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Author Topic: Black Exhaust Deposits from Petrol Engine  (Read 1689 times)

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Offline British Victory

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Black Exhaust Deposits from Petrol Engine
« on: December 01, 2017, 22:45:39 PM »
Running my ngh 25 after a twelve month lay up. to get it started I had to open the low speed needle a 1/4 of a turn.
It performs very well but the amount of black sh1te coming out of the exhaust is concerning me.
I have about a 33:1 petrol:oil mix, which is what I the makers recommend.
If I lean out the low speed needle by more than 1/8 turn she dies on me.
Is it because I ran it for about 20 mins at low speed?
Should have said, the oil is castrol power 1 racing fully synthetic.
« Last Edit: December 01, 2017, 22:48:17 PM by British Victory »
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Re: Black Exhaust Deposits from Petrol Engine
« Reply #1 on: December 02, 2017, 01:24:57 AM »
Could very well be too much oil.

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Offline Redbaronn

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #2 on: December 02, 2017, 09:58:21 AM »
Whats the spark plug looking like, could just need a bit of work to clear all the crap out.


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Re: Black Exhaust Deposits from Petrol Engine
« Reply #3 on: December 06, 2017, 08:28:07 AM »
Spark plug black and oily, I spent a little time leaning out the top end and bottom end got them as far as I can get them (I think!!!) and there's still black slime leaking out the pipe joins, not so much though.
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Re: Black Exhaust Deposits from Petrol Engine
« Reply #4 on: December 06, 2017, 09:29:03 AM »
Definitely too rich, the black oil deposits will now probably never go completely, the oil is doing what it is supposed to do stick to metal, no harm done better too rich than too lean


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Re: Black Exhaust Deposits from Petrol Engine
« Reply #5 on: December 06, 2017, 09:35:06 AM »
Definitely too rich, the black oil deposits will now probably never go completely, the oil is doing what it is supposed to do stick to metal, no harm done better too rich than too lean
I used to get a bit on my Zenoahs, since changing to Rock fully synthetic oil its all gone.

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #6 on: February 03, 2018, 06:30:46 AM »
Have a gf38 which has the same problem of black exhaust output. Wondering if a two stage exhaust could be used with the first box designed to catch the oil and a tap drain used after flight. Has anyone used such a config?

Marked as best answer by drone on February 05, 2018, 19:25:57 PM

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #7 on: February 05, 2018, 17:23:21 PM »
Iíve had this on quite a few of my petrol engines. The worst culprit was a Zenoah 80 twin in a 1/3 scale Cub.
 I ran this engine on the very best Bel-ray synthetic oil and the amount of black gunk underneath the model after a flight was horrendous.
 So after trying all the usual carb adjustments I threw caution to the wind and drained the tank and refilled with the petroil mix that I use in my strimmer , hedge-cutter , masonry cutter etc.
 What a revelation , no more gunk and a perfectly clean model.
 I think , and this is my reasoning only, the top quality synthetic was too good. It lubricated the engine brilliantly but it then came out of the exhaust much the same as it went in.

 The oil that replaced it in the premix was Halfords Garden machinery oil. A mineral oil that cost about £6 a litre.
 Now before anyone throws a fit. My Stihl cutter is nearly 20 years old and my Makita strimmer is 13 years old and they perform like new and they have only ever been run on a cheap mineral oil. Thereís no model engine made that gets a harder life than a petrol cutter , flat out in concrete and brick dust. The oil lubricates the engine but is burnt in the combustion chamber and comes out as smoke.

   Just my 2 pence worth.
« Last Edit: February 05, 2018, 19:25:47 PM by Marcol »
You only need two tools in life - wd-40 and duct tape . If it doesn't move and should, use the wd-40. If it shouldn't move and does use the duct tape

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #8 on: February 05, 2018, 19:27:37 PM »
Iíve had this on quite a few of my petrol engines. The worst culprit was a Zenoah 80 twin in a 1/3 scale Cub.
 I ran this engine on the very best Bel-ray synthetic oil and the amount of black gunk underneath the model after a flight was horrendous.
 So after trying all the usual carb adjustments I threw caution to the wind and drained the tank and refilled with the petroil mix that I use in my strimmer , hedge-cutter , masonry cutter etc.
 What a revelation , no more gunk and a perfectly clean model.
 I think , and this is my reasoning only, the top quality synthetic was too good. It lubricated the engine brilliantly but it then came out of the exhaust much the same as it went in.

