I am looking for advice on my 79 Jag 3000FC. I bought this sled cheap because the previous owner was unable to get it to run properly. It has very few miles on it, so I though I would "try". It did not come with an owners manual. I cleaned the fuel tank and replaced the fuel lines (including the one in the tank) and filter. Checked plugs. What should the gap be? Then added new gas. The carb was rebuilt about five years ago, but has not been run since. And the previous owner said it made no difference.

It will start, but I must play with the throttle and choke to keep it going. It will not run for long without having the choke "on". It also sometimes backfires through the carb. Pulling the left plug wire seemed to make little difference, although it did pick up a few rpms when I reattached the plug wire. When I got it back into the shop, I checked the plugs thinking the left one would be wet. It was not, and they both looked brown and dry.

I have read so many suggestions about similar problems on this site, that I am convinced I need to rebuild the carb, choke seals, choke adjustment, replace the CDI, coils, plugs.............in other words, I am totally overwhelmed with the information.

Any advice would be appreciated. I am a novice at this, but willing to learn. And the 24" of snow these past two days helped motivate me to get this sled running!

Thanks

clean and readjust the carbs first,,, see where that gets you,,,, (at least you will know its taken care of and you can go from there)

Are you running it with the belt off? That will rule out any clutching issues. Are you absolutely sure it's running on both cylinders? Does it have good compression on both cylinders? I have an '89 cougar that wouldn't rev past 2000 rpms. I banged my head against the wall for a long time trying to figure that one out. Turned out to be bad wires comming out of the stator...... Replaced all the wires and now she runs well.

Are you running it with the belt off? That will rule out any clutching issues. Are you absolutely sure it's running on both cylinders? Does it have good compression on both cylinders? I have an '89 cougar that wouldn't rev past 2000 rpms. I banged my head against the wall for a long time trying to figure that one out. Turned out to be bad wires comming out of the stator...... Replaced all the wires and now she runs well.[/b]



You do not want to sit and rev it up with the belt off,,, without any type of pressure on the motor, your asking for troubles....

Are you running it with the belt off? That will rule out any clutching issues. Are you absolutely sure it's running on both cylinders? Does it have good compression on both cylinders? I have an '89 cougar that wouldn't rev past 2000 rpms. I banged my head against the wall for a long time trying to figure that one out. Turned out to be bad wires comming out of the stator...... Replaced all the wires and now she runs well.[/b]


No, I had not thought of trying with the belt off. It runs on both cylinders for a short time, then reverts to just the right cyl hitting. I can pull the left plug wire and it is barely noticeble. Replace and pull the right plug wire and it will hit on the left but soon die. I have checked the spark on both cyl and they both are bright and consistent. Seems like at a higher rpm it will start to miss.

I start it with the choke on. Then after a bit, turn choke off. It will die within about 5 to 10 seconds. If I flip the choke on before it dies, it will start running again. This does not change when it is warmed up. Last night I pulled the plugs again after running for a few minutes. Both plugs were a little wet. But not dry like I mentioned before.

I will check compression today. Thanks for the come back and suggestions. Taking the belt off in a confined space should have been obvious?? Great suggestion regardless of a belt issue. Oh well!!

Wyoming

another thought you just brought up,,, your stator has high speed and low speed windings,,,, I had an old deere here one time that would only run right at high speed (over 3000 rpm) but as it fell below 3000 rpm, it would die. Now with this problem, I had both cylinders not firing,,, so you basically had to pull the recoil hard enough to get spark at the higher rpm and keep it running higher and it would run fine,,,,

I dont know if its possible to loose only one cylinder at a higher rpm if this is your problem (high speed windings bad),,,

I wouldnt worry about the belt just yet. When you get it running with the choke, then take the choke off and it dies,,, this sounds like a carb problem. I would get them cleaned up really good first. I would almost rule out the fuel filter/line/impulse line as you say it runs good with the choke circuit activated. If any of those were the problem, it wouldnt run right whether your choke was on or off,,,,

While your in there cleaning, take a good look at the boots between your carbs and motor and the boots between your carb and air box. Make sure they are not dried, brittle, and cracked. If they are, replace them.

clean and readjust the carbs first,,, see where that gets you,,,, (at least you will know its taken care of and you can go from there)[/b]


By cleaning the carb, I assume you mean taking it apart? It has a single carb, which I was hoping to avoid taking apart. For fear of not getting it back together again. To take apart and clean, do I need a carb kit, or can I put it back with the same seals etc? I did find a post about rebuilding a carb somewhere on this forum. I printed it out and will probably have to give it a try.

