TB Balance.

[Unklian]

Hi Everybody.

After servicing my Rockster and changing the plugs,
tickover was still down (850rpm) and the bike had been running a little rough.

I decided a TB balance was in order.

I constructed a manometer from the excellent guide found on this site.

http://obairlann.net/reaper/motorcycle/manometer.html

Connected it up and let it settle.

This was the initial result at tickover.



A slight turn on one adjuster brought the vacuum into line then I turned both screws
up a little at a time until tickover was at 1000 / 1050rpm.

Opening the throttle slightly to about 2500rpm, brought the following result.



Adjusting the right hand cable length balanced the levels again.
(This is VERY sensitive, about 1/4 turn of the cable adjuster).

Rockster is transformed.

Cheers for the advice on the manometer.
Total cost, £6.00 for the 1/4" tubing from ebay, an old bit of wood and
some old brass wire. Well worth the "expense" and an hour to make / use it.

Ian.

[riceburner]

Good to hear Ian.

What did you use? Water?

[Unklian]

Hi there.

Yes, just water.

The pipe is 1/4 i.d so I used two very short lengths of
screenwasher pipe to help it to fit on the TB stubs.

There is a little "bounce" but only about 1/4 to 3/8 of an inch in the tubing.

It is quite obvious when the TBs are balanced though.

I was worried I would need to use colouring or some thicker liquid but as you can see, water is just fine.

If it hadn't been readable, I had experimented with a rawlplug inserted into each end of the tubing.

The only vacuum passing by would have been through 2 very thin slits but it wasn't needed.
The only concern I had was whilst starting the bike, the water moves about 8" in the direction of the first suck!

Ian.

Ian.

[pieter1]

I want to balance the idle on my R1150 Rockster and try to use the Manometer technique as describe in: http://obairlann.net/reaper/motorcycle/manometer.html.

On idle i can get it in balance, but do not know how lean or rich the setting is. Should I start to balance this after 2 turns of the brass screw or when? You can balance this at any place between 1 to 2.5 turns of the screw.

Anyone did this before?

[boxermania]

pieter1

The brass screws have nothing to do with richening or leaning the mixture as they are an air bypass only to set the idle rpm. The screws should be at 1 1/2 turns CCW from lightly seated, then proceed to make equal adjustments on both until the manometer columns are balanced and your rpms are around 1100.

[NoRRmad]

As I understand it, "equal adjustments" are not the point. Back out the screw on the cylinder that has the least vacuum until the manometer is balanced. (Or is it the most vacuum? Well, it'll be obvious.) If RPM's are low, back out the other screw a bit and re-balance. Repeat until you're at 1100 RPM and balanced. If RPM's are high, screw one adjustment in a bit, and re-balance. Repeat until until you're at 1100.

[pieter1]

What you described makes sense seeing that the brass screws do not adjust the air/fuel ration but only the idle. The critical point is that 1100 rpm is the critical factor and to balance the cylinders at this point. How is the air/fuel ratio determined?

[Unklian]

How is the air/fuel ratio determined?

Clever Mr. Bosch sorts all that stuff out

[NoRRmad]

Air/fuel is adjusted by the Motronic computer, reading the O2 level by a sensor in the catalytic converter. It's completely automatic; there are no adjustments.

[Unklian]

Just a bit of an update......

Following the TB balance, tickover was improved but I still found power delivery "not quite right".

I decided to start again but this time I took out the brass adjuster screws.

They were filthy with burnt on petrol varnish and black crap.

Cleaned with celulose thinners and refitted.

Adjusted idle again and went for a ride.

Bike is like a new one, totally transformed.

I can't believe the difference.

Ian.