yet another carb spring/popoff psi question

[PatinMD]

Ran the ski on hose today, checking rpm and making sure everything is good to go on the water.

FNG disease hit when I saw the rpm hitting over 11K when I goosed the throttle. A little research and I realized the Tiny Tach I was using is for one spark per revolution engines. And it's not reset-able, as far as I can tell. It's model 2B. For anyone following the saga here, that means I've been setting the carb for a true low rpm of 1500 out of water (while it read 3K on tach). And the last time I had it on the water, it was idling at 10 - 11K not the 15K it should have been. Now that the idle rpm is set at 6K per the tach, the engine starts better and runs smoother.

FNG disease. Some experiences are harder to learn than others.

Looking for the next kind of warmer day in the future. Nothing in the 50's for the next week though.

 

[Mickirig1]

Learn something everyday. The more you learn, the more you know. I have chased problems on anything I own. It's never garden variety problems. Get the right pop off. The springs are out there.

 

[PatinMD]

Mickirig1,
thanks for the response.
I've given up on the spring. It took three purchases until i finally got a Sea Doo packaged spring, unopened, with the correct part number printed on the package, from a Sea Doo parts dealer. And the spring gave the same pop off psi as a 115 g spring, which was what I received on the second order. At 12$+ a try, I can't buy one from every business that says they have one, just to try it out.

In my research I read that when building one model of ski, even Sea Doo used 95 g springs with a .2 mm spacer (or some such small piece) under the spring to give it the same pop off as a 130 g spring, until they had the 130's manufactured.

If the ski runs almost perfect when I get it out, then I'll try to stretch the spring a little more to get to the 36 psi pop off. At this point, I'm looking to get it to run without shutting down in the first 10 minutes. I"ve grown to hate getting towed back...

 

[howie099]

To bad u can't find the spacer. It is always a $5 part that holds u back.

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[digital sol]

FYI: These guys are way cheaper than any dealerships for springs or any carb parts. Might be worth shooting them an email to see if they have or can get it. They were super helpful to me in the process of my rebuild and/or ordering carb parts the last few weeks.

http://www.jet-world.net/

 

[PatinMD]

thanks. I'll check them out.

 

[Strizzo]

wow, i guess that explains why it didn't want to idle in the water! i'd be surprised if the tach you have isn't able to be changed over to 2 sparks per revolution, even the cheapo $5 one i bought off of ebay could be changed to 2 sparks per rev.

 

[Sportster-2001-951C-Stock]

If it quit running after 10 minutes and wouldn't restart, I hardly think that was due to pop-off spring. Unless maybe it wasn't running quite right from the beginning and got worse as the cylinders came to temp.

An overheated engine will get tight and stop running. I've seen plenty full of sand in the cooling jackets that would run maybe 10 minutes before losing power.
An engine that's not getting fuel from the tank after 10 minutes will stop running. Fuel tanks that aren't able to fill with air to replace the fuel being sucked out of the tank will create an internal negative vacuum the fuel pump can no longer overcome. Loosen the fuel cap as a quick test, leak check all fuel line connections and pump (using an el-cheapo electric fuel pump good for transferring fuel, I used one yesterday to empty my fuel tank for winter) a tank of fuel through the tank if necessary to make sure it's not sucking air.

Could be the ignition system breaking down, those CDI units are getting older now. This is where a spare parts ski comes in handy. Or, a spark checker. Squirt a little pre-mix down the carbs, it should at least bark on that.

An overheated tight motor is often hard to crank.

Too much fuel or not enough, it's not clear to me by reading the thread problem descriptions.

 

[AdamXP800]

I haven't/can't read this entire thread. Something is not right here. There is no reason why this ski should not run with the stock carb set up. Why were you changing springs and all in the first place?



95 XP800!!!
Keep the 2 strokes alive!

 

[howie099]

something is wrong a 115g spring and 2.0 needle gives you a 32 pop off on the mikuni chart. If you are at 25 something has to be wrong. Maybe the arm? Take the old arm from the old carb and test it.

 

[Sportster-2001-951C-Stock]

Could be, the pressure gauge is out of calibration too.

Even so, too low of pop simply means you'll have fuel coming on sooner, lack of fuel won't be the result.

So the OP needs to determine if his carbs are passing too much fuel or if there's lack of fuel then go from there based on the symptoms, no need fooling with pop springs absent some diagnosis of the symptom.

 

[howie099]

If u take the spring, arm and jets if need be with the proper 2.0 needle u don't even need really check the pop off. It should be in spec. I don't think I ever had to adjust pop off unless I replaced a spring or arm.


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[PatinMD]

The stock carb had one correct jet, one wrong jet, and the wrong spring and nozzle.

