Topic: 2 Gauge Carb Sync on a 4 Cylinder Bike....order?

[gregripko]

I just need a little clarification....I have a 2 gauge vacuum tool for a carb sync.....and I've never known if there was a specific order to do a carb sync... anyone know the order and why this order is decided as being best? TY...


-Greg

[Markcb750]

Just because I am skeptical...

[BobbyR]

You did not say what bike, I assume they are similar. There is a reference carb. On the 750 it is #2 which is fixed and not adjustable. The other three carbs are adjusted to measure the same vacuum as that reference carb. The order you adjust the carbs is not important as long as the other three are equal to #2.

Now I will throw a turd in our punchbowl. You can't do all 4 with a 2 gauge set up. When you have guages on all four you will see that as you adjust one, the other three change. With four guages you keep going from carb to carb making adjustments until they finally all stabilize.

I guess you can do it, but it will take you all day and it will suck.

[gregripko]

Cb550k 76 (all carbs can be adjusted)


What if you adjust 2 to 1 ....3 to 1...4 to 1?

[Scott S]

 Order? Order a 4 gauge vacuum sync.

[BobbyR]

Cb550k 76 (all carbs can be adjusted)


What if you adjust 2 to 1 ....3 to 1...4 to 1?

I think you are setting yourself up for a a lot of frustration. You cannot set these two and set those two to each other. The idea of a carb synch is getting  1,2,3,4 all the same. As I said you will see each one change as you adjust the others. When I do mine, I will get 1 synched to 2. When adjust 3 you can see the other two change. Using the gauges you go from one to the other. You will adjust the same carbs several times until it they all match.

The idea of synching is to get all of the cylinders working together. Hopefully pulling the same amount of fuel and no one cylinder working more or less than the other.  You will hear and feel the difference at idle. Your first sych after a rebuild/cleaning takes the longest. After that they are usually fairly close, and you are just touching them up.

If you can afford a gauge set, it will save you time and frustration. 

[Duke McDukiedook]

For the reasons Bobby said you need a 4 port vacuum gauge. You need to be able to see the changes in vacuum on all the carbs at one time.

[bryanj]

You will chase your own rear end for days trying to use less than 4 gauges

[Mo]

Was the 2 gauge significantly cheaper or was it just lying around? You could (I think!) just buy another 2 gauge if the price was the issue.

[Dave Voss]

I agree with what others have said, although you adjust one carb at a time, you need to see how it affects the other three, and having to move the gauge setup around to check and verify the synchronization kinda defeats your ability to really know whether they are or not.  I use a Morgan Carbtune, the type with four vertical vacuum tubes, some folks say it is not as accurate as traditional round vacuum gauges, but it is easy to use and compact enough to travel with if you find the need to take it with you.

[iron_worker]

I think it's possible to do with 2 gauges but it will take some trial and error because like others said as you adjust one others vacuum level will change as well.

That said, I believe the #2 master carb is only a "feature" on the later PD style carbs. It was an attempt at stopping people from tampering with the carb too much I believe.

K1-K6 750s should have all carbs adjustable. K7-K8 have the #2 fixed carb. Not sure about the other size bikes.

IW

[totty]

I've used two gauges and been happy with the results. I balanced each carb to 2 then went through them all again with only very minor adjustments required, then went through then a 3rd time and no further adjustments were required.

Whilst any adjustment affects all readings, when using two gauges you're not trying to get all carbs to any specific value, just to match each one to either the fixed carb or if none are fixed then any carb of your choice.

[gregripko]

If I balanced 1 and 2 while 3 and 4 are capped.... Does the vacuum from the capped cylinders transfer evenly to 1 and 2? Or would it not transfer at all? Just trying to understand why the system I used wasn't working apparently... I was adjusting to cylinder 1 while capping the other two cylinders that I wasn't balancing.

Ex .

2 to 1 (cap 3 and 4) (lock 1 and 2 down after)
4 to 1 (cap 2 and 3) (now lock 4 down)
3 to 1 (cap 2 and 4) (lock 3 down)

I would never adjust a locked down cylinder

Money is tight but I thought with this method it would produce somewhat accurate sync.... After I do this method my idle does improve...

[strynboen]

you have to do it in more steps,, first step are 2-1-3-4. ect. then you  perhaps get 1 and 3 too low..then rice 1-3 and see to get it to line 2-4..and on and on to it line up....just to tight the schrev can make the adjust vrong..so care vhen tighting the bolts

it dossent matter hvat numbers are first. just easyest to hold 2 for marster


.just be care you not rice the rpm  and find syncro adjusted..and the idel vill be to high..and you have to do it again from a lower startpoint

if you not have the "feeling"let somone help you..vho can do it..and get it lerned..and yes have a blower or ventilator to run..it gets hot..
you have to use a 4 gauge set...to get the feeling..vhen you understand the show..and have done it 10 times..2 gauges can be used

sorry for my laungish

[Duke McDukiedook]

Buy another 2 gauge setup if money is tight. You will never get properly synched carbs with just a 2 gauge setup.

[Harsh]

I agree with what the others are saying about using four gauges.  There has got to be someone near you that has a 4 gauge setup that can either loan you the tool or have you swing by there place and use the tool there.

[gregripko]

I'll try to find one this week and maybe I'll get better results... Ty

[Schnell]

Buy another 2 gauge setup if money is tight. You will never get properly synched carbs with just a 2 gauge setup.

Bingo!

[JimJamerino]

Homemade carb balancer.  I made a 4-carb version based on the same principle and it worked fine.  For mine,  used some glass tea bottles zip tied to a board, tubing and rubber stoppers from Lowe's.  This one is only two, but a little adaptation will make it work.

Balancing Carburettors with home made manometer