Tuning a 2 stroke carb

[AKRISONER]

Hey guys,

im definitely a total rookie when it comes to small engines. I know enough to clean out a carb by taking it apart and putting it back together, but as far as tuning goes I’m at a bit of a loss.

the motor runs like a top however it recently has been having a major issue flooding when idling at low RPM. after taking the carb off it seems that the set screws were not adjusted correctly at all. So much so that I think the screw in the bowl was just leaking fuel like crazy.

I ended up finding a copy of the original manual and it’s instructions for tuning the carburetor utilizing the pilot air screw, (it gives a recommended number or turns from set) however it makes no reference the following screw on the bowl. 
 

I’m sure someone on here knows all there is to know about these things. First of all what is this particular set screw, and does anyone have a recommendation on where are they typically set?

let me know what you think! Heck if anyone knows a guy/shop that could get me in in a pinch to simply tune this thing correctly/is willing to point me on how to do it id be open to those as well. The motor runs so damn well aside from the flooding problem it’s a shame that I don’t trust it all of the time for trolling!

[John Bacon]

It looks like it may be used to drain the bowl for winterizing the motor.

[Hack_Fisherman]

Yeah, that’s a weird one. Is there a drain hole in that appendage? Looks like there might be. It’s the spring that’s throwing me. It does look like a jet, but why there? 
 

what motor is this for?

Edited May 4, 2021 by Hack_Fisherman

[AKRISONER]

2 hours ago, Hack_Fisherman said:

Yeah, that’s a wired one. Is there a drain hole in that appendage? Looks like there might be. It’s the spring that’s throwing me. It does look like a jet, but why there? 
 

what motor is this for?

Hey guys, yes there is a hole along what I would call where the shaft of that screw is that you can see plugs when the screw is tight. For it to maybe be a drain makes a lot of sense? By loosening that screw that hole will open and allow gravity to drain the bowl.

the picture here is of a knock off cArb from alibaba that matches the real one. (I’m actually kind of impressed that these motors from 1987 literally barely changed at all all the way until the 2000’s when two stroke carb engines were discontinued.  but the one on the 1988 suzuki dt15c is a mikuni

i guess suzuki nailed it so hard with these motors that there is no reason to ever change a thing. You’d be shocked at how well this motor runs.

[Hack_Fisherman]

30 minutes ago, AKRISONER said:

Hey guys, yes there is a hole along what I would call where the shaft of that screw is that you can see plugs when the screw is tight. For it to maybe be a drain makes a lot of sense? By loosening that screw that hole will open and allow gravity to drain the bowl.

the picture here is of a knock off cArb from alibaba that matches the real one. (I’m actually kind of impressed that these motors from 1987 literally barely changed at all all the way until the 2000’s when two stroke carb engines were discontinued.  but the one on the 1988 suzuki dt15c is a mikuni

i guess suzuki nailed it so hard with these motors that there is no reason to ever change a thing. You’d be shocked at how well this motor runs.

what I find odd, is why the spring? A spring means “setting”. No need if drain only. What’s the inside of the bowl look like? Besides the float and needle?

spealing of, could your float need adjusting? Could your float cause the carb to be flooding at idle/trolling speeds?

[AKRISONER]

16 minutes ago, Hack_Fisherman said:

what I find odd, is why the spring? A spring means “setting”. No need if drain only. What’s the inside of the bowl look like? Besides the float and needle?

spealing of, could your float need adjusting? Could your float cause the carb to be flooding at idle/trolling speeds?

Absolutely it may need to be adjusted/may be worn? It seems to function right but I honestly don’t know enough to know. Unfortunately I also looked heavily into just buying an entire new carb but cannot seem to find them anywhere.

this is where I wish I knew someone that knew more than I do about this stuff. I have no way of knowing if the float is totally out of whack or not.

this is the best I can do

strangely the manual doesn’t seem to even show this screw existing???

