400 Two Stroke Coolant Issue
 

I just picked up another project today since we are heading into the fall season up here in the north. I had a guy call me that had a 1995 Sportsman 400L. He bought it about a year and a half ago at an auction site. He drove it very little up until a couple months ago when he noticed that coolant was coming out one of the vent tubes on the engine. Not a lot of coolant, but just a dribble when the engine was revved up and nothing at idle. the engine doesnt overheat and it doesnt push any coolant out of the overflow bottle. I checked the radiator, but the coolant was clean with no traces of oil. I bought it from the guy since he basically wanted it out of his garage because he just purchased a new 2016 Chevy Pickup and the wife was being quite adamant about making room in the garage for her new vehicle. I could part this machine out for more than I paid for it, but will dive into the motor to see if I can trace the coolant loss issue and fix it. It runs great, is pretty quiet and tight, and doesnt have any abnormal knocks or clunks when it is running. It has all the tools and pouch, the original owners manual in like new condition and everything is in very good condition on this machine. He even had the original receipt from the dealer when this machine was new($5200 for a brand new sportsman in 1995, wow!). I have a brand new seal kit for this motor sitting in my toolbox that I double ordered on another machine I had so this was a factor on why I bought this machine. Is there other causes for coolant coming out of a vent? Bad base gasket or head gasket? I figure if I tear into the water pump, I might as well look into that too. I have a pressure tester for cooling systems so I will hopefully be able to pressurize it and narrow it down.

Thanks,
Mike

If it's the vent tube from the counter balancer cavity almost always water pump seals when this happens. Hopefully the c/b hasn't been sitting in coolant for an extended period of time. Not good on bearings plus corrodes everything up. I've had them to where there was a slight coolant loss every now and then, an occasional dribble out of the vent tube all the way to machines that gushed coolant straight out of the vent soon as you cranked them up. You can pressure test it if you wish and keep an eye out on the vent tube when you do. Sometimes you can even hear bubbling from the tube or cavity using a mechanics stethoscope if the seals are leaking. Head gaskets can blow and heads and cylinders can warp if the machine has ever gotten hot. Plus people always seem to forget using the bleed screw on the top of the head.This can cause one to over heat and blow gaskets.

Thanks OPT,

I couldn't get it to leak any coolant as I drove it around last night, but I could see where the vent tube was damp with coolant from previously leaking. I have the seal kit which has the water pump seals, crank seals and output shaft seal for the transfer so I will do all of those. I assume even if the water pump bearing looks good I should still replace it since I'm in there. I don't have the bearing but I plan on making the trip to the local atv shop that has it this weekend so I can finish this one up so I can ride it yet this fall.

Thanks,
Mike

Yes always replace this little bearing no matter how good the old one looks or feels. Nothing worse than having to go back in for something this small if it was to fail.This little bearing has to go through a lot of rpms in only about 3.5 ounces of oil splashed around.

i had a 96 with only 900 miles. I had to fix about everything on it. One of the strangest things for that machine, when the rear swing arm bushings wear out, it screws up the shifting! You can get fwd and neutral or rev and neutral. Stock plastic bushings were junk, I had bronze one made, fixed the shifting. When the muffler gets plugged, the exhaust gets hot and starts melting plastics, or worse! I removed the flame arrestor tube, replaced with a bigger tip with a screen, no more fires. When everything was right, it drove nice, but the 3 drive chain set up can drive you nuts. Sold mine, took the money and bought a nice Arctic Cat 400 FIS, end of my nightmare. The 4 stroke AC is way faster, uses half the gas, and imho, much better engineered.

I got the bearing this weekend along with a carb kit for this machine. I have the seals for the water pump and the crank seals so I will put them in since I will be in there anyways. Only thing about this job is the slotted nut that you have to take off. I can never remember if it's clockwise or counter clockwise to take it off. Once I get past that issue, the job seems to go pretty smoothly.

Thanks,
Mike

Slotted nut is left handed threads. Left to tighten,right to loosen. Use medium strength(blue) locktite on the threads when reinstalling the nut. If you don't have the socket for this nut tighten it with a couple good taps with a hammer and dull punch or chisel on the slots.

I got the case apart tonight and the seals were definitely out along with the bearing. Good news is the crank and counter balance bearings are in excellent shape. I cleaned out the counter balance cavity but am a little stumped on how to go about removing that little water pump bearing. The last 400 I did, the bearing came off fairly easy with a few taps. This one is on the shaft very well and I don't want to ruin the shaft trying to get it off. The shaft just had a dark coating of oxidation where the seals were and it cleaned up nicely so I don't want to take a chance on scarring it and cause the seal area to have a blemish. Any tips on how to remove this bearing? I am used to heat and a punch bit I don't want to cause any damage by attacking it the wrong way.

Thanks,
Mike

Heat and a little PB Blaster or WD40. Vice grips and small taps around on the vice grip jaws should remove it with no damage to the shaft.I had a small ball peen hammer perfect for jobs like this.

Thanks OPT,

I had a chance to get into the shop a little early so I messed around with the bearing before work. I used my micro torch and gave it a shot of deep creep and got my little hooked punch behind it and it popped right off. Cleaned it all up and shined the water pump shafter up and put it back together during lunch time. I haven't ever dealt with one yet that had a bad counter balance bit I can imagine just by looking at this thing, it's no easy job to replace one. All the bearings on this machine are very tight and are smooth when spun by hand so I think this one was just a breakdown of the seals because the counter balance oil was never changed since it was new or the oil was ran low causing the seals to wear faster. The guy I bought this from gave me a couple jugs of the polaris antifreeze so I will top it off, bleed the head, fill the counter balance and see if I got a winner with this old 400.

Thanks,
Mike

Sounds like you may have lucked into another decent forgotten machine. Yes seals are affected the most when setting up for extended periods of time. Crack,swell up and leak.

I filled everything up this morning and bled the system rebuilt the carb after that and she fired right up. No leaks and it runs great. The only thing I want to check is the fan sensor on the radiator. I ran the machine quite a bit and let it idle for a good 15 minutes but the fan didn't kick on. I don't think it gets hot enough to kick it on but I want to make sure the sensor works so it will engage the fan when it does get hot. I took temp readings with my handheld thermometer and the hottest I got was a little close to 150 at the head outlet but nothing hotter anywhere else. The fan works if I jump it so I know it works. My other liquid cooled 2 strokes will kick the fan on, but rarely and it has to be hot out. My xplorer has the fan wire hooked together so the fan runs all the time, a problem I plan on fixing in the next few weeks when I pick up a new sensor for it. Is there a way of testing this sensor?

Next question is about the charging system. When I bought this machine, the battery was stone dead. It won't even charge so I ordered a brand new one. That won't be here till tomorrow, but I noticed when I ran the machine, the bulbs for the indicators would get very bright and one actually got so bright, that it burnt out. I have more bulbs but won't put them in until I have a new battery installed. Is this common when the battery is completely junk? Does the charging system go into a full bore charge since the battery isn't able to soak up the voltage from the stator?

Thanks,
Mike

I know they can blow bulbs if you don't have a battery. All that electricity has to go somewhere. I guess a dead battery can cause the same thing. It must be really dead.

Sensors are easy to check.Check resistance on the two spade ends at room temp and then drop in hot water. Resistance levels should drop. If they don't then the sensor is bad. All the sensor does is close it's contacts when a certain temp is reached(around 190 degree) and provides the ground path for the fan to kick on. If the battery is weak or dead, can't hold a charge,the voltage from the regulator has to go somewhere else and the bulbs offer the least resistance and will pop.