TheSamba.com :: View topic - Dual carb setups, do you synchronize your carburetors?

Thu Jan 07, 2010 7:14 pm

I am going to print this page and have it engraved, this is some of the best and simplest carb tuning advice I have ever seen written. I have been tuning single and multi carb systems for years and the information progression here is the absolute easiest to grasp yet!!

Fri Jan 08, 2010 4:30 am

I have been using the home built manometer like posted earlier - But recently added a refinement. Added welding tips inside the tube near the carbs - acts as a restrictor and evens out pulses a bit, reduces the oil geting sucked into a carb. One tip - is you can just crank the engine to get a "close match" before you actually start it. This tool is incredibly accurate. Also, I use 50/50 2 stroke oil and kerosene. Nice blue color and easier to see.

Fri Jan 08, 2010 12:40 pm

If you have jets laying around from a Mikuni carb, they are very small, long and round and easily fit inside the small plastic tubing. They even out the pulses. The reason oil is used is so that there is no damage to the motor if ti gets sucked in. I use plain motor oil, I can see it just fine, even against an oddly graduated reference like a yardstick that has different markings on each side.

When I first got my motorcycle, I thought vibration was just the way it was.

Then, I synced the carbs. (I had to repair one carb because the mixture screw had been turned in so far the tip broke off in the seat!)

The bike went from oil-destroying heat on normal runs, to running very cool, gas mileage shot up 10 MPG at a minimum, vibration was gone, and it made a lot more power.

I haven't seen a single thread on synchronizing dual carb setups, and it made me wonder. Just like when unsuspecting people run dry gauze air filters and wonder why there is a ton of dirt INSIDE the carb!

Fri Jan 08, 2010 1:20 pm

Dale M. wrote: tundrawolf wrote: Dale M. wrote: Never used a uni-sync or a snail..... Always used best lean idle adjustment procedure.... Always do plug readings...... Always do engine balance with the "miss" test .....And one car has run 8 years with duals with no problems one for 4 years with no problems....

Your visual and aural senses are really going to be the final judge if carbs are right....

The minute you get everything set by a sync tool and you feel something is not right and you touch a adjustment screw, all the work with a sync tool is out the window....

Dale

Please explain your method..

" Carburetor Setup and Lean Best Idle Procedure" found any site that deals with WEBERS....

http://www.piercemanifolds.com/tech_spec.htm

"Miss" test is pulling spark plug wire out of dist cap one wire at a time and listening degree of miss engine develops on three cylinders... It's really easy to tell which side of engine is rich/lean depending on degree of miss... Then you richen up lean side by idle speed screw, lean rich side with idle speed screw.... Engine response is actually your sync tool.....

Any body that understands concept can usually straighten out bum adjusted carburetors in about 5-10 minutes..... Assuming no "other engine problem exist" and the linkage is adjusted properly...

Gentleman who has been building ACVW's and running Webers for over 30 years taught me procedure...

Dale

Dale, could you further explain what you mean by "degree of miss" for me and any other slow-pokes out there?

Fri Jan 08, 2010 1:50 pm

piezzi wrote: Dale M. wrote: tundrawolf wrote: Dale M. wrote: Never used a uni-sync or a snail..... Always used best lean idle adjustment procedure.... Always do plug readings...... Always do engine balance with the "miss" test .....And one car has run 8 years with duals with no problems one for 4 years with no problems....

Your visual and aural senses are really going to be the final judge if carbs are right....

The minute you get everything set by a sync tool and you feel something is not right and you touch a adjustment screw, all the work with a sync tool is out the window....

Dale

Please explain your method..

" Carburetor Setup and Lean Best Idle Procedure" found any site that deals with WEBERS....

http://www.piercemanifolds.com/tech_spec.htm

"Miss" test is pulling spark plug wire out of dist cap one wire at a time and listening degree of miss engine develops on three cylinders... It's really easy to tell which side of engine is rich/lean depending on degree of miss... Then you richen up lean side by idle speed screw, lean rich side with idle speed screw.... Engine response is actually your sync tool.....