Edited May 4, 2021 by AKRISONER

[Fisherman]

I'm leaning towards the float needle not seating properly all the way otherwise there would be no flooding, #8 in the last picture. After so many years the rubber insert degrades/dries out and then it needs replacement.

[AKRISONER]

18 minutes ago, Fisherman said:

I'm leaning towards the float needle not seating properly all the way otherwise there would be no flooding, #8 in the last picture. After so many years the rubber insert degrades/dries out and then it needs replacement.

this is really not good news if the case. I have been trying to find parts/replacement carbs for this thing to no avail. 😢

[Hack_Fisherman]

5 minutes ago, AKRISONER said:

this is really not good news if the case. I have been trying to find parts/replacement carbs for this thing to no avail. 😢

No rebuild kits anywhere? 

what model and year is it? 

[Fisherman]

I'm going to swing on a rotten limb here, I would believe that a lot of small parts such as needles and the tiny rubber gasket are interchangeable with others.  Do you have a model number of the carb, maybe I can look too.

[Hack_Fisherman]

26 minutes ago, Fisherman said:

I'm leaning towards the float needle not seating properly all the way otherwise there would be no flooding, #8 in the last picture. After so many years the rubber insert degrades/dries out and then it needs replacement.

That makes more sense. I thought the carb was freshly rebuilt for some reason not just cleaned. 

[AKRISONER]

Here’s the parts diagram

also that “screw” says “adjuster” whatever it’s adjusting I’m not sure

 

Year, I believe is 1988...its a Suzuki DT15C

 

Edited May 4, 2021 by AKRISONER

[Fisherman]

Somewhere on that carb will be an identifier letter or number or both.  Found this and says those needles are in stock.  https://www.boats.net/catalog/suzuki/outboard-by-model/dt-15/dt-15elj-beginning-vin-01501-822034/carburetor

It shows the needle number as the same for all 4 models of carb.

Looks like it's a Mikuni B24-18 carb.  Adjustments can be found here towards the bottom of the page. https://www.slideshare.net/fudjfjjskwekmem/suzuki-dt15c-1988-outboard-motors-service-repair-manual

Edited May 4, 2021 by Fisherman

[AKRISONER]

1 hour ago, Fisherman said:

Somewhere on that carb will be an identifier letter or number or both.  Found this and says those needles are in stock.  https://www.boats.net/catalog/suzuki/outboard-by-model/dt-15/dt-15elj-beginning-vin-01501-822034/carburetor

It shows the needle number as the same for all 4 models of carb.

Looks like it's a Mikuni B24-18 carb.  Adjustments can be found here towards the bottom of the page. https://www.slideshare.net/fudjfjjskwekmem/suzuki-dt15c-1988-outboard-motors-service-repair-manual

Hey Fish,

So i did some more digging and cross referenced the Vin# to determine the year. I believe that it is actually a 1992 Suzuki DT15c

The Vin# is 01502-232014

 

I pull that up on boats.net and I get the carb assembly code - 13200-89E10

Low and behold all of the associated parts appear to be in stock except for the entire assembly. This is back to the original problem that I was having not being able to find any replacements for that exact assembly. So I guess I ask, is it really that difficult to change the float and needle valve? There was a reference to a sleeve, would that not be fitted into the assembly itself. Let me know what you guys think.

 

Maybe someone knows a guy that could either A show me how to do the swap/B is willing to rebuild the carb if i get the parts for it. I have no idea how to disassemble/reassemble the thing to that extent but am willing to try if thats what it takes.

Edited May 4, 2021 by AKRISONER

[Fisherman]

Easy to change the needle, remove the float bowl while the carb is upside down.  Reason, on most floats there's a tiny rod that holds the float in place,  next you can remove the needle from the float, there's usually a small clip that holds it in place.  Assembly in reverse order.  Where the needle goes in, you should see a very small rubber "O" ring that the needle seats against.  when you change that out, pay attention to the in/out direction, one side may have a circular ridge.  If you but it in backwards, the needle may not seat properly.  When you put the float bowl back on, careful not to pinch the seal.   I've left a plethora of blue streak curses in the garage the first time I did one.  So far I've done the gas auger, chainsaw, weed wacker, a few outboards and a few lawnmowers. 

