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Discussion Starter · #1 ·
Hey y’all! I have a 1996 Formula 3 w/FAST pipes and stock can that I use for mostly ditch banging, ice fishing, and trail riding with the occasional pulling kiddos on sleds. I live in ND with elevation is 900-1300 ft. Any suggestions what jets I should run? My mains are 350 across the board but I’ve got a good miss on the PTO side and the plug is much wetter than the other 2. It appears to be getting spark. I think the jetting could be a factor but I’m open to suggestions! Thanks!
 

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2014 Summit X 154" 800 etec
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350 should be the correct setting for that elevation- maybe you could stand to use 330 but I dont think that's your issue. I would first clean all the carbs, paying special attention to the problem cinder. Check compression, you may have low compression on the PTO side. Also check the coil on that side, it could be weak and failing under load. Check your plug wires as well. Old plug wires tend to corrode at each end - unscrew the wires from the coils and plug caps , cut about 1/4" off each end re-install. The last thing I would check is the PTO crank seal - you may have a leak.

That should cover most common causes for your issues.

Good luck!
 

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Jason has given you some good starting points. I wouldn't be too concerned with the jetting itself simply because if all the jets are the same size which they should be and they were the problem all three cylinders would be running rich. Before I did too much I would switch the spark plug wires between cylinders 1 and 2. (PTO and center) and give it a try. If the wet cylinder moves to the center cylinder you will know you have a coil or wire issue assuming you have previously changed plugs which didn't solve your problem. Changing wires from one cylinder to another will not affect engine timing as all three coils fire at the same exact time. This is what is called a "Waste Spark System".
One problem which seems to show it's ugly face with carbs of this era is leaking needle and seat assemblies in the carbs allowing fuel to pass by the needle and flood the cylinder. The gaskets under the needle seats have been known to dry out, shrink slightly and allow fuel to pass by and flood the cylinder. Unless you know the maintenance history on this engine you should remove, disassemble, clean and reassemble the carbs with new gaskets as nedded and all three needle and seat assemblies replaced. If they aren't a problem now they wil be at dome point in time and this can lead to a carb flooding, filling the base with fuel and when you pull the rope the engine can fire and instantly bend a connecting rod. That is expensive and unnecessary if preventative steps are taken. Spend a little now to prevent spending a lot later.
On any of my triple cylinder sleds I always shut the fuel valve to off when I'm not running the engine so this flooding can't take place. I had to learn the hard way on my '97 Mach 1 when it was brand new with 51 miles on the clock. I was very fortunate the warranty covered the parts and labor.
If you have a compression tester or can borrow one a compression test of all three cylinders would be a good idea even before you do anything else. The compression readings should be within 10% of each other in all three cylinders. Trying to make an engine run well with low compression in a cylinder is likened to putting a Band Aid on a broken arm.
You could have other issues such as a stuck or broken petal in a reed valve or even a stuck RAVE valve but these would be the last thing I would be looking at as neither is very common. Usually a leak around a base seal will tend to lean a cylinder out but hey, you just never know.
Keep us in the loop and welcome to the forum.
Lynn
PS. I should have asked. How long have you owned this sled? Has it always bothered or is this issue something which showed up?
 

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Discussion Starter · #4 ·
Thanks, Jason! I was going to say Happy Thanksgiving to you but saw you’re Canadian so I’d be a month and a half too late! (my wife is Canadian). I should have mentioned that it seems to not have the issue at speed. If it is missing any snort I’m not seeing it - things borderline scary when it hooks up.
 