 

[PatinMD]

I finally got the ski out today. It went in the water and started just fine. It was running at idle of 1500 rpm as it should. It idled out of the harbor (4-5 minutes) then I opened it up to about 4000 rpm. It ran that way, nice and steady, for about 2 minutes. Then it died. It acted like it was fuel starved, I thought. But it could have been flooding. It died slowly, over about 5 seconds. The rpm's just dropped off until it stopped running. My instinct, hearing the rpms drop is to give it more throttle, which is what I did but there was no effect (although maybe it made it run longer as the rpm's dropped??)
I let it sit for about a minute, then it started right up again, ran steady at about 4000 again for 30 seconds, then died again. Waited again, but it didn't want to start. Finally it started again and instead of running at 4000, I gunned it to almost WOT. It ran for about 5 seconds before dying again. I waited again and tried it but it didn't want to start. Then it wouldn't even turn over. I waited again for about 5 minutes and it would turn over but wouldn't start.
I towed it into the harbor, and it still wouldn't start. By the time I got it home, it started on the hose and ran just fine. I noticed that it did hesitate badly before the rpm's ramped up if I gunned it quickly while on the hose.

I've pressure tested the fuel system. The gas is new. The oil was replaced with what I know is the correct oil. I replaced the carb. The carb has the correct jets and nozzle although the pop off is a bit low at 32 when the specs call for 36-40, but I've been told that much shouldn't keep it from running. The compression test was 140 and 145 if I remember correctly. The spark plugs are new. I cut the end off the plug wires and reseated the plug boots. The battery is 3 months old and was charged before it went into the ski. It's been charged since then after sitting for more than 30 days.

This ski was running when I bought it a year ago. It ran for 30 minutes or so at all throttle positions.

Any ideas?
One i'm toying with is the oil pump isn't putting out enough oil and the pistons are heating up and expanding. But I don't even know if that is possible without destroying the engine the first time it happened.
Someone asked if the fuel lines could be collapsing as the carb pulls fuel from the tank. I've looked at the lines and they look fine.
I keep looking at fuel issues. I can't think of any electrical issues that would occur with this pattern.

thanks in advance

 

[eavega]

Taking a stab in the dark, not knowing much about seadoos (but have wrenched a bunch on outboard motors), it definitely sounds like a heat expansion related issue. I wouldn't think its the pistons expanding, because if that happened it wouldn't even turn over. If it was fuel starvation, wouldn't it surge as the piston leaned out? Just a thought.

In the outboard world, behavior like that would point to doing a spark test either with an inline spark tester or a timing light. As the motor components warm up and expand, something may be shorting out. It can cause either a weak spark or no spark condition. Weak spark could flood the engine as it can't burn off fuel at WOT delivery rates efficiently. As the engine cools off and metallic components contract again, the short disappears.

You may not be able to run the ski on the hose long enough to get it to warm up and cause the fault, but its worth a try. Start the ski up at night or in a darkened environment, and observe the engine compartment. If you are arcing somewhere, it may be visible. Of course if its the coil or stator, it won't be as apparent.

Like I said, I don't know a ton about troubleshooting on seadoos, but I have had more than my share of outboards cross my work bench. The basics are all the same; engine needs fuel, compression, and spark. One of the three is causing the motor to not run.

Rgds

Eric

 

[howie099]

Did you pressure test it after you got home to verify the compression still the same? When the RPMs drop like that it is usually a fuel issue or you are loosing compression on the engine. Since you said the ski ran fine until you did a carb rebuild/replacement? That is correct?

 

[PatinMD]

If it quit running after 10 minutes and wouldn't restart, I hardly think that was due to pop-off spring. Unless maybe it wasn't running quite right from the beginning and got worse as the cylinders came to temp.


An overheated engine will get tight and stop running. I've seen plenty full of sand in the cooling jackets that would run maybe 10 minutes before losing power.
An engine that's not getting fuel from the tank after 10 minutes will stop running. Fuel tanks that aren't able to fill with air to replace the fuel being sucked out of the tank will create an internal negative vacuum the fuel pump can no longer overcome. Loosen the fuel cap as a quick test, leak check all fuel line connections and pump (using an el-cheapo electric fuel pump good for transferring fuel, I used one yesterday to empty my fuel tank for winter) a tank of fuel through the tank if necessary to make sure it's not sucking air.

Could be the ignition system breaking down, those CDI units are getting older now. This is where a spare parts ski comes in handy. Or, a spark checker. Squirt a little pre-mix down the carbs, it should at least bark on that.

An overheated tight motor is often hard to crank.

Too much fuel or not enough, it's not clear to me by reading the thread problem descriptions.

The ski ran for a good 30 + minutes during my trial run before buying it. It hasn't been run in anything but deep water since. Actually, it hasn't been run more than 15 minutes straight since I owned it. First trip out after purchase (which was 6 months after buying it), 15 minutes no problem with throttle, then it stopped running. I then found the carb was badly corroded as I started trying to fix it.
I've pressure tested the fuel system. But that is keeping air in, not bringing air in. I did open the fuel cap the second time it died and it didn't make a difference.

I can easily put a spark checker on it.
I'm sitting here thinking. If it was the (lack of or weak) spark, I would be pumping gas thru the engine and out the exhaust. But I don't remember smelling gas as I cranked the engine (a lot of cranking when it wouldn't start).

