flogging got worse rapidly and to the point of not able to run anymore.

 

Howdy Doug, First you need to fix your YICS blanking tool, trying to sync without it will be futile. Second either make a "manometer" or buy a 4 gauge vacuum tester. A color tune plug should only be used to adjust the pilot screws which control the idle mixture and you can do one cylinder at a time. As for your coils, if you are getting shocked by just getting close to your wires, it's time to buy new ones, you can't change just the wire as they are integral with the coils.

 

I'll do that to avoid another day like this. Thanks

 

The "plug wire" issue is more likely a problem with the cap, unless you can SEE that the wire is damaged.

You DO need to oil the YICS tool before using it; but you can't leave it installed for hours on end either. The YICS does need to be blocked, especially on a 550, or you'll never get an accurate sync.

If you do a good, accurate bench sync, using Polock's method of comparing the throttle butterflies to the tiny bypass holes in the top of the carb throats, it won't take much in the way of tweaking to get them sync'ed up the rest of the way.

And that's where an effective manometer comes in. The absolutely easiest way to accomplish the task is with a CarbTune or similar 4-stick device. The CarbTune is at the "top of the line" at around $100, and there are a number of slightly less expensive, similar devices available.

Or, build a 2-bottle rig or use a hunk of vinyl tubing lashed to a yardstick. The problem with any single gauge or 2-hole system is that you're not able to compare what all 4 are doing at the same time, so you have to go around and around re-comparing, because any adjustment you make will affect all 4, even with YICS blocked.

If you're starting with a good bench sync and have a proper manometer, the whole process takes all of 15 minutes, if that.

 

You don't HAVE to have the YICS tool in.

Dave Fox

 

Since the "loco" tool failed you, just stuff it with "oily rags" and get on with a proper sync.

I just looked on Ebay for the $25.00 BB tool and couldn't find it - got a link??

 

I will start today on the idle adjustment screws as they seemed happy at 2.5. With a little luck I will get it drivable for now.

 

UNIVERSAL MOTORCYCLE CARB BALANCER VACUUM GAUGE TOOL

It seemed to work. You just hook it up to #3 and you can quickly swap to the other 3 one at a time. If you hook up anything different than the base cylinder (#3) it gets way off. It seems to be pretty complex but is quick and easy to hook up. I would like to try something different though just for comparison.

 

Thats some good info Fitz, Thanks. I used the bench sync method you described. I pulled the carbs twice in the last two days and did that both times and set the idle mixture screws out 2.5 turns. Purred like a kitten both times.

 

I pulled the carbs toff he other day, did the bench sync adjusting the butterflies so they were lined up on the second little air hole (above the butterfly). Then screwed the idle adjustment screws out 2.5 revolutions. Put it back together all in about 35 minutes. Ran fine with no adjustments needed. I have also discovered the tear-down/install job is alot easier when the parts are warmed up.

 

There is no visible damage. I think the cap (plug wire end) just pulls off. I will wait.

 

I tell you man, that's the way I benched 'em. Still need to do a running vacuum sync, but she is running great without one. That method get's them VERY close.

 

That's what the bench sync is supposed to do!

 

Slow to respond, sorry about that, too busy riding the bike. The next morning it dawned on me. I got out my trusty short idlemixture screwdriver and made a quick adjustment . Back to spec on all 4 at 2.5 turns out. That fixed that. Thanks guys!