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Discussion Starter · #5 ·
Jason has given you some good starting points. I wouldn't be too concerned with the jetting itself simply because if all the jets are the same size which they should be and they were the problem all three cylinders would be running rich. Before I did too much I would switch the spark plug wires between cylinders 1 and 2. (PTO and center) and give it a try. If the wet cylinder moves to the center cylinder you will know you have a coil or wire issue assuming you have previously changed plugs which didn't solve your problem. Changing wires from one cylinder to another will not affect engine timing as all three coils fire at the same exact time. This is what is called a "Waste Spark System".
One problem which seems to show it's ugly face with carbs of this era is leaking needle and seat assemblies in the carbs allowing fuel to pass by the needle and flood the cylinder. The gaskets under the needle seats have been known to dry out, shrink slightly and allow fuel to pass by and flood the cylinder. Unless you know the maintenance history on this engine you should remove, disassemble, clean and reassemble the carbs with new gaskets as nedded and all three needle and seat assemblies replaced. If they aren't a problem now they wil be at dome point in time and this can lead to a carb flooding, filling the base with fuel and when you pull the rope the engine can fire and instantly bend a connecting rod. That is expensive and unnecessary if preventative steps are taken. Spend a little now to prevent spending a lot later.
On any of my triple cylinder sleds I always shut the fuel valve to off when I'm not running the engine so this flooding can't take place. I had to learn the hard way on my '97 Mach 1 when it was brand new with 51 miles on the clock. I was very fortunate the warranty covered the parts and labor.
If you have a compression tester or can borrow one a compression test of all three cylinders would be a good idea even before you do anything else. The compression readings should be within 10% of each other in all three cylinders. Trying to make an engine run well with low compression in a cylinder is likened to putting a Band Aid on a broken arm.
You could have other issues such as a stuck or broken petal in a reed valve or even a stuck RAVE valve but these would be the last thing I would be looking at as neither is very common. Usually a leak around a base seal will tend to lean a cylinder out but hey, you just never know.
Keep us in the loop and welcome to the forum.
Lynn
PS. I should have asked. How long have you owned this sled? Has it always bothered or is this issue something which showed up?
Thanks, Lynn! I did swap the plug wires around and the issue didn’t follow the wire. I thought I read that you’re supposed to use a different size jet in the PTO side than the middle and MAG? Then again, I’ve been inhaling a lot of exhaust fumes and gas vapors in the past day trying to sort it out so maybe I’m wacked in the head ;)
 

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Early on they were recommending one size smaller main jet in the center carb. 320 instead of 330. Most folks I know with F-111's of that era run the same size jets in all three cylinders.
I would be getting into the carbs at this point in time. These needle valves are a wear item and will lead to BIG problems.
 

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Discussion Starter · #7 ·
Early on they were recommending one size smaller main jet in the PTO carb. 320 instead of 330. Most folks I know with F-111's of that era run the same size jets in all three cylinders.
I would be getting into the carbs at this point in time. These needle valves are a wear item and will lead to BIG problems.
Sounds like a plan! Where are people ordering parts from these days?
 

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Lots of places still carrying parts for your triple. I use Dennis Kirk often enough.

Also use MFG Supply when desperate. They are a good source for hard to find aftermarket parts.

Here is a spec book for some older iron I find useful.

You'll see in that book they are calling for 330 mains and a 320 in the middle. Not sure if your pipes call for more gas but if not, I would say 350s are fat and could be leaned out a bit.
Agree it sounds like the carb. I might pop them all open if you're unsure what's inside. Good luck.
 

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PS Just notice that book calls for a fatter 55 pilot in the middle. I confirmed these numbers with the shop manual. So, a leaner main and fatter pilot in the middle. Curious.
 

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I have seen these specs all over the board. Here we're dealing with aftermarket exhaust. so this may be a trial and error tuning session. If in doubt go richer. You can always work down from there. Plug readings, cylinder head temperature readings and exhaust temperature readings for each cylinder are the only way you will ever get to optimum.
Everything has to be up to speed before starting to fine tune any engine regardless of what it is. Compression has to be within specs and the ignition including spark plugs have to be in new or like new condition. Any little variable can send you into La La land. If something is out of spec it's like running a marathon with a broken ankle.
 

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Discussion Starter · #11 ·
Another thing I noticed is there appears to be oil in the exhaust showing up in the shop floor from the exhaust pipe. Hard to say how much but a bit regardless. Could possibly be from it starting and idling in the shop but…
 

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Happy Thanksgiving!

That's not likely something to worry about at this point. At worst, you're getting too much oil so that's not going to hurt anything.

More likely it's normal 2 stroke accumulation in the pipes. Often happens when a sled is started a few times but not run up to operating temps. It might take 10 to 20 minutes of actual riding to get the pipes up to temp where they burn off the normal oil deposits.

When you pop the carbs and pull the jets you might need a magnifying glass to read the jet size. I know I do. Let us know what you find. Cheers.
 

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With regards to the oil from the pipe - check to make sure it’s “just” oil. I had a very small base gasket leak on my sled and it caused the middle cylinder to miss at low rpm until you rode for a few minutes and it cleared up. One way to check is to take a bit of the oily residue an put a dab on your tongue - if it has a slight sweet taste, it most likely has coolant mixed in and you may have a small base leak. Sounds gross but there ya go :)
 

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Check your choke plungers on the carb. Sounds like that one is sticking slightly & might be partially choking. Take the plungers right out and clean plungers & on the inside where they fit etc. I would also give 340/330/340 jetting a whirl. Running the trident/fast pipes with the original suitcase silencer kinda restricting. Not getting the full potential out of those pipes.
 
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