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Discussion Starter #1
Hey everyone, I'm hoping some of you could help me out here. I was out riding a couple days ago with buds, we stopped along the trail for about 20 mins, when it was time to move along again my sled wouldn't start. We tried brand new plugs, no luck. We tried gas line anti-freeze cause it seemed as though the gas wasn't getting to the cylinders. The plugs were dry, no matter much priming we gave it. Tried gas down the cylinders, didn't work! Checked the spark, seemed good although it was light out so we couldn't tell if it was a blue or white colour. Finally after holding it WOT and pulling for for probably 20 mins it started to fire, eventually it started but i had to stay on the throttle or it would stall. At the next stop it stalled as I was taking off my helmet, this time it would not start again. End of trip for me!

After getting it home, I rebuilt the fuel pump, removed and cleaned both carbs and synced them, and replaced the fuel lines. Now the gas is getting to the cylinders, I know this because the plugs are now wet. Damn thing still will not fire!!! :cussing::cussing::cussing:
 

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Discussion Starter #2 (Edited)
I should add that this evening I plan on cleaning all wiring connectors and then adding di-electric grease before snapping them back together. Just trying to eliminate possibilities before I get into the electrical components. I've also tried doing a search on this site as well as google but can't find this exact problem, lots that are similar but not the exact same issues. Any other ideas???
 

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Do you still have spark?
Compression okay?
Highly unlikely but is the fuel fresh? Stale fuel doesn't ignite worth a d*mn. Was there any water in the water traps when you took the carbs off?
 

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Discussion Starter #4 (Edited)
Do you still have spark?
Compression okay?
Highly unlikely but is the fuel fresh? Stale fuel doesn't ignite worth a d*mn. Was there any water in the water traps when you took the carbs off?
Retiredpop thanks for the reply, the fuel that was in was about three weeks old and before I left home I topped it off with fuel from a jug I had in the shed. That fuel wouldn't have been more than 2 months old. No there wasn't any water in the traps. I had checked the compression about a week ago, it was around 110 in one and 102 in the other. Not sure I did it correct though, what is the best procedure for checking compression? I'm going out to check the spark now since it is dark. As far as spark, one side seems to be a real strong blue spark and the other seems a bit weaker and kind of flashes between blue and yellow.
 

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Discussion Starter #5
Okay, I did a little more research and this is the method i've used to check the compression. Kill switch and ignition off, both plugs out, and WOT. 94-95psi in one and 100psi in the other. So the compression seems to alright. Now what????? :(
 

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Compression below 100 is very weak. When the sled was new, it probably had 130+. How many times did you pull the rope? I would give it at least 5 pulls or until the number quits rising.

If your gauge is accurate, consider some top end work. I would test the gauge on a sled that's running fine to see if you get a low reading on the other sled first, though.

Did you unscrew the plug caps from the plug wires? I would try that and while the cap is off the wire, look at the contact inside the plug to make sure it's clean. Before screwing the cap back on the wire, snip 1/4" off the wire so that the contact is making a more positive connection. It may not cure the problem, but will rule out the wire as a problem.

Now that you have fuel going to the carbs, you may have flooded the crankcase. On the front of the case under the exhaust are two small plugs. They will drain any excess fuel/oil from the case and may help in getting the engine started.

That's a few more things for you to try. If you have fuel and have spark, it should at least pop at 100 psi compression...

good luck!
 

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Discussion Starter #7
Thanks BCDan, I'll have another go at it tomorrow. My buddy has the exact same sled so I'll check his compression to compare.
 

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The compression does sound low especially if you are at low altitude in NB but that could be the gauge. It's a bit of a concern that you have dropped 8 to 10 points from a week or so ago. Do you have the kind that screws into the spark plug hole or one with the rubber that you just push into the hole? The screw in type are usually more reliable but as long as you use the same one on your buddies sled you'll get a good idea where you stand. While you're checking the spark plug caps be sure to check the other end of the plug wires too where they screw into the coil. I've had them loosen up as well. You can get solid core wires from NAPA if you need to replace them. As BCDan says though it should fire at 100 psi. I've run sleds at lower compression than that but they are hard to start. Keep us posted.
 

