1954JF

Hello New Guy, haha me too. I just did this project with a 1998 that I blew $1000 on to begin with. It was an Ugly Stick! It's not completely finished yet after months of spare time tinkering. A lot of reading and researching things. You can toss that crap vacuum operated Petcock for a simple mechanical one that cost very little and they work perfectly since this is gravity feed. The one I used was for a Yamaha Raptor? I can look back for the part number if you like this idea. The vacuum port on the carb will need a cap or plug it, that's all. The design intention was to shut off gas flow when engine is off. Maybe safe when your upside down with a hot engine on top of you but not something I plan on doing. I can turn the valve ON or OFF manually just fine and I know what I got without the worry of this diaphragm working or not and leaking thru. The 1998 has a Mikuni CV series and it's a very simple carb. I had a hell of a time getting the factory setting for the float which had been 'tuned' to never close the inlet , this is the the way I found it. Thus allowing gas through all the time and with this float needle adjusted incorrectly it ran terrible rich, and it would hydraulic lock the cylinder overnight, which I found out my second day of ownership. Thus a little gas in the oil. Float setting is critical for optimum running, (so I learned). I had the carb off three times just guessing on it until I finally got to read the manual from this website. (a Tremendous thanks to a generous member.) Forth time on this carb off was the charm. Mine had a deteriorated diaphragm in both the petcock and the carb to begin with. Two large cans of Gumout Carb Cleaner and a toothbrush and torch cleaning wires got it all cleaned up. Look through every jet too if you do this. A kit with the diaphragm plus a few brass items and tiny spring and O-ring for the pilot needle (which were not present when I took it apart) completed the carb fix. After getting the proper float height it purrs like kitten at idle and roars like a lion as you rev it up. Power and torque describe this oldie. Do not run alcohol or ethanol enhanced gasoline in these older machines. My exhaust system had been boogered up quite a bit also. I removed it all and had to fix the header pipe which was crushed by an automotive type U-bolt clamp and also the muffler pipe crushed the same. No sleeve gasket was present there where it belongs on this slip-joint and the header pipe was missing the ring gasket to the head. I purchased a pipe expander tool and hammered out the slip joints as good as I could get it. I bought both gaskets online, plus I brazed a hole in the pipe and placed a new nut on the damaged end of the muffler pipe which holds the heat shield attachment bolt. Worked for a few days with wire brush and sand paper to remove surface rust cleaning it all down to metal (several pieces/parts) then sprayed it with 2000 degree ceramic paint. It is holding so far. New oil, new filter, new sparkplug, new air-filter, new rectifier, new battery, new tires, purchased a plastic welding kit and a hot-stapler plus stainless staples and wire mesh and plastic welding rods to repair fenders (mostly the mud flaps), new seat cover, removed the racks, foot rests, and several other parts like front bumper and lights, belly pans rock guards, shocks, all were wire brushed sanded and painted. The rusty shoulder bolts that fasten the fenders are needing recoating and I'm thinking gun bluing solution to remain original looking. I used acid to remove the rust. This was an outdoor farm vehicle? It's all there and it is a solid runner now. Every part seems tight and right. Shifts solid and brakes are good too. I used linseed oil-turpentine solution on the plastics to renew the finish. It is slow drying but works great. I figure after gun-bluing the fender bolts they will get the oil finish too. I would rather buy new shoulder bolts but don't know where, these are button-heads and metric with a specific shoulder diameter and length. The rectifier was another new experience for me. I did not know they could allow overcharge or high voltage in the system. The ICM box communicates with the rectifier and limits the engine from revving too many rpms so as to hold voltage down if this rectifier fails it's purpose on the high side. Yep, mine would not rev-up without sputtering and bogging but it idled just fine. This overcharge could ruin a $650 ICM box (no aftermarket?) or blow fuses and maybe melt wires. That was in the mix when I stated this project. I added a Voltage gauge now so I know what I got for output and battery condition. Whew.. a learning experience. You can view the manual from this site. Replacement parts are available but not much for OEM out there. No body plastics at all that I could find. Too bad ..these are great ATVs. Stick with it and learn something. The guys here (or gals) can help you and encourage you too. The original carbs are the way to go if possible (in my opinion). Oil in the coolant bottle sounds like a head gasket but you can rent a tool from many auto-parts stores to test that theory. Autozone or O'Reilly. Radiator pressure check is a simple hand pump attached in place of the radiator cap it also includes a pressure gauge and you pump-up pressure and watch the gauge to see if it holds steady or leaks down. Sometimes used to find or see external leaks like pinholes in hoses or radiator coils, but also if it's a head gasket leak the gauge pressure will fall off. Enjoy these things or you could sell it to me if you like. haha, just have fun and swear a lot while fixing things. Jack ..out

That sounds like great stuff, I've tried many products. Loctite is usually good.

