Starts great, runs great, 5 minutes later dies

Discussions about AS400, AS450, AS500, AS600, AS650, AS650CE
Chicago_AS600
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Joined: Wed Aug 16, 2017 5:08 am

Starts great, runs great, 5 minutes later dies

Post by Chicago_AS600 » Mon Aug 21, 2017 11:24 pm

I have a AS-600 I picked up on eBay and have since rebuilt the carb, starter assembly, new fuel lines, new spark plug, and new exhaust valve. It starts great - one pull w/ choke on and then flip to run and fires on the 1st or 2nd pull. I rev it up a bit and then go. It will run great for about 5 minutes and then it will just die while underway (not from going full throttle to idle). Won't re-start but after an extended time it fires right back up. Last week I had it working great - out 4 times ranging from 10-25 minutes. Saturday on the 2nd trip out this behavior started. Did the same thing a couple times Sunday. I pulled the spark plug - it looked good and no water in the engine. Took the starter assembly off - nice and dry inside so the ignition isn't getting wet. I also topped off the gas tank thinking it was related to the level of fuel in the tank. No changes. Any idea where to look next? Thanks.

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Hec In Omaha
Posts: 32
Joined: Thu Sep 15, 2016 3:14 am
Location: Beaver Lake, Nebraska USA

Re: Starts great, runs great, 5 minutes later dies

Post by Hec In Omaha » Tue Aug 22, 2017 5:56 pm

Chicago_AS600,

Welcome to the forum!

Things to check


* Make sure the Aqua Scooter is air tight! Fill up a bath tub with water and set the aqua scooter in the water and submerge it. Now blow as hard as you can into the snorkel tube. Actuate the throttle a couple of times while doing this. You should only get bubbles coming out of the exhaust. Nowhere else! Check for bubbles at carb gasket, carb elbow hose clamps, hoses, starter housing etc.

* Take a look at the large tube that runs on the right side of the tank. It has a u shaped trap in it. Is there fuel laying in the trap? If so then you may be missing the little duck valve that's installed in the small hole in the filler neck of the tank. The duck valve prevents fuel from sloshing into this vent line. The large line is how the fuel tank is vented to atmosphere. If fuel fills the trap, the tank will not vent properly, and therefore stop the flow of fuel to the carb. This line must remain clear of fuel!

* Check your carb settings. The jet screw closest to the engine controls idle Air fuel mixture. The jet screw that is closet to the tank (Forward Most) controls the high speed Air fuel mixture. I normally start out with each screw at 1-3/4 turns open. Once started I will adjust the idle jet screw first. Turn the idle jet adjusting screw Clockwise until the engine speeds up (Leans out) and then begins to die. Count how many turns of the screwdriver was needed to get the engine to stumble. Stop the engine! Then repeat the procedure from 1-3/4 Turns open but this time open the screw (Counter Clock wise) until the engine begins to stumble. Once you know how many turns open and turns closed are needed to get the engine to stumble you can set the screw to midpoint between those settings.
The high speed jet is adjusted by holding the throttle down and either opening and closing the high speed air fuel screw until max RPM's are achieved. Once max RPM's are found open the screw about 1/8 turn to ritchen the mixture a bit.
The idle stop screw is adjusted so that the engine will continue to idle with out dying in the water. You set this after the air fuel adjustments are done. My Idle stop screw is just about fully screwed in.

Lake Michigan is cold! So if you allow the Aqua Scooter to idle for over 20 mins with out revving the engine, water will accumulate in the muffler chamber and eventually stall the engine. Remember that water is a by-product of combustion. I hold the nose up and gun the throttle every now and then to make sure this doesn't happen.

Keep us posted!

Hec
If its not broken, then I can't fix it!

Chicago_AS600
Posts: 16
Joined: Wed Aug 16, 2017 5:08 am

Re: Starts great, runs great, 5 minutes later dies

Post by Chicago_AS600 » Tue Aug 22, 2017 8:05 pm

* Take a look at the large tube that runs on the right side of the tank. It has a u shaped trap in it. Is there fuel laying in the trap? If so then you may be missing the little duck valve that's installed in the small hole in the filler neck of the tank. The duck valve prevents fuel from sloshing into this vent line. The large line is how the fuel tank is vented to atmosphere. If fuel fills the trap, the tank will not vent properly, and therefore stop the flow of fuel to the carb. This line must remain clear of fuel!
I definitely have some fuel in that line on occasion....but the parts diagrams indicate the duck valve is only for late 400s?? Or is that when it started? I have a 600? Do you have a picture of one by chance?

