Aftermath of carb rebuild, and using 1 vacuum gauge to sync?

Prior to this weekend's carb rebuild/clean, my Seca 750 was running like hell. It wouldn't idle and required large amounts of throttle to keep the bike moving when letting the clutch out. It hardly had any power at any speed.

After getting the carbs off, they really weren't that dirty. I was expecting large amounts of varnish from a bike that had been ridden only 300 miles a year for its 27 years. I did find that the adjustment screws were all different values.

After reassembling everything, the bike is a completely different machine. It idles smoothly, and has POWER. I almost did a power wheelie when I nailed the throttle in 1st at 4k, thinking it was the bike it used to be.

I have a few questions though.

1) My homemade sync gauge was a failure. Carb #3 (starting from throttle side) just kept sucking fluid up in to the engine, so I just kept fooling with the screws until the idle smoothed out. I'm sure they're still out of sync though. There is slight hesitation under heavy throttle, then POWER. Can I sync them just using a single vacuum gauge like this? I'm assuming it's possible 1 at a time.

2) My speedo housing is making a horrible noise once I get going and the needle has fallen from view. Is it repairable?

Thanks for your help.

 

Re: Aftermath of carb rebuild, and using 1 vacuum gauge to s

The sync is a pita with a reading on all 4 carbs at once. If you get them all even, you can check it the next day and see they are a little off and if you set it up again and ckeck it on another day, they are a little off again. I can't imagine trying to do that with one gauge. I'd get the manometer from chacal. Its the one I have and found it as the most important tool, along with the yics tool, you need.

 

The Old School Method
Single Vacuum Gauge Synchronizing of Carburetors
by: Rick Massey
Special to XJBikes.com
All rights reserved.

First, you need one vacuum gauge. (There's none better than the one sold at Sears for $19.95) and your home-made YICS tool.

You need some vacuum line. Get ten or twelve feet. You'll be making-up lines to run from each carb out to the side of the bike where you'll hook-up the Vacuum Gauge.

You need a few small, hollow, plastic-barrel vacuum line connections. (Those little things you use to plug one vacuum line into another.)

One medium-sized fuel filter; with ends that will fit the hose.

One red plastic spray tube ... like the one taped to a can of carb cleaner.

Four regular Golf Tees. (Just steal 'em from your dad's golf bag)

5-minute epoxy.

Masking tape and a "Sharpie"

OK kids ... Let's ROCK!

Prep:
Fabrication of the "Vacuum Restriction Valve." (Absolutely necessary)


Take the skinny red tube and run it through one of the hollow, plastic hose connectors.
Seal that hollow connector with epoxy; leaving a length of the red tube extended from each end.
(This fabricated little-metering device will be the all-important "Vacuum Pressure Restrictor" that will allow you to read the vacuum gauge without the extremely WILD fluctuations on the meter you'd get if you tried to get a vacuum reading without it.)

When the epoxy hardens; cut-off the extraneous ends of the red tube -- flush.

Using a short length of vac line ... attach the restrictor to one end of the medium-sized fuel filter.

(Now you have a restrictor attached to the fuel filter. You just made what you NEED to get the needle on the vacuum gauge "Quieted-down" enough to get an accurate reading without the meter being so wildly fluctuating as to be useless. You have Baffled-Restricted-Regulation and this softens the harsh, impossible-to-read fluctuation, the indicator would have, without it.)

Hook-up and Sync:

The rest is by the book.
YICS tool inserted.
Four Vacuum lines run from the Carb Intakes over to where it will be convenient for you to connect these four lines up to Vacuum Gauge ... each marked with a little tape label for one through four. Stick the golf tees in the ends of these lines ... and get ready to sync the carbs.

Attach your "Old School - Baffled Restrictor" to the vacuum line coming from Number - 3 with the red tubed restricted end plugged into the vac line coming off the engine.

Plug the Vacuum Gauge into the Fuel Filter end. You're officially restricted and baffled for testing ...

So, let's do it!

Run the bike and get the vacuum reading of Number 3 (Three) ... to check for good vacuum on three and to observe how the needle of the gauge is still going to MODERATELY "Vibrate" as it measures engine vacuum.

Sneak the rev's up to 14 > 16-hundred rpm's and the fluctuation will become rapid enough for you to read the vacuum that the hole is pulling.

Mark the gauge face with a short strip of masking tape and mark the tape with a check-mark. Don't let the tape strips block you from seeing the vacuum gauge needle during the sync.

