• This site contains eBay affiliate links for which Sea-Doo Forum may be compensated.

bog off idle when cold...

Status
Not open for further replies.

suke

Well-Known Member
So last year after my semi restore I unfortunately worked my summer away. I only put maybe 5 hours on my ski. The first time I took it out it ran like a champ all day until I went to put it back on the trailer. It started to bog but would clear up on its own. The last time I took it out it bogged off idle for like 10 mins. The would run like stink until I turned it off and beached it. Went back out after 20 mins or so and same thing.

So here's what I've done or did:
1. During the resto completely cleaned and rebuilt carbs. Blew air through all passage ways and no obstructions.
2. Today I pulled the raves and they looked pretty clean. I cleaned them anyways. Bellows look new and no holes or rips. The PTO side was slightly blocked in the passage way on the rave mount. Cleaned it and reassembled. Doubt that was it though.
3. Pulled water box rave. Bellows were fine in that too.
4. Plugs look a good dark tan
5. Battery is always on a tender and is good and strong.
6. Brand new fuel selector and hoses were switched to black fuel hose at time of resto.

I keep going back to carbs, but can't get over why it'd clear up after a while. Anything I'm missing?
 
To me it sounds like the two little circles in the fuel pump. If they don't seal well the pump will not hold pressure at lower rpms. Maybe the O-ring gasket or diaphragm on the pump carb moved on you during assembly? I would go over all those fuel line connections though first. Make sure they are not loose on the fittings or folded over into a kink anywhere. Make sure your fuel bowl O-ring is OK.

Before any dis-assembly you can also try to open up the two ls needles 1/8-1/4 turn.
 
To me it sounds like the two little circles in the fuel pump. If they don't seal well the pump will not hold pressure at lower rpms. Maybe the O-ring gasket or diaphragm on the pump carb moved on you during assembly? I would go over all those fuel line connections though first. Make sure they are not loose on the fittings or folded over into a kink anywhere. Make sure your fuel bowl O-ring is OK.

Before any dis-assembly you can also try to open up the two ls needles 1/8-1/4 turn.
Ugh those little diaphragm things were a PITA. The little check valves if that's what you're talking about. I thought about messing with the LS jets but it's just weird it clears up after a while. I'll check the easy stuff you mentioned. Want to actually get out and ride my ski this year so want to take the rest of the off season to troubleshoot.
 
Yeah, it does sound like a fueling issue, make sure those transition pilot ports are whistle clean while you're in there, I think sometimes some aluminum oxide can grow in them too, corrosion from fuel absorbing moisture. Those carbs really should be zinc instead of aluminum, IMO.

Also, the accelerator pump nozzles could be plugged?
 
No accel pump on the 96. Yeah those check valves are a pain. If you poke through or tear the rubber grommet that holds them then a leak can be created there. I tend to leave them now if they are looking great. I used to change them just to change them cause they were in the kit I paid for.

When your in that fuel bowl look for beads of water. Water build up will make them act like that sometimes.
 
Last edited by a moderator:
"It started to bog but would clear up on its own."

Actually this kinda sounds similar to too much fuel, "dark brown plugs" is also a consistent description.

I do have my settings a little rich. Saying I should lean it out a little? I wouldn't think enough to bog, but I guess you never know.
 
No accel pump on the 96. Yeah those check valves are a pain. If you poke through or tear the rubber grommet that holds them then a leak can be created there. I tend to leave them now if they are looking great. I used to change them just to change them cause they were in the kit I paid for.

When your in that fuel bowl look for beads of water. Water build up will make them act like that sometimes.

I did poke through one but replaced it with another from the kit. Don't believe the ones in there are torn.
 
Worth trying to lean it out a little...oem settings are usually on the fat side of safe even with a bore. Its interesting that it gets better as it gets warmer thats a description you dont hear every day.
 
I do have my settings a little rich. Saying I should lean it out a little? I wouldn't think enough to bog, but I guess you never know.

