paragliding training center
The Minari uses the Walbro WB-37 carburetor. To do this properly takes patience and time. There is no easy way -- unless you have plenty of money to spend on engine rebuilds. If adjusting the carburetor is something beyond your skill level, we can adjust it for you but you will have to ship your engine to us and we will fly and tune it for the approximate altitude that you fly in. Figure on spending $250-$300 for this. Contact us.
It is ALWAYS safer to run an engine too rich than too lean! If you have midrange issues, a fix given on the WB-37 page.
If you are careless adjusting the high speed jet, you can burn up your engine! You must install a CHT on the engine which will help prevent disasters.
This table gives the safe range for setting the high speed needle at the respective ambient temperature. The needle turns CCW are from fully in. The turns are expressed in minutes where 60' = 1 turn. This table is from the Minari user manual. It is always better to set the needle at the maximum for safety.
Temp Cº -10 0 10 20 30
MIN 65' 60' 60' 55' 50'
MAX 90' 85' 80' 75' 70'
After the basic adjustment is done, the setting can be fine-tuned.
Close the main jet by 1/32 to 1/8 turn and fly the engine at full throttle briefly. If the CHT remains at or below 170º C, you have leaned out the fuel mixture sufficiently to gain a small amount of power output and smoother running. Depending on the CHT, you may have to make the mixture leaner or richer, as required.
You must have a CHT installed to adjust your carburetor at high alitudes. It is also a good idea to install a tachometer at the same time. Miniplane-USA has all of these items. Follow these instructions for doing the basic adjustment of the carburetor. Adjust the low speed for your altitude and then close the high speed needle 1/8 of turn, fly the engine, and observe the CHT. If the temperature is safely below the maximums, close the needle another 1/8 of a turn. The basic purpose is to achieve a smooth running engine at all speeds. It is always better to run too rich than too lean.
The Minari manual specifies that the low speed needle be set to the same number of turns as the high speed needle. This is not particularly helpful. This page has the information pilots need to better adjust the low speed system. It is easy to do.
Here is an example of a pilot who adjusted the high speed jet incorrectly and burned up his engine. The chrome plating turns blue around 900 degrees F. The exhaust gases right at the manifold were probably 1,300ºF - 1,500ºF! That the chrome plating turned blue so far down the exhaust pipe demonstrates just how hot everything got. The piston seized and the entire top end of the engine was destroyed. Do not be careless and ignorant, like this pilot, and burn up your engine.
This photo is of the same engine. The lack of the right kind of oil and lean running condition got the lower connecting rod bearing (red arrow) so hot that the bronze rear side-bushing began to melt and disintegrate. The engine will have to be completely rebuilt -- an expensive and unnecessary mistake made by the pilot.