[smitty55]

Once you get the float disconnected check to see if it has leaked and has gasoline in it. If so it will not float at the same level and not seal the needle valve completely. Just a thought.

[AKRISONER]

19 minutes ago, smitty55 said:

Once you get the float disconnected check to see if it has leaked and has gasoline in it. If so it will not float at the same level and not seal the needle valve completely. Just a thought.

I ended up buying a totally new float and needle valve, plus a new bowl gasket. I am slightly concerned that there’s no sleeve listed on the parts diagram for the needle valve. I’m hoping it comes with it!

going to give this a shot! Wish me luck!

thanks everyone that provided their two cents. Any more tips on how to do this work are certainly appreciated

[Hack_Fisherman]

Smitty has a good point. I’m sure nobody uses anything with cork floats in them anymore, but an old trick was to coat them in model aircraft dope to keep them floating. 
 

my useless trivia for the day

[Fisherman]

Well hope it all works out, I'm going to swing on a limb again and say of all the carb rebuild kits I've used, the needle always came with the little rubber "O" ring if that's what they're referring to as the sleeve.

[Fisherman]

Hahaha, I think Smitty, Hack and myself should open a carb rebuild shop.

[Fisherman]

One more thing before the end of the story,  once you have the new needle in there and float bowl, before you attach the cover,  carefully turn everything right side up,  gently raise the float and blow in the gas inlet.  You should not get any air escaping, once you let the float hang a bit, you can blow through it.

[AKRISONER]

5 minutes ago, Fisherman said:

One more thing before the end of the story,  once you have the new needle in there and float bowl, before you attach the cover,  carefully turn everything right side up,  gently raise the float and blow in the gas inlet.  You should not get any air escaping, once you let the float hang a bit, you can blow through it.

If this all goes horribly and I’m stuck without a working carb for this motor, I can assure you I will be reaching out to someone and begging them to let me bring them the carb to them to get it put together correctly.

im probably most nervous about adjusting the float’s level. There’s instructions but they aren’t exactly clear what you are actually supposed to do aside from ensure that the base of the float should be 23-25mm away from the top of the carburetor body flange...great except I have no idea what the carburetor body flange is lol 

and I hope you are correct about that needle valve o ring being included, part of me feels like it may not be because I am ordering everything as parts rather than as a “rebuild kit”

heck I couldn’t even find the part number for a new gasket to attach the carb to the intake manifold.

[Fisherman]

I'm probably most nervous about adjusting the float’s level. There’s instructions but they aren’t exactly clear what you are actually supposed to do aside from ensure that the base of the float should be 23-25mm away from the top of the carburetor body flange...great except I have no idea what the carburetor body flange is lol.

 

I've never had to adjust the float level, maybe lucky.  The flange is where the top of the float bowl itself meets body of the carb. 

As long as the float is resting "level" when the needle is fully seated up inside where it shuts off the gas, then you're fine.

Edited May 4, 2021 by Fisherman

[Big Cliff]

I think Smitty is on track but if you can get it to me I will check it out for you. My son is a marine mechanic so if Ican't do it I know a guy 😊

[AKRISONER]

1 hour ago, Big Cliff said:

I think Smitty is on track but if you can get it to me I will check it out for you. My son is a marine mechanic so if Ican't do it I know a guy 😊

Extremely generous of you cliff! If I can’t get it running myself I will definitely make the trip! I have a trip into the Bush planned at the end of the month so I gotta get this thing running smoothly by then so that it doesn’t strand me somewhere in the middle of bloody nowhere.