What is a bog? My definition is a lean condition where the throttle response is flat, the engine often quits running b/c it runs out of fuel to burn, but my definition of this word doesn't mean you're not experiencing a rich condition.

If it's already too lean, then of course leaning it out further will make the symptoms worse. Remember, it's not desirable to run a 2-stroke lean, it's best to err on the rich side and turn it back towards lean, stopping at the point where the engine just begins to run correctly. By the description of bog, it's hard to know if it's too lean or too rich except if too lean you will likely find it stalls occasionally or often when it falls on it's face. If too rich, it just takes a few seconds to clear out excess fuel, while doing this it will probably four-stroke some, and run rough but not stall. Four-stroking sounds like an engine miss, when a 2-stroke is reaching a point of being too rich(always start on the rich side), it will begin to miss, firing every other stroke, which is where the term four-stroking comes from. When tuning a two stroke it's important to keep an adequate balance of fuel in the crankcase so that when the throttle is opened, that fuel in the crankcase is swept up into the cylinder, acting like an accelerator pump would(you have no accelerator pump on your carbs, crankcase fuel balance is your accelerator pump). If too much fuel and it can't burn it all and just kind of chugs along without quitting, if too little and there's nothing to burn as the throttle is cracked open, the engine will stop running. During idle, the idle mixture passage feeds fuel and there is a slight delay time when the throttle is first cracked open before the transition pilot ports begin flowing, thus a careful balance of fuel lying in the crankcase (a puddle of fuel+oil) is necessary to compensate for the throttle pilot transition. Too much fuel doesn't hurt anything really, but it makes for sluggish throttle response and burning sensation for the eyes, with excess pollution.

The worse thing you can do to a 2-stroke is run it too lean though, a lean bog leads to a potential lack of lubrication b/c fuel carries oil throughout the crankcase and cylinders, thus if there's a lack of fuel there's also a lack of lubrication.

An overly rich motor loads up on fuel and cannot burn the excess, so when you shut it down the excess fuel remaining inside the crankcase and cylinders will likely make it harder than normal to restart while hot without opening the throttle a good ways, maybe 50% or more. So if your hot restart is improved by opening the throttle 50%, then I'd say it's probably too rich in the low throttle position, idle mixture screw controls this, set as per factory spec or slightly lower by maybe 1/8 turn and see if your symptom improves. If it improves then try the factory setting and see if driveability is acceptable under all conditions.

A quick test I use to see if an engine is bogging too lean would be to richen it up briefly by pulling the choke while it's stumbling/bogging, if it's too lean, then it should immediately catch with a brief pull on the choke.

Often if an engine is too rich as your idling along at no wake speeds, you will be able to detect unusual amounts of unburned fuel wafting around, it may even be enough to burn your eyes slightly. Soot and dark color on your plug center electrode is an indicator your mixture is too rich, the plug electrode isn't hot enough to burn away the fuel film. If I put a brand-new set of plugs in my motor and run it for 30minutes across the lake at 30mph, the insulators will have a yellow tinge on them, not brown or dark brown. Once my plugs have more than 10hrs on them, the insulator color settles out to a cardboard brown and I can get two seasons on them without fouling from soot/oil deposits, including fogging between use. When they foul, I clean them to see if I can squeeze another season from them b/c I pride myself on being a cheapskate, LOL

Anyway, bogging is a somewhat subjective term, when I have a lean condition I call it bogging, or a lean-bog, describing a condition where the engine actually runs out of fuel with nothing to burn, thus it falls on it's face and quits as the throttle is cracked open. If too rich, I call it four-stroking b/c the engine still runs, doesn't stall, but misses and runs rough until the excess fuel clears out. Soot quickly forms on the plug insulators during a rich condition due to the partially burned fuel. This soot can be burned off once the plugs come up to temperature, this is how plugs are self-cleaning. If too rich, the plugs will tend to foul more often than usual.

I probably repeated myself once or twice trying to explain.....
 
