912 100Hp running rich?

[Downunder]

My plugs are pretty black and exhaust is sooty....

 

Would this be from flying in summer? Some days it's been almost 30 degrees at 2000 Ft......

 

Should I consider adjusting the needles or as winter is approaching, leave it and see?

 

Is there any potential damage occurring currently?

 

Only using 98 ulp.....Vortex.

 

Cheers...

 

 

[metalman]

http://www.casa.gov.au/ADFiles/piston/rotax/2013-0055-E.pdf

 

I would be checking this AD

 

 

[Ultralights]

i found with my 912, that a dry sooty powdery residue was caused by oil being to cool. but with mine, it was only the front 2 cylinders that were black and sooty, the rear were perfect colour.

 

 

[Downunder]

Metalman2...My serial is not on the list, so I hope that's not the problem. http://legacy.rotax-owner.com/si_tb_info/alertbulletins/asb-912-062-ul.pdf (mine is ULS, not certified)

 

Thanks Ultralights, I'll check the rear plugs (only checked the front) but temps were hot, very hot. Using AeroShell Oil Sport PLUS 4

 

Cheers...

 

 

[cscotthendry]

Downunder: If you have an adjustable prop, it might be worth checking that your engine is revving out to what Rotax reccommend under full power. If not, the prop may be over pitched. Also, if your carbies are not synched that can cause one side of the engine to be labouring and running rich. The 912 engine operates like two separate engines and if the carbies are not balanced, the engine on one side is dragging the other.

 

 

[facthunter]

Checking plug colour is only done with a cut from a high power setting. Taxiing will nearly always cause the colour to be darker or sooty.The amount of fuel you use per hour is a good comparison and indication if something is going wrong. Also IF you are running rich the oil will become darker quicker.

 

As the carburetters wear they tend to get richer. Another cause is blockage of the air filters. Nev

 

 

[Downunder]

Scott, Both front cylinders are the same (black) but I need to check the rear....

 

Nev, Engine has done 80 hrs so maybe the carbs are wearing in and getting slightly richer...Will clean the filters.....powdery soot in the exhaust, so would be surprised if that was just from taxying.

 

 

[crashley]

As facthunter says the only way to check if a rotax is running rich by looking at the plugs is to run the engine hard for quiet a while and then cut the mags and then pull the plugs and check them only problem is this then involves a glide back to the airstrip and towing it back to the hangar

 

This is because the rotax engine runs very rich at idle especially the front two cylinders

 

I dont believe after 80 hours the carbies are going to be worn enough to run richer than when new

 

The only thing that can really change is dirty airfilters

 

 

[Ultralights]

in the rotax line maint manual, the front plugs being a dry black sooty, and rear ok, was a symptom of oil temp being to cool, this is how i found out, and sure enough, covered up 1/3 of oil cooler, oil temps now about 95 in cruise. all is well again. oil temps on cooler days were at about 70 deg before covering the cooler.

 

 

[gregrobertson]

I have had the same problem with my 912 ULS. I spoke to Wal at Bert Floods about it. His advice was to check the float level but not to change the needle position in the slide and let the engine get a few hours on it. I now have 148 hours up and it now seems to be getting better fuel economy. Wall also suggested to try BP Ultimate and see if it made a difference. It seems to.

 

Greg.

 

 

[Sapphire]

Float levels in carbies are usually out. The tabs for adjustment bend easily and so vibration always move the adjustment slowly to rich. The needle valve controlling the fuel level wears and allows too much fuel to the engine. Enrichment systems [sometimes called choke, but is not] can leak excess fuel through. If your carby is old it needs an o/h.

 

 

[Downunder]

Thanks everyone for their replies...It gives mw a few things to look into.

 

Greg, I was running ultimate before but have moved over to vortex, so there might be something in what you say....will try ultimate again.

 

I realised recently my car (an old Hyundai) definitely doesn't like the vortex and uses more fuel as compared to 91 octane.