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Discussion Starter #1
So I'm thinking a bad stator but hoping to get some guidance....kinda learning as I go.
The symptoms - sled runs great when its cold, once it gets hot say 10-15 minutes it starts to lose power and eventually stalls. The spark plugs are soaked and there's no spark. I replaced the CDI not too long ago ,plugs and wires are new. I also unplugged the killswitch/tss from the harness and didn't make a difference. Right now the sled isn't home, I'll have to go get it when it cools off, its a 488 cc liquid cool/carbed model with about 4500 miles-
thanks and stay well !
 

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Could be a bad stator. You need to OHM test it when it doesn't show any spark. Use a spark tester or a screw driver to test for spark. Fouled plugs won't show spark.

Stator has two separate systems: A. Lighting, B. Ignition.
Typical stator ignition/spark (B) system OHMs are
Brown/white to Black/red: 164 OHMs
Brown/white to ground: 0 OHMS

If it tests okay, then you might want to see if it's flooding when warm. If so, this can be bad float needles/seats, wrong choke setup, sunken floats, plugged bowl vent hoses, dirt in needles/seats, fuel pump leak into crankcase via pulse hose.
 

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Discussion Starter #3
Could be a bad stator. You need to OHM test it when it doesn't show any spark. Use a spark tester or a screw driver to test for spark. Fouled plugs won't show spark.

Stator has two separate systems: A. Lighting, B. Ignition.
Typical stator ignition/spark (B) system OHMs are
Brown/white to Black/red: 164 OHMs
Brown/white to ground: 0 OHMS

If it tests okay, then you might want to see if it's flooding when warm. If so, this can be bad float needles/seats, wrong choke setup, sunken floats, plugged bowl vent hoses, dirt in needles/seats, fuel pump leak into crankcase via pulse hose.
Gotcha, I'll have to run it on a stand until it fails and then check . Unfortunately the little snow cover we had is gone.
I cleaned and rebuilt the carbs and set the floats recently... But you mentioned plugged bowl vent hoses ? come to think of it I think they have plastic plugs in them, could that be an issue ?
 

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So I'm thinking a bad stator but hoping to get some guidance....kinda learning as I go.
The symptoms - sled runs great when its cold, once it gets hot say 10-15 minutes it starts to lose power and eventually stalls. The spark plugs are soaked and there's no spark. I replaced the CDI not too long ago ,plugs and wires are new. I also unplugged the killswitch/tss from the harness and didn't make a difference. Right now the sled isn't home, I'll have to go get it when it cools off, its a 488 cc liquid cool/carbed model with about 4500 miles-
thanks and stay well !
Did you disable the ignition key switch also? If so, sure sounds like the stator. Easy to tell with a digital ohm meter soon as the problem happens....ohm the coil wires. Seems like a coil is open.
 

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Discussion Starter #5
Did you disable the ignition key switch also? If so, sure sounds like the stator. Easy to tell with a digital ohm meter soon as the problem happens....ohm the coil wires. Seems like a coil is open.
Yes the ignition and tether is disabled. I'll try and make it fail tomorrow and check for a open.
Thanks guys, appreciate the help 1
 

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Gotcha, I'll have to run it on a stand until it fails and then check . Unfortunately the little snow cover we had is gone.
I cleaned and rebuilt the carbs and set the floats recently... But you mentioned plugged bowl vent hoses ? come to think of it I think they have plastic plugs in them, could that be an issue ?
Absolutely. If atmospheric air pressure is trapped in the float bowls when empty, then the pressure buildup when fuel is pumped in will cause fuel to flow at a great rate right into the engine even when not running. This might cause easy cold operation even without much choking, but when warmed up, it will be way too rich.

If float bowls are full when first started, and vent hoses then are plugged, atmospheric air pressure will not be able to enter to force fuel through the jets once a vacuum is created by air flowing through the carb bore.

Either way, you must not plug the float bowl vents on any carb.
 

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Discussion Starter #7
Okay, so just to be clear we are talking about the vent hose that comes from the bottom of the float bowl ?
Yes they do have plugs in them, the sled came that way...must have been something the previous owner did. Where should they go, to the airbox or just loose in the bellypan ?
 

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Those tubes are the water traps on the bottom of the float bowl.
The carb vents should be small 1/8" (ID) line running from upper portion of carb body up to handlebars or to airbox (on some models).
 

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Do you have a shop manual for your machine. I have several different years and probably have the one for your machine. I'd be happy to email you a copy if you'd drop me a PM with your model and year, and email address.
 

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Gotcha, I'll have to run it on a stand until it fails and then check . Unfortunately the little snow cover we had is gone.
I cleaned and rebuilt the carbs and set the floats recently... But you mentioned plugged bowl vent hoses ? come to think of it I think they have plastic plugs in them, could that be an issue ?
Why? More importantly, do you have the skills? You shouldn't have to set the floats unless the wrong needle/seats or parts were installed/misinstalled.