Any body that understands concept can usually straighten out bum adjusted carburetors in about 5-10 minutes..... Assuming no "other engine problem exist" and the linkage is adjusted properly...

Gentleman who has been building ACVW's and running Webers for over 30 years taught me procedure...

Dale

Dale, could you further explain what you mean by "degree of miss" for me and any other slow-pokes out there?

It's simple.... When you pull a spark plug wire off of dist, you go on 3 cylinders.... This produces a "miss"....IF you pull a wire and the is no or little noticeable difference in way engine runs this cylinder is not really working (carrying its share of load) and is being carried by others...... If you pull a wire and miss becomes bad, engine shakes and shudders and tries to die, that cylinder is doing most of work (carrying most of load) ..... There is different degree of miss according to how much each individual cylinder is "working" (carrying load) ..... If you pull each wire in succession and the "miss" is about the same as any other cylinder that are pulled you probably have fuel air pretty well in balance in each cylinder.....

The miss factor is probably equivalent to completely closing off the idle mixture screw on one cylinder (at a time) and engine tries to run on three... But this is not productive as it screws with adjustment...

Its a look and listen thing..... The engine is telling you things, you need to learn to understand what its saying....

Dale

Fri Jan 08, 2010 3:31 pm

Dale M. wrote: piezzi wrote: Dale M. wrote: tundrawolf wrote: Dale M. wrote: Never used a uni-sync or a snail..... Always used best lean idle adjustment procedure.... Always do plug readings...... Always do engine balance with the "miss" test .....And one car has run 8 years with duals with no problems one for 4 years with no problems....

Your visual and aural senses are really going to be the final judge if carbs are right....

The minute you get everything set by a sync tool and you feel something is not right and you touch a adjustment screw, all the work with a sync tool is out the window....

Dale

Please explain your method..

" Carburetor Setup and Lean Best Idle Procedure" found any site that deals with WEBERS....

http://www.piercemanifolds.com/tech_spec.htm

"Miss" test is pulling spark plug wire out of dist cap one wire at a time and listening degree of miss engine develops on three cylinders... It's really easy to tell which side of engine is rich/lean depending on degree of miss... Then you richen up lean side by idle speed screw, lean rich side with idle speed screw.... Engine response is actually your sync tool.....

Any body that understands concept can usually straighten out bum adjusted carburetors in about 5-10 minutes..... Assuming no "other engine problem exist" and the linkage is adjusted properly...

Gentleman who has been building ACVW's and running Webers for over 30 years taught me procedure...

Dale

Dale, could you further explain what you mean by "degree of miss" for me and any other slow-pokes out there?

It's simple.... When you pull a spark plug wire off of dist, you go on 3 cylinders.... This produces a "miss"....IF you pull a wire and the is no or little noticeable difference in way engine runs this cylinder is not really working (carrying its share of load) and is being carried by others...... If you pull a wire and miss becomes bad, engine shakes and shudders and tries to die, that cylinder is doing most of work (carrying most of load) ..... There is different degree of miss according to how much each individual cylinder is "working" (carrying load) ..... If you pull each wire in succession and the "miss" is about the same as any other cylinder that are pulled you probably have fuel air pretty well in balance in each cylinder.....

The miss factor is probably equivalent to completely closing off the idle mixture screw on one cylinder (at a time) and engine tries to run on three... But this is not productive as it screws with adjustment...

Its a look and listen thing..... The engine is telling you things, you need to learn to understand what its saying....

Dale

That makes a lot of sense now.......thanks for the clarification!

Fri Jan 08, 2010 5:17 pm

Dale M. wrote: It's simple.... When you pull a spark plug wire off of dist, you go on 3 cylinders.... This produces a "miss"....IF you pull a wire and the is no or little noticeable difference in way engine runs this cylinder is not really working (carrying its share of load) and is being carried by others...... If you pull a wire and miss becomes bad, engine shakes and shudders and tries to die, that cylinder is doing most of work (carrying most of load) ..... There is different degree of miss according to how much each individual cylinder is "working" (carrying load) ..... If you pull each wire in succession and the "miss" is about the same as any other cylinder that are pulled you probably have fuel air pretty well in balance in each cylinder.....

