1989 90 HP Yamaha 2 Stroke (ETLF) Excessive Smoke

[FishNowWorkLater]

At startup the motor smokes really bad and smokes for about 2-5 minutes. Once it clears up it's fine and doesn't smoke much at all. I replaced the check valves in the oil supply lines as one was stuck open. I've tried to adjust the oil linkage rod (I have the Mikuni oil pump). I'm guessing with the throttle plates wide open I need to adjust the linkage so it's just about at the stopper (for wide open) There is no stopper for idle/closed. All 3 carbs have been taken apart, adjusted and cleaned.

What else could I be missing here, I don't understand how excessive oil is getting to the cylinders after sitting for a while.

Mods please remove the image below if it goes against forum policies.

[robert graham]

I understand that with the Yamaha Autolube system in the case of a malfunction the system defaults to full open/maximum flow….to protect the motor. My 1999 C90 Yamaha is a premix model so mine is different from yours, but maybe/hopefully one of our Autolube experts here can offer their expertise/ideas.

[brian3006]

Sorry this is no more help, but I have a 1990 150 that is similar to yours. a big cloud of smoke on start-up.. I have done all the same things you have to no avail... only happens after sitting for a bit.. Finally got tired of fooling with it and it has been like this for many...many years now. Other than smoking on start-up, no other issues have developed. spark plugs never foul...

I did switch to a synthetic "ashless" 2 stroke oil and that did seem to help quite a bit in regards to smoke on startup.

I also have a 2001 90hp model like yours. it smokes slightly at startup. I did have to replace one of the check valves that had failed. But I would just consider it normal. doesn't smoke anywhere near like my older 150

I have noticed on my 90, that even with new and/or working check valves...a drop or two of oil would still drip into the intake if the motor was tiled up.. this oil would naturally get sucked un right away at startup and contribute to smoke on start

[FishNowWorkLater]

The check valves in the oil supply lines are the only things keeping the oil from flowing into the intake. Those all seem to be working just fine - I think the next step is to replace the actual oil lines. My thought is if there is any type of leak around the clips it could let air in and allow that oil to drain into the intake?
The check valves will not allow oil to flow past them, but the lines after the check valves have oil in them and there is a vacuum created in the line which prevents oil from draining from those lines.

Just throwing darts at this point - again it seems like a pretty simple system and I can't wrap my head around the excessive oil/smoke.

[Keithbaja]

Without seaing your motor on start up and knowing down/off time I can't say for sure. But remember gas/Fuel evaborates but oil doesn't leading to a oil rich start.. Ahh.. Early morn cup of coffee, sun rising, fish jumping and a smell of two stroke oil on start up leading to great day on the water...

[FishNowWorkLater]

Without seaing your motor on start up and knowing down/off time I can't say for sure. But remember gas/Fuel evaborates but oil doesn't leading to a oil rich start.. Ahh.. Early morn cup of coffee, sun rising, fish jumping and a smell of two stroke oil on start up leading to great day on the water...

Hi Keithbaja -

I agree, that initial startup always had some smoke as expected and it cleared up within 10-30 seconds. I've had this boat/motor for quite a while at this point. As far as smoke goes - think of fogging oil burning off for about 2-3 minutes every single time it sits for more than a few hours. It's a lot more than normal and just started happening within the last few weeks.

I love the smell of 2 stroke oil burning in the early AM or early evening, but this amount of smoke is not pleasant at all.

[Borkabkln]

My premix 1996 Yama 150 puts out a HUGE cloud of smoke on first start up. Clears up in 30 secs though. Motor is new to me so I just thought this is normal for a two-stroke

[FishNowWorkLater]

Here's what mine looks like (not mine but similar smoke)

[99yam40]

does it make a difference if the motor is tilted up or not when shutdown for a period before the motor smokes like that?

[FishNowWorkLater]

does it make a difference if the motor is tilted up or not when shutdown for a period before the motor smokes like that?

I've had it tilted all the way down for about 3 days - still smoked just like that.

Tilted up for a while and it smokes too.

[Keithbaja]

WOW, your correct. That's a bit heavy !! All the pumps that I've work with don't have a stop. A scribe mark (line) or a small notch. I'd recommend a de-carb after you fix the issue and don't have your prop pointed at the wife's white Porsche....

[FishNowWorkLater]

WOW, your correct. That's a bit heavy !! All the pumps that I've work with don't have a stop. A scribe mark (line) or a small notch. I'd recommend a de-carb after you fix the issue and don't have your prop pointed at the wife's white Porsche....

I went and tested the 3 new check valves, low and behold one was bad (stuck open). Part is on order. The carbs are all off and getting cleaned again. I'll update again once I have the new one installed. Fingers crossed.

And you must mean her now blue Porsche?

[99yam40]

how are you testing the check valves?
if you use a syringe ,you might try using some gas or some other solvent in it to flush it out to see if it will clean out and start working again.
but then I do not know what could stick it open to begin with, there should be filters/strainer in place to keep stuff from getting into the pump

[FishNowWorkLater]

how are you testing the check valves?
if you use a syringe ,you might try using some gas or some other solvent in it to flush it out to see if it will clean out and start working again.
but then I do not know what could stick it open to begin with, there should be filters/strainer in place to keep stuff from getting into the pump

I tested it with a MityVac with the inlet side of the check valve in a small container of 2 stroke oil. I tried cleaning it out but it was just stuck open and I couldn't get it to close at all.

[brian3006]

I went and tested the 3 new check valves, low and behold one was bad (stuck open). Part is on order.

I learned the hard way a long time ago that new does not necessarily mean good.