Hi, I'm a new FL350 owner. Bought this atv about two years ago but had nowhere to ride it, so it sat with intermittent startups (run it for five minutes every month, etc, put around the yard). Finally moved to a place with open land, so I repalced the spark plug, fuel filter, fuel lines, intake [reed] boot, both clutches, drive belt, and fuel cap. When i would run the odyssey, when the Engine is cold, the thing had no power. itll top out at about 30mph. Thought the clutches were bad, so i replaced them with comet 94c's, but it didn't fix the issue. I discovered that if i run it for about 5-10 minutes, it warms up enough and makes the expected power. Trouble is, once it warms up, a new problem exists; if i get on it for more than a few seconds, it starts to choke/bog and backfires. If i let off the throttle, it usually doesn't stall, but sometimes i need to choke it to keep it running.

Checked the compression and it has 125psi on a cold Engine. That seems ok, right? The previous owner rebuilt the top end right before selling it. I took the carb apart multiple times and cleaned and set everything to standard settings. Jet need is set to notch #3, 142# main jet, 45 pilot jet. Air screw is set to 1.5 turns. Idle seems ok. Float is set to 16mm, float valve seems intact. Btw, I live at 0-1000ft elevation from sea level.

One thing i noticed is the pulse tube from the crank to the fuel pump is a little loose on the crank side. Even with a spring clamp, i can tug it off with one hand with a little force.
Also, not sure if i should clean out the fuel tank. I did notice a few rust flakes in the fuel filter.

Spark plug is a dark brown (im replacing it today). Suggests that its running too rich. Not sure why i need to choke it to keep it running at times though.

Based on teh fact that its slow when cold, and bogs/backfires when warmed up tell me something obvious? Btw, this is my first two stroke, so I'm learning as I go along. Any suggestions or help would be greatedly appreciated.

You probably have your problem already figured out. Clamp that pulse line tight. What's probably happening is once you use the fuel in the float bowl the fuel pumps not replacing it fast enough because the pulse isn't right. Clamp it and let us know. Choking it helps because there's not enough fuel. You must get this corrected. Remember on a 2 stroke NO FUEL=NO OIL poofkaboom

Also what are you mixing the oil at? You'll want to run a high quality oil mixed at 32:1.

Keep coming back to edit this. You'll also want to let it completely warm up before riding it. You risk a cold seizure when you run it hard when it's cold. Metal expands when heated. The aluminum piston expands at a greater rate than the steel sleeve and can lock it up. They run like crap when they're cold anyway. Why risk it.

For the mix, I'm using 32:1 Honda 2-stroke oil (the blue stuff).
I'll try getting a new hose for the pulse line. The weird thing is sometimes the odyssey just dies/chokes even when not running WOT (Wide Open Throttle). Like putting around with less than half throttle. Would this pulse line explain the slow performance when cold?

I understand not running it hard when cold, but with the way it is performing, I almost have to give it more than half throttle just to get moving. it just doesn't seem "normal". But maybe it is.? One other weird thing, when the Engine was cold last night, it had full power immediately. i wasn't riding it hard until i got it warmed up, but half throttle would take off without straining the motor (( Internal Combustion Engine ? )).

Have you done a leakdown test on this Engine? No 2 stroke will run good when cold. That's strange. Brings air leak leak to my mind. When I got mine it would run great, then like shit. Very inconsistent. I was running waaay lean. Changing jetting had no effect which keyed another problem to me. Turned out I had a leaking crank seal. If you have an air leak(leaking seal or gasket) this is all just chasing your tail. It will never run right if your not controlling how much air goes into it.

Also have you ridden anything with a CVT before? You gotta give it some juice before it starts moving.?depends on where your clutch is set. Kinda like a "stall" converter in a car. Mine doesn't take off till I'm almost at 4,000 rpm.

I haven't worked on 2 strokes for 20 or 25 yrs but I got a fl350 and had to start from scratch. If you post it up here you will get answers for sure. These guy's have helped me ALOT. But I had a similar problem with mine and it turned out to be the shift switch on the back of the tranny. To check it all you have to do is unplug it and ground the two wires, I took mine to the battery and that fixed it. But be warned that it can start in gear and want to take off if you throttle it. Also check and clean all of your conections that can have alot to do with it also. Hope it helps Billy

Leak check it, for sure. Air leaks make two strokes act very inconsistent.

Have you serviced the fuel pump at all? Could be full of garbage after years of riding and/or sitting.

Have you dumped the old fuel and replaced with fresh? If not, definitely do so.

Did you replace the fuel tee / valve (16710-VM0-770)? These can go bad over the years.

Pop off the carb boot and reed cage and check the reeds?