What is a bog? My definition is a lean condition where the throttle response is flat, the engine often quits running b/c it runs out of fuel to burn, but my definition of this word doesn't mean you're not experiencing a rich condition.

If it's already too lean, then of course leaning it out further will make the symptoms worse. Remember, it's not desirable to run a 2-stroke lean, it's best to err on the rich side and turn it back towards lean, stopping at the point where the engine just begins to run correctly. By the description of bog, it's hard to know if it's too lean or too rich except if too lean you will likely find it stalls occasionally or often when it falls on it's face. If too rich, it just takes a few seconds to clear out excess fuel, while doing this it will probably four-stroke some, and run rough but not stall. Four-stroking sounds like an engine miss, when a 2-stroke is reaching a point of being too rich(always start on the rich side), it will begin to miss, firing every other stroke, which is where the term four-stroking comes from. When tuning a two stroke it's important to keep an adequate balance of fuel in the crankcase so that when the throttle is opened, that fuel in the crankcase is swept up into the cylinder, acting like an accelerator pump would(you have no accelerator pump on your carbs, crankcase fuel balance is your accelerator pump). If too much fuel and it can't burn it all and just kind of chugs along without quitting, if too little and there's nothing to burn as the throttle is cracked open, the engine will stop running. During idle, the idle mixture passage feeds fuel and there is a slight delay time when the throttle is first cracked open before the transition pilot ports begin flowing, thus a careful balance of fuel lying in the crankcase (a puddle of fuel+oil) is necessary to compensate for the throttle pilot transition. Too much fuel doesn't hurt anything really, but it makes for sluggish throttle response and burning sensation for the eyes, with excess pollution.

The worse thing you can do to a 2-stroke is run it too lean though, a lean bog leads to a potential lack of lubrication b/c fuel carries oil throughout the crankcase and cylinders, thus if there's a lack of fuel there's also a lack of lubrication.

An overly rich motor loads up on fuel and cannot burn the excess, so when you shut it down the excess fuel remaining inside the crankcase and cylinders will likely make it harder than normal to restart while hot without opening the throttle a good ways, maybe 50% or more. So if your hot restart is improved by opening the throttle 50%, then I'd say it's probably too rich in the low throttle position, idle mixture screw controls this, set as per factory spec or slightly lower by maybe 1/8 turn and see if your symptom improves. If it improves then try the factory setting and see if driveability is acceptable under all conditions.

A quick test I use to see if an engine is bogging too lean would be to richen it up briefly by pulling the choke while it's stumbling/bogging, if it's too lean, then it should immediately catch with a brief pull on the choke.

Often if an engine is too rich as your idling along at no wake speeds, you will be able to detect unusual amounts of unburned fuel wafting around, it may even be enough to burn your eyes slightly. Soot and dark color on your plug center electrode is an indicator your mixture is too rich, the plug electrode isn't hot enough to burn away the fuel film. If I put a brand-new set of plugs in my motor and run it for 30minutes across the lake at 30mph, the insulators will have a yellow tinge on them, not brown or dark brown. Once my plugs have more than 10hrs on them, the insulator color settles out to a cardboard brown and I can get two seasons on them without fouling from soot/oil deposits, including fogging between use. When they foul, I clean them to see if I can squeeze another season from them b/c I pride myself on being a cheapskate, LOL

Anyway, bogging is a somewhat subjective term, when I have a lean condition I call it bogging, or a lean-bog, describing a condition where the engine actually runs out of fuel with nothing to burn, thus it falls on it's face and quits as the throttle is cracked open. If too rich, I call it four-stroking b/c the engine still runs, doesn't stall, but misses and runs rough until the excess fuel clears out. Soot quickly forms on the plug insulators during a rich condition due to the partially burned fuel. This soot can be burned off once the plugs come up to temperature, this is how plugs are self-cleaning. If too rich, the plugs will tend to foul more often than usual.

