1998 Suzuki 25HP

[RTT231]

I recently bought a 1998 suzuki 25hp engine and i'm starting to tune it up myself. I rebuilt the carburetors and not knowing each high speed nozzle would be slightly different in each carb I mixed up the 1st and 3rd carb high speed nozzles. One nozzle has part # 23A stamped on it, the other has part # 108A. I was wondering if these numbers made sense to anyone since they do not correspond to part numbers listed at my suzuki parts dealer. # 108 A is slightly longer and the hole is bored out slightly wider than # 23A as well. If anyone can shed some light on this so I don't put the wrong high speed nozzle in the wrong carb I would appreciate it. Unless... both of these numbers are wrong and maybe the previous owner of the engine mixed up all 3 carb high speed nozzles.

Thank you

[Solarman]

After checking the parts diagram for a '98, dt25, it appears all 3 carbs have different jets, none seem to be your numbers, but all jets should have size numbers stamped on each to match the parts page?

According to this parts page, every jet, including the high speed nozzles & main jets, low speed pilot jets, air mix jets, (etc.) are all different numbers for your motor.

The dt25 service manual may give you more detail on the different jets for your carbs. But according to this parts page, from 1998-2000, each of your carb has different jets between carb #1, carb #2, carb #3, as described on the right side, for your jets.

It is possible, someone has changed the jets in the past, I doubt this is the first time the carbs have been cleaned.

The parts page I looked at is from browns point marine (click link below).



Fig. 6 - Carburetor - Suzuki DT 25C Parts Listings - 1989 to 2000


Good luck, sorry I can't help more.

[RTT231]

Thanks, I did by the owners manual and spoke with someone at Browns Point thats where i buy my parts. I guess the only real fix would be to order the high speed nozzles for my engine and see if they match up to the parts that i have. The numbers stamped on the parts were not referenced in the owners manual or on the suzuki parts website. Thanks anyway i appreciate it.

[RTT231]

Also, I looked at several diagrams on measuring the float height. My engine was running ok but started to stall a few times until it was warm. I measured the float height and it was about 15mm higher than it should be according to owners manual. Is that possible for the engine to still run ok with float height that far off ?

[Solarman]

It is possible that the motor would still run fine. The float measurement dictates the amount of fuel that is in the bowl. If the amount is too much then fuel will overflow the bowl and run out of the throat of that carb (that cylinder would then act like it is flooding out) when running. If to low then the motor will pull the fuel out according to the throttle until the bowl runs out of fuel. When it runs out that carb will affect performance at higher speeds (surging, or that cylinder dropping out from too little fuel).

Generally the high speed jets don't affect the motor running at about 2k RPMs or below. The idle, air mixture circuit, and computer should control from start up, and warmup until the throttle plates open to the point that a vacuum is created at the high speed nozzle, and fuel is pulled from there.

Good luck. Post back when able.

[RTT231]

Thanks for your help.

I put all three carbs back and adjusted floats so they were level when inverted. I was told by a reputable Suzuki mechanic that the specs for float height in owners manual are not very accurate. Specs for my engine were 12-14mm. At 14mm the floats were very low so I changed them all back untill they were level when inverted. I put all carbs back on and started engine. Third pull it fired up and sounded great. I noticed that starting was effortless and much easier than last year before I stareted working on it. I shut it down and started it again after couple minutes and it fired right up. I inspected engine and noticed the third carb was dumping a bunch of fuel. It looked like it was coming from the overflow but was hard to tell. It was a constant stream of fuel leaking out. I took all carbs back off and ordered all new gaskets for carb and bowls which I should have replaced from the start but they looked almost brand new.

Any Ideas why ??? all jets are adjusted the same 1-1 1/2 turns open and all floats are within 2 mm of one another but only the third carb was leaking. I also checked to see if pin was sticking when u invert the carbs and they seemed to be moving freely. Any help would be greatly appreciated. The coastal duck season opener is around the corner and now I'm scrambling.

Thanks

[Solarman]

What causes fuel to overflow is too high a float setting, or bad needle valve and seat. If you blow into the fuel line on your leaking carb that air has to stop going through the needle valve when the float is raised up to level. If air still goes through, so will fuel. If the air still doesn't shut off when you raise the float, then replace that seat and needle valve. It should not take much force to shut air off, remember that fuel lifts that float to stop the fuel.
If the top two carbs aren't leaking leave them alone.

Yes, the low speed jets should be the same for all your carbs. The factory engineered the motor that way, so if the manual says to set them at 1 turn out, set all carbs the same.

Good luck.

