96 Sea Doo XP800 - Flooding on Hot Starts

[Salt1972]

Our 96 Sea Doo XP800 has been in storage for 4 years. We emptied the tank, cleaned the filter / separator, replaced the fuel, new AGM battery, pulled plugs and flame arrestor - sprayed fogging oil, primed and started on the hose. Ran for 20 minutes-- flawless. Started on the trailer 15-20 times over the next 2 weeks. We could hardly get our finger off the starter button before it started. It can't be this easy, right?

We go to put it in the water. Pre-start on the trailer- check. Put it in the water and it won't start. Pull it out of water and it's severely flooded. Strong smell of fuel. Using full throttle and 30-50s of starter, we were able to get it started, but each subsequent hot start was severely flooded and required full throttle and excessive starter time before clearing black smoke and heavy oil/fuel residue out exhaust.

I assumed the needle/seats were leaking fuel and flooding. So, I pulled the carbs and rebuilt them with new Mikuni kits & needle/seats. Tested pop-off - no leaks. Re-install. Started immediately and ran on the hose for 5 minutes. Shut down. Go to re-start and it's FLOODED.

Where do we look now? Any ideas what might be causing this?

 

[kenfyoozed]

Did you do a leak down on the carbs to verify the diagram isn't holding open the needle valve?

 

[Salt1972]

Did you do a leak down on the carbs to verify the diagram isn't holding open the needle valve?

Thanks for your help Ken--

I'm not familiar with the leak down test. I did hold pressure with the pop off pump for 10 minutes and it held pressure - 20psi. My gauge only goes to 30, so I could not verify the actual pop off pressure, but Bill (??Watercraft Magic) used to help extensively on these and said the pop will be fine with the OEM spring. What we're looking for is no leaks / holding pressure. Is that the leak down?

 

[mikidymac]

Yes. If it holds pressure that’s not it.

If you ran it for 20 minutes and again 5 minutes on the hose you burned up your carbon seal driveshaft seal.

If it’s flooded when sitting it has to be a leaking needle and seat. I would also check your pressure relief on the gas tank. Try leaving the gas cap off in see if it still floods.

Something isn’t correct with your carbs.

 

[kenfyoozed]

The Seadoo Carb Rebuild Thread

post #8.... halfway through post.... leak down with the covers on....

where did you get your parts from?

 

[Salt1972]

post #8.... halfway through post.... leak down with the covers on....

where did you get your parts from?

I'll do the leak down test with covers on.

We purchased the rebuild kits on eBay from ATV Plus. The needle & seats were EBay > Bay Area Powersports.

We replaced the gray fuel hoses several years ago--- except for the on carb hoses. I changed those out today when I re-assembled, but I did not go to lengths to clean the green. I didn't notice any green anywhere except the external surface on the fittings. Sounds like I should pull them again and go through the cleaning and pop off tests extensively.

 

[kenfyoozed]

I would follow that carb cleaning thread extensively. Also were the carb kits genuine Mikuni ones?

 

[JeremyD615]

I’m not sure about the seller on your carb kits, but if they came in original Mikuni packaging they should be fine. Do they have the red anodized nipple on the diaphragms? If not, I’d get the correct kits.

On the needles and seats, I could be wrong, but I believe Bay Area Powersports sells aftermarket needles. That may be the source of your problem there...

 

[Sportster-2001-951C-Stock]

Both cylinders flooded or just one? Divorced fuel pump or on carburetor? If fuel pump diaphragm has a hole in it, fuel can travel from fuel pump through pulse hose into crankcase. All of above applies as well.

 

[Salt1972]

OK- Finally got some time to re-engage today. I started thinking about what @Sportster-2001-951C-Stock said about both cylinders flooding... it's not likely that both carbs would exhibit the exact same failure. I've also seen a few references to bad fuel selector valves. I'd never considered that might be the issue, especially since we had over fueling. To check the vent and selector:

1. Routed fuel line around fuel selector valve - Reserve to fuel separator/filter to carb.
2. Installed a new vent line.
3. Tested with fuel cap off

It seemed immediately better on the hose. So, we went to the lake. It was still sluggish to start, but would do so with full throttle. On top, everything runs GREAT. On low/mid, it's sluggish and sputters. It's possible that I didn't get the low speed circuit 100% clean.

Here are the remaining problems:

1. Hot starts still require full throttle and behave as if a little flooded.
2. low/mid circuit seems dirty.
3. We have a bit of cavitation on full throttle.

I don't know if running some Sea Foam has a shot at cleaning the carbs or whether I should bite the bullet and clean them.

No idea what's causing the hot start flooding.

Cavitation - it catches up and runs full speed just fine. It's only on acceleration from idle. There's no visible nicks or issues with the impeller.

Appreciate any and all ideas. Thank you for your help!

 

[mikidymac]

DO NOT RUN Seafoam! It will not fix anything and removes the lubricant from the engine parts.

Did you ever verify you used actual Genuine Mikuni carb parts?

