Air bubbles in fuel lines

[mejim707]

Make sure you test the carbs for leakdown once they are all back together. Should hold 10 psi for ever.

They do use very little oil, that is the beauty of oil injection.

Man, I thought I did this. They both pop around 35, and drop 5 or so PSI and seem to stay put. No bubbles and pressure seems to hold. If there's no bubbles, wouldn't that also suggest they're holding? Maybe I'll just go ahead and replace the needle and seats. The mikuni kits did not come with these. And they cost $55 a piece! I would have at least expected to get those parts with it.

Incidentally, the springs that come with these genuine mikuni kits are no good for these carbs. They don't seem to offer an appropriate pressure. The "black" ones in the carbs already are perfect however. Just an observation.

 

[mejim707]

This is when I tested them a few days ago.
MAG
Dropbox - Video Jul 03, 6 23 26 PM.mov - Simplify your life

PTO
Dropbox - Video Jul 03, 6 38 33 PM.mov - Simplify your life

Regardless I'm going to be pulling them and doing this again.

 

[Sportster-2001-951C-Stock]

I marked the oil tank level before heading out. how much oil can that tank hold? It's around half full right now.

I ran the boat for a little over an hour at idle to about 1/2 to 2/3 throttle for most of the time. I don't see much of a drop at all. I would think it would drop the level 1/8" to 1/4" after that amount of time. Maybe it's just me being naive. I'm also OCD so I'm going to pull the oil pump again to make sure the shaft is still secure lol I'm learning a lot but I had no idea how foreign these boats would be to me. It's good to learn though.

If you were to burn 12.5 gallons of fuel, a quart of oil should bring it back to your line. I don't know how much the oil tank holds but it's definitely more than a gallon. More than 1.5 gallons perhaps.

I agree if it wasn't oiling, you'd know it. Are your plugs at least brown or more likely very dark brown? Most of that brownish color is decomposed oil unless your carbs are very rich. Fuel is sooty black, the prevalent color when putting around.

Here are my plugs, they start off white they transition to yellow after about 20 minutes then begin to darken brown. These are after numerous hours of mixed speeds including mostly 20~30MPH cruising with some no wake speed, not a WOT plug chop:

 

[mejim707]

If you were to burn 12.5 gallons of fuel, a quart of oil should bring it back to your line. I don't know how much the oil tank holds but it's definitely more than a gallon. More than 1.5 gallons perhaps.

I agree if it wasn't oiling, you'd know it. Are your plugs at least brown or more likely very dark brown? Most of that brownish color is decomposed oil unless your carbs are very rich. Fuel is sooty black, the prevalent color when putting around.

Here are my plugs, they start off white they transition to yellow after about 20 minutes then begin to darken brown. These are after numerous hours of mixed speeds including mostly 20~30MPH cruising with some no wake speed, not a WOT plug chop:View attachment 42029

Thanks Sportster, I'll pull the plugs tonight and look. I was able to start it again last night when I got it home and let it sit for a little bit. Definitally fouling the plugs again even though the pop off tests looked good. I posted videos of the tests above.

Any suggestions on a good place to find replacement needle vales if I need to replace mine? Local shops need to order them and they're asking $35 a piece. Seems very steep to me. Amazon has part number "786-35015" but it will take many days to get it.

Thanks!

 

[mejim707]

I did fine this at the watercraft superstore. Seems like a reasonable price. I may just order the 1.5 from here unless you guys have a better suggestion.
Mikuni Super BN Needle and Seat

 

[JeremyD615]

Keep in mind that that one gallon of oil to 50 gallons of fuel is about what it should use at higher throttle settings and this is a variable rate system. At half throttle or idling around you will use far less than that... My Speedster for instance has a 2.5gal oil tank and I’ll go through seven or eight 26gal tanks of fuel before I have to even think of refilling it.

 

[mikidymac]

I did fine this at the watercraft superstore. Seems like a reasonable price. I may just order the 1.5 from here unless you guys have a better suggestion.
Mikuni Super BN Needle and Seat

No, the watercraft superstore are not genuine Mikuni!

Once you get the carb all back together and the diaphragm and cover on then you pump the carbs to 10 psi and see if they hold pressure. This will tell you if your needle and seat are leaking and is not the same test as pop-off.