Authors Note:
It's a good idea to practice pulling a golf tee out and covering the hose with your thumb. This will keep the engine from stumbling and possibly stalling.

Checks and adjustments:

Read the Vacuum being pulled by Number 2. Mark maximum vacuum drawn by 2 with line of tape.

Get your magic fingers ready to do the "Carb-Shuffle!"

Pull-out the baffle and block the vacuum with your thumb until you can insert the golf tee you have ready between your lips or behind your ear.

Measure the vacuum being drawn by Number 1. If the max vacuum being drawn by Number 1 is NOT the same as you have MARKED for Number 2 --ADJUST the SYNC SCREW on Number 1 ... until the Vacuum drawn by ONE is the SAME as the Vacuum drawn by TWO!

Two down ... two to go! But, here's where it gets tricky.

Plug-in to Number 4. Set the Vacuum drawn by Number 4 -- to -- the BASE Vacuum you measured for Number 3. (Actually check 3 again ... adjust 4 to match 3 -- because 3 is the Base Vacuum Port, has NO sync screw adjustment, and usually has the petcock vacuum hose connected to it.)

At this point you start TWEAKING. From here until the rack's in-sync ... it's all down hill!

The engine should be sounding pretty darn good; right about here. But, we need to finish it off!

Just hook-up to Number 2, now ... and bring the vacuum being drawn on Number 2 -- UP or DOWN to match the value of Number 3.

They'll be no need to adjust Number 1. Number 1 is connected to Number 2 and goes right along for the ride when you sync Number 2 to Number 3 ... and you ...

HEAR the results of synchronizing all four of your carbs with only one vacuum gauge.
Let what I have outlined, here, be your guide ... but, don't be afraid to get creative with where to have the golf tees ready to pop-in the lines!

When you wrap-it-up ... the One - through - Four ... Final Measurement should be all right on the same value -- right across the board.
Yes? DONE!
No? Tweak until you nail it!

Can you believe that we used to have to do it this way? Compared to the MotionPro Carb Sticks -- It's like being in Bedrock ... spending a little time with Fred and Barney doin' a little Stone Age Tweaking'!

Editors Note:
Spend a few bucks for these valves at a Pet Store Fish Tank Section ... and, you won't need the Golf Tees.
Get a China Marker ... and you won't need Tape Arrows.
You can mark right on the Gauge!
Be sure to have a RESTRICTOR to keep the Guage from fluctuating widly.

IMG]http://i254.photobucket.com/albums/hh107/RickCoMatic/Yamaha/gang-valve-4-1.jpg[/IMG]

 

This was all you really needed to say, Rick. Coulda saved yourself a lot of typing...

Actually it's a matter of simple economics: How much is your time (and frustration) worth? For me, a set of 'stix' paid for itself the first time I used them.

 

Re: Aftermath of carb rebuild, and using 1 vacuum gauge to s

Thanks a lot Rick. After that, and adjusting the float levels, this bike better run like a swiss watch!

 

Re: Aftermath of carb rebuild, and using 1 vacuum gauge to s

I've got a home made sync tool. Worked real well. the yard stick and ATF variety.

Ryan if your bike is rideable and you want to give it a go send me a PM. I'm just over in Essex.

 

I have just begun to bookmark everything Rick says.

 

Re: Aftermath of carb rebuild, and using 1 vacuum gauge to s

+1 ^^^^

The only thing you need to ensure is that the hose is "folded" in the middle so that both hose ends are the same length.

It's the best tool in my garage :wink:

 

I think the least amount of "Fuss" in getting the Carbs synchronized, >>for the Member who wants to get it done without a lot of plumbing << is the "One-Gauge with the Aquarium Quad-Valve Improvement".

Single-gauge accuracy. No liquids or variables. Along without having to juggle Golf Tees and having a run-away Engine suck-up liquid.

After the lines are hooked-up to the Vacuum Ports ... a simple opening and closing of an Air Valve is all you need to do.
Transferring from Hole to Hole to get the value is almost instantly accomplished.

 

If you bench sync the carbs with any degree of accuracy they won't suck the oil out of the homemade manometer before you can correct it.

 

Re: Aftermath of carb rebuild, and using 1 vacuum gauge to s

I admire the courage and sense of adventure that leads to the homemade sync tools,,, but,,,, I just ' LUUUV' my Morgan Carbtune.

Cheers, Murray