 The oil that replaced it in the premix was Halfords Garden machinery oil. A mineral oil that cost about £6 a litre.
 Now before anyone throws a fit. My Stihl cutter is nearly 20 years old and my Makita strimmer is 13 years old and they perform like new and they have only ever been run on a cheap mineral oil. Thereís no model engine made that gets a harder life than a petrol cutter , flat out in concrete and brick dust. The oil lubricates the engine but is burnt in the combustion chamber and comes out as smoke.

   Just my 2 pence worth.
I'll give you tuppence for that idea and remember tuppence brought down a bank in mary poppins  :D ;D
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Re: Black Exhaust Deposits from Petrol Engine
« Reply #9 on: February 05, 2018, 19:40:00 PM »
I think we can get carried away with buying the best racing synthetic oil possible.

But the kind of life our model petrol engines lead , they donít need an oil that protects up to 30,000 rpm

Iíve yet to meet a modeller that has worn out an engine with normal use.

I forgot to say that the mix is 50:1. All I do is put a few extra millilitres of oil in the first tank full of a new engine and after that itís ďgot to earn its keepĒ. 
You only need two tools in life - wd-40 and duct tape . If it doesn't move and should, use the wd-40. If it shouldn't move and does use the duct tape

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #10 on: February 05, 2018, 20:07:45 PM »
Sh1te, we'll be putting castor in them next  :ev
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Re: Black Exhaust Deposits from Petrol Engine
« Reply #11 on: February 06, 2018, 11:36:53 AM »
I have always run my Zenoahs on standard oil, usually supermarket stuff but was persuaded to try Rock Synthetic. I will never go back, runs cleaner, engine feels freer and has more power. Never need to clean the models at all.

Offline Redbaronn

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #12 on: February 06, 2018, 15:59:03 PM »
One thing to remember the engine manufacturers guidelines ie fuel / oil mix is to cover all eventualities which include installation, environment and users which is why most manufacturers  say use 30:1 just to cover themselves, the more oil the more mess you get.

I have always used a good synthetic oil (for 15 years plus) and a 50:1 mix (two strokes only) and ensuring the engines have a good flow of cooling air over the fins, the models stay clean and free from exhaust deposits

The other thing to make sure is the air/fuel mix is right.
If the spark plug has a grey/brown coloured electrode then the fuel/air mix is about right

Offline paulinfrance

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #13 on: February 06, 2018, 17:33:47 PM »
Most of our club members use the ready mixed petrol from garden stores, it doesn't smell as much as the 'real' stuff
in the car either. ^-^


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Re: Black Exhaust Deposits from Petrol Engine
« Reply #14 on: February 07, 2018, 09:28:05 AM »
You will probably find it is Aspen an Alkylate petrol https://aspenfuel.co.uk/
Perfect if you can afford it, I used for a few years, supposed to prevent carb diaphragms  hardening during storage, among other things, ideal if you store your petrol planes in doors as the fumes from it are minimal.
It certainly burns cleaner, apart from that found no significant other benefits.

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #15 on: February 17, 2018, 18:40:55 PM »
Trader easily found for aspen fuels and a gallon was purchased for £18.50, so will be interested to see how the engine performs on this fuel.

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Re: Black Exhaust Deposits from Petrol Engine
« Reply #16 on: February 17, 2018, 21:39:26 PM »
Trader easily found for aspen fuels and a gallon was purchased for £18.50, so will be interested to see how the engine performs on this fuel.
I gather the benifit is lack of smell. If that's a problem  (living in a flat maybe) then it's worth it. Otherwise stick to Morrisons at 1.14 a litre. 

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