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Discussion Starter #9
I snipped about a half an inch off the plug wires last night, it started to fire but didn't catch. This morning I went back out and drained the crankcase, there was a bit of fuel in there. I put new plugs in again, pulled it over a few times on full choke and it started but before I could flip the choke to half it died out. Pulled about five times on half choke and nothing, pulled about five times with no choke and nothing, pulled another ten times on full choke still nothing except the strong smell of fuel. I drained the crankcase again, this time a lot of fuel came out. Tried a few more pulls on full choke still nothing. So my question is this, would it be possible that the sled is flooding due to the rear being higher than the front, like about 2-2 1/2 feet higher?
 

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The only reason it would be flooding is because there's too much gas going into the engine. A stuck inlet needle/seat to the float bowl is the most common. You could also have a choke plunger stuck open, which would make the air/fuel too rich. Other problems could be a float that is not set correctly or a hole in the fuel pump diaphragm that will allow fuel to enter the crankcase via the impulse line.

I'd remove the carbs and check the inlet needle and choke plungers first. The plunger should move freely in the bore and there should be a neoprene seat in the bottom of the plunger. It's normal to have a small groove in the neoprene, but if it's really worn, you may want to replace the plungers.

Having the back higher than the front will slightly increase fuel pressure, but in a properly operating system, that should not contribute to flooding.

When you are trying to start it, and it starts to flood, don't apply the choke. Hold the throttle open wide and crank a few times to clear out excess fuel. And when applying choke to a cold engine, don't touch the throttle; the enrichment circuit in the carb needs the slide to be at the bottom to work properly.

How much play is in the throttle lever? The spec for that is 0.010" to 0.030". If there's too much (or too little) the throttle safety switches could be activating, keeping the engine from starting. That's something else to check...
 

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I would have said check for fire and check for fuel first, but it sounds like those are covered. It rather sounds like a compression problem; that's the third easy trouble shooting deal I'd want to look at.

I would suggest turning the engine over by hand, using the clutch. It doesn't have to be fast, but pulling it around will give you some idea what each cylinder is doing in terms of holding pressure. (Sometimes the more rapid rotation you get with the starter can fool the gauge a bit.) You'll be able to feel it by hand. It should resist pretty good when you turn the clutch by hand.

It sounds like you are at the point where I'd be looking in the 'windows' (pulling carbs and exhaust manifold to have a look inside the ports). Visible inspection of rings to make sure they are intact as well as clean and freely moving is critical. If a ring is slightly stuck - more probable on the exhaust side, that could give you low compression and potential to break rings, score cylinder, etc. I would also like to know that my piston skirts- intake side- are intact. That can really mess up file flow conditions are make engine run poorly if at all.

If your machine is actually a 500, the liquid, not the fan, pulling a head and getting into the coolant is more than I'd do at this point, but I'd sure do it if you've got the 488 fanner engine.
 

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Discussion Starter #12
I would have said check for fire and check for fuel first, but it sounds like those are covered. It rather sounds like a compression problem; that's the third easy trouble shooting deal I'd want to look at.

I would suggest turning the engine over by hand, using the clutch. It doesn't have to be fast, but pulling it around will give you some idea what each cylinder is doing in terms of holding pressure. (Sometimes the more rapid rotation you get with the starter can fool the gauge a bit.) You'll be able to feel it by hand. It should resist pretty good when you turn the clutch by hand.

It sounds like you are at the point where I'd be looking in the 'windows' (pulling carbs and exhaust manifold to have a look inside the ports). Visible inspection of rings to make sure they are intact as well as clean and freely moving is critical. If a ring is slightly stuck - more probable on the exhaust side, that could give you low compression and potential to break rings, score cylinder, etc. I would also like to know that my piston skirts- intake side- are intact. That can really mess up file flow conditions are make engine run poorly if at all.

If your machine is actually a 500, the liquid, not the fan, pulling a head and getting into the coolant is more than I'd do at this point, but I'd sure do it if you've got the 488 fanner engine.
I have turned the motor over via the primary and it seems to have good compression when doing it that way. I have not thought of removing the exhaust to have a look at the rings, I may have to do that. The sled is infact the 500 liquid, right now that is about the only thing I'm sure of! LOL.
 

