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rectifier
08-07-2016, 05:25 PM
Picked up an ATC200 a couple weeks ago to keep my 185S company.

When I bought it, it was running great. 2 weeks later, the float sank and the oil got diluted with gasoline. So, I swapped the float for a spare laying around and changed the oil. The guy I bought it from was quite insistent that he had run only synthetic for years, and that I should stick with synthetic blah blah. I like synthetic oil myself, but don't like to spend the big bucks on Amsoil. So I put in Mystik 10W-40 ATV, which I have run for 2 years in my ATC185S with zero problems and no smoke.

I fired the bike up and rode for about an hour. The next time I started it, it smoked like a 2-stroke. The smoke is not as blue as 2-stroke exhaust, it's more of a greyish colour, however it is definitely oil smoke.
What happened here? I know synthetic can creep past valve guides and rings, but supposedly it always had synthetic before. Also I switched the 185S from 15W-40 Rotella to the Mystik product with no ill effects.

I just adjusted valve clearances, though I don't think it will make a difference.

atc007
08-07-2016, 05:29 PM
Pull the breather hose off your cases. Below the carb. If the smoke is bellowing out there,{ it will be} It is cylinder seal, If it's clear, it's valves. You can tear it down and fix it,orr,,, put the old oil out of your car or truck in it, they don't seem to smoke on that.

rectifier
08-07-2016, 07:02 PM
The blowby gas was clear.
I actually blame that breather hose for fouling the oil. The leaking fuel collected in the airbox and went down that hose into the crankcase. On my 185S that hose has been cut, and in the Honda shop manuals it shows that hose not being attached to the airbox, but just going straight down. So, I cut it. I'm not sure what purpose it serves.

After setting the valve clearances, I drained out about a cup of the synthetic and topped up with 15W-40 conventional diesel (Supertech) to thicken it up a bit. Fingers crossed, but the smoke has stopped.

A bit of a WTF moment but maybe the pure synthetic was just too thin for worn valve guides? Or, could the clearances have had some effect? They were slightly too tight, actually pressing lightly on the valves.

atc007
08-07-2016, 07:09 PM
Clearances would have zero fault. I think you are right. The thinner oil must have wept down the guides. It smoked steady, the entire ride,or cleared out after a good warm up?

rectifier
08-07-2016, 07:26 PM
It smoked steady for the entire ride, though the smoke was thickest after a minute or so. Early smoke made me suspect valves, but it threw me for a loop how it didn't smoke at all before the oil change.

After adding the diesel oil it blew a puff on startup and then cleaned right up. After 5 minutes of riding or so smoke suddenly started pouring from the tailpipe but it was likely just residue burning out of the muffler, as that went away in a minute and did not return.

Now I'm letting the bike sit for a bit to see if it will smoke on startup again.

I agree clearances shouldn't make the slightest bit of difference but sometimes strange things happen! The motor pulls over easier with them set properly, at least.

fabiodriven
08-07-2016, 09:23 PM
15w40 is fine in those. If it likes it just stick with that.

rectifier
08-08-2016, 10:35 PM
Probably will change it to straight 15W-40 at the next oil change. I ran it for an hour checking my sheep last night with no smoke at all, then fired it up today to about a minute of smoke.
Definitely coming down the valve guides.

atc007
08-08-2016, 10:59 PM
You have to pull the engine to do valve seals on that one unfortunately. Heavier oil won't hurt a thing. If it runs good, I'd run it!