Low tech, but accurate, carb syncronizer

Back in "the old days" when British sports cars had SU carbs, we used to stick a piece of rubber tubing in one ear, and pass the other end by the mouth of each carb, listening to make sure that the pitch of the air flow was the same.

This method could be made absolutely accurate if, instead of putting the tubing in one's ear, he held it next to the microphone of an electronic guitar tuner, which would read out exactly what the pitch of the airflow is.

Electronic guitar tuner! Low tech?

Actually that's a great idea. An electric guitar tuner is pretty inexpensive these days.

Hello Vance:

The ear method is low tech, and cheap, but just as accurate, and more reliable than any method which uses a separate indicator for each cylinder. The guitar tuner idea was just an afterthought:-)

Interesting. Carbs are close togather would this make difference??

Hello Dan:

Nope, doesn't make any difference. You will hear the pitch of the carb inlet you are holding the tube closest to.

Anyone who isn't deaf can detect even the slightest difference in pitch as he moves the tube back and forth between carbs.

Back in "the old days" when British sports cars had SU carbs, we used to stick a piece of rubber tubing in one ear, and pass the other end by the mouth of each carb, listening to make sure that the pitch of the air flow was the same.

This method could be made absolutely accurate if, instead of putting the tubing in one's ear, he held it next to the microphone of an electronic guitar tuner, which would read out exactly what the pitch of the airflow is.

but I still play around with my old Carb Sticks.........works great, just a little more clumsy to hook up. Got one ear not so good, but probably would be able to use the good one like you said.

Hello Rich:

Actually, if you used a separate tube in each ear and held each over a different carb, the difference between the carbs would result in a third(harmonic) frequency equal to the difference between the two primary carb frequencies. Then you could simply adjust one carb until the harmonic frequency is reduced to nothing.

That is accurate enough for concert piano tuners:-)

When you use the tube to listen to each carb where do you put the end of the tube? Do you take off the air filter and insert the tube at the top?

When you use the tube to listen to each carb where do you put the end of the tube? Do you take off the air filter and insert the tube at the top?

Probably it would be best to put the end of the tube in your ear rather than some other orfice!

Hello Rich:

Actually, if you used a separate tube in each ear and held each over a different carb, the difference between the carbs would result in a third(harmonic) frequency equal to the difference between the two primary carb frequencies. Then you could simply adjust one carb until the harmonic frequency is reduced to nothing.

That is accurate enough for concert piano tuners:-)

so when you do this and your eyes go to the right you just adjust the carbs to the left till you see strait ahead ?

Let me get this right Duh ,If I use the tube in the ear method, holding the other end by the carb openings( underneath where the air filter sets )I want to listen for the difference in the sound of each carb and adjust them to sound the same? Does it matter which carb I chose to start with or do I look for one that sounds more diff than the others? Next question what screw am I looking for to adjust? Hope this all doesn't sound dumb, but I want to learn to do all this stuff myself. Thanks for the help, would love pics

If you really want to try this old method......and if you are not tone deaf like me...I have seen people do this.and also do a carb tune with a coke bottle at the exhaust on Harleys.....I can play a radio....but sure cannot tell any tone differences in any tube.......

Do not worry about which carb to start with......on the RSV you have two carbs on one side and two on the other.......take either the left or right set one at a time and tune that set of carbs so they sound the same....that is all there is to it.......then go tune the other side .........then balance both sides to each other. It will get it in the ball park.......it is not exact like a carbtune is.

I honestly would ignore this method......and go purchase a carbtune and professionally tune up your bike. The savings in fuel alone will soon pay for the tools needed to do a professional job.

OK, being an overzealous amatuer musician, I just happen to have a fully chromatic Korg tuner. I also have a clip to hook to an accoustic instrument in which I plug into the input side of my tuner. This cancels everything else out and the only thing that's tuned is what ever is hooked up to the clip. Do ya figger this would work if I were to clip on to the end of the hose?

