Should the boat die while out of water running on hose when I rev it?

[uraceulose]

I finally got one of the engines fired up on this thing, the other engine has two broken exhaust studs that I found.

My issue is that even after letting it run for a minute on the hose it wants to die when I rev the throttle up to about 1/3 throttle.

It’ll idle fine but once I open the throttle it wants to die unless I bring it right back to idle. Any ideas what I need to adjust or is this normal? I pulled all 4 carbs and rebuilt to the best of my ability. A couple of the fuel block screws I was unable to loosen even with an impact screw driver so I had to leave alone. The engines ran great before I pulled the carbs off and put them back on.

 

[racerxxx]

Gotta get the carbs apart

 

[uraceulose]

Color me surprised. What am I looking for if I’m able to get those screws out of the carb plate?

Like I said, it ran great before pulling them off and the ones I didn’t get all the way torn down are the same as when it ran good. I don’t understand why I need to tear into them when it was running good and nothing had changed on the ones I didn’t get apart but I’ll tear them back off. At this point I’ve had them on and off about 3 times in the last month.

What am I looking to adjust or clean out?

Are there any forum members you guys know of that will rebuild them?

I bought 4 carb rebuild kits but could only get into one side of 2 of the carbs.

Got one of the 2 broken exhaust studs out and I found that ground strap you were talking about in my other thread from one mag cover to the other. It’s easier to see with the pipe removed.
Getting those grounds cleaned up tonight and working on drilling the other one out.

The seadoo dealer here won’t touch 2 strokes any more and the local 2 stroke guys seem like they don’t know a lot about these motors. Dr Honda told me to keep away from them.

 

[uraceulose]

These are the screws I can’t get out on 2 of the carbs...

 

[uraceulose]

Seems as though it would be related to the jets and not the off idle performance especially while not under load? The way I understand it is that under that plate are the jets and I was able to replace the gaskets, clean out filters, clean out needle, seat as well as the low speed mixture screw/needle etc

 

[uraceulose]

Oh I also sprayed carb cleaner into the little holes in the throat of the carb to try and get some carb cleaner back up into the jets that way while I had them off.

 

[100dollarbill]

I had problems with those same screws. I used one of those screwdrivers that you whack with a hammer and it turns it 1/4 turn at a time.

 

[uraceulose]

Yeah that’s an impact driver..I have 2 of them and with my smallest bit still started to strip those soft screws. I don’t know what the heck I’m gonna do. Really don’t see how there is something messed up when I didn’t touch that area of the carb and it revved fine before pulling it off

 

[uraceulose]

I can drill the screws out if absolutely necessary and will go get a good small bit from the local metal yard if that’s the route I’m forced to go.

 

[uraceulose]

Ok another question, I’ve been tinkering.

When I run it on the hose using the idle setting method in the manual..it idles at 3500 rpm and wants to die when I open the throttle passed 1/3. But if I back off the idle screw and let it down to idle at say 2500 rpm on the hose disregarding the idle setting instructions in the service manual, then it will let me rev it up to 3500 rpm or so before it wants to die again.

My question is what should the idle speed be when the boat is out of the water running on the hose? And isn’t there some type of safety that won’t let it rev above 3500 rpm while in neutral? Each of these times when I’m running out of the water I’ve only had the boat in neutral.

Also, got the exhaust stud and broken bolt fixed!

Thank you guys for any more pointers or advice

Donnie

 

[mikidymac]

Those aren’t Phillips screws, they are JIS Japanese Industrial Standard so you need a JIS screwdriver for them and they won’t strip.

Spraying carb cleaner down the bore won’t do anything.

 

[uraceulose]

Thank you will get the JIS driver. I sprayed it backwards through the orifices into the jets not just down the bore..

 

[Sportster-2001-951C-Stock]

FWIW, some of the boats have a neutral rev limiter. That's probably not part of the issue you're working on now but just an FYI for later on.

