Quantcast
Jump to content

  • Join Today, It's Simple and FREE!

    As a member, you can post in our forums, upload your photos and videos, use and contribute to our downloads, create your own member page, add your ATV events, and even start your own ATV club to host your own club forum and gallery.  Registration is fast and you can even login with social network accounts to sync your profiles and content.

Brian Haley

Early 2000s Polaris Trail Boss 325 4 Stroke Fuel Issue

Recommended Posts

I wanted to ask this question before I pull this thing apart and dig into the carb. Very seldom used for a couple years but took it out the other day and it ran like crap. Blows black smoke on throttle (unburnt fuel) and sound like a multi cylinder engine with a misfire. Won't rev very high on full throttle but seems to be smooth at about 1/3 or less throttle. Choke doesn't seem to do anything and thinking perhaps it's stuck closed. If I turn off the fuel and let it run for a minute It will rev like normal under full throttle until it stalls out from no fuel but as soon as I open the fuel line again it goes right back to running rich/flooding.

 

Any help or ideas would be great. Trying to avoid tearing it apart and rebuilding the carb but the only thing I can think is the choke is stuck cause with the fuel off it will rev just fin seemingly as it's emptying the float bowl.

Share this post


Link to post
Share on other sites


Most likely what you think it is. Usually the carburetor is the culprit here, take it off and clean it good.  If your not familiar with doing this you can go to YouTube and you will find a ton of videos to help you out. Also some fresh fuel and a new plug should fix it up. 

 

Share this post


Link to post
Share on other sites

Sounds to me like a clogged main jet. Clean the carb thoroughly

Sent from my SM-N920V using Tapatalk

Share this post


Link to post
Share on other sites

Update and I hope someone can shed some light on this. So I cleaned the carb and no change in fact it seemed to get a little worse but I now believe that's because it needed some adjusting that I couldn't really do because of the way it was running. I still thought it was a fuel issue and it may very well be but I bought a new carb. It was cheap enough on amazon so I went that route. Installed the new carb and it starts and runs at idle better than before and smells much less rich but it would still not rev on throttle. It revved a little better with the choke on but still backfired and popped pretty badly and would not rev very high. I started thinking it could be timing so I did some searching and I found that was not likely the case but many people were saying it will run like crap without the air box installed and sealed. I had my doubts but I tried it anyway and it was the same. Without the airbox I tried covering the air intake and it flooded with fuel and stalled as would be expected. Once I put the air box on I covered the air intake again and it revved then began to stall so I covered half of the opening and bam it revs like it should.

I'm debating covering half the opening with some duct tape and just go with it but I figured I would ask if anyone had any ideas for a proper fix. I suppose the issue could be not enough fuel in the mix or too much air since it idles fine but I'm not completely sure how to adjust it. Mixture screws are usually meant to adjust at idle and my issue is off idle with both the old and brand new carb.

Does anyone have any ideas?

Share this post


Link to post
Share on other sites

Topic moved to Polaris forum and added manufacturer to topic title 🙂

Share this post


Link to post
Share on other sites


I don’t think the tape is a good idea. I would go back to the factory carb and set your fuel/air screw to 2-1/2 turns out from a snug tight position.  That should get you running enough to tune it. Either 1/4 turn in or out. The higher it revs while turning the better. Lower the idle if the engine revs to high. 

Now as far as not running right and air box etc.  Yes the air box and filter need to be in place. And that needs to be done prior to adjusting the fuel/air screw.  

Now after that is done you should check spark quality as well as add a new spark plug.  Make sure you have a good spark.

Is the fuel fresh ? And the valve (petcock) on the tank flowing good fuel ?

 

 

Share this post


Link to post
Share on other sites

I would also check the quality of your filter boot and intake boot for cracks, ect. Make sure they are all tight.

Sent from my SM-N920V using Tapatalk

Share this post


Link to post
Share on other sites

In your initial post you described a rich fuel condition that got worse as you increased throttle. You were right too think along the line of a choke stuck closed or other obstructions in the intake. Next you removed and cleaned your carb to no avail. There is one item often overlooked when cleaning a carb. The needle jet which sets just above the main jet. It is a small (usually brass ) tube with a series of small holes in the side. If those holes are restricted or clogged your fuel mixture will be too rich. Make they are clean and be careful not to alter their size. Your new carb on the other hand has a lean condition and most likely could be corrected with a larger main jet. 

Share this post


Link to post
Share on other sites

For the time being I'm gonna close off part of my air intake of the filter box cause I need it for tomorrow and it will run decent. Unless I'm wrong and the pics I found online are also wrong it doesn't appear I can adjust the air/fuel mixture screw with the carb on the quad.

One part of my question was overlooked. Am I correct in thinking that the mixture screw only adjusts idle mixture? One more thing. On the bottom of the float bowl there is a nipple with a shut off screw next to it. The original carb had nothing connected to it and the replacement had a rubber hose on it but I have no idea where it should be connected. What is the purpose of this nipple? It appears to just be a way to drain the float bowl.