[RTT231]

Ok. Thanks for your help. Parts came in today ill be changing the gaskets and check the float height and needle valve again. Ill be putting it back together tomorrow and hope it works out. I get what your saying about the float height and needle and I understand how it all works getting fuel into bowl. Im just a little confused because all three float heights were above parallel when I took them apart and no fuel was leaking. Then I lowered them as to spec and then raised them back to parallel after speaking with a mechanic (still lower than they were before) at the dealer where I buy parts as he suggested. Thanks for your help. Ill let u know how it works out.

[RTT231]

I changed all gaskets and seals on carbs. They looked real old and fuel was leaking from my third carb after i put carbs back on and started it last week. I only changed the float height on third carb and put them back on engine. It would not start this time for some reason and previously it started on second or third pull. I used a little starter fluid because it was only thing I could think of to rule out some type of electrical problem. Fired right up. I pulled plugs and they were not very dirty I only had about 20 hours on them tops I changed them last season. Is there anything anyone can think of as to why its not starting now. It was just running last week and all I did differently was change float height minimally on the third carb and now it wont run without a spray of starter fluid. I know it can probably be a list of things. I even pumped out old fuel from filter before starting just in case and bowls were empty. At end of last season I also changed fuel filter, oil filter, and plugs. I just dont get why all I did was adjust float height on that third carb since it was a little higher than others and now it wont run when it ran before with a leaking carb. I know im rambling a little but this motor has me frustrated. im about to give up and take to a mechanic. But if anyone has any idea what might have happpend or something else I can try I would appreciate your insight. Thanks

[Solarman]

Try setting all idle air mix screws at 1 turn (what did the manual tell you to set them at?).

Give that a try and let us know. Good luck.

[RTT231]

Manual says 1 1/2 - 2 turns out. I did mess with them while trying to start it but always kept them between 1 1/2 and 2. It was weird because after it started with starter fluid I would let it sit for a while (15-20 min)then try again and it started right up no problem. But when it sits over night it wont start. It sounds like the kill switch is on when I pull the cord. It doesn't even sound like it wants to start. I'll give that a shot and see what happens. I know its really tough to diagnose a problem with out having engine in front of u but if u can think of anything else let me know.
Thank You

[Solarman]

I suggested one turn out from lightly seated closed because it sounds like it is too lean. Yes, it is difficult to feel your motor out from where i'm at. But you're adding a starting fluid (not good for 2 strokes because your motor needs premix, oil and fuel when it starts). So, by closing the air mix screws for each carb down to 1 turn, you are increasing fuel & oil mix, with less air (making idle setting richer).
Try running motor a little while with it richer. If your motor seems to smoke a little more that's normal. Then you can open each air mix screw 1/4 turn. Any further adjustment should be dictated by the color of the plugs after running a couple hours, should be a tan to chocolate color ( light, not dark).

Do you use the choke when first starting? And do you pump the bulb up ttyl firm? By sitting overnight, it could indicate you have a siphoning effect allowing fuel to return to the tank after extended periods? What type of choke do you have on your motor? If primer style, it may not be working? If manual lever that closes choke plates at the front throat of carbs, that usually requires several good pulls of start rope to provide fuel to motor.

Good luck, post back when able.

[RTT231]

Ok Ill give that a shot. My engine is oil injected I dont have to mix fuel. The choke is manual also. I usually dont have to choke engine unless its very cold. And I do pump the ball several times untill its firm. I tried a variety of things to start this engine and it just sounds like it doesnt want to turn over. When I give a little throttle while im pulling the cord the tone of engine gets muffled like it has too much fuel and flooded out. I will try adjusting the carbs like u said and get back to you. How many times would you pull the cord before u try adjusting something. I gave it about 10-12 pulls before i get disgusted and stop. lol The plugs after one season still have some white I can see but they are that light brown like u said. Ill post back soon.
Thanks again

[RTT231]

So with manual choke like I have u suggest choking engine for several pulls?

[RTT231]

Thanks a lot you saved me a good amount of money because I was ready to give up.
I think that solved my problem. I kept choke on, adjusted carb to 1 turn out, pulled cord roughly ten times, and it fired up. I turned air mix screw maybe just under 1/2 turn out looking for smoke. however engine was not smoking hardly at all unless when I rev engine. I didnt want to keep turning screw out because then I will be back at 1 1/2 to 2 turns again like before.
Now that i know it will start, stay running, and re start no problem. Is it normal for my engine to take that many pulls from a cold start or could something else be off, in your opinion? It re starts on first pull effortlessly even after it sits 10-15 min. One other thing I adjusted when engine was staling last year was the Idle speed screw. Is that or anything else critical to getting engine to start with less pulls or is that normal and I should just be happy with that?
Thanks