Thank you for your suggestions.

Wyoming

not hard to do, and you do not need a carb kit unless your gaskets are messed up or you tear them when you pull it apart. A single carb just makes it that much easier to clean, but also throws another wrinkle in the fold,,,, with a single carb, you should be having the problem on both sides, not just one. I am also assuming you have 1 coil,,,, if you have good spark and it runs on one cylinder really well (no matter the rpms) then I would rule out the stator and cdi. There is a chance that you have a bad plug boot, or bad plug wire??? I had a 90 prowler that had a bad plug boot,,,, it would run fine for a while, then run like crap for a while. As long as it was just sitting there, it ran fine, so it was really hard to find the problem. Once I found it, replaced the wire, it was a world of difference.

Even if your problem is spark, I would still pull the carb and clean it,,,, this should be done every year.
As you look down on your carb, there will be a lid that screws off the top of the carb,,,, unscrew this slowly as there is a spring in there. It is not really tight and will fly off and hurt someone, but if you dont realize it and it gets away from you, you may loose parts,,,, (I did this on my first rebuild LOL) once you get that off,,,, unscrew your chock cable from the carb and then its one screw that holds the carb to the intake boot and you can pull it right off,,,,

After you have done it once, your gonna realize it really isnt that hard,,,,

good luck and let us know if you have anymore questions.

another thought you just brought up,,, your stator has high speed and low speed windings,,,, I had an old deere here one time that would only run right at high speed (over 3000 rpm) but as it fell below 3000 rpm, it would die. Now with this problem, I had both cylinders not firing,,, so you basically had to pull the recoil hard enough to get spark at the higher rpm and keep it running higher and it would run fine,,,,

I dont know if its possible to loose only one cylinder at a higher rpm if this is your problem (high speed windings bad),,,

I wouldnt worry about the belt just yet. When you get it running with the choke, then take the choke off and it dies,,, this sounds like a carb problem. I would get them cleaned up really good first. I would almost rule out the fuel filter/line/impulse line as you say it runs good with the choke circuit activated. If any of those were the problem, it wouldnt run right whether your choke was on or off,,,,

While your in there cleaning, take a good look at the boots between your carbs and motor and the boots between your carb and air box. Make sure they are not dried, brittle, and cracked. If they are, replace them.[/b]

not hard to do, and you do not need a carb kit unless your gaskets are messed up or you tear them when you pull it apart. A single carb just makes it that much easier to clean, but also throws another wrinkle in the fold,,,, with a single carb, you should be having the problem on both sides, not just one. I am also assuming you have 1 coil,,,, if you have good spark and it runs on one cylinder really well (no matter the rpms) then I would rule out the stator and cdi. There is a chance that you have a bad plug boot, or bad plug wire??? I had a 90 prowler that had a bad plug boot,,,, it would run fine for a while, then run like crap for a while. As long as it was just sitting there, it ran fine, so it was really hard to find the problem. Once I found it, replaced the wire, it was a world of difference.

Even if your problem is spark, I would still pull the carb and clean it,,,, this should be done every year.
As you look down on your carb, there will be a lid that screws off the top of the carb,,,, unscrew this slowly as there is a spring in there. It is not really tight and will fly off and hurt someone, but if you dont realize it and it gets away from you, you may loose parts,,,, (I did this on my first rebuild LOL) once you get that off,,,, unscrew your chock cable from the carb and then its one screw that holds the carb to the intake boot and you can pull it right off,,,,

After you have done it once, your gonna realize it really isnt that hard,,,,

good luck and let us know if you have anymore questions.[/b]



I'm having almost as much trouble trying to use this forum as with the sled!! But, I'm learning!

When I say it runs with the choke on, I do not mean to imply that it runs well. It's still not right....just that it will keep running. I'll give the carb cleaning a try. I am not familiar with the stator? It has one coil.

Could you explain to me what will happen from running without the belt? It is a problem because the motor will over-rev or something else?

Thanks for the encouragement!

Wyoming

I think your problem is electrical. A single carb would run bad on both cylinders if the carb was bad. Check and double check the spart plug wires and the boots where they connect to the spark plug. Also check compression. Get a cheapy compression gauge from the parts store. I check compression without giving it gas. Some people check compression while giving it gas. Either way, a good top end should have at least 110 on the gauge. My old cougar has 70 on the gauge and starts well and runs well, but doesn't have much power.

