balancing carbs

[Thatchman]

Hi guys.

I have a problem that I am looking for some help on. I have a Raptor 582. One EGT reads normal. ie as it has since new. The plane is 44 hrs old. The other used to be close but is now about reading up to 100 degrees lower. I replaced plugs 10 hrs ago. There is some oil leaking from the one outlet manifold as well.

from what I have read on the site, it would appear that one of the carbs is running too rich and they need to be balanced.

Is this an easy thing to do and can someone try to explain how it is done. I am hesitant to fly until I have sorted it out.

[RudiGreyling]

Hi Thatchman,

before you adjust anything, swap your 2 EGT probes around and check if the symptomns prevail on the same cylinder. If the problems jumps to the other cylinder you know you have a suspect probe.

I had the same problem, low reading probe, caused by a fualty probe, on the way out.

If you have isolated it to the probe, check all you wiring connections for that probe run all the way to the instruments. IF all is fine, buy a new probe.

Regards
Rudi

[Morph]

First do as Rudi says

Next to set your carbs up do the following

Setting up the carbs

Check that the jetting in the carb is correct.

503
Jet Needle 11K2 - Circlip position #2 from top
Needle Jet 2,70
Main jet 158 at Sea Level
Main Jet 150 at Highveld (typical, check carb jeeting charts for your altitude)
Idle Jet 55
Turn the idle airscrew in all the way and out again 0.5 turns (this is bottom front left side of the carb)

582
Jet Needle 11G2 - Circlip position #3
Needle Jet 2,72
Main Jet 165 at sea level
Main Jet 158 at Highveld (typical, check carb jeeting charts for your altitude)
Idle Jet 45
Turn the idle airscrew in all the way and out again 1.0 turns(this is bottom front left side of the carb)

Make sure that the needle circlip is below the plastic spring holding cup and NOT ABOVE

Turn big idle adjustment screw completely out until it no longer makes contact with the piston. Make sure that the piston is completely closed (down) and not hanging on the cable.

Turn the idle screw in until the piston rises by about 5 mm, make sure that both pistons are at the same height. Some guys put two plastic straws into the port and under the piston so they are sticking out of the port. Then as you screw in the idle screw the piston lifts and the straw starts tilting. Adjust both carbs to the same level

Open the throttle (engine off) and stop when the bottom of the piston just meets the top of the port. Make sure that both pistons are at the same level, this can be adjusted at the adjustment screw through which the cable goes.

The throttle cable should have approx 1mm free play at idle.

Also check that the choke cables have the same free play when closed.

Start the engine and get it up to operating temp. Adjust both idle screws equally to get an idle of 2000rpm. You may fine tune the idle air adj. screws if necessary to try and get it running smoothly.

Adjustment of the float lever - remove the float chamber and the float lever should be parallel to the float chamber edge, adjust by being the part that activates the float needle valve.
Here you go

Then go fly and see how the motor runs wrt the EGT's
The piston with the high EGT is more lean. (richer runs cooler because the fuel/oil mixture is higher than the air mixture). Therefore the one with the higher EGT is getting more air, i.e. the piston is further open than the other. Either adjust the throttle cable at the top of this carb down (to drop the piston) or the other one up to lift the piston and reduce the rich setting. Adjust to within 25deg C of each other at cruise.

Check here for more detail viewtopic.php?t=2494

[Thatchman]

Hi Rudi and Morph

Thanks for the reply's. I will follow the steps next week and will let you know what the outcome is.

[Thatchman]

Hi Morph

I found the info on the links very informative (to a novice).

I flooowed the steps to check if the carbs are balanced and they look perfect as far as I could tell.

I started the Raptor and took the revs up to 3000. The EGT's were within 10 degrees so it looks like it is only at cruising revs and full power that there is a difference.

The only other thing that is different on the trike is that oil has started to leak from the one exhaust manifold. Each manifold should have four bolts holding it on was is only fitted with three. I am told that they are all like this.

Could it be that at higher revs, cold air is sucked in from the manifold and is causing the EGT to drop?

[Morph]

First retorque the exhaust manifold. Go to Midas and buy a Allen Key set of heads for your torque wrench. I have looked at the 582 and they only have 3 bolts on each side.

195in/lbs (16.25ft/lbs)

They must not leak as the two stoke motor requires the pressure from the exhaust manifold and silencer to function correctly.

Then try again. If they are still out at cruise power do the following
1. Determine which of the two is hotter (This side will be running slightly leaner than the other one, which is why it is hotter)
2. loosen the lock nut at the top of the carb where the throttle cable enters the carb. Adjust the cable slightly up. Do this a little at a time. re tighten and go for a flight. Check what the EGT's are doing. By doing this you are increasing the fuelmixture to the piston resulting in a cooler operation. This way you can get the EGT's quite close. I have mine within 5 deg at full and cruise power. Up to 25 is acceptable.