I'm at my wits end.. losing mag cylinder

Summitt22

Summitt22

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Dec 31, 2012
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41
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48
Location
Winkler, MB
Hey,

I've replaced my stator with a used E-bay unit, took care of a rub through on the wire harness, cleaned the carbs twice, took out my coil and ran with a different one, replaced spark plug caps, tried 3 new sets of spark plugs, inspected reeds, tested compression (105/106). All of that and I still have the same issue.

Today when I had the other coil installed, I ran the sled until I lost the mag side cylinder then I pulled that spark plug lead off while it was still running - didn't make a difference in how the sled ran. Turned the sled off, swapped spark plug leads (mag side to left side and vice versa) then ran the sled until I lost a cylinder again. This time I pulled the left side spark plug cap off and the sled died instantly.

That tells me that it's a mag side cylinder issue and not a coil/electrical issue. I should mention that I had just put a new plug in the mag side cylinder right before I re-started the sled.

Here's the issue I'm having : A cylinder cuts out then it won't go faster than 50 mph. I'll stop and let it idle for a couple minutes and sometimes the 2nd cylinder will start firing again and it'll run great for 100 yards or so then I lose the second cylinder again. The cylinder seems to cut out sooner the more "load" I put on it.

I had an issue a few weeks ago with the pipe, there was a big piece of metal floating around in it. I had to cut it open, remove the 4"x5" piece and have it welded back up. I had blown the pipe off of the collector before I had it removed. I've blown the pipe off of the collector once since I took that big chunk of metal out of there. Is a restriction the only real cause for having that pipe blow off ?

Any ideas ? I've spent more than 15 hours working on this thing trying to eliminate issues as potential causes. I'm about ready to sink it in the lake...
 
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Summitt22 said:
Hey,

I've replaced my stator with a used E-bay unit, took care of a rub through on the wire harness, cleaned the carbs twice, took out my coil and ran with a different one, replaced spark plug caps, tried 3 new sets of spark plugs, inspected reeds, tested compression (107 both cylinders). All of that and I still have the same issue.

Today when I had the other coil installed, I ran the sled until I lost the mag side cylinder then I pulled that spark plug lead off while it was still running - didn't make a difference in how the sled ran. Turned the sled off, swapped spark plug leads (mag side to left side and vice versa) then ran the sled until I lost a cylinder again. This time I pulled the left side spark plug cap off and the sled died instantly.

That tells me that it's a mag side cylinder issue and not a coil/electrical issue. I should mention that I had just put a new plug in the mag side cylinder right before I re-started the sled.

Here's the issue I'm having : I'm having an issue where I lose spark on one cylinder, then it won't go faster than 50 mph. I'll stop and let it idle for a couple minutes and sometimes the 2nd cylinder will start firing again and it'll run great for 100 yards or so then I lose the second cylinder again. The cylinder seems to cut out sooner the more "load" I put on it.

I had an issue a few weeks ago with the pipe, there was a big piece of metal floating around in it. I had to cut it open, remove the 4"x5" piece and have it welded back up. I had blown the pipe off of the collector before I had it removed. I've blown the pipe off of the collector once since I took that big chunk of metal out of there. Is a restriction the only real cause for having that pipe blow off ?

Any ideas ? I've spent more than 15 hours working on this thing trying to eliminate issues as potential causes. I'm about ready to sink it in the lake...
Click to expand...

Sorry man but this is hard to read. You mention you have verified it is not a spark issue but then say you are loosing spark on one cylinder.

Ok, based off the first part of this, I am going to guess you may very well be sucking air on the mag side. Have you checked your crank seals? What do your plugs look like? Post some pics of the plugs and this metal piece that is in your pipe if you still have it. Spray some ether around the cranks seal and see if you pick up the cylinder.
 
I get that, this part is what I was trying to figure out a couple weeks ago :

Here's the issue I'm having : I'm having an issue where I lose spark on one cylinder, then it won't go faster than 50 mph. I'll stop and let it idle for a couple minutes and sometimes the 2nd cylinder will start firing again and it'll run great for 100 yards or so then I lose the second cylinder again. The cylinder seems to cut out sooner the more "load" I put on it.

I copied/pasted it from an earlier post, but I should have modified it stating that I am NOT losing spark on that cylinder.

Today, I tested it with another coil and I'm pretty sure I've ruled out the problem being electrical as it is limited to the right cylinder (mag side). I'd run the sled until I lost combustion and suspected it was the mag side cylinder cutting out. With the sled idling I pulled the mag side plug lead off of the cylinder and nothing changed. When I tried the same thing on the left cylinder (non-mag side) the sled died instantly. I got the same results when I swapped spark plug leads, regardless of which plug lead was on what cylinder, the mag side cylinder was always the one not firing.

Hope that makes more sense, sorry about that ?

I'll google how to check my crank seals, the left plug has a nice tan color to the electrode whereas the mag side plug is always full of fuel after it's been cutting out. 3 times I've been running it, lost the cylinder & hit the kill switch. When I pull the plugs they are as described.

Here's the piece of metal I pulled out of my pipe :

image_zpsc0f31fb3.jpeg

image1_zps05ce13d7.jpeg


There was another smaller piece that came out of there, it was about 2.5"x3".
 
