Synch vs Balanced

[Calvin Blackmore]

You obviously know nothing of motor design. There are specific tollerances allowed in mass production. A certain amount of "slop" if you want to call it that. Piston bores are NOT exactly the same diameter. Which is why when you have a piston kit installed, the pistoned are numbered and matched the bore that was cut for them. The pistons themselves are not the same diameter. Your valve clearances are not the same across the board. The seats are not wearing the same...etc etc etc.

This causes each cylinder to "breathe" differently than another.

I suggest from now on, you check your information before you start spouting yourself.

If these things were all the same, there would be no adjustment, no need for adjustment, and you couldnt adjust them...

Thanks, have a nice day.

OH my god a proclamation form mr motor god
I obviously know nothing cause i dare to disagree with you.
newtonian physics is the key here

I need you to tell us all what the difference is cyclinder to cylinder or else quit spewing olf wives tales about balancing


what is the maximum difference you have ever measured god forbid measured cylinder to cylinder

its pure silliness to assume that so many bikes that performedd like perfect meticulus watches off a mass assembly line would be subject to this sort of thing.

numbers please?

[Fenixgoon]

OH my god a proclamation form mr motor god
I obviously know nothing cause i dare to disagree with you.
newtonian physics is the key here

I need you to tell us all what the difference is cyclinder to cylinder or else quit spewing olf wives tales about balancing


what is the maximum difference you have ever measured god forbid measured cylinder to cylinder

its pure silliness to assume that so many bikes that performedd like perfect meticulus watches off a mass assembly line would be subject to this sort of thing.

numbers please?

clearly you know nothing about manufacturing. or machining. when you machine things, you specify tolerances - the allowable limits over or under the specified dimensions (for example, I just had some steel machined for me with +- 0.01" tolerances - no length should deviate from my specified drawings by more than 0.01" over or under)

no two products are exactly identical - but they do need to fall within certain manufacturing tolerances about which engineers design in order for things to work properly.

[Steve]

The balancing that is being discussed here is NOT the balancing of rotaional or reciprocating masses.

What is being balanced is the amount of air/fuel mixture that each cylinder is allowed to ingest.

When each cylinder is allowed to ingest the same amount as all the others, they are "balanced".
It will affect the smoothness of the engine running because all the power impulses will be the same.

Everybody get your testosterone back in check.

.

[TheCafeKid]

Break out your verniers and go take measurements yourself bub. They asked for an explaination on why/what a carb balance was/is and why it is needed.
I am not a motor god, never claimed to be. However, I can tell you that this is fact, not fiction, not made up. Hell, take a valve shim. Measure it. Brand new. Marked say 2.70. Is it? Huh? nope. Might be 2.69. Maybe 2.71. Maybe 2.70 on one side and 2.69 on another. Im not saying they're going to have some massive difference in size between one piston to another. Its miniscule. but its there. And that and uneven wear factors across the four cylinders are why carbs need balanced..

Why are you arguing this anyway? Have you never done a carb sync? ever? Ever taken compression readings? Are they the same across your four cylinders??

Im sorry, YOU must be the motor god. Your motors are all perfect, run like swiss watches, and have matching compression all the way across the board. We bow to your superior intellect and mechanical skillz

Troll...

[cowb0y]

What if your vacuum lines are off?

[cowb0y]

I am havin a low end problem and I justed finished the high rev method to tune the carbs. Seems to run better, but still slugs/serges at 2k. Most noticable in first gear. Other than that smooth. Wondering if I should just ride it and not worry or try to get it all smooth for better gas mileage??
What are your thoughts, CafeKid?

[TheCafeKid]

I am havin a low end problem and I justed finished the high rev method to tune the carbs. Seems to run better, but still slugs/serges at 2k. Most noticable in first gear. Other than that smooth. Wondering if I should just ride it and not worry or try to get it all smooth for better gas mileage??
What are your thoughts, CafeKid?

Again I'm not motor god. Can only tell you what has or hasn't worked for me and my semi educated guesses as to why. Without knowing other factors involved (first what bike are you talking about? Have you adjusted you valve clearances. This is part of basic maintenance and will effect running. Carbs clean? Stock jetting? Stock intake and exhaust system? Etc) stumbling or surging is usually a symptom of being lean. However what I sometimes have trouble with when the bike us running very close to right is discerning whether what I'm feeling is a result of being too rich or too lean. Plug chops taken at the throttle position that you seem to have the trouble with will be most telling.

[TheCafeKid]

What if your vacuum lines are off?

What lines are off and why?

[cowb0y]

What lines are off and why?

The two vacumm lines on the carbs; between 1&2 and 3&4.

I have a dyna jet kit in with stock air box (pods tryin my patients) and harley fish fin pipes. Read with dyna kit, to leave vacumm lines off.

Bikes an '80 GS 1100L with an '83 tank. Been havin issues with petcock in "On" so been runnin it in Prime (PRI) with much success. I jus swap it to ON when I park for a while so bowls dont over flow.

Also, havent done a valve job yet and have put 3500 miles on it since I bot it. So plannin on that soon. Have been gettin 45-47 mpg, so not too worried.