No leaks or bubbles anywhere there shouldn't be.

I don't let it idle much at all - usually full throttle all the time!

Working on carb adjustment tweaks but I think I'm pretty close. Starts easy and runs well...until it dies several minutes later (which is a new issue that started this weekend).

Thanks

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Hec In Omaha
Posts: 32
Joined: Thu Sep 15, 2016 3:14 am
Location: Beaver Lake, Nebraska USA

Re: Starts great, runs great, 5 minutes later dies

Post by Hec In Omaha » Tue Aug 22, 2017 8:59 pm

Chicago_A600

The duck bill valve is definitely supposed to be there on an AS600. Remove the fuel cap and you will see a molded section in the tank with a small hole in it. It's like a small protrusion that makes inserting a gas can spout a Pain in the A$$! The little rubber duck bill valve is inserted into that small hole with the pointed end facing up. The duck bill valve looks like a miniature pencil eraser that you slide over a pencil. You know the one that looks like a little pyramid. At the top of the pyramid there is slice in it to allow vapor flow through it. I will post of picture of mine when I go home tonight. One thing that could also be causing your problem is a bad ignition coil. Bad ignition coils will work when they are cool and quit when they heat up. Then they crap out all together.

During the carb rebuild did you set the height of the little lever that actuates the fuel pump diaphragm? Its height should be level with the carb housing machined surface. Also make sure the O-rings behind the air fuel adjustment screws are in good shape.

Also apply some dielectric grease in the spark plug boot and then put the boot back on the spark plug.

How are the internal fuel lines inside the tank? If one of those has a small crack it will cause you problems.

Hec
If its not broken, then I can't fix it!

Chicago_AS600
Posts: 16
Joined: Wed Aug 16, 2017 5:08 am

Re: Starts great, runs great, 5 minutes later dies

Post by Chicago_AS600 » Tue Aug 22, 2017 10:45 pm

Thanks for the quick reply.

I do recall the area under the gas cap - just can't picture exactly what mine looks like. Left the AS at the harbor. Will check it out tomorrow. I know I'm getting fuel in that line though - easy to tell with the new yellow tygon tubing vs. the original green tubing. Hopefully that is it. Perhaps I knocked it off while filling the tank? Do you know if there is any commonly available replacement vs. ordering from Aquascooter in AZ?

Anyway to check the coil?

I set the level on the carb following the Walbro HDA instructions. I should be good there. The kit did NOT include o-rings for behind the needle valves though.

I did put grease on the spark plug.

Internals in the tank is a possibility also. I have a USB scope camera I can stick in there after emptying the tank.

Had a blast last week when I got this thing running. Was surprised Saturday when it started acting up late in the day.

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Hec In Omaha
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Joined: Thu Sep 15, 2016 3:14 am
Location: Beaver Lake, Nebraska USA

Re: Starts great, runs great, 5 minutes later dies

Post by Hec In Omaha » Wed Aug 23, 2017 1:50 am

Here are the pictures I promised.
The blue line is connected to a hose in the tank that is connected to the duck bill valve well. You could simply disconnect the forward end of the large hose and suck on it to see if you draw fuel in it. If you do you may have cracked internal tank hose or missing duck bill valve. Make sure the large hose didn't get pinched between the engine and fuel tank when you installed the tank! Been there done that!
Replacing the ignition coil is job best left to someone with the proper tools. A special Flywheel puller is required to remove the flywheel. Don't try it without it! If you need an ignition coil, upgrade to the new style. I hope this helps!

One more trick to try. The next time your AS600 acts up and wont start, try holding the throttle open and blowing real hard into the snorkel tube. This will purge out any excess fuel vapor from the air side of the tank and engine. Excessive vapor in the air side of the tank is also an indication of either a missing duck bill valve or internal fuel line issue. Worst case it could also mean that there is a breach between the fuel side of the tank and the air side of the tank. If you see fuel laying in the air side its time to start investigating how its getting in there.