So, initially my plug leads weren't long enough to swap them from one cylinder to the other but I figured out a way to make it work. I got the same results with my coil as I did with my buddy's, it's always the mag cylinder that stops firing (regardless of which plug lead is going to it) although I believe it still has spark.

Here's a video of what it does :
http://youtu.be/J-eieZhvRF0

The cylinder cuts out between 6-7 seconds, if I leave the plug leads on and let it idle sometimes it will start firing again on it's own. Most of the time if I shut it off, it'll run on both cylinders at start up.

The TORS is disconnected, I tried pulling the TPS off which didn't make much of a difference either way.

Compression was 106 on the mag cylinder and 105 on the other.

As far as spraying ether (I bought a can), the seal is buried underneath the recoil, flywheel, and stator. How are you supposed to get anywhere near it with ether ?
 
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losing cylinder

mine did the same thing a few years back, check your piston skirt on the exhaust side of the motor,it might be broke off
 
Seems to me its acting like its running out of fuel when cylinder is under high demand.

Some ideas:

Fuel issues
-check carb float level
-when cleaning carbs check to see if there are top hat shaped screen filters under the float needle and seat...they may be plugged
-check for kinked fuel line
-check carb vent lines are not kinked or plugged
-check/replace tank fuel filter
-check/replace fuel pump
-ensure fuel tank is venting

Spark issues:
-check stator[heat causes issues with electrics]
-coils
-when cylinder dies like that have a spark plug in your pocket and place it in plug cap to see if there is spark at that moment

Cylinder issues:
-damaged piston's rings can stick when the pistons are hottest and cylinder will loose compression then rings free as piston cools[maybe a long shot]
 
sideshowBob said:
Seems to me its acting like its running out of fuel when cylinder is under high demand.

Some ideas:

Fuel issues
-check carb float level
-when cleaning carbs check to see if there are top hat shaped screen filters under the float needle and seat...they may be plugged
-check for kinked fuel line
-check carb vent lines are not kinked or plugged
-check/replace tank fuel filter
-check/replace fuel pump
-ensure fuel tank is venting

Spark issues:
-check stator[heat causes issues with electrics]
-coils
-when cylinder dies like that have a spark plug in your pocket and place it in plug cap to see if there is spark at that moment

Cylinder issues:
-damaged piston's rings can stick when the pistons are hottest and cylinder will loose compression then rings free as piston cools[maybe a long shot]
Click to expand...

I'm thinking you might have something with the fuel issue, I pulled the fuel pump apart expecting to find a fuel filter in there but I didn't. Then, I looked in my gas tank and saw that my fuel filter wasn't attached to the line - it's just loose in the tank. I also noticed that if I turned the little plastic elbow enough the fuel line on the inside of the tank would come up out of the fuel.

I switched the fuel lines around on my carbs, I'm going to see if this is a fuel pump issue. If I lose the left cylinder (non-mag) then I'll have figured this thing out

I put a different used stator (E-bay) in the sled which made no difference - both tested good and tested the coil. Regardless of which spark plug cap/lead is on either cylinder, it's always the mag side cylinder that cuts out - confirmed by pulling spark plug cap off & swapping spark plug leads.

rj21 said:
mine did the same thing a few years back, check your piston skirt on the exhaust side of the motor,it might be broke off
Click to expand...

Thanks for the suggestion, I had the pipe/2 into 1 collector off yesterday.. Guess I'll have to pull it off again and take a look at those skirts.

Thanks !
 
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I would check the reeds and needle/seat on that cylinder. It sounds like over fuel condition if the plug is wet. Did you do a leakdown? Not sure what the deal is but I have been seeing lots of cracked up reeds and needles stuck in the seats this year causing issues like this.
 
I've looked at the reeds, the top reed on either side is just starting to pull away from the cage. There may be 1/32" gap, I ordered new reeds and a new coil today. Otherwise the reeds looked like they were in good shape.

I didn't do a leak down test, will look at having that done.

I've had the caps apart 3 times now, how can you inspect where the needle seats ? It's kind of buried in the carb isn't it ? Both slides/needles move up and down without any sort of binding, both needles are relatively secure in the slides.

What about the spark arcing from the cap ? Normal without a plug I'd assume ?
 
I'm talking about the main needle and seat in the float bowl. It's the part the floats are connected to. It's basically the fuel valve that the float operates.
Check the tech section for the carb part break down and proper cleaning methods. If the needle is stuck half way in the seat, it won't shut the fuel flow off and it will keep the fuel flowing into the float bowl. Fuel coming out of the vent lines is usually an indication of this. The only other thing that comes to mind is a blockage in the exhaust. It could be that your exhaust side skirt broke off the piston and is stuck in the manifold.

You could pull the exhaust manifold and roll the motor over to have a good look at the exhaust side of your piston and inspect the manifold. You can also get a good look at the intake side of the piston if you pull the reed cage while you have the carbs off to inspect the needle and seat. I would say you want to pull the seat right out and look behind at the intake passage.
 