Squirting pre-mix after it dies and won't start would answer if it's a fuel problem. Thanks for that one.
I'll also look into methods of testing the CDI units. Although the spark tester would help with that.

It was hard to turn over right after dying. But after a bit, it would turn over fine, just wouldn't catch. It was as if it didn't have a spark or didn't have fuel - I mean it wasn't almost catching, it was just spinning from the starter.

Good stuff you put out there. Thanks

 

[AdamXP800]

A weak battery will cause it not to fire also



95 XP800!!!
Keep the 2 strokes alive!

 

[PatinMD]

Did you pressure test it after you got home to verify the compression still the same? When the RPMs drop like that it is usually a fuel issue or you are loosing compression on the engine. Since you said the ski ran fine until you did a carb rebuild/replacement? That is correct?

I did not pressure test it right after it stopped running. Then it ran fine once I got home.
The ski ran for 30+ minutes during the trial run before purchase. 6 months later when I tried to run it it stopped running after 15 minutes. When I tried to rebuild the carb, I found it in such a state that I don't know how it was running at all. I couldn't rebuild it and I had to replace it. The replacement needed different jets and N&S.

Thanks

 

[PatinMD]

A weak battery will cause it not to fire also

Can the battery be weak enough to turn the starter (and engine at a regular speed, not slowly) but too weak to create spark?

 

[howie099]

If u have a bad or weak battery it won't start.

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[PatinMD]

I'll check to make sure the battery is being charged while the engine is running. I can do that on the hose.
thanks

 

[Sportster-2001-951C-Stock]

I'll check to make sure the battery is being charged while the engine is running. I can do that on the hose.
thanks

You should see at least 12.5 volts at the battery before anticipating it will start, if voltage at the battery drops under about 11V while cranking there's a good chance there isn't enough voltage to operate the CDI ignition. Remember, even if there's enough high voltage to jump the spark gap in open air, this might not happen during the compression stroke, it's more difficult since plug voltage must be higher across the gap during the compression. Usually in this case though, the problem is the plug itself (ie: the voltage rises enough to either jump the gap or bleeds down the side of a contaminated ceramic center electrode insulator).

Since the first 30 minutes of the water testing went well, I'd say the carburetor calibrations were correct and you should go back to where those were. Also, this means the cooling was adequate.

I don't recall if this ski has the DESS system or the older simple lanyard switch but the older simple lanyard switches were notorious for poor connection in the switch and often were found to be the cause of ignition issues.

One way to eliminate the possibility of no or lack of fuel flow is to run a hose from a small fuel tank like drop a hose into a gallon can of pre-mix and see if this makes a difference. You have to be certain the fuel pump can pump fuel and also that it's not sucking air.

If you're unsure of the oiling system, you could run pre-mix in the fuel tank to temporarily supplement the oil supply, a dry carb though doesn't pass fuel thus won't pass oil as well, in this case. commonly we see plenty of roasted 2-stroke motors due to one carb is dry and thus one cylinder isn't receiving it's oil and fuel through that carb so take precaution and heed the notion of carbs not fueling correctly b/c this always leads to engine damage in all cases for 2-strokes. Too much fuel where the plugs tend to foul is safer than lack of fuel.

I tweak my 2-stroke carbs till they're on the clearly on the rich side of the rich/lean conundrum then go back toward lean gradually till the plugs run a normal color and normal power is produced. That is, it's much better to be slightly on the rich side of the knee point. A 2-stroke will literally put out it's peak power and run like stink with gobs of power as mixture reaches that knee point, then over the cliff of seizure shortly afterward due to not enough fuel. Go richer till you hear that 4-stroking rich burble then back toward lean till it cleans up. These carbs cannot be tuned out of water aside from correcting gross problems, they don't make power on the trailer and the plugs will run stone cold.

One more thing to investigate is the condition of battery cables b/c salt gets under the insulation and corrodes them into pencil-lead thickness. So if battery voltage remains over 11V while cranking there could be enough loss through the cables to allow CDI module voltage to drop under about 10V, which is approaching the lower operation limit.

Keep plugging away, you'll find it!

 

[Mickirig1]

Go and look at all the connections. Pull apart junction plugs and look at them. Look for green powder on wires. You can have pin holes that cause wires to corrode. Put Dielectric tune up grease in the junction plugs and to protect connections. Clean and protect all your ground connections. Borrow in induction timing light for cars. See if when it will not start if you have spark to the plugs. The old owner may of sold if for the exact reason. No one could figure it out. WE WILL!

 

[howie099]

You use the KIS system which is we use in IT (Keep It Simple). Do the most basic test first and go up from there. Like load test the battery, check the battery cables, and so on. Does the DESS give you 2 beeps when you attach the lanyard and on testing that system. Since you know the ski ran for 30 minutes than sat for 6 months. I guess we should of ask did you put up for storage anything after it sat that long? Just test every system the ski has since you really have no long term use on it it is hard to judge. Sometimes it just a stupid battery or a loose ground..