Example: My riding buddy once rebuilt his carbs. It didn't run right. He replaced the stator, still didn't run right. Weeks of trying various things including pistons and rings. Still poor running. Finally, we pulled his rebuilt carbs. Found one of his main jets laying in the float bowl!!!!

Cost him lots of $ before his mistake was discovered.
 

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Discussion Starter #11
Why? More importantly, do you have the skills? You shouldn't have to set the floats unless the wrong needle/seats or parts were installed/misinstalled.

Example: My riding buddy once rebuilt his carbs. It didn't run right. He replaced the stator, still didn't run right. Weeks of trying various things including pistons and rings. Still poor running. Finally, we pulled his rebuilt carbs. Found one of his main jets laying in the float bowl!!!!

Cost him lots of $ before his mistake was discovered.
do I have the skills ? nope but its a good way to learn and I don't have much into the machine LOL
the carb boots needed to be replaced (disintegrating at flange ) so I figured I might as well since it was sitting for a while. The float tabs were visibly different so I looked up spec and set them-
so yes I've wasted some time with it but learned a few things. If I took it to a shop and got it sorted out I suspect it'd cost more than the machine is worth. I absolutely agree that a manual would be good and I'll take him up on that offer .
Thanks for all the help !
 

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do I have the skills ? nope but its a good way to learn and I don't have much into the machine LOL
the carb boots needed to be replaced (disintegrating at flange ) so I figured I might as well since it was sitting for a while. The float tabs were visibly different so I looked up spec and set them-
so yes I've wasted some time with it but learned a few things. If I took it to a shop and got it sorted out I suspect it'd cost more than the machine is worth.
I absolutely agree that a manual would be good and I'll take him up on that offer .
Thanks for all the help !
Sadly, many folks want to save a few $ and end up learning the hard way. I run a small engine repair shop from home. For at least 30 years. I've worked on engines of all kinds for much longer. I don't need the extra income. I try to teach all my customers how to do their own repairs if they contact me before they waste a lot of $. Some still have to learn the hard way. I could write a best selling book on this.:bc:
 

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Not directed at OP , agreeing with PI on some people:
/If your only tool is a hammer, everything looks like a nail. :)
 

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Discussion Starter #15
yep you are absolutely right ! I knew I was going down a rabbit hole with this LOL
I have another sled which I rode this season so its not like I was down and out. I have a digital VM, going to check the values at plug today -
if this isn't the problem I think I will cut my losses .
 

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so back to the carbs, I watched it carefully running on a stand. 1 carb is overflowing out the vent tubes, I suspect flooding that cylinder. Switched carbs l to r and the problem followed. What would you guys be looking for ? needle and seat, choke setting etc
 

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so back to the carbs, I watched it carefully running on a stand. 1 carb is overflowing out the vent tubes, I suspect flooding that cylinder. Switched carbs l to r and the problem followed. What would you guys be looking for ? needle and seat, choke setting etc
Pressure test it.
 

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so back to the carbs, I watched it carefully running on a stand. 1 carb is overflowing out the vent tubes, I suspect flooding that cylinder. Switched carbs l to r and the problem followed. What would you guys be looking for ? needle and seat, choke setting etc
Could be anything from leaky floats, improperly set float level to a bad needle/seat assembly...or maybe some crap stuck under the needle. Bad or poorly set chokes will make a sled run rich or foul the plug.
On another note, careful what carb boots that you buy for replacements. Kimpex for one brand are junk. Their too hard. Imo, try to buy genuine mikuni boots if still available.
 

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so back to the carbs, I watched it carefully running on a stand. 1 carb is overflowing out the vent tubes, I suspect flooding that cylinder. Switched carbs l to r and the problem followed. What would you guys be looking for ? needle and seat, choke setting etc
I'm guessing that you set one float too high. If so, pressure testing by turning carb upside down and applying 5 psi of air pressure to the fuel inlet won't show the problem.

Instead, test rightside up in a vise using fuel poured into a clear fuel line till full when held alongside the carb and vertically. Include a tee with a low pressure gauge in the line. Add up to 5-6 psi air pressure and watch fuel level drop a bit as it fills the bowl. If it keeps dropping and starts to leak out of various orifices, stop. Then drain fuel, removes float bowl and check with just air pressure while holding it upside down. Spray WD-40, etc around all places it may be leaking while under pressure. If no leaks are seen, then float is likely set too high or float is full of fuel and can't rise enough (Low buoyancy) to close needle/seat.
 

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Gotcha, I'll have to run it on a stand until it fails and then check . Unfortunately the little snow cover we had is gone.
I cleaned and rebuilt the carbs and set the floats recently... But you mentioned plugged bowl vent hoses ? come to think of it I think they have plastic plugs in them, could that be an issue ?
On your rebuild did you replace needle and seat? If so did you use genuine Mikuni parts or some other brand? There are some cheap ones out there that aren't worth installing.
 
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