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Discussion Starter #1
Hey guys, haven't posted here in a while but still browse from time to time, and I don't think anyone has posted about this...

I have a 1991 350L Trail Boss. It starts up and runs and rides great, but it has an annoying gas leak that I can't figure out. At idle, no gas will leak out, but when you rev the engine, gas will leak out where the carburetor slides into the rubber intake that meets the cylinder head. What could cause this? I replaced the rubber intake as well as tried another known good carburetor, and it did the same thing. This doesn't keep the machine from riding, but it makes the garage smelly. Also it doesn't leak if the engine is not running.

2nd question. How in the bloody heck do you get the breather back on these things? I got it off no problem but after cleaning the carb, I cannot get the breather to go on. I have to be doing something stupid, but this drives me crazy because i have turned basically every other bolt and nut on this thing but i can't get the dang breather back on. So it runs right now with no breather, but i think the breather helps hold the carb tight against the intake, which could be part of my gas leak problem?

much help appreciated...
 

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Discussion Starter #3
Thanks for the reply. I don't think the problem is from a dirty carb. This quad starts almost always on the first pull, rides great all day long. Throttle is smooth and responsive, no hesitating or popping, cracking, etc...

The only problem is the gas leak. it's not leaking from the drain tube or the carb body itself. But rather where the carburetor goes into the rubber intake. The intake is probably 6 months old (old one was dry rotted). You can see the gas start bubbling from the intake, and it then runs backwards down the front of the carb and drips down the center of the quad, by the transmission.
 

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Discussion Starter #5
Thanks! I've been here since May 2011, but have only posted a few times, mainly when i've been having issues with my trail boss. I got it in May of 2011, and after doing the top end rebuild, i've really had no issues with it whatsoever other than this gas leak.

I'm gonna take a look at the intake hopefully tomorrow and gonna check everything and make sure it's good and tight, and i'll get back to everybody.

Regarding my breather. It came off with no problem, but going back on the access seems way too tight. I can fit it in there without the rubber boot on it that connects to the carb, but when putting on that boot it is almost impossible. Am i missing something or does anyone have any tricks / tips...
 

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Discussion Starter #8
Wanted to update everyone on where I am at with it right now. Had taken the advice of a friend and ended up replacing the stock reed valves with Boysen reeds. Apparantly poor/old reeds will cause gas to pool up in the intake, and then blow back through the carb going the wrong way. Put the Boysens in this morning, tightened everything up, and no more gas leak from intake. It is now puking out of the carb overflow tube, which i'm sure is due to the floats being out of adjustment. Gonna take another whack at it in the morning, but i'm pretty sure im' getting close to solving this gas leak problem...

Here is what i've done since purchasing it in 2011:

New Carburetor from polarispartshouse.com

Replaced Clutch Cover

Rebuilt top end at 5,300 original miles (Stock piston was in great shape but was scored due to factory oil pump going out, went to pre-mix right after with no problems)

New Front Tires.

New Boysen Reed Valves..

I'll have to put some pics of her on here sometime soon. She's really in great shape for being a 1993...
 

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Discussion Starter #10
Okay update this morning: Gas leaks are solved. No more leaks from intake or overflow. Now have discovered new problem:

After about 5 or 10 minutes of riding, 4 wheeler will stall out like it's running out of gas. I have verified that it isn't vapor locking, as riding with gas tank open has no effect. neither does pushing the throttle override button, which should rule out CDI trouble..

One thing to report: the times it runs out of gas, when i pull the fuel line off, it is bone dry, nothing comes out. The 4 wheeler will fire right back up, and it will also run just fine with choke full open when it starts to die, but once it "recovers", it will start smoking and sputtering. when choke is flipped off, it runs fine again for another 5 or 10 minutes before it does the same thing.

What does this sound like to the experts? I am leaning towards a fuel tank / fuel petcock problem, as this thing has no fuel pump and the petcock appears to be gravity fed.. Will ordering a new petcock fix the problem?
 

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Discussion Starter #11
Problem indeed appears to be in the tank / petcock. Both are off the machine. The tank, which is plastic, is soaking in hot soapy water in the bathtub, and the petcock was removed and sitting in a glass of vinegar.

BTW, the screens on the petcock looked terrible. there were debris and sludge all around them, with only tiny openings for gas to flow through. I think i've found the problem. I can't wait for them to finish soaking so i can put them back on and see if that was the case. The gas tank had tons of flaky nasty stuff floating in it when i removed it. I replaced the carburetor in 2011 when i first got it, but never cleaned out the tank or petcock, as i thought they "didn't look that bad". I think i learned my lesson. wish me luck that this is all it is. I think it's really all it can be at this point...
 

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Discussion Starter #12
Update: It ended up being the petcock. Even after cleaning, something was still wrong. Gas only dribbled out of it, even when i was using a vaccum pump to suck from the vaccum hose on the tank. I am told that the gas should flow out freely in the on position.

New petcock should arrive tomorrow. I'm hoping that's all she wrote. looking forward to a big ride on sunday with some friends, my polaris was running so good even though it was running out of gas. those 10-15 minutes it would run was awesome...
 

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Update: It ended up being the petcock. Even after cleaning, something was still wrong. Gas only dribbled out of it, even when i was using a vaccum pump to suck from the vaccum hose on the tank. I am told that the gas should flow out freely in the on position.

New petcock should arrive tomorrow. I'm hoping that's all she wrote. looking forward to a big ride on sunday with some friends, my polaris was running so good even though it was running out of gas. those 10-15 minutes it would run was awesome...
Good to hear. I just got the same machine in pretty rough shape but I hope to get her going. It runs but 4x4 isnt working and gas pours out the carb when it's sitting. Shocks are done too. Don't know if it's worth the cash.
 

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UPDATE: Got the 4x4 working and putting new shocks in this weekend.

Got it all cleaned up and running. The 4x4 hubs were bone dry. Bearings and seals all looked good so i just cleaned any dirt of the seals and put it back together and filled with atf-f works great now.

This site is a wealth of information. Thanks
 

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Rebuilt top end at 5,300 original miles (Stock piston was in great shape but was scored due to factory oil pump going out, went to pre-mix right after with no problems)
I have also just disconnected my oil pump. Can you tell me what ratio you are mixing your oil at? I heard 40:1 but she is really smoking up a storm and fouling the occasional plug.

Thanks
 

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Discussion Starter #16
Rebuilt top end at 5,300 original miles (Stock piston was in great shape but was scored due to factory oil pump going out, went to pre-mix right after with no problems)
I have also just disconnected my oil pump. Can you tell me what ratio you are mixing your oil at? I heard 40:1 but she is really smoking up a storm and fouling the occasional plug.

Thanks
I am sorry for the late reply, my wife and I have been busy renovating our house, i haven't had much time to be on the internet.

To answer your question, I too am mixing gas at 40:1. It is smokey until it warms up, then there is only a burst of smoke when i dog it. 40:1 is what Polaris prefers and although i'm sure it would be safer to run a leaner mixture of fuel, i have always erred on the side of caution with this old machine, and had no problems. Good luck!
 
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