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6hp smokes a bit at idle

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bigjohnson

Regular Contributor
I have a 1978 6hp 6804b that I got used for cheap.
Replaced the fuel pump carb rebuild impellor and fuel lines and it starts and runs great except it smokes a bit more than I like
At idle.
I run 50:1 mixture.
Brass idle screw set at 1 1/2 turns.
What can I try to reduce the smoking except replace the rings.
 
Well-----On a 2 stroke motor the rings have nothing to do with smoke.----Just more proof that oil / lubrication in 2 strokes is not well understood.
 
bigjohnson said:
I have a 1978 6hp 6804b that I got used for cheap.
Replaced the fuel pump carb rebuild impellor and fuel lines and it starts and runs great except it smokes a bit more than I like
At idle.
I run 50:1 mixture.
Brass idle screw set at 1 1/2 turns.
What can I try to reduce the smoking except replace the rings.
Click to expand...

Like Racer said, rings won't help the smoking. My 76 6hp John smokes a bit at idle. On Evinride XD30 oil it smokes more, on Havoline multi purpose TC-W3 multi purpose oil it smokes less. Both mixed at 50:1. You can change your oils but you might have to de-carb if it then sticks the rings, happened to me after switching to a synthetic. Not the oils fault, just years of lack of maint from previous owner. Adjust your idle mixture properly also snd that will keep the smoke to a minimum. Some motors it is 1.5 turns, some more, some less. Just make sure you don't idle lean.
P.s. When switching oils, make sure the oil is approved for 50:1 mix, most are.
 
The motor will tell you if it is too lean on slow speed mixture.----It will stop running.----No damage will result from too lean on low speed mixture.
 
Yea
You never know the complete history of a used motor. I make the assumption that the
Guy before me did not take care of it so I have to adapt to the fact.
I have some evinrude "engine tuner" that I might run thru it and see
If that cleans it.
 
As the above have said, there's supposed to be smoke. That's the 2cycle oil in your fuel. Does it still smoke after the engine is warmed up? Sometimes the oil needs the engine to run hotter before it completely burns up in combustion. You might try mixing less than 50:1 if you think the smoke is excessive.
 
ALL the oil that you put in the gas goes through the engine. Then some of it burns (makes smoke), and the rest goes out the exhaust, into the lake. It is hoped that it would all burn, but in reality that is not the case. Some goes into the lake. Would you rather see a bit of smoke or would you rather see an oil slick on the lake?

It's winter time. Are you running it in a barrel? The barrel collects and concentrates the smoke. It will be much cleaner on a boat on the lake and with the idle needle properly adjusted.
 
This is along the lines of what I say.----Many folks are confused by this " smoking " and lubrication of 2 strokes.-----On a 4 stroke engine smoke is deemed to be a bad omen.-----On a 2 stroke it is normal.-----2 strokes are wonderful.-----They run in CLEAN oil all the time.----The lubricating oil is introduced into the engine via the fuel.-----Years ago folks would come into the shop with a 2 stroke with the " it won't start " complaint.-----Then they would comment that maybe they have the wrong mix ratio.-----Fact is that the ratio has nothing to do with the STARTING of the motor.-----It will start on a 10:1 mix or a 1000:1 mix.-----On 1000:1 it won't run for very long.
 
Yep, alot it is a different concept, "an engine made to smoke". Some oils smoke more, some less. I ran Evinrude XD30 50:1 and it smoked at idle and some smoke at full. Mixed next batch with Halvoline at 50:1 (I know, it's cheap and taboo to many) and the smoke lessened, most the unburnt oil is probebly half way along the Mississippi headed to the gulf. I ran for almost 10 years in my power saw SAE#30 non detergent for premix at 20:1, and it would give a puff at idle or when you bumped the throttle, but not more at wide open than regular oil. Same plug for atleast 5 years, give you the carb was adjusted as correct as I could get it also.

P.S. Not promoting Havoline or SAE#30 for anyones equipment. The saw was a garbage dump rebuild and the 2 outboards are of no consequence. As to the #30 premix, inside of the engine looked as clean if not cleaner than one ran on normal 2 stroke. It ran on 120:1 Amsoil for a spell as well. And 20:1 bar and chain oil. Didn't like to idle with that stuff. Was trying to lunch the saw, aside from running it with no oil, that is too easy...:cool:
 
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Brother, Amsoil is 100:1 max. Anyway, to clarify......the OP is asking about smoke....Gator brought up a great point....testing in a barrel? We would like to know. If so, the cowling should be removed and fresh air even supplied with a fan. Why...? Exhaust gas is filled with hydrocarbons.....when added back to intake air, motor runs rich, then creating more hydrocarbons and even LESS oxygen to use for combustion. In this situation, it becomes IMPOSSIBLE, to accurately tune your low speed mixture.
Yet another thought. These thermostats often fail allowing the motor to run too cold, this will create more smoke as well. Thermostats are designed to keep powerhead at roughly 145 degrees for cleaner and more efficient operation.
 

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Had it in a barrel and in a garage so maybe that's it but I've
Run other 6hp and they did not smoke so much.
I'll adjust the lean rich while on the lake.
 
I use 24:1 on my 3hp 1966 Lightwin. When running barrel it always smokes quite a much, but when driving on boat, i have visible smoke only during cold start, but none during normal drive. During drive, just some smell of oil near the engine, but nothing visible. It is always important to use good quality 2stroke oil.
 
Evinrude, what fuel is available for you in Finland? Can you get clear, pure petrol, with no ethanol? Last spring I bought 5,500 liters for my stock here when prices were at an all-time low. Final cost about .50 USD per liter. Octane is 91. Good to hear from you. I grew up with the Finish immigrants who came for the opportunity to mine for iron ore in Hibbing MN. Most worked into the skilled trades......very talented.....learned so much from the Fins. Still learning, never will stop.
Brupp, my mailbox doesn't work right here...seems always full. Give it a try again, are you related to Rupp furniture family? Note: Bar and chain oil? Really?
 
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We have High (98E5) and low (95E10) gas available from gas stations. E5= ethanol max 5% and E10= Ethanol max 10%. I never buy E10. I dont like these Ethanol things, but it is not possible to buy ethanol free gas on here. So i use 98E5 gas. Even my daily driven car likes 98 more than 95. If it could be possible to buy ethanol free gas, i would sure only like to use that one. I really know what ethanol makes to fuel systems and lines, example my Lightwin, the fuel hose broke just after one season use. Yes it is nice to always write on here when possible, now we are middle of winter and i am only waiting for new summer to come, and boat-trips with Evinrude Lightwin. Motor is ready for new season, only need put gas on tank when summer is here again.
 
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Hey Tim, box says "still full". Yep, bar & chain oil pre mix. Was a "lets see what will happen" thing with a junkyard saw.
 
This mailbox is ridiculous. Okay, thanks. 4 cycle oil is not formulated to burn cleanly....when 2 stroke oil came out, I started putting fishing lures in my tackle box instead of tools and spark plugs.
 
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