Check the head pipe & silencer and make sure they aren't plugged?

Air filter is clean? Right size? No mice living in there?

Have you checked compression when its warm? And are you using the pull-start or electric start for the test? With throttle held wide open?

Thanks everyone for the good advice and suggestions.

For the trans switch, the previous owner grounded one of the wires - if memory serves me, i believe the green one is grounded, but the black one is disconnected and not grounded. I will ground it tonight to see if that helps. I left it alone figuring the reverse speed shouldn't apply to my issue, but you never know.

Fuel pump has not be serviced to my knowledge. A few months ago my Oddy was dying after 5 minutes of riding. I swapped fuel pumps with an extra i had, but the issue was related to the gas cap. I am considering finding a good used keihin pump just in case.

Fuel T valve appears to be working. based on the manual, i could only blow it in the one direction (i forget which way at the moment).

When I did inspect the reeds, they were not cracked and flexed ok. They were coated in oil/gas, so they were sticking a little bit. I cleaned them up.

Haven't checked the head pipe/silencer, but i did remove that latch on the silencer and revved it a little to clear out any build up as the manual suggested. I'll have to check the pipe more thoroughly.

Air filter is clean. no mice.

For the compression test, Engine was cold if i recall correctly. Electric start with full throttle.

Also one other thing. When warmed up, the FL350 doesn't smoke excessively, and when i let it idle, the rpms were revving slowly to a higher idle. I adjusted the stop screw, but it seemed to return to a higher rpm idle on its own.
Seems like I have an air leak somewhere. I'll try to pick up plumbing caps to test the crank pressure.

reverse switch on the tranny is only a safety switch so you can not start it in gear.

Bingo! You definitely got an air leak. Just gotta find it now. The no smoke at rpm and revving at idle
Is exactly what was going on with mine.

its your pulse tube. shcnge your clamp and make sure its tight.

If I remember it is lso a rev limiter for reverse. I was having a similar problem and that fixed it. Thanks Billy

I replaced the pulse line and clamped it tight. Took the Oddy out for a ride and even after ten minutes of putting around, it refused to pick up speed above 30. Feels like its not revving fully, but hard to tell since its kinda loud. Definitely not hitting powerband.

I decided to to ground the change switch wire which the previous owner left dangling. When i cranked it, the wire started smoking. I stopped and noticed that the wire heated up enough to melt through the rubber. When i consulted the manual's wiring diagram, i discovered the previous owner hacked the wiring schema to hell. I hate wiring, and wasn't something i wanted to fix. But I guess now I have no choice. I'm only hoping I didn't just fry the CDI (Capacitor Discharge Ignition) or damage the starter...

At least in the stock harness, there is a fuse in the positive lead right off the battery. So if they removed the fuse...they aren't so smart.

So i got the wiring worked out and started it up. Took it for a ride with the two change switch wires grounded. Was still slow for the first five minutes. Once the Engine warmed up, it started ripping and hitting powerband. But after ten minutes, it was back to the usual backfiring and power cutoff. Letting go the throttle and sometimes choking it Keeps it running, but I still have an air leak somewhere. I suppose I'll head out to Home Depot over the weekend and get some plumbing caps to test the crankcase seals.
Almost wondering if if I have a timing issue. Is there a way to check that?

This might be a dumb question, but I was checking my exhaust manifold to measure for the pressure test, when i noticed the oil leakage. Picture may not be the greatest, but would be any concern? Should I replace the exhaust gasket?

http://www.pilotodyssey.com/Siliconesealer.htm

that's the unburned gas/oil

Better known as spooge!
Run less oil-gas mix
32-1 mix not 20-1
Randy

Randy

i have been running 32:1.

your leaking between the pipe and the manifold. Remove the pipe and clean both the inside of the pipe and the outside of the manifold and go get some yamabond from the yamaha dealer and put a layer on the inside of the pipe and the opuside of the manifold and reassemble. Make sure you use enough to stop the leak. works great for all my machines

It will also be much quieter. Mine was leaking at every connection. Last sunday I resealed my pipe and it really made it quieter. I had some concerns with this though. Now if I seal the point where this sludge is running out(which I did) where will it go? In my silencer? Will it eventually plug it? Will it just blow it right out the silencer? All gains? Is nice not seeing this junk on the floor under my buggy but I know its got to be going somewhere. Maybe im over thinking it? I can get myself in trouble with that at times. I'm not concerned about rust since it's oil, just that It might cause another problem later. Thoughts?