OK, being an overzealous amatuer musician, I just happen to have a fully chromatic Korg tuner. I also have a clip to hook to an accoustic instrument in which I plug into the input side of my tuner. This cancels everything else out and the only thing that's tuned is what ever is hooked up to the clip. Do ya figger this would work if I were to clip on to the end of the hose?

I think you need to try it and report back with your findings, then be prepared to "show and tell" at the next Maintenance Day........................................

You will still have to start with #2 being the base carb, seeing as there is no adjustment on # 2 other than the throttle screw,,which will adjust all carbs at once.

So it's the same sequence:

# 1 to #2

# 3 to #4

# 4 to #2

#1 is left rear

#2 is left front

#3 is right rear

so #4 has to be right front

It will also remain very important to make sure that the RPMs reamian very constant from cylinder to cylinder.

I use to have an LC 1500 which was a V-twin and I made a really cheap but very accurate tool for sinking the carbs. I think it would work on the V4's as well. I'll try to explain how the tool works..... Get (2) 1 quart canning jars with lids. Get a few feet of small clear tubing. Drill 2 holes in each of the lids just large enough for the tubing to fit snuggly through. Cut a piece of the tubing long enough to reach from the bottom of one jar to the bottom of the other jar with the jars sitting side by side, lids on and the tubing going through the holes in the lids. Get 2 more pieces of tubing about 3 feet long and stick them through other hole in each of the lids about 1/2 inch. Seal tubes with silicone to the jar lids. Fill each of the jars about 1/4 full of water. Connect one of the longer hoses to the reference carb and the other long hose to one of the other carbs. If the carbs are out of sink, water will flow from one jar to the other. Adjust carbs until water doesn't flow. Move to another carb but always compare remaining carbs to reference carb...looks like reference carb would be #2 on these Yamahas. It's hard to explain but I can e mail a pic if anyone wants it.

Would it be possible for you guys to post pics? As someone who's never tuned a set of carbs before, and has a need to do so, that would be very helpful to me. I really appreciate the ideas but pictures may answer questions.

If posting is a problem, I'd be glad to assist - just message me.

The most accurate carb tuner is a mercury manometer.

For us, a four tube mercury manometer makes the process easier as you can hook up all four carbs at one time and make adjustments and see instantly the results.

You also can use a set of gauges or a steel rod in an air cylinder like the Morgan Carbtune, but they may have inaccuracies as they are mechanical devices, unlike the column of mercury in a manometer.

The problem with a mercury manometer is the EPA wants to lower the amount of mercury that is spilled into the environment. this is very good of them.

So most manufacturers have stopped making mercury manometers.

But I have found a source of good old fashioned "Carb Sticks" for $55. A lot lower priced than MOST of the other tools on the market, and MUCH more accurate, as mercury cannot go out of calibration. Just don't spill it and DON'T PLAY WITH IT!!!!

http://www.saber-cycle.com/store/media/parts/08-010.jpg

(Click-able image)

The most accurate carb tuner is a mercury manometer.

 

For us, a four tube mercury manometer makes the process easier as you can hook up all four carbs at one time and make adjustments and see instantly the results.

 

You also can use a set of gauges or a steel rod in an air cylinder like the Morgan Carbtune, but they may have inaccuracies as they are mechanical devices, unlike the column of mercury in a manometer.

 

 

The problem with a mercury manometer is the EPA wants to lower the amount of mercury that is spilled into the environment. this is very good of them.

 

So most manufacturers have stopped making mercury manometers.

 

But I have found a source of good old fashioned "Carb Sticks" for $55. A lot lower priced than MOST of the other tools on the market, and MUCH more accurate, as mercury cannot go out of calibration. Just don't spill it and DON'T PLAY WITH IT!!!!

 

http://www.saber-cycle.com/store/media/parts/08-010.jpg

(Click-able image)

I'd like to be able to sync my carbs too. Where can I get a Carb Stick like that? That's a great price! I promise not to drink the mercury!

Cheers,

Joe