Did you test carb pop-off and leak down?

Without the two questions we are just going to be chasing our tails here.

 

[Salt1972]

DO NOT RUN Seafoam! It will not fix anything and removes the lubricant from the engine parts.

Did you ever verify you used actual Genuine Mikuni carb parts?

Did you test carb pop-off and leak down?

Without the two questions we are just going to be chasing our tails here.

1. Check- No Sea Foam.
2. The bags / parts say Mikuni...
3. When assembling the carbs, I did a pop off test and they did not leak/held 15psi for 10 minutes. After starting this thread, I tested while the carbs were mounted on the engine by removing fuel supply / return, plugging return, and pressurizing supply. Again, they held 15psi for 10+ minutes.

Thanks for your continued help.

 

[mikidymac]

Try disconnecting the red wire on the voltage regulator in the front electrical box next to the gas tank. It is really common to fail on this year and can cause all kinds of strange symptoms.

I would also check the compression. The hard starting is troubling.

 

[GGuillot]

1. Check- No Sea Foam.
2. The bags / parts say Mikuni...
3. When assembling the carbs, I did a pop off test and they did not leak/held 15psi for 10 minutes. After starting this thread, I tested while the carbs were mounted on the engine by removing fuel supply / return, plugging return, and pressurizing supply. Again, they held 15psi for 10+ minutes.

Thanks for your continued help.

I've bought carb kits for my two 787 skis from bayareapowersports. Which kits did you buy? they sell from cheap aftermarket to genuine. The genuine kits I've purchased for a 787 run $136 w/OEM needles/seats.

Aside from the kits used, what spring was used? one from the kit? original? and what was the pop off psi on each carb? To err on the side of caution, I spent an extra $11 shipped for some 80 gram springs.
On both skis, both sets of carbs for the 787, I was getting 34-36 psi on pop off for each carb. I didn't adjust anything, the result so far has been no run issues, smooth transitions, starts easily hot or cold in the water or out.

 

[GGuillot]

2. Installed a new vent line.
3. Tested with fuel cap off

Check and clean the fuel vents (ck valves), they can gum and cause pressure issues in the tank, which in turn can cause run/start issues.

 

[Salt1972]

OK... So there used to be a guy called Bill @ Watercraft Magic-- He was the Sea Doo guru. Last time I needed these carbs built, I just bit the bullet and sent them to him. Is Bill still around?

 

[mikidymac]

Sadly Bill passed away around April. RIP.

PWC Muscle here does to carb rebuilds.

 

[Salt1972]

Sadly Bill passed away about a month ago. RIP.

PWC Muscle here does to carb rebuilds.

Sorry to hear. He was very kind and when those carbs arrived, the ski ran perfect for many years. I'm convinced there is an art and possibly sorcery involved in good carb work.

 

[Sportster-2001-951C-Stock]

Sorry I can't read all the replies so this may sound repetive but original poster needs to perform a pop-off test b/c it sounds like he's pig rich at low speed.

 

[Sportster-2001-951C-Stock]

Again, they held 15psi for 10+ minutes.

Thanks for your continued help.

If you must hold throttle near wide open to get a hot start going, this indicates there's too much fuel sitting in the crankcase. Holding the throttle open adds air as you crank, finally after pumping air through the crankcase the partial pressures of air to fuel will become within flammable limits of ignition and this allows it to fire off. Incorrect ratio outside of flammable limits cannot burn well, and difficult to ignite.

So it sounds like the crankcase is fuel flooded(ing). There are several things that can allow this to happen, many posts above suggested these. Also could be the low speed (idle) mixture screws are too many turns off the seat, this would load up the crankcase with excess fuel at low speed and the residual stays there until it evaporates away or gets pump out, which could be days if it's sitting, certainly not minutes.

An RV out of tolerance can result in hard starting b/c the engine isn't breathing properly, and low compression can as well. Don't forget, a bad battery can be an issue if voltage while cranking approaches 10V there's a good chance the ignition system doesn't fire the plugs. I trust you must've checked for spark and battery voltage while cranking during your hot restart troubleshooting.

If there was a lack of fuel from say a passage in the fuel system was clogged or not getting fuel for whatever reason then, squirting some pre-mix fuel in the carbs will get it to fire off. Then of course if additional fuel isn't supplied, it won't keep running.

 

[Sportster-2001-951C-Stock]

Yes good, if the metering needles are operating it's necessary. So too is a reasonable idle mixture else excess fuel
builds at low speed. There's a reason there's too much fuel, if this is the case, could be the fuel pump diaphragm is leaking, a hole in this diaphragm would send fuel down the pulse line into the crankcase, bypassing the carburetor. Easy to pressure test the fuel pump port with a few lbs of air pressure to confirm.

 

[POPPS]

Yes, had similar symptoms, rotary valve-clearance was off, (and so primary combustion/ compression) ,and after running (hot motor),was hard to start. Went thru 2 starters at the dealer before a seasoned racer diagnosed it for me.