I probably repeated myself once or twice trying to explain.....
OK this is starting to come together a little bit. When it finally does clear out I can look behind me and see a big cloud of white smoke. Once that's done I can ride the piss outta it off idle, mid throttle, etc and it'll fly. My plugs have at most 30 mins and they're dark brown. I am running pre mix and run a primer, so no choke.

I'll get a pic of my plugs soon, and it bogs and will not accelerate but doesn't shut off even if I keep on it.
 
Last edited by a moderator:
Worth trying to lean it out a little...oem settings are usually on the fat side of safe even with a bore. Its interesting that it gets better as it gets warmer thats a description you dont hear every day.

Yeah that's what really throws me off. If it just always bogged I'd say OK Carb needs to be richened up......but then it clears out and off we go!
 
OK this is starting to come together a little bit. When it finally does clear out I can look behind me and see a big cloud of white smoke. Once that's done I can ride the piss outta it off idle, mid throttle, etc and it'll fly. My plugs have at most 30 mins and they're dark brown. I am running pre mix and run a primer, so no choke.

I'll get a pic of my plugs soon, and it bogs and will not accelerate but doesn't shut off even if I keep on it.

A primer really does the same thing as a choke, just it has it's own fuel source which probably isn't plumbed from the carburetor. Really dark plugs could be from the extra oil in pre-mix, especially if there's a ton of oil in the fuel. Dark brown is sorta too darker than I like but at least you're not white or gray from being too lean, dark plugs are gonna foul a little quicker if they don't heat up enough to burn the insulator off to about a cardboard brown. Expect maybe a darker color with the extra oil but gray or white is definitely too lean and means trouble for most marine 2-strokes. Of course it runs fine up top, and that's where a large degree of the insulator color comes from due to heat it burns off the insulator then gets recoated again at low speeds b/c the plug insulators cool off.

I think it wouldn't hurt a thing to try leaning out the idle mix screws a bit, maybe 1/8 turn less than factory spec but at least try factory spec and see how that does. All's fair pretty much, down in the low throttle range b/c motor isn't making tons of heat there so as long as mid and upper range aren't lean(Brown = doesn't sound like they are) you don't have to worry about seizure unless one cylinder isn't fueling. 2-stroke cardinal rule #1: No fuel means no oil, which leads straight to damage.

White smoke is usually steam or water vapor, so maybe we're talking about an internal water leak in the engine or the exhaust being full of water and spraying out a water mist? Could be a launching angle issue? Maybe try idling around a bit and instead of taking off like normal shut it down just as it bogs and yank the plugs to see if one is wet with water? If some water gets in the crankcase somehow from say maybe launching, that water could sit there in the bottom of the crankcase until you open the throttle then that water gets thrown up into the cylinder and briefly shorts the plug out? Kinda a long shot, just an idea.

Or, maybe there's something amiss with your waterbox/exhaust manifold filling up with too much water, I'm not familiar with how that one's plumbed, just an idea for consideration.

Think about how you launch, and if maybe water is somehow entering the crankcase during launch?

I still lean towards maybe you're a tad on the rich side on the idle screw(s), and a cold motor doesn't burn fuel quite as well as a hot one can.
 
Another thing too, since you're premixing, there will be more oil residing in the crankcase during idling periods b/c it's still receiving the same ratio. This would especially be true if the engine was cold, there would be a more pure oil puddle laying in the crankcase waiting to get slung up into the cylinders as soon as you hit the throttle. So you might be experiencing momentary oil fouling.

Normally, most of the oil found in the bottom of a 2-stroke crankcase is pretty much just oil, it's almost as thick as if it hadn't been mixed with fuel in the first place and it lies in a puddle in the bottom of the crankcase. Judging the volume of this puddle is a great way to determine if the oil/fuel ratio is sufficient to keep an oil puddle in the crankcase, when tearing down a 2-stroke engine, you want to see a good amount of oil coating on the rotating assembly, else your oil isn't doing it's job (crap oil, too thin mix, or whatever).

