Thanks for the tip Jerry. I already have one Lo Gague so only have to
purchase another (now ordered over the internet @ 14.50 including
carriage).
I had a long chat with Conrad Beale (AKA Skydrive) and he showed me the
Rotax setup (or rather the one that he uses) . It is not a Skydrive approved
accessory but it is the one he uses to set up the 912 engines. It consists
of two dial type vacuum guages and a valve (fish tank tap !!!) to damp out
the oscillations. Rotax will sell you this setup if you need one - cost
about 50.
The readings are taken directly from the balancing tube takeoffs (simply
remove the alloy balancing arm and substitute the vacuum guage takeoffs).
The guages are standard dial guages - Gunsons make a similar guage priced at
about 20 each. It is possible to get away with a single guage but two are
much easier to use but if you do this ensure the unused takeoff is closed
off otherwise a lean mixture on this side will cause problems (possibly even
damage !).
Note- the Rotax maintenance manual refers to a takeoff point on the
carburettor but it is very difficult to reach especially when the balance
arm takeoffs are available. I understand that newer engines have a separate
plug in the manifold for balancing purposes but if you use this then the
balancing tube needs to be disabled/ plugged as this evens pressures
between the left and right side of the engine making it very difficult to
get a true balance reading.
Note the pressure readings are taken at the manifold side of the carbs and
NOT the air filter end. We are measuring suction/ vacuum rather than
airflow.
First set up the engine at idle speed using the idle stop screws. Make sure
the throttle cables are not overriding the throttle idle screws. Start with
the screws fully backed off (use a feeler guage to check when the screw
contacts the throttle arm) Then turn the idle screws clockwise until the
engine idles smoothly at about 1400RPM.
The mixture control screws are set separately by closing them and then
opening up by one and two thirds turns. This should be done before checking
the balance.
NOTE - mixture control screw is not the same as the idle screw.
Once idle balance is satisfactory then balance the manifold readings at
about 3000RPM using the cable adjustment nuts. Once this is OK then recheck
the idle settings.
It is worth noting that if the spark plug colouring is uneven this is likely
to be due to an imbalance between the carbs and not a mixture problem. I was
going to modify the needle settings as my RHS plugs were running on the
black side but was advised that setting up the balance correctly would
probably cure this without tampering with the mixture.
Hope this info is of interest.
Carl Pattinson
G-LABS
----- Original Message -----
From: "LTS" <lts@avnet.co.uk>
Subject: Re: Carb Balancing
I purchased two low pressure gauges from Gunson. Not expensive and bought
over the net. Easy. Skydrives are more expensive but easier as they come
with control valves.
Jerry
Jerry@ban-bi.com or LTS@avnet.co.uk
www.Ban-bi.com or www.avnet.co.uk/touchdown
----- Original Message -----
From: "Dean Wiegand" <dwiegand@surewest.net>
Subject: Re: Carb Balancing
> Check the motorcycle shops in the area. Many have
> relatively inexpensive, mercury scale, multi-carb,
> balancing meters for the 2 or 3 or 4 carbs on the
> bikes. Should look like:
>
> http://www.motoworldracing.com/carb_synch.html
>
> If you do purchase one, get the 4 scale unit, obviously
> you could use it for other applications....or talk your
> EAA or PFA group into the purchase.
>
> I would lend mine (used on my MG Midget with dual SU
> and Honda Interceptor with 4 Mikuni) to you but
> shipping to/from UK will exceed the cost.
>
> Dean Wiegand
> Sacramento CA USA
> dwiegand@surewest.net
> kit A259
>
>
> -----Original Message-----
> From: forum-owner@europaclub.org.uk
> Pattinson
> Subject: Carb Balabcing
>
>
> My Rotax manuals are less than helpful when it comes to
> setting up the
> carbs. I dont really believe that setting up the
> balance at idle RPM will
> give a satisfactory result throughout the RPM range. So
> at what speed should
> the balance be set up - 3000RPM, 4000 RPM.
>
> Also how do you set up the mixture - at present the
> plugs on the RHS are
> black while the LHS are ok (pale brown) - do I need to
> lower the needle or
> adjust the balance ?????
>
> Does anyone have suggestions or ideas on how to set up
> the carbs on the
> Rotax 912 and also any reccomendations on suitable set
> up equipment.
>
> I understand Skydrive have a balancing kit but have no
> idea how good it is -
> price 50 approx.
>
> I have also come accross a device called Carbtune II
> intended for bikes. (
> www.users.myisp.co.uk/~carbtune/carboprn.html )
>
> Any tips/ reccommendations would be greatly
> reccommended.
>
> Carl Pattinson
>
> G-LABS
>
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