1990(?) Suzuki DT20 problems

[Wagoneer]

So this is my first venture into the 2-stroke world, I've had two 4-strokes before this. I can't get this motor to stop smoking. I'm running a 50:1 oil mix, I have the carbs adjusted to where it seems like it's running perfect. The motor performs great and can idle all the way down to a chug, but it smokes like crazy! I'm assuming excess gas is somehow making it's way into the crankcase? Where are the problem areas with this? It's smoking like it's running extremely rich, but the engine doesn't run like it's rich. Zero stumbling off idle, revs up nicely, good throttle response, but it's smoking from the exhaust at the back of the engine, and through the prop exhaust and out through the port on the back side of the shaft as well.

Also, the condition of the motor was basically unknown when I bought it. The guy was extremely mechanically challenged and just basically said, "it runs good."

I have lots of experience with rebuilding carbs, but this mikuni carb that's on it looks like no other I've seen. Is the screw right above the choke plate the idle mixture or high speed mixture? If it's the idle (which its acting like it is) where is the high speed mixture screw?

After running it in a barrel for about 30min I had chunks of what smelled like oil lining the top of the water and chunks that were stuck to the engine at the water line. I'm scared to ask where the heck is this coming from? Lower unit? Or does that happen from a super rich fuel mixture?

Sorry for the amateur questions, like I said, this is my first 2-stroke.

[keakar]

lol, 2 strokes always smoke a lot, if they don't smoke then they blow up.

the only way a 2 stroke engine gets lubricated is from excess oil in the gas so no smoke means no engine lubrication and very shortly no motor.

relax, your motor is working just fine, its supposed to smoke a lot

[Solarman]

low speed mixture, dt20

That mixture screw is the low speed/ idle mixture screw. The high speed is a fixed jet generally located in the center of the float bowl, where the needle valve and float assy Are.
The idle mixture screw only adjusts the air mixture at idle. So, closing it adds less air causing a richer mixture. opening the screw adds more air, causing a leaner mixture. The manual will tell the general setting ( 1-1/2 turns ), but a couple of my motors run best about 1/8 turn plus, or minus.
And I usually add an extra ounce of oil over the 50/1 ratio. Plugs are cheaper than motors. Likewise, I always shake my portable tank, on my small motors before starting to insure a good mix if it has been sitting awhile.lol.
Good luck happy motoring. And they do smoke a bit.

[Wagoneer]

Huh, so constant smoking is normal? Like we're talking I can visibly see a constant puff of smoke coming from the small exhaust port at the back.

I have people telling me to seafoam it. I generally try and stay away from seafoam. Any thoughts on that?

I also have it mixed a little more than 50:1. 23L of fuel and I put in 500mL of oil.

Oh well, maybe I'll stop worrying and just her for a rip and get her cleaned out and see how it goes.

I miss the cleanliness of my little DF6 already but I'm sure that'll change once I open up the DT20!

[Wagoneer]

And what should the fuel mixture be set at? I have mine at 2.5 full turns out from all the way in (full turns being full 360deg rotations). Seems to be the happy spot between sputtering (rich) and searching for idle (lean).

[keakar]

well as the rings wear it will smoke a little more then when everything is new and tight but the smoking as well as light oil sheen it leaves behind is the pollution that caused then to switch over to the 4 strokes and the newly redesigned 2 strokes that only smoke a little.

people just aren't used to those older engines that smoke a lot and that's where the comments are coming from.

since you are mixing it with a little extra oil that also adds to excessive smoke.

I always mix it 50/1 as instructed and if im partially filling a tank I put the gas first then add the right amount of oil for the gallons you added and shake the tank to get it mixed well.

you should always round it off to the next full ounce so if you need 1 1/2 ounces oil add 2 but I wouldn't puty a full ounce over on purpose because its not needed and fouls your plugs sooner as well as making extra smoke. also most 6 gallon gas tanks can hold 7 or 7 1/2 gallons if filled completely so never go but what the tank is "supposed" to hold. when I get near the bottom of the tank i'll pour the last gallon or so into my lawn mower gas so I can restart a new tank with the proper oil mixture added first for the gas I know it holds or just what I intend on putting in it, the lawn mower then will just smoke a little.

its been a while so I don't remember the number but figure it out to see how much oil you need for each gallon and use a baby bottle to measure since they are cheap and premarked with measurements and you can always find em at garage sales for almost nothing

[Wagoneer]

I have a 6gal tank but it ended up holding about 23L and a bit. So I put in a whole 500mL of oil (25L gas, 500mL oil would be perfect 50:1). Maybe I'll use a bit of the tank and then put in another 2L and shake it up.

I have a feeling it just needs a good run. The compression is great (120/115 dry) and it starts on the first pull and can idle down without stalling in seconds so I know it's running really well.

I have lots of people telling me 75:1 mix is completely safe with new oils today but I somehow don't trust that. I'll try putting in a few liters of gas to make it a true 50:1 and maybe try 60:1 and then see how that goes. But like what was said earlier, plugs are cheaper then fried rings.

Thanks for the help guys! Any other suggestions are welcome.

[Wagoneer]

So I've been researching a lot about what mix ratio this engine needs and man it's confusing! Apparently Suzuki labelled them all at 100:1 ratio until '88 when they withdrew it and said it needed 50:1. That is a HUGE difference. I can only assume they had problems with premature wear with 100:1? The majority of people I've talked to some small engine mechanics say I'm crazy for running 50:1 and should go up to at least 75:1. A few have said unless I'm going to be running around at WOT 100% of the time I should be running 100:1.

Yikes... Seems even Suzuki themselves are confused on what ratio to run.