 

[uraceulose]

Gotta get the carbs apart

Okay I’m pulling carbs tomorrow or Sunday. Once I get them apart what I am looking for?

If the other side engine runs well, I will probably send these 2 carbs off for professional rebuild but I want to take one more run at this.

 

[uraceulose]

Also, if it makes a difference...I Kept the oem stock needle springs in each carb to hopefully not mess with pop off pressure.

 

[racerxxx]

That's what you want. Just check everything, spray carb cleaner thru every port. Verify when you spray that the cleaner actually comes out the orifice(s). Make sure that little clear plastic check valve on the valve body is centered between the 2 little dots on either side. That check valve only goes on one way, I've seen carbs where people put it on wrong, that has to lay perfectly flat, if you over tighten the screw you can deform it, watch it as you tighten it. Test the check valve, I always hold my finger over the one hole in the valve and with my mouth test the valve works properly. Turn your low speed needle in slowly until it just bottoms out, count the turns in, then remove it. Blow carb cleaner thru it, verify the exit. Polish the brass needle with 0000 steel wool. I always put a little silicone grease on the threads of the needles before I install them. Install it, just bottom it out, then back out the correct number of turns per spec. Remove the hi speed needle, same thing as the low. Did you replace the needle and seat lever arm or did you reuse the original one? Did you check that it was level. Did you do a pop off test? Very important that the needle doesn't leak while pressurizing for a pop off test. If it leaks the needle and seat are bad, yes, even if it's brand new.

Google for mikuni sbn flow diagram or mikuni sbn parts and you can get the pdf that had the flow diagram, very helpful in understanding what goes where when you're cleaning and where you should be looking when spraying carb cleaner. Always wear safety glasses, it inevitably will spray back at you.

 

[uraceulose]

Thank you so much. I did leave the stock needle and seats in each one however I replaced the seat lever arms. I’ll double check that the arm is level as well as those check valves laying flat.
No, I did not check the pop off pressure. I don’t own a gauge that would work but I’ll buy one now and spend the $50.
It was one of those things where these carbs seemed really easy to rebuild so I kind of tore into it and tried to clean out the orifices then put it all back together and did one carb at a time.
Luckily now that I’ve been so far into this thing for a couple months now, and thanks to you guys here on the forum..it’s actually pretty simple to pull this thing apart.

When rebuilding, all I essentially replaced was the gaskets between each fuel block, case opening, cleaned everything out and got the check valves replaced on the 2 carbs that I was able to get the “jet block cover” screws out of. I also have a set of JIS impact screw driver bits on the way. If the screws are too stripped to remove, should I replace the carb or attempt to very carefully drill out and save the threads?

 

[uraceulose]

Ok so I got the carbs pulled back off today and had some time to dig in. Found that I had used the gasket that has the bigger of the holes in it of those holes on the top side of the photo. I’m pretty sure that I was supposed to use the smaller holed gasket?

Also, where the 2 round check valves (the circular ones not the tiny single one) are...is that supposed to be dry or wet with fuel? Mine was pretty wet but the engines were ran an hour before I pulled the carbs off and apart. The one on the left of the photo is the gasket I installed between the fuel pump block part and the carb body.

 

[uraceulose]

How do I test that little check valve for working properly? My pop off pressure tester should be here any day. I’ll check my service manual but do you guys have advice on what pressure I’m looking for it to pop off at? How do I use the tester?

Thank you again

Donnie

 

[uraceulose]

Getting it figured out. One of my check valves was floppy, one of the gaskets I had installed was the incorrect one as well. I also got the pop off specs out of the service manual. Also cleaned everything out really good and blew compressed air thru everything after. Used steel wool on the needles and synthetic grease on the needle threads per racerxxx and service manual recommendation.
I also was able to get the metering block off the one carb by banging on an old screw driver until it was able to get a bite on that screw. Also bent the needle lever/arm to where it was flat/straight like it should be.