Next up, I pull the covers and see if I can see inside. I should mention this decompression worked fine until one day I had a fuel issue that slogged the combustion chamber full. Leak through caused hydraulic lock. I pulled the fuel line and plugged off the tank then pulled the spark plug and then pulled the rope and it had gas spewing forth like a fountain out the spark plug hole for a moment. After this episode I was replacing bad fuel system components and when I finished that work, the decompression has no longer worked. I don't see any correlation there. Something stopped working inside on or by the cam. thank you

I'm looking for someone with knowledge about the Suzuki 500 'automatic de-compression' system when starting. It may be the same on many others in design, I do not know. It stopped working and one comment I got suggested I needed a new battery then use the electric starter. My starter is fine and works fine. But I know enough to realize decompression while starting allows for these tiny starters and batteries to be used instead of larger ones like on a car or truck. Over working the starter or punishing the battery is not the way to go. I guess it was my fault for putting it the way I did. 'Very hard to pull the rope because decompression is not working'. Does anyone have a diagram of the head and internal parts. 1998-2002 Suzuki 500 ATV's. I see nothing outward on this head for a decompression lever or linkage. Old dogs never die? or maybe they do from pulling that rope starter. thanks for any help

OK you have some other 'loading up' problem causing this. It's not uncommon in carbureted vehicles, there is more fuel going through the engine than gets cleanly burned. RICH. By loading up I'm speaking to the muffler and the bang. Burning rich causes excessive heat that leads to the bang pow or puff you hear from the exhaust pipe when you shut it off. It depends how much is in there (the muffler). We have to find which little item is not right. I've seen this in so many cars and trucks. I'm thinking something in the carb itself now. It took me awhile to solve this the first Mikuni CV I worked on I had it out and checked it over three times finding and fixing obvious things like the diaphragm, then tiny little parts that had been left out by the previous owner. It took me a long look on a zoomed in diagram of that carb to spot this. Then I found a video on Youtube I believe titled Mikuni Carbs 101. Like a class online about Mikuni's. I ordered a kit with a new metering rod diaphragm that had many little brass parts and a few tiny washer and O-ring that goes on the adjustment needle. In the end I got it regulating fuel properly. If your problem gets worse it could load the muffler enough to do this backfire while riding it and could blow that muffler out, maybe hurt you. FYI... https://www.pure-gas.org/ I can tell you from experienced small engine shops mechanics I've talked with and they will tell you and my own knowledge of this, most gasoline today contains ethanol. It's another joke on the citizens. Our taxes are for the rulers to play with. Ethanol is grain alcohol and alcohol destroys rubber components sooner or later things fail. The ethanol enhances octane cheaply so they put it in every grade these days from low to the highest octane. I have tried to tell guys having vacuum petcock or Mikuni Carb issues about this debacle. I often hear the words from their mouth, "I only buy the best high octane premium gas" and they don't believe me when I say "so what", it still has alcohol blended in. A new petcock that may be the Chinese duplicate fake copy has the Chinese rubber in it. They make rubber from the tree and clay is added as a stiffener. The Chinese use more clay to make the parts containing expensive rubber cheaper to produce. This higher clay content makes the rubber stiffer and it cracks sooner than expensive more pure rubber. Ask any devout DUCK Hunter which chest waders last the longest. Not the Chinese ones. When ethanol was introduced to the gas pumps most all of the auto industry had prepared for it. The small engines industry did not, and years later they had to played catch up. Older carbureted engines still work fine but you need "Pure Gas" which can be found everywhere in the US and Canada. But not without looking for it. Only two states in the US have it commonly by opposing government rules to change to some alcohol in all grades while farmers and other smart people know it is necessary for some older equipment or you buy the newer stuff. Here is a link to good gas. https://www.pure-gas.org/ This is super helpful for everyone. Put in any area code or city and they map or list out stations that provide non-alcohol gas at one of their pumps. This is to satisfy us the customers who need this. We filed consumer complaints to get this accomplished. You will pay more at the pump. I've got over a dozen older carbureted small engines. They keep running for a reason. I don't mean to bore people with this sort of comment but I am sure many younger folks don't know this history.

So your reply is saying you had trouble with the new petcock? Or something else is still a problem? Is the new petcock a vacuum design like the original or the manual type with ON-OFF-RESERVE? I just want to be sure of what we are discussing here. If you are saying you changed that vacuum petcock to a standard petcock or old style it will be just fine for what the purpose or intention is. You need to plug off the vacuum hose line or that affects the carburetion. I'm sure you already did that. The vacuum design petcock is solely for the purpose of shutting the fuel OFF when in a Rollover situation, by way of the engine dies and no more vacuum so that petcock closes fuel flow then. What if the engine doesn't die right away. This stinks in a way. You have 'PRI' position which is fuel 'ON' always like the normal ON and/or RESERVE would be, which they want you to use PRI to start your vehicle when there is no vacuum present, then they want you to move the lever switch to 'ON' and/or 'RESERVE' with no real 'OFF' position to mechanically close that petcock. This system relies on the rubber diaphragm inside the petcock to function as the shutoff when engine stops or is shut off. Now when that rubber goes bad and leaks (and it eventually will happen) the fun begins with issues. It will contaminate the fuel line and possible the fine screen under the needle seat or the needle seat itself and the carb too as rubber degrades or disintegrates. The issues begin. Lets try and figure what else might cause your problem or problems.