 

[racerxxx]

No, the watercraft superstore are not genuine Mikuni!

Once you get the carb all back together and the diaphragm and cover on then you pump the carbs to 10 psi and see if they hold pressure. This will tell you if your needle and seat are leaking and is not the same test as pop-off.

It actually does say it's brand is Mikuni. It will come with a WPS sticker on the bag. I've ordered from there before, years back.

 

[mikidymac]

It actually does say it's brand is Mikuni. It will come with a WPS sticker on the bag. I've ordered from there before, years back.

Good to know Racer, you have to be careful with WatercraftSuperstore because they are owned by SBT and sometimes substitute SBT stuff.

Here you can see on there website it says "Brand: SBT" so be careful.
F


Mikuni SBN Replacement Needle & Seat Sea-Doo/Polaris/Yamaha/Tigershark

$14.95

Brand: SBT
SKU #: 709SB005
Shipping Weight: 0.10 pounds
Quantity in Basket: None

• Details
• Applications

1.2mm Needle & Seat Replacement for Mikuni SBN 38/44

 

[racerxxx]

I've ordered from Niche multiple times, kits, jets, needles and seats. Always in stock no messing around and always ships the same day I order. You just have know what you want and what you're looking for.

Niche Cycle Supply - NCS

 

[mejim707]

No, the watercraft superstore are not genuine Mikuni!

Once you get the carb all back together and the diaphragm and cover on then you pump the carbs to 10 psi and see if they hold pressure. This will tell you if your needle and seat are leaking and is not the same test as pop-off.

Thanks for the reply. Ok, I'll do that. I'll test pop off again tonight, then I'll reassemble and using the inlet I'll pump to 10PSI and let it sit.

Do you have any suggested suppliers to get the needle and seat if I need them?

If the needle and seats aren't leaking, is there any other way for the cylinders to flood? Again, if I turn off the engine one water and start it back up within a few a minute or so if fires right back up without issue. Thankfully, because I went to check the engine bay and it stalled while out pretty far. But if I wait 5 - 10 minutes it will not start. Get it back home and it starts.

Thanks

 

[racerxxx]

Good to know Racer, you have to be careful with WatercraftSuperstore because they are owned by SBT and sometimes substitute SBT stuff.

Wait, I did not order there. It was Atlantic jet sports. My bad. But..... WCSS is selling oem parts now too so I think they're upping their game. It's always a call away to find out if it's genuine or not. My bad Mik

 

[mejim707]

Keep in mind that that one gallon of oil to 50 gallons of fuel is about what it should use at higher throttle settings and this is a variable rate system. At half throttle or idling around you will use far less than that... My Speedster for instance has a 2.5gal oil tank and I’ll go through seven or eight 26gal tanks of fuel before I have to even think of refilling it.

Ok, thanks for that info. So maybe the fact the level didn't move much is ok. I'm not sure how much gas I used but the gauge still reads full so it must not be much. I don't know the size of my tank but it's not small. This is the part number for mine 275000145. It looks like it could hold 1.5 - 2 gallons.

 

[mikidymac]

Wait, I did not order there. It was Atlantic jet sports. My bad. But..... WCSS is selling oem parts now too so I think they're upping their game. It's always a call away to find out if it's genuine or not. My bad Mik

They are tricky, I just used their search for a generic 1996 XP and all the needle and seats that came up are the SBT brand not Mikuni.

I have just been buying them through Amazon Prime using the actual Mikuni number and they come as Genuine Mikuni in WPS bags.

 

[mikidymac]

Ok, thanks for that info. So maybe the fact the level didn't move much is ok. I'm not sure how much gas I used but the gauge still reads full so it must not be much. I don't know the size of my tank but it's not small. This is the part number for mine 275000145. It looks like it could hold 1.5 - 2 gallons.

They don't use that much oil. I typically get 5-6 full tanks of fuel (50 gallons) to one gallon of oil.

 

[mejim707]

Awesome thanks guys. I appreciate the links and suggested providers.

 

[mikidymac]

The number you want for the 1.5 is 786-35018-1.5 this has the new ethanol resistant tips.