As a motor sets cold. most of the oil up in the cylinders, under the piston crowns and everywhere that isn't trapped by surface tension runs down and puddles down in the bottom of the crankcase. So when you first fire it off, that puddle gets thrown around and some of it gets slung up into the combustion chamber. Makes me wonder if this is causing your hesitation issue, in which case I think you can't do much about it, just make sure your idle mixture isn't overly rich, the idle should be fairly smooth and the motor should fire each stroke, not every other stroke or occasionally missfire every third or forth stroke.
 
It'll idle fine all day long. That part is bang on. Off idle is when it starts to sound like it's bogging and won't go any faster. It'll do it all day if I let it sit for a few mins. I did notice the last time I took it out hot starts I had to give it throttle to get it going.
 
It'll idle fine all day long. That part is bang on. Off idle is when it starts to sound like it's bogging and won't go any faster. It'll do it all day if I let it sit for a few mins. I did notice the last time I took it out hot starts I had to give it throttle to get it going.

If the engine is flooding out at low speed, or flooding out while sitting heat soaked, then one of the rubber tipped metering needle/seats may be leaking or sticking, allowing fuel to dribble into the intake tract while shut down. Also, a plugged fuel tank vent can cause flooding, there's often a check valve in the fuel tank vent that releases at a specific vapor pressure that should be less than your carbs pop pressure by a fair amount, so if that check valve is stuck or gummed, the pressure in the fuel tank can build to a point fuel is forced through the carbs and into the crankcase. Try opening the fuel tank cap at the end of riding around, to relieve pressure, and see if that helps the heat-soaked restart.
 
Simple. When it starts bogging, blip the choke. If it remedies the problem and the ski takes off, its running lean. If it chokes out and dies, its running rich.

Just an FYI my 583 skidoo sled runs like a bag of shit until it warms up and I have to prime it to get high revs off idle until the thermostat opens. Once running it goes like a bat out of hell. Now in the summer, that seadoo should run well after about 30 secs-1 min of running.

**This is assuming your carbs are clean and rebuilt properly.
 
This might be a good time to point out that a cold engine shouldn't be revved hard for the first few minutes following startup, to allow the cylinders time to come up to temp.
 
This might be a good time to point out that a cold engine shouldn't be revved hard for the first few minutes following startup, to allow the cylinders time to come up to temp.
I idle out of a no wake zone which is about 100yards or so before I give it any throttle. When beached same thing...have to idle out just as far before I can get on it.
 
Simple. When it starts bogging, blip the choke. If it remedies the problem and the ski takes off, its running lean. If it chokes out and dies, its running rich.

Just an FYI my 583 skidoo sled runs like a bag of shit until it warms up and I have to prime it to get high revs off idle until the thermostat opens. Once running it goes like a bat out of hell. Now in the summer, that seadoo should run well after about 30 secs-1 min of running.

**This is assuming your carbs are clean and rebuilt properly.
Choke has been removed. Carbs were cleaned and rebuilt before I got a hold of the ski. I did it again myself to make sure it was done right and they looked really clean. I'm going to pull the carbs and make sure it isn't a leaking needle and seat. I had a similar issue but it caused Mega hard starts and I was using the wrong springs. Pop off was also way too high for my jetting.
 
You have aftermarket f/a's, right? Ugh I hate tuning those. Stock settings and air box. Boom, they run great :)

Yeah, but I got my settings from one of the best tuners in the country. So that I'm not too concerned about. It ran perfectly fine first time out. I did err on the fat side of his specs.
 
Just saying. Usually with the aftermarket parts it's harder to tune than the old reliable "set it and forget it " seadoo stock settings :)
 
Just saying. Usually with the aftermarket parts it's harder to tune than the old reliable "set it and forget it " seadoo stock settings :)

Yeah I could def see that getting it perfect would be a pain, but this scenario is far from usable. There's something DEF wrong.
 
Status
Not open for further replies.
Back
Top