Not sure what the check next. Did a leakdown test today. Plugged both exhaust and intake with freeze plugs, piston in BDC and hand pumped around 9psi into the pulse tube. Only problem is my pressure gauge doesn't start incrementing [5] psi until after 10 psi, so there is a single space to represent 0-10 PSI if that makes sense. Didn't see the pressure gauge needle drop, so i let it sit for over 50 minutes. Barely moved if any. So i don't think i have a air leak. I'll try to find a more accurate gauge, but like I said the needle didn't really move and when i released the pressure, it had a good amount of air still in it after 50 minutes.

The spooge makes me think I am jetting too rich. I've got the curved fin head and my top end's compression is also around 120 after warm up. It was around 124ish when cold. Seems to lose a few pounds when warmed up. I guess I should take off my head and inspect the rings. I'm thinking I need replacements.

I'm running out of ideas other than weak compression.

What elevation are you at when testing the compression, your testing with the throttle wide open?

Assume this has the stock jetting and no modifications?

Engines will backfire in a lean condition, years ago I was riding my Pilot at the Badlands and the Engine backfired then died turns out the fuel filter was plugged up with dirt creating a low flow problem to the carb when the carb would starve for gas it would backfire then die, pulled the choke and nursed it back to camp to address fuel flow problem.

Even properly tuned and jetted 2 strokes will run rich when cold so your not backfiring because you have enough fuel to prevent it once the Engine is up to temp and the combustion temps and efficiency goes up then your running lean.

Now would be a good idea for you to go through the whole fuel system ensure its clean and no blockage 350's are known to have all kinds of fuel system problems this is brought on by age not by design, dirt rust in the tank, fuel pick up tubes rusted off or blocked some with rust, gummed up carb, fuel pump, fuel lines, dirty fuel filter, pulse line from the fuel pump to the Engine lose cracked or leaking.

Whats the history of this machine last time the top end was removed and inspected as per the service manual? Reason why I ask is sometimes excessive carbon buildup can cause a Engine to backfire, if your compression is actually low because of ring and cylinder wear and not because of elevation or your compression tester being slightly off calibration then it could be a carbon problem.

A huge exhaust leak usually close to the Engine can also cause a lean condition and the Engine to backfire, looking at your spooge your pipe is not sealed.

Excessive spooge is not always a result of the jetting being too fat, if your spark plug is all black then your too rich then can blame the spooge on jetting, as a engines parts wear out like rings and the compression drops then combustion efficiency drops way down, it takes longer for the Engine to warm up to proper operating temp and the whole time on warm up its running excessively fat making spooge, leaving the choke on too long during start-up also can cause spooge problems use the choke as little as possible soon as the Engine will idle without the choke turn it off.

While the pipe is off take some pics of the piston through the exhaust port if you can.

Thanks

Looking at the results of your leak down test you don't have a major leak in the crank case.

I live in southeastern PA - Elevation is between 0-1000ft above sea level. And throttle was wide open during compression tests.
I tuned the carb with stock settings - 142 main jet, 45 slow jet, 1.5 turns for air screw, 16mm float level, jet needle at 3rd notch.
Looks like I have boysen reed petals in the stock reed stock (minus the curved limiter petals), and an UNI foam filter. Other than those two things, everything is stock.

When I bought it, the top end was freshly rebuilt and wasn't even broken in. I probably put a total of 3 hours on the thing. I don't really know the history of the Oddy. I was new to them at the time, so I didn't ask the technical questions of how the rebuilt was done. I know the guy who did the rebuild was known as an Odyssey Master and has an extensive history with these vehicles. I believe it considering some of the modifications he did (no key start, lower oil levels in oil balancer, change switch hacks), he must have good experience with them.

Fuel flow is a very likely issue. When i run the petcock on reserve, my fuel filter gets clogged with rust flakes and gunk.
I'm also thinking there is an issue with the rings because during the break-in period, the throttle got stuck near WOT (Wide Open Throttle) position. The Engine kill switch wasn't working at the time, so my friend panicked and didn't know what to do. I ran over and cut the cut to kill it, but i would the Engine was screaming for a good 10 seconds and it wasn't even fully warmed up yet. Was hoping that wouldn't screw me over down the road, but I'm thinking it has.

I don't think i have a carbon issue, because everything seems clean in the exhaust port. Here are pics to make a call.

Address the rust in the gas tank.

Almost looks like some vertical scuffing on the cylinder wall in the top picture on the intake side of the cylinder?

Also looks like a brown tint on the cylinder wall like blow by from the rings or is that just the oil ?

Thanks everyone for the advice. I sealed up the exhaust flange with silicone and the backfiring/bogging went away. Took it for a few rides and it remained strong (it even felt like it had full power with a cold Engine - i didn't rev it too high since it was cold).