I had this same problem a few years back. The problem was due to one of the plugs that plug into the CDI box. Moisture had at made it past weather tight seal at some point and plugs conductors where arcing out internally. Plug deteriated to the point conductors would not stay in there keepers. Plug smelt burndt as iI diconnected it. i chased my tail for a month on this. new coils,new stator,harness checked point to ponit. Got to the point where i was pulling out harness and started cdi box. Boom there it was. Hope this helps.
 
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Okay, in that case I've looked at how the needle moves and there doesn't appear to be an issue. Both floats/needles move with ease. Although I'm not really sure about the float height adjustment process. From what I can understand, the "tang" is supposed to be level with the bottom of the carb body if you will - the tang is supposed to be level with the surface where the float bowl meets the carb. Is that correct ?

I've checked both exhaust skirts on the intake and exhaust side - manfold was taken off, everything looks fine there aside from a little blow by on the pto piston.

I did have a big piece of metal break off the inside of the pipe, I thought there might be something restricting the exhaust so I bought a used can. It showed up today, I'll pick it up tomorrow.

Whenever I lose a cylinder, it seems like it's always the mag side cylinder. If I swap spark plug leads/caps from one cylinder to the other, it's still the mag side that cuts out. Although, the sled seems to run better on the pto cylinder alone when it has the proper plug wire/cap on. When I lose a cylinder and have the caps switched around, it doesn't run as well on the pto cylinder alone with what should be the mag side plug wire/cap.

I checked the connections from the wire harness to the CDI, no corrosion/rust etc. Everything there looks as it should.

Thanks for the suggestions/help guys, keep it coming !
 
So... after a solid month of working on this thing I got it figured out.

Initially I thought it was an electrical issue, I'd read another thread where a guy described my sled's symptoms to a "T". He put a used stator in and that fixed his problem, so I did the same but my problem (losing mag cylinder/bogging under load, cruising at 45mph etc). I thought it was an electrical issue until I swapped spark plug wires from mag to pto cylinder and the mag cylinder was still the one cutting out.

If it had been an electrical issue I would've expected it to switch cylinders when I swapped plug leads.

Next I suspected an air/fuel issue with some help from guys here and other people I talked to. I swapped fuel lines from one carb to the other, but it was still the mag cylinder cutting out. That eliminated the fuel pump as the problem. I'd had the carbs apart 3 times, everything looked clean and the needle valve(s) that are actuated by the floats moved nice and free.

Today I thought I'd remove the float,needle and seat from the mag side carb. There wasn't any gunk on the needle, and it slid right out of the seat. When I pulled the seat out of the carb, this is what I found :

image4_zps3b261996.jpeg


Piece of plastic that was obstructing fuel flow above the needle seat on my thumb :

image4_zpscc8b8d31.jpeg


So, after swapping stators, 5 sets of plugs, removing the engine and fixing a couple rub throughs, replacing the can/muffler, testing the coil, this little piece of plastic (I'm guessing from the inside of the gas tank) was my issue all along.

I'd like to thank everyone who offered suggestions, or possible fixes. Thank you !!! ;)!
 
I wander how that really got there.There is a fuel filter in the gas tank and there is no way that plastic can get past the filter.So this is weird for sure but does stand out as the problem for sure.Good you found the problem.
 
sure thats plastic

Could that be dried up oil or stabil. I have taken some carbs apart before that had similar type balls in bowl . It was dried oil.just a thought. O ya good job finding prop.bbbbrrraaa
 
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bluemonster1 said:
I wander how that really got there.There is a fuel filter in the gas tank and there is no way that plastic can get past the filter.So this is weird for sure but does stand out as the problem for sure.Good you found the problem.
Click to expand...

My fuel filter had come off of it's metal "tube" connected to the fuel line going out of the tank, the filter itself was loose and floating around the bottom of the tank.

jasburrito said:
Could that be dried up oil or stabil. I have taken some carbs apart before that had similar type balls in bowl . It was dried oil.just a thought
Click to expand...

It's plastic, 100% sure of that..

I've added to everyone's rep who posted on the issue, thanks again ! I put 35 bog free miles on yesterday playing around in some drifts with buddies.
 
taylzee said:
I'm talking about the main needle and seat in the float bowl. It's the part the floats are connected to. It's basically the fuel valve that the float operates.
Check the tech section for the carb part break down and proper cleaning methods. If the needle is stuck half way in the seat, it won't shut the fuel flow off and it will keep the fuel flowing into the float bowl. Fuel coming out of the vent lines is usually an indication of this. The only other thing that comes to mind is a blockage in the exhaust. It could be that your exhaust side skirt broke off the piston and is stuck in the manifold.

You could pull the exhaust manifold and roll the motor over to have a good look at the exhaust side of your piston and inspect the manifold. You can also get a good look at the intake side of the piston if you pull the reed cage while you have the carbs off to inspect the needle and seat. I would say you want to pull the seat right out and look behind at the intake passage.
Click to expand...

This was exactly what I needed to do, and it solved the issue. I assumed that because the needle moved freely in the seat that there wasn't an issue with it, of course what I didn't know was that the issue was between the seat and the body of the carb. Thanks again taylzee !!
 
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