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Discussion Starter #13
The only reason it would be flooding is because there's too much gas going into the engine. A stuck inlet needle/seat to the float bowl is the most common. You could also have a choke plunger stuck open, which would make the air/fuel too rich. Other problems could be a float that is not set correctly or a hole in the fuel pump diaphragm that will allow fuel to enter the crankcase via the impulse line.

I'd remove the carbs and check the inlet needle and choke plungers first. The plunger should move freely in the bore and there should be a neoprene seat in the bottom of the plunger. It's normal to have a small groove in the neoprene, but if it's really worn, you may want to replace the plungers.

Having the back higher than the front will slightly increase fuel pressure, but in a properly operating system, that should not contribute to flooding.

When you are trying to start it, and it starts to flood, don't apply the choke. Hold the throttle open wide and crank a few times to clear out excess fuel. And when applying choke to a cold engine, don't touch the throttle; the enrichment circuit in the carb needs the slide to be at the bottom to work properly.

How much play is in the throttle lever? The spec for that is 0.010" to 0.030". If there's too much (or too little) the throttle safety switches could be activating, keeping the engine from starting. That's something else to check...
I'm thinking the inlet needle should not be stuck as the carbs were just thoroughly cleaned two days ago, and the inlet needle was moving freely then. The throttle lever free-play is within spec as is the choke lever free-play. Do you mean there is supposed to be a neoprene seat attached to the bottom of the plunger? If so it is no longer.


Retiredpop;
The plug wires seem to be firmly attached to the coil pack, and I did manage to check the compression on an exact sled with 2500 miles on the motor. It was 118 and 120, quite higher than mine. my motor has 9500 miles on it. The fella I bought it from told me he did the top end but I'm not so sure about that.
 

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Okay, there are 2 problems unrelated to each other for the most part.

The low compression would be worn rings and/or worn cylinders. Your compression dropped quite a bit over a short period of time. When the first no start out on the trail occurred was it running okay up to that point or did you have an instance of it just quitting suddenly as if you hit the kill switch while you were riding? If that occurred that day or any previous day it is a good indication of a lean seizure. Been there myself:rolleyes2: If you have something like a bend-a-light or maglite with a fiber optic adapter you can look down the spark plug hole and check out the top of the piston for damage. If you pull the exhaust as mentioned above you should be able to see the piston top when it is at BDC. Although this is serious it is probably not the cause of it not firing and running.

The other problem seems to be a carb malfunction. If the inlet needle is stuck open it will fill up the crankcase with fuel even when it is sitting. I get the idea that is not happening - correct? That pretty much leaves a problem with a choke plunger not seating properly in it's bore. It could be that something has lodged itself in the bottom of the bore. The neoprene seat is not real noticeable unless you look right at the bottom of the plunger.
 

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I snipped about a half an inch off the plug wires last night, it started to fire but didn't catch. This morning I went back out and drained the crankcase, there was a bit of fuel in there. I put new plugs in again, pulled it over a few times on full choke and it started but before I could flip the choke to half it died out. Pulled about five times on half choke and nothing, pulled about five times with no choke and nothing, pulled another ten times on full choke still nothing except the strong smell of fuel. I drained the crankcase again, this time a lot of fuel came out. Tried a few more pulls on full choke still nothing. So my question is this, would it be possible that the sled is flooding due to the rear being higher than the front, like about 2-2 1/2 feet higher?
It kind of sounds to me like your excess fuel trouble might be related to a liberal use of the enrichment (choke) system. (Earlier you mentioned getting it started by much pulling with WOT.) WOT is the quickest way to cure a flooded engine with the older Mikuni round slide carbs. When the engines starts on full "choke" and dies before you get the lever snapped down. The next pull should be on a no "choke" condition, WOT, because the engine is a bit flooded. But I would be looking in the intake side also just to make sure everything is good with the pistons. If a piece of a skirt is gone, you've changed the timing and vigor of the intake process which can seriously affect what's getting into the cylinder or not.
 