By the way what color tank does your AS600 have? This will help narrow down how old it is. They originally came with orange, then yellow/green, then red & white.

Hec
Attachments
IMG_5532.JPG
Duck Bill Valve Removed on a toothpick
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Duck Bill Valve
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My AS600
If its not broken, then I can't fix it!

Chicago_AS600
Posts: 16
Joined: Wed Aug 16, 2017 5:08 am

Re: Starts great, runs great, 5 minutes later dies

Post by Chicago_AS600 » Wed Aug 23, 2017 4:02 pm

The one on the left is mine. We are guessing it's a late 90s build b/c the one on the right was purchased by another guy on the dock in the mid 90s. The serial # on mine is a lot higher (assuming serial #s are sequential - which we don't know). Do you know if the tank halves can be split on this style?
2_AS600s (Small).JPG
Two AS-600s
I'm also working on a AS-450 for a different guy on the dock. It hasn't been in the water for 30 years. After your message I looked inside the gas tank. The vent line inside of the tank is disconnected. I also pulled his duckbill valve and shot some photos. I'm bet the line in my tank is loose also - or I'm missing the valve. Will know for sure later today. Hopefully I can get his line replaced and in the water soon. The tank on his is orange and molded in one piece out of a textured (vs. smooth like the 600) plastic. Inside line replacement may be difficult.
Duckbill1 (Small).jpg
Duckbill1 (Small).jpg (59.04 KiB) Viewed 2198 times
duckbill2 (Small).jpg
Last edited by Chicago_AS600 on Thu Aug 24, 2017 3:19 pm, edited 1 time in total.

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Hec In Omaha
Posts: 32
Joined: Thu Sep 15, 2016 3:14 am
Location: Beaver Lake, Nebraska USA

Re: Starts great, runs great, 5 minutes later dies

Post by Hec In Omaha » Thu Aug 24, 2017 2:58 am

That AS 450 will require a complete tear down and reseal. I will replace all bearings, o-rings, seals, hone the cylinder ( if it isn't scored up bad),install new piston rings (if piston isn't scored up) on anything 5 yrs or older. 30 years of sitting will result in cracked seals. The rear prop shaft housing is packed in marine grease. I bet that's all dried up too. While you are at it, I would upgrade the front and rear crankshaft bearings to fully sealed ones. I think the old AS450's have a point type ignition system like the AS400's. I would upgrade that as well.

The tank hoses are tricky to replace. You will need forceps and flexible wire. The wire is inserted into hose connections in the tank then the hose is slipped over the wire to guide the hose over the connection.

I believe the tanks have an upper and lower half either fusion welded or glued together.
Good luck and keep us posted!

Hec
If its not broken, then I can't fix it!

Chicago_AS600
Posts: 16
Joined: Wed Aug 16, 2017 5:08 am

Re: Starts great, runs great, 5 minutes later dies

Post by Chicago_AS600 » Thu Aug 24, 2017 3:13 pm

Had the AS-600 running at 1:00 yesterday! I used weed wacker line to feed thru the bottom vent hole and ran a new hose down the line and forced onto the inside tube nipple at the bottom. On the top I used forceps. I also tuned it w/ a tachometer to achieve the highest RPM. Works great.

I had the AS-450 running also - but had a fuel leak. Need to pick up some more fuel line....I was just short of line and gambled the old line would work. Should be going shortly. It had great compression and spark before I had started the re-awakening so I don't think I need to tear it down that far. I'll evaluate after running a bit and take another look at the seals. Front was replaced.

Thanks!

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Hec In Omaha
Posts: 32
Joined: Thu Sep 15, 2016 3:14 am
Location: Beaver Lake, Nebraska USA

Re: Starts great, runs great, 5 minutes later dies

Post by Hec In Omaha » Thu Aug 24, 2017 3:21 pm

Great news! So did that solve the AS600 stalling issues? By the way, I have seen the same duck bill valves underneath weed wacker and chainsaw gas caps. If you have a source for old lawn equipment parts you may get lucky.


Hec
If its not broken, then I can't fix it!

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