Share this post


Link to post
Share on other sites

You are correct on the idle mixture screw. The rubber hose should be routed down to the bottom of the machine and left open. It is a drain hose.

Share this post


Link to post
Share on other sites


Regarding the drain hose...it's also connected to the overflow tube inside the float bowl.  If the float valve ever sticks open, the excess fuel will run out on the ground instead of filling up the crankcase with gas.

You'll need one of these tools to adjust the idle mixture with it running.1519871349_s-l1600(2).thumb.jpg.e453529e4c76ffb4e87d4c137fd2ff38.jpg

Share this post


Link to post
Share on other sites

Starting to think I have multiple issues going on. Going to replace my very old and worn fuel lines to make sure none are collapsing off idle as that explains getting too much air and backfiring. Also I ordered a new petcock cause the original does not fully shut off the flow. (noticed that when I had the tank off the quad) It's only a drip but I still want it to shut off. Once that is done I'll have to see how it runs off idle and continue to figure out why I'm having mix issues. I appreciate all the info. 

Share this post


Link to post
Share on other sites
3 hours ago, Ahren Longo said:

may have a stuck float in the carb. That will make it flood too.

The old carb didn't idle all that well but was seriously bad off idle. The new carb idles fine and still has issues off idle which leads me to believe I had 2 problems. Old carb off idle seemed to be flooding gas based on black smoke and raw fuel smell. New carb seems to be either starving for gas or just getting too much air cause similar sound with no rev and sputters and backfires but no smell or smoke and choking the air intake partially it smooth's right out and revs fine. Going to replace all my fuel lines to make sure I don't have any collapses.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Similar Topics

    • By AimlessMoto
      Hey guys, new here, but haven't found ANY answer to my specific problem on a Suzuki dedicated ATV forum, so here's to hoping!
      I acquired a 95' Quadrunner 250, 4x4, (LT4WD) for practically nothing with no spark. The PO had tossed in a used stator which didn't fix the problem... so I went all routes (though cheaply) to narrow down the initial problem of no spark. 
      Plug, coil, CDI (caltric) and stator w/pickup (caltric) were purchased and installed. And it RAN, but bogged horribly and would not rev past 1/4 throttle. 
      I checked fuel flow, vacuum lines, all the normal stuff, no issues. I decided to check the valves and cam... well, there was one problem. The cam was 1mm under the lowest spec in the manual. So, in-came a new cam, Stage 1 Hotcams... also threw in a new set of shindy valves, lapped them, replaced the valve seals, and the timing chain. 
      Back together again (w/stock airbox and new oiled filter). Now it idles even better, still boggs at 1/4 throttle, but will rev past it if you hold the throttle open for a second. Ahaha... success!
      So I was able to ride it above 1/4 throttle once I had momentum... could shift through the gears, all was good as long as I kept it over 1/2 throttle. Took a long enough ride to break in the cam properly at least so I won't have to worry about that. 
      Now, I start fiddling with the carb. It's clean as a whistle, stock, with stock jets (new replacement Mikuni jets). Same problem. 
       
      I start thinking, maybe this is fuel related and the bike is having an issue transitioning from idle jet to main jet... so I LOWER the needle by raising the clip 1 spot. Now it revvs up in neutral with no bog, but it boggs about the same trying to ride it. So I move the needle down again with the clip on the top slot. Better, but still has a bit of bog at 1/4 throttle. 
      The last bit of advice I got was to ditch the CV carb... so I sprung for a brand new Mikuni VM30-83 round-slide. Bolted it up, blew into the vacuum tube to fill it with fuel (no vacuum port on this one) and she fired right up... but there is still a bit of bog, it's just masked by the fact that I'm not waiting for the vacuum diaphragm to open. 
       
      So I feel like each little step brings me closer, but not perfect. I'm now wondering if this is still in-fact a carb tuning issue (I have some jets I can fiddle with and maybe lean-out the idle jet a little.) OR if the cheap-a** Caltric Stator/Pickup is what's causing these issues. 
       
      I have a 95' KingQuad with 400 miles on it... like new.. runs like a top... I've tried both the stock QR and the Caltric CDI boxes on it, and it revvs up and runs like a champ. 
       
      The only unknowns between the two systems are the carb, and the stator/pickup. My next step in troubleshooting is to rip apart the King Quad and test it's CDI on the Quadrunner... but considering there is no change to how it runs I doubt it will lead to a solution. 
       
      HOWEVER... I tried the stock CDI just recently after running the Caltric this whole time, and the bike runs like garbage. Hardly idles, and won't rev up at all. So, that is my one smoking gun telling me that it's either the pickup coil or the stator itself. 
       
