ATV Help & Brand Specific Topics

Good work. I like that you cleaned and inspected the drive system and didn't just condemn it out of hand, and then you got it working. Even if it does need a bit of work after a while it lets you test everything else. It's important we use our discretion when choosing what needs replacing. That's good work..

Well after driving it around a bit and having to replace a stuck thermostat it seems to be running well and has good power I have noticed gear oil coming from the front diff pinion seal area so I guess I'll be exploring that issue sooner than later.

When a carb starts backfiring it's normally because the mixture is too lean. It can be caused by badly retarded ignition timing or tight valve clearance, but mostly it's a lean mixture, especially if it does it more as you open the throttle more. The flooding out the overflow is a different problem..

Well the circumstances should be considered here.. It takes about 20 minutes before the trouble starts manifesting.. A blocked fuel tank breather could cause problems like that. A blocked vent normally causes a fuel shortage as the tank starts to get a vacuum in it and the fuel stops flowing. It can happen though that a blocked vent can cause the carb to flood, but it's normally when the bike gets parked in the sun and the tank pressurises. It is possible though that in this case a blocked vent, despite the fuel being taken out of the tank as the engine runs, is actually letting the tank pressurise as the engine or sun warms the tank up. Check the fuel tank and the carb breather hoses are attached to the right place, and that they are clear.

I've since switched to another carb,I've read online a lot of people switched to smaller carbs due to flooding issues. This worked for me . Switched from the original vm34 to a vm32 from my 85 2wd bike. It was running perfectly, UNTIL, get this : Bike runs for 15mins or so till it gets hot. Then it backfires a bit and makes popping noises through the carb. Then it spitters and cuts out like it don't wanna run . Let it sit for a bit to cool down then starts back up like nothing happened. don't know if this is a fuel pump issue or some sort of electrical or mechanical issue? Man I thought I finally had this bike ready to take on a run. Guess not

it is the coil. Had this happen to me and had a second unit to swap parts. Did everything except for the coil as you need to drain the oil to replace it. If I remember correctly,the coil sent that much.

Thanks for the update! Good work! Glad it s running and driving. Always glad to hear a project getting back on the road.

New belt installed and also did a 25 year overdue service on the primary drive, it was really nasty and corroded. It's working good now. Took it out of the shop yesterday and did some riding around the yard and it seems to be running well. I did track down another electrical issue that I'll take care of this evening. It would lose power to the main switch intermittently and I finally traced that to a terminal in the connector that plugs into the starter solenoid. I'm also going to flush the cooling system and install some antifreeze

Yeah could be that Ww. If the carb's just been off then, yup, the rubber could be split. Good idea. Most of the time though, bad vacuum effects the idle more than it does an engine at revs. If they will start and idle, (even with a vacuum leak), then they will generally rev up and run pretty much as normal. There are exceptions though, such as the carb moving in the rubber, or the rubber flexing and letting air in.

lean pilot....

intake leak check the intake boot between the carb and the head, check that seal

awesome

check all of your grounds and cant forget to check the fuses...

I think there's a manual in here called "Polaris 1999-2000 Service Manual" that does all the models, including that Magnum 500.. If I didn't get it from here, let me know and I'll upload it to the service manual section.

You might try manualslib.com i have good luck finding manuals there.

I'm looking for a service manual for a 1999 Polaris Magnum 500 4X4. Thank you

Not speaking to Greg or Gw here, because I can see and know they are both thorough and logical, but for those that do struggle with electrical problems.. A "voltage drop test", is the way to find bad connections. Look it up and understand how it works. We have to look for the bad connection with full load on the connection. We can go around watching milli-voltages, or checking resistances, and never find the bad connection (and associated voltage drop), if we are just depending on our super precise digital meter.. And for the same reason, most of the time it's best to use an old fashioned test light (with a bulb that uses a bit of power), to quickly trace power, rather than the digital meter. And the other thing that I suspect causes a lot of difficulties and reluctance to do all the tests needed, is people try to work on their quad with all the body work on it. Most body work comes off relatively easily if the bolts are greased. Whenever a quad needs some work under the body work, it's nearly always worth taking the few minutes to pull the plastics off. And it's true of electrical as well as the fairly mundane, such as valve adjustment.. And it's a good time to check the wiring for chafing etc..

