The importance of synchronizing carbs

[Monkey Wrench Cycles]

I did this writeup on another forum and thought some people here might benefit from it as I explain what synchronizing(synching) is, and why it's important to synch your carburetors/throttle bodys, and most importantly the benefits like better gas mileage. Feel free to post any questions.

Here's the link:
http://www.twtex.com/forums/showthre...+synchronizing

[Jiggles]

Originally Posted by Monkey Wrench Cycles

I did this writeup on another forum and thought some people here might benefit from it as I explain what synchronizing(synching) is, and why it's important to synch your carburetors/throttle bodys, and most importantly the benefits like better gas mileage. Feel free to post any questions.

Here's the link:
http://www.twtex.com/forums/showthre...+synchronizing


Just bored and figured i would start a thread on carb synchronizing. I always get ppl telling me they dont think its important, or the "my bike runs fine, why should i mess with it?"

Well this thread is to document the advantages of carburetor synchronizing and to answer any questions about the procedure.

First and foremost, your bike HAS to be in mechanically sound shape for synch'ing to do any good. If your valves are out of adjustment then it will all be for naught and wont make one bit of difference in the running of it.

What is carburetor synchronizing and what is the purpose of it?
It is to match all throttle bodys/carb butterflys so that they all open/close at the same time.

What are the advantages of synching my carbs/T.B.s?
There are many advantages including:
Steady idle
Smoother power delivery throughout the rpm range
More power
Less vibration
Better gas mileage
Longer engine life

Lets explore WHY the above mentioned is true, starting from the top and moving our way down.

Steady idle: When your bike is not in synch the butterflys are opened at different points when at idle, causing the idle to fluctuate from different amounts of air and fuel to enter on different cylinders. This can also cause a rough idle.

Smoother power delivery throughout the rpm range: We all know that a rich or lean condition will cause surging. Synching will make sure the air/fuel ratio consistent throughout the cylinders, keeping one cylinder from compensating for another, which in turn equates to a smoother running bike.

More power: When the a/f ratio is optimal your bike makes more power.

Less vibration: This is a common one that people have no idea about. It is more prevelant on some bikes than others. The goldwings are the worst about vibrating when the carbs/T.B.s are out of synch. Because of different amounts of a/f to enter the engine, making one cylinder want to run faster than another and messing with the harmonics of the engine it can cause a vibration to occur.

Better gas mileage: Speaks for itself. When you are running an optimal a/f ratio in all your cylinders, you get the best gas mileage. When one or more cylinders is running out of synch from the other/others it is making them work harder to compensate, thereby wasting gas.

Longer engine life: When the engine is not delivering the correct amount of a/f to each cylinder, it works one cylinder harder to compensate for the other/others as well as the slightly lean condition that can occur. All of this can shorten the life of your engine.

Lets address some other related questions.

Why should i perform a tune-up and valve adjustment before synchronizing my bike?
Because if your valves are not opening the specified amount they should it will not create the vacuum your bike needs to draw the correct ammount of air and fuel into the engine.
Ex. Your intake valve is to loose: This will cause it to not open far enough, or long enough to draw the correct ammount of air and fuel into the cylinder before the valve shuts. This will not only cause your bike to run bad but will mess up any synchronization you do on your bike because the engines vacuum is not what it should be.

My bike is fuel injected, why should i synch my Throttle bodys?
Not all bikes that are fuel injected have synchronizing procedures for the throttle bodys, but a good portion do. Dont think that because your air/fuel ratio is determined by the ECU, that you dont have to synch the Throttle bodys. Throttle bodys have butterflys just like carburetors do and if they aren't opening/closing at the same time it can throw everything off just like carburetors.

In conclusion, everything mentioned above will be more pronounced on some bikes versus others. The main factors being whether your bike is a two cylinder, inline 4, or flat 4/6. All that aside ANY bike will benefit from a carb synch after all other maintanence is performed

[Monkey Wrench Cycles]

Thanks. I'm at home on the iPad and can't copy/paste paragraphs.

[Jiggles]

Originally Posted by Monkey Wrench Cycles

Thanks. I'm at home on the iPad and can't copy/paste paragraphs.

Tap and hold part of the paragraph, the press select all, then copy, and then paste

[Snake]

Thanks for the paste Sean.

[Dr. Ew]

How often/miles you recommend to sync the carbs?
Non synch carbs possibly cause the engine to slightly rev at times? Barely noticeable on the rpm gauge but audibly noticeable.

[Monkey Wrench Cycles]

Originally Posted by Dr. Ew

How often/miles you recommend to sync the carbs?
Non synch carbs possibly cause the engine to slightly rev at times? Barely noticeable on the rpm gauge but audibly noticeable.

Every bike will give you that check in the manual on general maintenance schedule checklist. Most bikes it's around 8-10k miles.

It definitely needs set after any carb work or when the valve adjustment is done as either will change the synchronization.

If they are out it can cause erratic idle as you are essentially opening one carb more than the other and thus putting more fuel in one cylinder.

[Dr. Ew]

Ty sir.

[CZroe]

I'm positive that mine are out of sync.

[gfloyd2002]

If this has motivated anyone to synch their carbs, the DIY can be found here.

[Greyfox]

I'm new at this. When synchronizing the carbs, do I need to remove / release the throttle cables? or just leave it as it is and balance the carbs directly using the screw in the middle?

[CynicalC]

Originally Posted by Greyfox

I'm new at this. When synchronizing the carbs, do I need to remove / release the throttle cables? or just leave it as it is and balance the carbs directly using the screw in the middle?

Make sure the bike is warmed up and idle is adjusted properly before you start. Leave the throttle cables attached. They play no part in it as there shouldn't be any tension on them at idle.

[Monkey Wrench Cycles]

Originally Posted by Greyfox

I'm new at this. When synchronizing the carbs, do I need to remove / release the throttle cables? or just leave it as it is and balance the carbs directly using the screw in the middle?

As mentioned above, leave the cables as they are. You are balancing the carbs by a screw on the throttle linkage(not the idle screw) by way of vacuum. Do make sure its warmed up as stated. As a note it does no good to synchronize carbs if the valve adjustment is out of spec. A valve thats not opening all the way will not draw the same vacuum as one that is opening to spec. A valve thats to tight will actually push air back through the intake so either way, not good.

I always start with the basics. First i replace spark plugs, then check valve adjustment, then synch carbs. That way your covering all the major bases and your not doing double the work. There are many good writeups on doing valve adjustments and carb synchs.

[Skippii]

I've got to agree...it is kind of important...here are my plugs...

[Greyfox]

So the one is running lean and the other is running rich?

[Skippii]

Originally Posted by Greyfox

So the one is running lean and the other is running rich?

Yeah...well, one is running VERY rich, and one is running EXTREMELY lean.

[NDspd]

Originally Posted by Skippii

I've got to agree...it is kind of important...here are my plugs...

HOw many miles is on your bike and what year is it?

[Skippii]

Originally Posted by NDspd

HOw many miles is on your bike and what year is it?

it's an 06 with 25,000, but this was taken after a ride where I lost an exhaust gasket--you'd never have this kind of discrepancy in normal conditions.

[NDspd]

Originally Posted by Skippii

it's an 06 with 25,000, but this was taken after a ride where I lost an exhaust gasket--you'd never have this kind of discrepancy in normal conditions.

Huh, bummer man. thanks for the info