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Discussion Starter #16
Okay so here's an update;

I realized today while driving to the parts shop that I had removed the needle from one of the carbs, I did this when cleaning the carbs cause it was slightly bent. No wonder it was flooding!! Anyhow today I replaced both needles, I figured if I'm gonna replace one I might as well replace both. I thought that once they were in that my troubles would be solved but it's still not starting. I'm starting to get slightly annoyed at this point! Is there supposed to be air in my fuel lines? I put on clear lines when I replaced them, and I'm noticing air pockets in the feed line to the fuel pump and also one of the carbs. Just wondering if this normal. I'm hoping to have a look at the Pistons sometime this weekend.
 

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Discussion Starter #18
Short of taking the carbs off again, everything seems to check out. So i thought I would go back to the obvious stuff. The gas that i used from my shed was in a container that doesn't really seal that well, so I was considering the water in the gas scenario again. I poured about half a litre into a clear container from this jug to check for water, and there appears to not be water in the gas. I'm now considering to empty the tank on sled and refill with fresh gas. If that doesn't work then I'll once again pull the carbs and clean.
 

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Discussion Starter #19
I opted not empty the fuel tank, at least for now. I re-checked the compression(same method as last time) and it read 89psi on both?!? So that is really low. I checked two other sleds of the same year and model, one had 2500miles @ 120psi and the other had 5600miles @ 110psi. So this summer I'll have it bored and I'll do the top end.

I also rechecked the spark, this time I stuck a screw driver in the plug cap and laid it across the motor. Both sparks were orange, one had a slight bluish tinge but overall orange. So I guess I'll be replacing some electrical components as well!

I really appreciate you fellas helping me out with this, I'll keep the thread updated after the major work is done through the summer. Thanks again!!!
 

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Discussion Starter #20
So here's the update....

I did manage to determine why the sled wouldn't start! I decided to pull the head and as soon as I did I could see that the pistons were banged up and gouged all around the edges. The rings actually didn't seem to be that bad of shape. I then pulled the cylinder block and was amazed that the sled had run at all!!! There were grooves and gouges all over the bore. The bottom end seemed to be good, no wiggle in the crank, so I left that as it was.

Fast forward to this past October, I placed an order for pistons and rings, gasket kit and a few other odds and ends. Well the order didn't arrive until the week before Christmas, bummer, not much time to get it up and running before the snow. I should also mention that I had picked up a second hand cylinder block over the summer, not in perfect condition, but it was in much better shape than the original block from my sled. I didn't have any time to work on it before the holidays for obvious reasons, so as soon as the new year landed I was working on it as much as I could. I put the new components together and checked the compression. 112 psi in one and 115 psi in the other, perfect or so I thought! I pulled and pulled but it wouldn't run. It would start every now and again but then immediately die. So I then checked the spark, it was good. By this point I was completely puzzled!! I figured I would tear the carbs apart again even though I had cleaned them before storing it last spring, it's a good thing because there were all kinds of particles and gunk in them from sitting through the summer. Put the spotless carbs back on and was certain it would now fire up. WRONG. Again I pulled and pulled with the same outcome as before. At this point I'm ready to burn it, except it isn't worth anything so it seemed kind of pointless besides giving me a bit of gratitude. ;) I decided to take a break from trying to get it to run, and replaced worn out suspension components and then put a newer set of bars on off of a Fusion.

I had picked these bars up last night, they came with the brake/light assembly and also the throttle control. I got a very good deal on the bars as well as the Fusion seat and tank, so I couldn't pass on it. So this morning I decided that since I had finished with my suspension that I would put on the new bars, I was trying to avoid messing with the motor! So after an hour or so I had the new bars on and a 3" riser I had also gotten. It was looking good!!! So I figured what the hell, I'd gotten the other stuff done, I'll try and pull it over a few times. Couldn't hurt right?

I pulled exactly three times, VROOM!!! I could not believe it! I let it run about a minute then shut it down. I thought must have been a fluke. So I pulled again, VROOM!!. It fired up again!?! Wow....okay. That was simple, I guess. The best I can figure is it must have had something to do with the TPS on the old throttle assembly. So now it runs, it's idling high but I'll do some adjustments and have it running great in no time. Hopefully I didn't just jinx myself!! :eek:

Thanks again for all of the help last years guys, this forum truly is the best!

Cheers.
 
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