How to cure a smoking 2 stroke engine

kparenteauOctober 1, 2007


I just acquired a nice, older Homelite BX-90 Bandit gas blower. Starts nice and runs good. I would like to cure it's blue smoke issue. I know the first thing to look for is oil / gas ratio. What else can I "clean up" to make the blower stop blowing blue smoke.

I would also appreciate the correct oil/gas ratio for this blower.

Currently I add a tiny bottle (2.6oz) of homelite oil to a gallon of gas.

I would love to have this running clear, or as clear as I can get for a 2 stroke.

Thanks All...

Thank you for reporting this comment. Undo

With the engine tuned properly (i.e. not too rich) and with good synthetic or semi-synthetic oil, you should be able to clean up your exhaust. I don't have any visible smoke or stinky two-stroke exhaust smells out of any of my saws/blowers/etc.

For the past few years I've been running the recently discontinued Mobil Racing MX2T at 43:1 (and still have enough oil for another 400 gallons of mix...), and it is smoke and stink free. I also had good results with the Echo semi-synthetic oil. Stihl's new full-synthetic oil is supposed to be excellent in terms of lubrication and low smoke levels, and comes in nice little 1bottle-1gallon mix bottles. Any of the good semi- or full-synthetic oils should provide excellent lubrication at 50:1, or 40:1 if you want to be on the oily side.

While you're at it, you might as well check the air filter and pull the exhaust (make sure it is flowing freely, no excessive carbon buildup, etc.).

    Bookmark   October 1, 2007 at 10:32PM
Thank you for reporting this comment. Undo
nevada_walrus(Boulder City)

2.6 ozs/gallon is 50/1 and is the norm these days when using a good quality air cooled power equipment 2 stroke oil. I don't know how good the Homelite brand is so you might want to try Echo, Stihl, Husqvarna or one of the other quality equipment branded oil. I really don't think you need to use the more expensive synthetic or semi synthetic but they won't hurt anything.

computerusers last line regarding the exhaust system may be the cause of your smoking. Carbon blockage of exhaust port or spark arrestor screen will cause poor combustion and exesive smoking. Also keep the engine revs wide open, or full idle. Half throttle on small 2 strokers tend to create a rich run condition.

    Bookmark   October 1, 2007 at 11:13PM
Thank you for reporting this comment. Undo

You might have to remove the jug and piston and decarbonize the top of the piston and head dome. Homelites are usually very easy to dissamble with an access cover on the bottom end. Just note which way the piston came out by marking or looking for the dot on the connecting rod and make alignment make if the jug has four bolts instead of three, usually they are offset anyway. With everything marked you can remove the piston out of the jug. also check and clean the ring groove. Now you can look at the bore and see if there any scuffing. I would also remove the muffler and clean out the mufflerexhaust port as suggested.

    Bookmark   October 2, 2007 at 9:54PM
Thank you for reporting this comment. Undo

rcmoser what does someone use to reseal the crank case after removing the jug?
Also removing the exhaust muffler to clean. drops all kinds of nasty's into the cylinder. but I'm sure all of you blow that out with compressed air after reinstalling muffler. right?

    Bookmark   October 2, 2007 at 11:00PM
Thank you for reporting this comment. Undo

It sounds like the fuel/air mix may be rich. I would check the carb adjustment. Make sure the air filter is clean & the choke isn't partially closed.
I agree a decarb might be in order, but I would try Sea Foam first. Besides decarbing the engine the Sea Foam will also clean out the carb innards. I've used it with good success.

    Bookmark   October 2, 2007 at 11:37PM
Thank you for reporting this comment. Undo

Normally the jug to crank case has a thick paper type gasket that 95% of the time can be reused if you don't rip it taking it apart. The crank case cover usually has a cup shape and a tiny o-ring sometimes on weedeaters, I haven't taken that blower apart he has so can't comment on how the crank case sump is assembled.

Even it you don't remove the jug all the dirt and carbon may end up in the crank case sump. When you flood these engines by pushing the primer bulb accidently too much all the fuel collects in the crank case sump. IMO thats why it takes along time to get them to start and run correctly.

My suggestion with the muffler removed would be if you had the jug off, then a through clean up can be preformed. Most of the time this is all two cycles need. Carb. cleaner, wire brush, thin bladed long screwdriver, or ice pick will aid in breaking the carbon loose after it has soaked for minute, two or three. Insecting the jug bore and piston, connecting rod bearing, you will know if the smoke was from carbon or the engine is worn out. I take small power equipment engines apart all the time and rarely have to have new gaskets.

