DT115 Bogging after Fill-up

[ScubaSteve]

Long story short, motor was running fine on my way to the fuel dock.
After filling up, motor is bogging down around 4200 RPM. It will come down to about 3500 rpm and then surge back up.

I would immediately think water in the gas but perhaps it's something else.
Didn't appear to be any water in the separator filter.
Any other insight on what I should check? Fuel pump, fuel filter, carbs, primer bulb?
Primer bulb has given me issues in the past, but only around idle. Seems to lose pressure.

Trying to get my hands on a small portable tank, this way I can rule out the fresh gas as an issue.

[Solarman]

Yes, try the portable tank first, if not the problem, check the fuel pump, including the clear disc check valves inside. If those check valves are cradled/ broken, your pump will not supply adequate fuel to carbs at wot. Suzuki fuel pump kits do not have the check valves, but mikuni repair kits for Suzuki's seem to include them.

Let us know what you find out. Good luck.

[ScubaSteve]

Ran the motor on Friday.It starts fine but runs almost like it's on 3 cylinders.

I pulled the fuel pump apart and found that one of the clear disc check valves is completely cracked, as Solarman suggested. I'm guessing that this is causing the motor to flood and the pump is not supplying the correct amount of fuel at all RPMs.
Hoping to get a new pump from Browns Point this week as I can't find a diaphragm rebuild kit. Seems silly to spend $120 when all I need is a little clear disc.

[Solarman]

Did you check the mikuni site like I suggested, $20 - $30 for rebuild kit that has those discs?

Mikuni Fuel Pump Rebuild Kit D52-21 (DF52-176) (SKU 002-223)

Good luck.

[ScubaSteve]

Solarman, those gaskets only have 6 bolt holes.
My fuel pump has 8 bolts and then the one in the center.
Do you think the clear discs are all the same?

[Solarman]

Actually, I think I sent the link of the kit I believe was for my dt140. I hadn't even looked to see if it was for my motor fuel pump, our for yours? Was told it was for mine, but never looked?

If possible see if they have a different one that matches your pump exactly. Let me know what you find out.
Thnx.

[ScubaSteve]

Nobody carries a complete rebuild kit for the Suzuki pumps.
I have a complete fuel pump on order from Browns.
They offer the 2 large gaskets but not the smaller bits separately.
Hoping to have it by tomorrow and I will post the results of my next sea trial.

[Solarman]

Thnx Steve for pointing that out. Mine also has the 8 bolt pattern. But my pump had the mikuni name on top. Will see if I can find the number on it, and call. The price for new is outrageous for those little discs, they should be included in a rebuild kit. And, no i'm not sure if same discs in the 6 bolt kit?

Good luck with the new pump. I think it'll make a difference, and check hole (on motor) for any blockage before new pump goes on. Let us know when installed and tested.

[ScubaSteve]

Got the new fuel pump installed this morning and went for a test run.
Motor runs great, from idle to WOT.
Can't believe that little plastic piece is so vital to the fuel supply.

Side note: I e-mailed a supplier about the clear check valve discs.
Sounds like the dimensions for the discs are 4mm ID by 19mm on all of the applications. Planning to order some replacements and keep my rebuilt fuel pump as a spare.

[Solarman]

Glad to hear you're back into boating again. Yes, those discs don't last forever, but they are critical to proper fuel pump operations. Another thing is, when they crack, often they fragment, and usually those pieces will lodge on the backside of the needle valve seat blocking fuel flow into the float Chambers.

Good luck, happy motoring, and fishing.

[ScubaSteve]

I was reading about that exact problem on a different forum.
Lucky for me, my compromised disc was still completely intact