Thats great news! Good work finding the loose ground sometimes they are hard to track down.

Good work Greg.. Those mud wasps are little mongrels aren't they ? And so fast to get into things !

Well finally some good news. Pulled the stator roter off and sure enough it had a sheared key, replaced the key and it started up. That brought to light another issue. It would start easy the just die for no reason, I suspected it may be the carburetor even though it's been replaced I did have to evict a mud dobber nest that had made a home in the fuel inlet because the fuel line was disconnected when I got it. Well I've been searching for other reasons why it would die suddenly, just about ready to dive into the carburetor when I decided to look into why the aftermarket led flood lights were dim. I found a bad or non existant ground between the engine and frame. I ran a new ground wire from battery negative to the frame the started it up and it sat and idled for a good 15 minutes and did not die. Now when the new drive belt comes in maybe I can actually test drive it. Still a few other things to look at but it's coming along.

Are you sure the fuel isn't leaking between the float needle seat and the carb body ? Does that bike have a fuel pump originally ? Is that carb made to run with a fuel pump ? If not, then the carb on it will have big float needle jet, and it will struggle to seal against even one pound of fuel pressure. The normal pressure for a bike with gravity feed is only about, er.. probably a quarter pound of pressure. Water gives 0.4Lb of pressure for every foot of height, and most fuel tanks are only a few inches above the float needle jet, and, fuel is lighter than water and gives less pressure.. The fuel pressure is very low. You can get different sized float jets for carbs and depending on the fuel pressure they are designed to operate with. the size of the jet can vary by a factor of three or more. Using the wrong size float jet can cause flooding or fuel starvation.. If you are sure the seat to carb body is sealed, then I'd recommend resetting the float height to specs and rigging up a gravity fuel feed temporarily(without the pump), to see if that cures the problems

Hey folks, thanks for the responses. I've since gave up on the Chinese carb. Went back to the original fuel pump, drilled hole put valve in intake Boot etc.. still same troubles. I'm back to the regular OEM slider carb now, the original that is supposed to be on the bike. I got it from a friend, he's been using it on his ATV (same year and model as mine) for years with no issues. I put it on mine, it worked perfectly, for about 20mins riding. Then it started flooding when I would let off the throttle. It would sputter and sometimes almost cut out before it picked up again. But this is only after about 20mins of riding in 4th and 5th gear on a road throttle nearly wide Open. As soon as i let off, it seems it wants to sputter and flood out. I went and cleaned the carb inspection the needle and seat etc, cleaned tank replaced fuel petcock... New fuel filter. Still same issue. Do you think I should set the needle height a little lower? Or the float tab a little higher? The float tab is at about 35 degrees as it is . Is there some other type of issues I can be overlooking? Already tried adjusting the air fuel screw, still didn't make any difference. I should note, that the intake boot is from a newer model Suzuki lt4wd bike. It's a tad bit larger diameter than the old slider carb boots. That being said , I cut off about 1/2 inch of the boot, since there is an inner lip that's smaller diameter than the outside of the boot where the carb fits. The inner lip seals perfect with the older carb accompanied by a hose clamp. No leaks, sealed great, as well the rear boot is sealed great too. Don't think that could cause an issue would it ? I know it's a carb flooding issue because the overflow tube leaks gas when this happens, and it cut out once or twice and wouldn't start after that , plug soaked. Kind of boggled, since it was taken off the same type of bike working fine, and now doesent want to work properly on mine.

Yup, check the power supply and the earths to the cdi unit, and check/clean the main switch and the kill switch contacts. Clean if possible(kill switch) or check with an ohm gauge.

There are many things it could be, but the way you describe it sounds like its loosing connection after initial spark maybe arcing from a loose ground. I would check to make sure the coil is grounded and also that you have good ground to your CDI. You know you are getting voltage there or it wouldnt spark at all, if all that checks out you can check the harness and start switch for possibly corroded terminals. I assume you have tried a new plug.