The miss factor is probably equivalent to completely closing off the idle mixture screw on one cylinder (at a time) and engine tries to run on three... But this is not productive as it screws with adjustment...

Its a look and listen thing..... The engine is telling you things, you need to learn to understand what its saying....

Dale

This is excellent information! Have you compared the results to a manometer or vacuum gauge?

Sat Jan 09, 2010 7:10 am

Tundra, there have been a LOT of post on dual carb synching, I have posted my version of the manometer 3 or 4 times. But the posts usually start with "Damn Kadrons" or something like that LOL.

Have to tell all that doing a real serious tune is worthwhile. I got together a bunch of jets. my manometer and some chassis dyno time. Made a 7-8% increase in power with mostly jetting (I had to resynch since I had to pull the carbs because the body is on the on the buggy.) The car idles on all 4 cylinders and the gas mileage is waaay better. Synching properly is critical for all normal driving.

Sat Jan 09, 2010 8:40 am

tundrawolf wrote: Dale M. wrote: It's simple.... When you pull a spark plug wire off of dist, you go on 3 cylinders.... This produces a "miss"....IF you pull a wire and the is no or little noticeable difference in way engine runs this cylinder is not really working (carrying its share of load) and is being carried by others...... If you pull a wire and miss becomes bad, engine shakes and shudders and tries to die, that cylinder is doing most of work (carrying most of load) ..... There is different degree of miss according to how much each individual cylinder is "working" (carrying load) ..... If you pull each wire in succession and the "miss" is about the same as any other cylinder that are pulled you probably have fuel air pretty well in balance in each cylinder.....

The miss factor is probably equivalent to completely closing off the idle mixture screw on one cylinder (at a time) and engine tries to run on three... But this is not productive as it screws with adjustment...

Its a look and listen thing..... The engine is telling you things, you need to learn to understand what its saying....

Dale

This is excellent information! Have you compared the results to a manometer or vacuum gauge?

Do not own/have any of those tools... Do no know anybody who has them....

Dale

Tue Jan 12, 2010 9:33 am

I tuned the kadrons on my T4 last night with the "lean best idle" method. WOW, what a difference!

Wed Jan 13, 2010 4:20 pm

Dells or IDFs I would use the flow-meter for dialing in throttle plates, but I find it doesn't give you a good indication of how rich or lean it runs. Kadron there is no point in using the tool since it will always tell you that there's a flow difference even if the carbs are balanced properly. Kadrons I use the lean-to stumble then back off an eighth trick and sync the throttle plates by feel until any movement on either idle speed screw changes engine speed the same. Dells and IDF's you just sync the throttle plates with a flow meter and use the engine-miss technique to tune, but I found surprisingly that using the jetting and initial settings from the "Dellorto Superformance" book was within an eighth turn on a couple screws from perfect on more than one setup.

Wed Jan 13, 2010 5:13 pm

So how do you guys pull the plug wires off while running? In my younger days, I figured you'd only get zapped if you had a bad plug wire. As I get older, I like to take more precautions :lol:

So do you use the pliers they have for the job, or just grab a wire and hope you pull it away from the cap quick enough for it not to try and complete the circuit through you?

Wed Jan 13, 2010 5:55 pm

If you are pulling it out of the cap, just make sure you are not grounded to the car or standing in a puddle.
I rarely get zapped pulling plug wires. But then, I pull them at the plug.

Wed Jan 13, 2010 7:58 pm

Russ Wolfe wrote: If you are pulling it out of the cap, just make sure you are not grounded to the car or standing in a puddle.
I rarely get zapped pulling plug wires. But then, I pull them at the plug.

And the is probably the most likely way to get ZAPED because plug wire is still HOT.....

Dale

Wed Jan 13, 2010 9:19 pm

A genuine VW plug wire with a good bakelite end wont arc, due to the distance the spark has to travel to get you.