    Bookmark   October 3, 2007 at 6:45PM
Thank you for reporting this comment. Undo

remoser Thanks for your explaination, technology confuse's me :(

    Bookmark   October 3, 2007 at 10:12PM
Thank you for reporting this comment. Undo

I urge you to reconsider running that engine lean on oil. I think you would want a small amount of smoke because afterall it is a two stroke engine. These homelites are notorious for vibration leaks especially at the cylinder to crankcase gasket. If you decide to run the engine lean on oil and those bolts loosen up the engine draws in outside air. This happens very quickly and unless your familiar with these engines, you may miss the symptoms. This lean run will starve the piston for lubrication and once the cylinder scores thats it, the engine looses compression and its trash.

    Bookmark   October 4, 2007 at 7:46PM
Thank you for reporting this comment. Undo


So I'm going to try and clean the exhaust and muffler.

So am I to just unbolt the muffler and clean around the exhaust area. Wire brush the muffler??

I'm new to this, but would like to cleanup the blue smoke issue if it's not my oil/fuel mix.


    Bookmark   October 6, 2007 at 5:06PM
Thank you for reporting this comment. Undo

Unbolt the muffler, look inside the exhaust port and turn the engine over until the piston covers the port (this keeps junk out of the cylinder), use a wooden dowel or stick (as not to scratch things) to break out chunks of carbon. It's not necessary to get the port shiny clean, you just want good exhaust flow. If you can see carbon build-up inside the muffler break that out also. You may want to tap the muffler on the driveway to see it any carbon inside the muffler will break loose. Keep in mind that niether of these may be your problem and just being black on the inside with some crust will not be causing the problem.

Does the blower smoke all the time or just at high/low speeds?

    Bookmark   October 6, 2007 at 8:00PM
Thank you for reporting this comment. Undo

Greetings all

Some very interesting comments and replies, I am studying motorcycle mechanics atm and there is a question about a 2 stroke engines regarding the blue smoke. From what i gather from all the comments and question i have decided to express my opinion also, to maybe help the problem if i can. I do not know the bike your talking atm so maybe someone with the same bike has more expirienced if it has mechanically involed as well. There is a way of making 2 strok run cleaner but you will get smoke one way or the other, the problem is despite the small amount you may put to the engine to lubricated in order to keep it clean (but not at its best lubrication) it is impossible to do anything other then provide the right amount needed by the engine at full load. inevitable this means that at lower speeds or start up there is an excess of oil which results in oily exhaust and build of carbon, as the others said the problem you have is the build of carbon and in this case that the explaination as to why you get that build of carbon in your engine/exhaust.

Something you need to know is wheather your bike has a pre-mix lub system or a pump system. to simplify this a pre-mix means wehater the oil is mixed with the petrol before getting to the chamber or having a pump will either injected directly. You can easily find that in ur manual or by checking the throtle. a pump will be connected to the throttle were a separeteing wire will be used for the throtle and the pump. this is important because of the ration, the pre-mix has a ratio of 20:1 to 50:1depending on the engine and the oil used. a pump has 100:1 at idle speed and 20: at full throtle. I hope you can see from the ratio the different in oil use, but always check the oil by the manufacter and the engine itself obiously.

Having said that using the wrong oil will cause smoke. carbon in the piston will cause smoke. having setted the throttle, pump incorrected, such as smaller wire, will cause smoke. Richer mix will cause smoke.

But at this case all you need to do is check weather u have pre-mix lub or pump then check you are using the right oil and then check the mixture is right, by adjasting the carb, then clean the ex port as the other said. and then check the bike to see if its better. if not open the engine up, its shouldnt be a problem with the right tools and you using the manual and then check the piston for carb.

I hope this answer some of your questions, it wont take you long to do it and i hope good luck to you.

Please as i said i am a motorbike mechanic studen so any comments are approciated

    Bookmark   January 7, 2009 at 4:33PM
Thank you for reporting this comment. Undo
davidandkasie(Z8 MS)


1st this thread is over a year old since the LAST response.

2nd, this is abot a leaf blower, not a motorcycle. the oil is mixed directly in the gas, not a seperate tank.

    Bookmark   January 8, 2009 at 12:38PM
Sign Up to comment
More Discussions
Electrolytic Rust Removal
Has anyone tried this, using a battery charger, "washing...
Electric shredder motor will switch on but won't spin the blades
Hello, I have an electric garden shredder that will...
Lindsay Durdle
Dewalt 3800 pressure washer, open hole between pump and engine.
Hi, I just bought a dewalt 3800 pressure washer gx...
Best gas leaf blower?
Can anyone recommend a good gas powered leaf blower?...
Sears air compressor engine won't run when plugged in
Sears Paint Sprayer/Air Compressor Model No. 106.153542...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™