I think your problem is electrical. A single carb would run bad on both cylinders if the carb was bad. Check and double check the spart plug wires and the boots where they connect to the spark plug. Also check compression. Get a cheapy compression gauge from the parts store. I check compression without giving it gas. Some people check compression while giving it gas. Either way, a good top end should have at least 110 on the gauge. My old cougar has 70 on the gauge and starts well and runs well, but doesn't have much power.[/b]


I think I have found at least part of the problem. I noticed that the left side of the carb had an arm with a plastic bushing......with nothing in the bushing. When I got the carb off, I see that it must have gone to the oil pump. Can't find anything in the bottom of the compartment, so it must have been removed and not replaced at one time? I am going to look for pictures to see if I can find out what it should look like... and maybe rig something up.

I checked spark again, and the left cylinder has no spark. It seems to be intermittent though because yesterday, it did some of the time. Which would sound like the bad wire problem that was suggested. Have not been able to check the compression yet.

We are 60 miles away from the nearest town that would have any parts. Plus, we are snowed in with the 24" we had. This was part of the storm that hit Denver. It's just that the national weahter people forgot anyone lives in Wyoming?? All this snow, and here I sit, in the shop!! And in reality, it has probably been four or five years since we had enough snow to ride.

Thanks for everyones suggestions and help!! I'll let you know as things progress. I also have a 1976 JD 440 Cyclone that we are working on. I think it has fuel problems.

Wyoming

I think I have found at least part of the problem. I noticed that the left side of the carb had an arm with a plastic bushing......with nothing in the bushing. When I got the carb off, I see that it must have gone to the oil pump. Can't find anything in the bottom of the compartment, so it must have been removed and not replaced at one time? I am going to look for pictures to see if I can find out what it should look like... and maybe rig something up.

I checked spark again, and the left cylinder has no spark. It seems to be intermittent though because yesterday, it did some of the time. Which would sound like the bad wire problem that was suggested. Have not been able to check the compression yet.

We are 60 miles away from the nearest town that would have any parts. Plus, we are snowed in with the 24" we had. This was part of the storm that hit Denver. It's just that the national weahter people forgot anyone lives in Wyoming?? All this snow, and here I sit, in the shop!! And in reality, it has probably been four or five years since we had enough snow to ride.

Thanks for everyones suggestions and help!! I'll let you know as things progress. I also have a 1976 JD 440 Cyclone that we are working on. I think it has fuel problems.

Wyoming[/b]

You can have a bad coil firing only one cyl. intermittently. Seen it happen many a time. Go with Green goblins idea first. replace they wires and boots. If that does not cure it replace the coil this would be the next problem.[Enclosed is a diagram of your carb, exploded view. Also never run the engine without the belt your engine or clutch can over rev and could cause serious injury!!!attachment=31887:carb.gif]

Thanks for the info and the picture. Tonight, I got it running!! Not far as it was too dark out. Besides replacing fuel lines, filter etc., I did take the carb apart and soak it in carb cleaning fluid. I rigged a turnbuckle to replace the missing rod from the carb to the oil pump. Put it back together and it ran rough at first. Some tinkering with the pilot screw and letting it warm up seemed to make it smooth out.

I can't explain the spark problem. It seemed to have a weak spark on the left cylinder tonight when I first fired it up. I did move and poke the plug wires and maybe that helped, but I did not notice it at the time. I'll give it a try tomorrow and see what happens.

Also was able to get the Cyclone running. It had a plugged filter in the tank. We'll give it a better test tomorrow too. I am guessing I will have to clean the carb on it as well.

Are plug wires and coils something that I would find at the local shop for this old of a machine? I have seen them on one of the web sites someone suggested.

On the Cyclone, the fuel filter is barely 1/8 full of fuel. Is this normal? The AC is about half full. They both have an inline paper looking filter about one inch in diameter and two inches long.

With the large inline filters, is the tank filter necessary?

If you know you won't be riding for a month or more, do you do any precautionary things to the fuel..... i.e. add fuel stabilizer? Or drain the fuel and run the engine day?

Thanks for taking the time to respond. I am seeing things much more positively tonight that two days ago!! I think it's great that all of you are willing to help. Giving me a starting place and an order of how/what to trouble shoot was the best help.