I have been using the older 786-35015-1.5 with no issues but they aren't as ethanol resistant.
Amazon
NEEDLE VALVE SQUARE PUMP 1.5
by Mikuni
$16.95

• Made by Mikuni
• Mikuni # 786-35015
• 38-46mm Square Pump Super BN watercraft carbs.

 

[mejim707]

The number you want for the 1.5 is 786-35018-1.5 this has the new ethanol resistant tips.

I have been using the older 786-35015-1.5 with no issues but they aren't as ethanol resistant.
Amazon
NEEDLE VALVE SQUARE PUMP 1.5
by Mikuni
$16.95

• Made by Mikuni
• Mikuni # 786-35015
• 38-46mm Square Pump Super BN watercraft carbs.

Nice thanks! I’ll probably end up getting these anyway but the delivery takes so long. I won’t get them for a week or more :/

 

[mejim707]

The number you want for the 1.5 is 786-35018-1.5 this has the new ethanol resistant tips.

I have been using the older 786-35015-1.5 with no issues but they aren't as ethanol resistant.
Amazon
NEEDLE VALVE SQUARE PUMP 1.5
by Mikuni
$16.95

• Made by Mikuni
• Mikuni # 786-35015
• 38-46mm Square Pump Super BN watercraft carbs.

One quick thing, if you have a moment can you take a look at those two videos I posted earlier? Just a few posts back. Drop box links.

When I conducted the pop off test it seems as though it popped two times in a row. I watched someone else’s video and it popped one time and not twice. I’m wondering if this is causing more fuel than is needed to get into the cylinders,.

Sorry for all the questions and being a pain. I really appreciate all the help you all have given. Yesterday was mostly a success and that would have been possible without this great community!

 

[mikidymac]

The double pop is very strange. I haven't seen them do that. I also use a lower pressure gauge so it is easier to see the exact pressure it pops, like a 0-60psi.

Put a paper towel over the carbs so it doesn't spray WD-40 everythere when it pops.

The big thing is you want it to pop clean and fast then immediately hold pressure, not hissing and leaking off the pressure after it pops.

 

[racerxxx]

The closer the gauge is to your working pressure is the most accurate. But I believe I use the 0-60 genuine mikuni pop off tester not the 0-30.

 

[mejim707]

Ok, pulled carbs again and did the pop off test on the mag. Not looking good fellas. I guess after that day out it’s now showing it’s true colors.

Sometimes it seeps then pops a few times. Or it just pops two times in a row. I’m not sure what’s up with this. I’ll get the new valves but this multiple pop thing is concerning.

I will say though, once this issue is sorted it’ll probably run like a beast.

One other note, while out the boat took on no water. Is this normal? I thought it was supposed to take on a little to cool a bearing if it’s a carbon bearing. If it’s not a carbon bearing is there something I should be greasing?

The more I learn the more I question.

 

[Sportster-2001-951C-Stock]

No worry if you don't see water in the bilge, that's very good. There's usually a little in my bilge, about a cup seems like. The carbon seal usually leaks a little but doesn't have to, the water around the drive shaft inside the rubber bellows cools it.

It's a good idea to replace the needle and seat when the carbs are being rebuilt, the rubber tip takes on a minor groove and begins to stick in the seat. The rubber tip is also impregnated with graphite which wears off.

 

[mejim707]

I’d like to get your guys opinions. I went to a local Sedoo repair shop. The guy said you can intermingle the 1.2 and 2.0 needle and seat kits. Also said all needles are the same so I could use them in my current seats. He looked at the needle tips and said they look fine.

He also said pull the low speed and high speed adjustment screws out, blow out the ports then reinstall them until they’re seated. Turn the low speed ‘T’ out 1.5 turns and the high speed out ‘just a crack’. Not sure what that means.

Thoughts?

 

[racerxxx]

Ask yourself this....Do I really want to pull these again for the 25th time? Lol. I would never mix parts, to his eyes they might look great, to a pop off test they might look different. No, you need a 1.5 not a 1.2 or a 2.0, but the right one, the 1.5, that's why they make it. The needle is provably the same but the hole in the seat is different. It's really not worth the headache if you ask me. Literally what's another weekend or 2 until you get the right stuff. I know weekends are scarce, weather, blah, blah, blah. I'd rather my boat be top notch. Sorry to sound negative, but that's my opinion.