You are right in stating the exhaust is holding fuel either a rich vapor collection or actual raw liquid. That muffler is extremely hot and will ignite either. When it's cold put your finger inside the tailpipe and wipe the surface to see if it's black soot. Indicating a rich fuel mix. If it doesn't backfire while running it is telling you it's collecting and holding a little bit inside that muffler and when the engine stops breathing/running the excess in the muffler ignites from heat inside of there. I've seen mufflers blow up an split out on cars. I know you said you had the carburetor off a couple times but a couple things need checked again. Mikuni's CV series choke is an enrichment needle that sends extra fuel for starting from cold. Not like most American carbs that actually cut off the air intake to make the carb pull more fuel in. Set the correct slack in that choke cable and check that the spring is on that plunger needle at the end of the cable where it screws into the carb. It must close correctly when you move the choke lever to OFF. Next, I know the float setting is critical on these carbs so make sure it is set to the service manual float height. My 1998 500 Quadrunner is set at 17mm or 0.67" +/- .04" that's about 11/16ths of an inch. This is with the carb upside down measuring from the rim of the float bowl up to the highest point of the float. Use a machinist ruler or calipers. Bend the tang on the float that rides above the needle to adjust up or down. Be sure the needle has a good clean point with no damage and no obstruction in the seat, like a fine crumb of rust or something that might prevent a seal. Now go to the top of the carb and remove the cover and gently lift and inspect that metering rod diaphragm for fine splits or cracks. Also someone may have re-jeted at some point which could make it run rich so check those jets. The factory jets on my 98' are; Main #130 and Slow #55. The mixture adjustment screw is on the carb bottom on the engine side of the carb on mine. It's set about 2-1/2 Turns out and very hard to get at with the carb mounted. You need a #1 flat blade screwdriver about 1-1/2 to 2" length. If the engine fully heat up it's very hot work turning that needle screw. These are the things I would check if mine were running rich. When a float and needle aren't seating good you can get so much fuel it can hydraulic-lock from a full cylinder of gas when the engine is off. I am not a fan of the problematic vacuum petcock safety design. I replaced mine with a common On/Off/Reserve petcock and plugged the vacuum port at the carb. Works fine. Good luck out there

You can find a couple guys that did good Youtube videos on testing these parts. Type in the search box ATV stator check or the pick-up coil testing also, using volt/ohm meter, and then try rectifier too. Some real good videos on electrical output or charging issues diagnosis.

laugh and cry we all make mistakes sometimes, I mean with the girls.

Great choice and so is 15w-50 both good until the dead of winter subzero, if you go out then drop that first number a notch.

Hello, I'm new here. Interesting topic 'motor oils'. I've been riding motorcycles since the 1960's. I've been riding ATV's since they were ATC's in the the 70's and 80's and still own them. I used to buy the expensive oils from Castrol and even Pennzoil Racing oil which claimed superior qualities. Quaker State full synthetic was my choice when they introduced that. But I don't use that in my older ATC's or ATV's. Wet clutches. Now days with high prices I have investigated Super Tech Oils from Walmart. This oil is a collaboration between three major companies. First Warren Oil owns it. But Pennzoil and Exon Mobil produce it with very high quality standards. It's tested and proven a winner at a much better price. What I have always used is still in the charts in my owners manuals and I could upload the chart if interested. 10w-40 which can be used year around, and 20w50 if you have hot summers in your area, or work your machine like I do. These are my first choices. I have never had any engine failures ever. The 1985 Honda Big Red 250ES pulls a log splitter, a trailer stacked full of firewood, a farm harrow section on a sand beach, and has a snow plow for winter. This machine is a testament to Honda back in those days and the fact oil and filter plus air filter equals longevity. There is a wide range on the charts which give an ambient temperature range that each viscosity is suitable for use in. The two I picked cover everything I need weather wise. If I had unusual extremes cold or hot I could choose differently. Example; 10w-40 conventional oils are good from -4 F to 104+ F. Super Tech All Mileage Synthetic Blend Motor Oil SAE 20W-50, 5 Quarts $17.36 today, not too bad $3.47 a quart. I recently purchased a 1998 Suzuki LT-F500F 4x4 Quadrunner that needs some maintenance. This is why I'm here to listen and learn. I have done my own maintenance on many things from lawnmowers and chainsaws to old cars and trucks to newer stuff and never find an end to learning new things.