Why no need for Throttle Body Balance on some bikes?

rat_race

Hi -- decided to NOT do it myself, and instead got my dealer to do a Tiger 800 full service (very expensive!)...

However, it really is like a new bike (and it's only 2 years old) -- I suspect mostly due to the Throttle Body Balance.

I was wondering though, why do some fuel injected bikes not need this balance? I have a Ninja 250, which is fuel injected -- but there is no need to balance the throttle bodies, it seems.

My guess is that it's because it's a 2-cylinder and there'd never be two pistons firing at the same time and so it doesn't really matter if they're not both the "same".

However, that is a wild guess. Can anyone shed some light?

arybvtcw0eolkf

rat_race wrote: »

Hi -- decided to NOT do it myself, and instead got my dealer to do a Tiger 800 full service (very expensive!)...

However, it really is like a new bike (and it's only 2 years old) -- I suspect mostly due to the Throttle Body Balance.

I was wondering though, why do some fuel injected bikes not need this balance? I have a Ninja 250, which is fuel injected -- but there is no need to balance the throttle bodies, it seems.

My guess is that it's because it's a 2-cylinder and there'd never be two pistons firing at the same time and so it doesn't really matter if they're not both the "same".

However, that is a wild guess. Can anyone shed some light?

My R1100S is a twin (boxer engine) and needs the throttle bodies balanced.. And boy does it make a difference to the bike

rat_race

Zaire Alive Sandblaster wrote: »

My R1100S is a twin (boxer engine) and needs the throttle bodies balanced.. And boy does it make a difference to the bike

Hmm, yeah. So the question remains...

Where are you, CJHaughey?

two wheels good

All multi-cylinder bikes need to have throttle bodies balanced (if fuel injected) or carbs balanced. A single cyl doesn't 'cos there's only one throttle body/carb.

The procedure is to balance the vacuum in each inlet manifold a) when the throttle is closed - tick-over and b) as the throttle opens and the butterfly flap in the throttle body or carb opens.
The objective is to have the same fuel charge (air/fuel mixture) going to each cyl at each throttle opening. Then the combustion force on each piston will be the same. Result - smoother running
If one cyl is underpowered you could think of it as like cycling with one wonky pedal or running with sharp stone in one shoe.

With a boxer twin an additional complication is it has two throttle cables which can stretch over time but at differenet rates. Then opening of throttle butteflies is no longer synchronised.

CJhaughey

Any multicylinder engine with throttle bodies or carbs should have them balanced.
Maybe your 250r has been set well from the start and never became unbalanced?
Its not rocket science its just making sure the cylinders flow the same amount of air at idle.
If you are happy with it then leave it alone.
Balancing carbs/TB is usually a simple enough task with a balancer which you can make yourself out of plastic hose, plywood and some ATF.

rat_race

Thanks.

It's not that my 250 doesn't need it in view -- I don't know, it probably does! It's just not mentioned in the maintenance schedule anywhere, and I was curious as to why it wasn't mentioned. Hmm, still not sure.

The 250 is idling poorly, and I'm in the middle of a full service & valve check (praying to **** that I don't need to adjust them, getting at anything on this bike seems to be a nightmare)...

Now I'm wondering if the poor idling is down to throttle bodies...

CJhaughey

rat_race wrote: »

Now I'm wondering if the poor idling is down to throttle bodies...

After you clean/replace the airfilter/sparks/oil filter/valve clearance then check the balance of the TB's often poor balance is related to valve clearance being out of spec,most often the exhaust valves.

two wheels good

A slight imbalance won't cause any harm. I bet completing all the other service jobs will improve running so much you wouldn't notice anyway.

Other thoughts...
- check there's some slack in throttle cable and throttle arm is hitting the stop on close.
- could the tick-over be a bit too low?
- don't be tempted to tinker with balance without a guage.
- consider changing\cleaning fuel filter (no idea what type your bike has)