Glad you are willing to share whacha know. I appreciate it.

[TheCafeKid]

The two vacumm lines on the carbs; between 1&2 and 3&4.

I have a dyna jet kit in with stock air box (pods tryin my patients) and harley fish fin pipes. Read with dyna kit, to leave vacumm lines off.

Bikes an '80 GS 1100L with an '83 tank. Been havin issues with petcock in "On" so been runnin it in Prime (PRI) with much success. I jus swap it to ON when I park for a while so bowls dont over flow.

Also, havent done a valve job yet and have put 3500 miles on it since I bot it. So plannin on that soon. Have been gettin 45-47 mpg, so not too worried.

Glad you are willing to share whacha know. I appreciate it.

Wow, thats quite a combo there...LOL. If youre having problems like ya say, its not really relative to RPMs, but throttle position. The carbs are broken into different circuits, which are feeding different throttle positions (some positions are a bit of a combination of circuits..) If, while just cruising along, no matter the speed, but only using about 1/8-1/4 turn of the throttle, it may be that your pilot circuit is just a bit lean. Try opening the mix screws a 1/8 turn or so till it seems better. But if its more 1/4 or so turn of the throttle thats giving you trouble (it might help to mark off the throttle positions with tape, 1/8, 1/4, 1/2, so on) it might be that you simply need to drop the needle clip on your needles a notch lower, effectively raising the needle and alowing more fuel to flow in earlier stages of the needle circuit. Like I said, plug chops are the most effective and telling as to whether you are lean or rich in any given throttle position.

Valve adjustment will slightly change the way your motor breathes, so you may find after adjusting the valves, that your problems actually go away. Id seriously suggest checking your clearances, and adjusting them if need be per the manual.

[Dan Ruddock]

Tolerances in volumetric efficiency from cylinder to cylinder are very small unless the engine is a piece of junk.

The carbs need to be flowing the same volume of air throat to throat for the engine to run smoothly. This is why they need to be synched. Dan

[Steve]

The two vacumm lines on the carbs; between 1&2 and 3&4.

I have a dyna jet kit in with stock air box (pods tryin my patients) and harley fish fin pipes. Read with dyna kit, to leave vacumm lines off.

Those are not exactly "vacuum" lines, they are "vent" lines. Generally recommended to leave them off if you are running pods. If using stock airbox, the lines should go back over the airbox and rest in quiet airspace. The determination is not the Dynajet kit, it's the type of air filter and where the dead air space is.

Also, havent done a valve job yet and have put 3500 miles on it since I bot it. So plannin on that soon. Have been gettin 45-47 mpg, so not too worried.

You don't need a "valve job", you need a "valve adjustment". BIG difference.

YOU have put on 3500 miles, how long before you got the bike were they adjusted? If you have no idea, it's WAY past due. Gas mileage is no indication of whether the valves need to be adjusted.

.

[cowb0y]

Guess I'll see into puttin the vent lines back on. Glad to get this kinda stuff cleared up.

The symptoms lead me to believe the pilot jet circuit issues. What are the stock and other incremental pilot jet sizes.

I have adjusted the mixture screws (ones most forward and top outward flat head screw available with carbs mounted and bike running) to the highest idle, one carbs at a time, with the engine cooling in between. Which smoothed out my 3-4k bogging down.

Now just a surge/slug at 2k, so probably 1/8 throttle. Maybe I need to go up in pilot jet since the main jet is larger than stock, and then readjust the air mixture screws individually again.

Whacha guys think?

[Mysuzyq]

Tolerances in volumetric efficiency from cylinder to cylinder are very small unless the engine is a piece of junk.

The carbs need to be flowing the same volume of air throat to throat for the engine to run smoothly. This is why they need to be synched. Dan

Not understanding the reason for the confusion...the term (carb sync/balance) seems pretty self-explanatory.....balancing the function (metering) of the carbs to each other, for uniform performance. Balancing engine components (cranks etc) or compensating for discrepancies in manufacturing are not being addressed here.

[TheCafeKid]

Not understanding the reason for the confusion...the term (carb sync/balance) seems pretty self-explanatory.....balancing the function (metering) of the carbs to each other, for uniform performance. Balancing engine components (cranks etc) or compensating for discrepancies in manufacturing are not being addressed here.

Yeah, im not getting it either. A motor is nothing more than a big air pump.. You're balancing the amount of A/F that is drawn by each cylinder. Each one isnt going to draw the same for WHATEVER reason. It is the vacuum created by the motor that draws air thru the carb which draws air across the jets/venturi what have you that delivers and or mixes fuel. Each cylinder may or may not create more or less vacuum than the adjacent one. If the carbs are all set the same, this would cause an un even pulse. One cylinder loading up on AFM and the others less...

WHY each cylinder may not pull the same as the next is DUE to manufacture discrepancies, un-even wear pattern from one to the next, etc etc etc. The SAME reason compression rates are NOT the same from one cylinder to the next.

The same can be said for the carbs themselves..

I am not arguing about balancing actual motor parts, etc. Im talking about balancing the amount of AFM each cylinder is allowed to draw... that is all.