capt17

I have a hand-me-down Saito .82 on my newly maidened UCD 3D .46. (Sweet combination from what I could tell during my first few flights) Anyways, this is my first four stroke experience and after my third flight I noticed that my exhaust looks black/carbon-like. What is this? I am running Omega 15% and have an O.S. F plug, swinging a 13x6 MAS. It seems to be running great. I was running it a bit rich just to be safe and am going to lean it out next day. Any suggestions? I am fearing the worst. I haven't taken the engine yet apart due to the fact I'm not very 4-stroke savy yet. Thanks for the help!

Fflier9

My Feedback: (4)

just cross your fingers it's not pieces of the cylinder sleeve like what happened in my 46..

da Rock

It's a hand-me-down. Any idea how much it was used before you got it? If it was well used, and you're running it at higher rpm than the previous owner did, or running it hotter than he did, the the ash you're seeing could be deposits he made that you're burning out.

Any time you run higher rpm than before, the friction heat will be greater. And with IC engines the combustion temps can be higher as well.

Also, if the previous owner used fuel with a large castor oil content, you're buring out the varnish that left. Castor is an excellent component but the amounts we used in the old days and some still use isn't needed and left lots of varnish.

If you KNOW for sure that you're not running lean, don't sweat it. One thing you can do for sure is to add a click or two richer to the needle and test fly. See if you still have enough power and if the coloration goes away.

Oh btw, if the previous owner did not fly 3D, then that engine for sure is seeing lots more heat now. 3D doesn't provide cooling like sport flying does. Also, look at the cooling venting in your UCD. You need 1 and 1/2 more exhaust venting to intake opening area for non-3D flying. So you want that at minimum for 3D, IF you don't hover all the time.

bkdavy

My Feedback: (1)

Typically black exhaust indicates something vibrating loose. Check you're muffler connections for any rubbing.

Brad

capt17

Thanks guys! BKdavy, yes my muffler had vibrated loose when I noticed the blacker exhaust, and Rock I have a feeling I am burning out some older oil as well. I just ran it again after tightening the muffler and it looks as if it is lightening up. Looks like it was a combination of both! If these were metal shavings I would see a serious power issue after a tank or two right?
Thanks for the help. I don't know what I would do without these forums!

alfredbmor

Use one full gallon of Cool Power for your next flights, this fuel does not have castor oil, only synthetic, it will clean your engine, then you can go back and use castor oil based fuel. A 13 x 6 prop is on the lower side of the range of the engine, mine turns a 13 x 8 or a 14 x 6 around 8,500 ~9,000 rvm. The worst scenario is that you could need new bearings and a new ring but it is a cheap fix so I would not bother, those are great engines.

da Rock

Good thing about the fuels nowadays is that almost all use synthetic for their oil, some use all synthetic, some have a percentage of castor. I don't know of any that's readily available that's 100% castor for it's oil. And that's a good thing about the fuels nowadays, for sure. Castor is great to have, but not so great to have as all the oil in the mix.

combatpigg

My Feedback: (3)

I've played with raising compression and found that high compression makes the exhaust darker.