Wyoming

Hopefully I am too late and you are out and about.

The sled you have is a good runner and depending on the shape worth spending a little extra. You'll get lots of use from it.

I restore, and tune vintage sleds and funny thing is I had a customers 77 jag that had a similar problem. I went through most of what you guys was discussed and finally fixed it by replacing the pistons and rings.

All suggestions so far are excellent and should be done ( especially if it hasn't run for a while). Clean, clean, clean the carb. Soak it and use lots of air to blow out the passages. Take off the recoil(if it has one), pull the flywheel, and blow out anything living in the stator.

Although lots of talk re the stator has gone on check the spark before seriously digging into the electrical. If the spark at the plug is big blue and fat chances are the stator/coils are fine. Removing the stator will mean additional work when putting it back together. Another thing is the stator has two windings one is for the lights and the other is for the spark. CDI's typically work or not. If they don't work the machine won't start.

You mentioned blow back from the carb and not getting rpm. I am not 100% sure unless I see it but a lot of Arctic Cat engines fire both plugs at the same time (unlike alternate sparking). If your rings are worn then the fuel will blow past the rings on the off cylinder when the piston is moving down and when the ignition fires it will blow out through the carb.

Do a compression check.First dry and then wet (remember to hold the throttle wide open while doing the check). If compression is less than 100 or the low cylinder is less than 80% of the high then get a set of rings or piston kits. I would lean to the compression because if your getting a nice fat bvlue spark at the plugs the timming is way out to blow back through the carb.

Thanks for the info. It is running better from use I assume. It still will backfire though the carb, but only when cold. Once warm it does not. It starts right up from cold. I have come to the conclusion that the spark problem is probably my inexperience at checking it out. I would not have thought I could have missed it that far, but since it is running without the missing problem now...... It does have a good blue spark.

I hope mine does not have the rings/piston problem. I have yet to check the compression. Probably a dumb question, but, you mention checking wet and dry and with the throttle open. By dry, do you mean just pull the rope? And by wet do you mean squirt a little fuel in the plug hole and pull the rope? Throttle open in both instances?

With everyone's help, I also now have the JD Cyclone 440 running. I have parked it because it has pulled out several cleats. It is a great machine with only 1300 miles. I also rebuilt the carb on my Yamaha 250 Enticer. Just got it going this afternoon. Today was the first time I have ridden the Yamaha. I think I'm going to like it.

I am not intentionally a vintage collector. But, the price was right on all three and sometimes I don't know enough to say no!!

Sorry for the delay........

Vintage sleds are great pieces of machinery and areesily fixed buy the average person with a minimum of inexpensive shop tools so don't throw the baby out with the bath water or be scared to get your hands a little dirty. For a few bucks there is still a lot of fun left in these machines.

You mention backfire out the carb when cold but not hot. This could still be a ring/compression problem. When cold rings are not expandes as much as when the engine is warmed up and therefore compression is lower and more blowby will occur. When the engine heats up the rings create a better seal.

To do the compression check.

1 Remove the plugs from all cylinders.
2. Dont have to But I remove the carb (cause I'm really old school) just to make sure no fuel reaches the cylinder as this may skew the reading a bit not a lot but a bit.
2 insert the compression tester into the first cylinder ( a screw in one with a max pressure needle is best and easiest).
3 do the dry test first by holding the throttle open and spin the engine while watching the compression guage. You should see the needle fluctuate up and down as the engine spins. Watch the readings. I generally take the average reading but you can go with the highest. Record the reading and repeat the procedure on the other cylinder.
4 Do a wet test by squirting a little oil in the cylinder and repeating step 3. Record these readings also.
5 There will be a difference between the wet and dry readings because the oil creates a better seal around the rings. If the difference is large then the rings are worn and need to be replaced. If compression is below (some say 80 psi I say 100) the maufacture specs then rings are needed.

If rings are needed I would suggest replacing the pistons as well. Shop around for piston kits. The kits will include the pistons, rings, circlips, pin and usually a new pin bearing. SHOP around the prices vary a lot from suppliers.

If you have to get into pistons and rings replace te crank seals as well and make sure to hone the cylinders to remove the glaze (If no rebore). If you oversize on the pistons and rebore make sure to hone the cylinders and that the ports do not have sharp edges as this couldl catch the rings and break them.