      Has anyone had a problem even CLOSE to this? I can't image the carb would be causing this many issues, especially going to 2 different ones, both with stock jetting to OEM, and exhibiting the identical symptoms... the only change is when different CDI's are plugged in, or when the needle valve leans out the mixture. 
      Also, I checked the piston, rings and bore when I had it apart and they're like-new... no scoring, rings are loose, cylinder is still round and has honing marks still int he bore. Stock piston, stock bore size and it has 160psi compression. Battery is brand new, and I've tried 3 different R/R's, none of which change any symptoms, but slightly vary the charging voltage by .2-.5 of a volt depending on which unit. Also tried a new coil which changed nothing. 
      ANY help would be appreciated. Too much invested to not get it running right. 
    • By David Barsukoff
      Hey, I just bought the kids a LT80 and noticed a small puddle under the machine after they were riding it for a bit. I'm wondering if anyone knows why the fluid coming from the fuel shut off is a red colour, and would have any ideas of where this issue is coming from? I haven't had a real good look at it yet, thought I would ask first. 

    • By John Ford
      i ordered a keihin carb for my 07 trx 90 and it fits nicely but the new cable they sent is way too long and i can't make it work.  the old honda cable cap [that fits on top of the carb] is too small to fit.  the keihin cap is approx 3/4 or 19mm.  honda cap is more like 1/2 in.  the keihin has a rubber boot on the cap where the throttle cable goes through . i don't know how to find the right length [most cites don't give the length].  i'm not sure how cables fit into that boot  and do i need to add the length of the boot to the cable?  the old honda cable is 28 inches total, but the cable movement is only approx 2'' which would not be enough to reach the actuator block on the keihin.  looking to find a throttle cable compatible with the keihin.  any help, please.
       
       
    • By JacobSlabach
      got 7 atvs off CL recently for a good price.  one of which is a yamaha warrior.  anyone know where the vin is printed on this bike?  Haha good place to start as I do not know year or size yet.  The former owner says needs exhaust ans and clutch work.  he said it ran fine until the clutch cable broke and then I couldn't get the new cable adjusted right and it would grind gears.  things I see:  clutch cable locked up again, no brakes, carb leaking (green with algae around the bowl and has gelled gas stalagtights on it), aftermarket exhaust melted the airbox so I need something different and a new air box.  I would like the use the current exhaust if I can but I have a feeling its a redneck fix as it looks like there is an ace bandage holding it to the exhaust pipe (its an aftermarket slip-on exhaust), so I'm not sure about that- lets get the bike running first.  also, battery (looks brand new, what a shame) is dead, 0 volts.  Otherwise, bike looks to have not been wrecked, and plastics are ok (it sat outside under a 'tarp' for 3+ years since it was run last).  any tips and advise on where to start first would be awesome as this is my first clutched bike (manual).
      the clutch is my main concern- I've never rode a clutched bike so I dont even know what its supposed to feel like.  lol I'm spoiled on my automatic polaris 
    • By Roy Anderson
      I have a 2002 Suzuki LT-F500F, and am a first time atv  owner. I rode two wheel bikes for many years, and now, two months in to being a new at owner, am just not enamored with the thumb throttle, and I’m wondering if anyone has tried a conversion to a typical twist grip throttle as found on all motorcycles? If so, how do you like it?
  • Similar Tagged Content

    • By Travis Mitchel
      Hello all just recently acquired this atv which as you can see in the pics that it has had an unsheltered life. i did get it running and put some used tires on the front.
      It still needs a bit more well needed maintenance, chains tightened and oiled. needs an airbox or air cleaner and other misc items.


    • By mike rhoades
      View File Polaris 1996-1998 ATV Light Utility Service Manual
      Service manual for 1996-1998 Polaris ATVs and light utility vehicles covers: Magnum 2x4, Trail Blazer / Scrambler, Sportsman 4x4, Magnum 4x4, Trail Boss / Sport, 6x6 / Magnum 6x6,  Xplorer 300 / Xplorer 400, Sportsman 500 & Xpress 300 / Xpress 400
      Submitter mike rhoades Submitted 03/02/2019 Category Polaris ATV  
    • By mike rhoades
      Service manual for 1996-1998 Polaris ATVs and light utility vehicles covers: Magnum 2x4, Trail Blazer / Scrambler, Sportsman 4x4, Magnum 4x4, Trail Boss / Sport, 6x6 / Magnum 6x6,  Xplorer 300 / Xplorer 400, Sportsman 500 & Xpress 300 / Xpress 400
    • By colin james
      View File 1985-1995 Polaris ATV Service Manual
      This is the service manual for 1985-1995 Polaris ATVs. Download all the chapters for the complete manual. 
      Includes the following Polaris ATV models:
      Scrambler, Trail Boss, Cyclone, Big Boss, 250, 350, 400, Sportsman, Trail Blazer, Sport, & Magnum. 
      Submitter colin james Submitted 11/25/2018 Category Polaris ATV  
    • By colin james
      This is the service manual for 1985-1995 Polaris ATVs. Download all the chapters for the complete manual. 
      Includes the following Polaris ATV models:
      Scrambler, Trail Boss, Cyclone, Big Boss, 250, 350, 400, Sportsman, Trail Blazer, Sport, & Magnum. 
  • Recently Browsing   0 members

    No registered users viewing this page.


×
×
  • Create New...