This is where it does get a little tricky as the 400 harness has a 10 amp circuit breaker that ties in with the fan which is triggered by the radiator sensor,BUT you have the same breaker also, but do have a LR 60 module that works in tandem with the oil sensor in your oil cooler to kick on the fan. Usually set at a higher fan kick on temperature than the radiator equipped sensor. Item #32 on the parts break down.Dirt Cheap Yamaha, Honda & Polaris OEM Parts & Accessories – Cycle Parts Warehouse The sensor on the head is a hot warning light to the instrument cluster. If you can work around these,then anything else shouldn't be a problem.

 

So the whole point of the radiator / oil cooler sensors are to trigger the relay for the fan? If that's the case than I should be able to easily work around that. I have a few temp gauges, I'm going to try and hook one up to the sensor on the head since it is a "swap" I'd like to know exactly where the temp is rather than a light. Should a Guage work off that sensor or is it designed to just send a signal after a certain temp?

 

Don't think a gauge tied into the temp sensor would work,but possible. Resistance in both the temp sensor and radiator sensor decreases until a ground path is created which completes the circuit for the radiator sensor to trigger the fan.Temp sensor is set to complete the ground path and trigger the hot light at 205 degrees. You might be better off hooking a remote temp sensor on the return line to the radiator and using a dash gauge to keep a check on actual temperature.Tying the oil cooler thermistor(sensor) harness to the radiator sensor may or may not trigger the fan to come on quick enough as most oil cooler sensors(same basic setup as on the 300 2 stroke,325-330 four stroke) are set to trigger at higher temperatures for the fan to kick on. 260 degrees fan on,290 degrees triggers the hot light by way of the oil cooler thermistor signal to the thermistor module(LR60) that I mentioned earlier that you have on the 335 wiring harness.Plus these fans especially on the 325-330 oil cooled engines hardly ever kicked on unless under heavy loads or super hot.That's why I'm thinking a remote temp gauge to keep a check on temp,plus the water cooled fan on the 400 needs to kick on before 205 degrees.Trail Tech TTO Temperature Meter Digital Gauge 16mm in Line Radiator Hose Sensor | eBay

 

Like the oil cooler the oil tank on a dry sump motor redirects the oil away from the heat of the motor for a short time before recirculating back into the crank case.

It gives the oil a short time to cool off like a oil cooler does. The oil tank even has cooling fins to help the process.


Unlike a wet sump without a oil cooler where as the oil remains in the crank case at all times and never gets away from the heat of the motor for a cool down moment.

 

Plus less resistance on the crank shaft and internal moving parts rather than slogging through a couple quarts of oil.More efficient use of horse power.British bikes did it for years as well as well as the first generation Honda 750s with a separate oil tank. Harley never changed using them unless you count the V-Rod or the new 750.

 

Thanks for all your info, it has seriously been a huge help! I got some more work done today, got the radiator mounted up, and all the hoses hooked up and the overflow bottle mounted. I had to fabricate some mounts for the upper radiator support but that was it. The radiator I purchased had a sensor on it so I cut the plug off the oil cooler sensor and tied it on to the radiator sensor, hopefully it works but we will see. If not I will just wire the fan to a switch. Thanks for the link on the in line hose sensor, I'll order one of those and get that hooked up to keep an eye on things. Now I am just going to clean the carb and replace the messed up throttle cable and drop the e-clip on the needle jet, change the oil and fill with coplant. What steps should I take to "bleed" the coolant system and oil system? I saw that the upper vent line off the oil tank has almost a "manufactured" slit in it and the only thing I could think of was some sort of bleeding system..

 

Slit in the oil tank vent line is there mainly for colder climates where moisture venting from the tank could freeze if not for the slit,essentially blocking off the vent line leading to the air box. Have heard of oil tanks exploding,possibly if this ever happened could have been due to pressure build up. First few Magnums and Sportsmans models that came out I had to make this slit myself because of a bulletin we received about freezing lines. As far as priming the oil pump up wouldn't hurt to pinch off this tank vent line with vice grips(before the slit) for a couple minutes after it's cranked up.This allows the pump to prime up quickly. May or may not hear an air hiss from the oil tank after you release the vice grips. Bleeding all the air pockets out of the radiator,lines,engine can take longer. Just jack the front end up,tires off the ground a little,leave the radiator cap off and have the engine at an idle. As the air pockets are remove through the top of the radiator the coolant level will drop. You can squeeze the coolant lines if necessary to help. Usually when the fan kicks on the level will really drop,then you can top off the radiator and coolant bottle and replace the cap. Let the fan cycle on and off a few times and either check for the hot light,or in your case check that the coolant temperature gauge gets no higher than 195 degrees or so.If the fan doesn't kick on before the temperature reaches 212 degrees or coolant spews out of the overflow bottle,then you may have to toggle the fan.Like I mentioned the fans on the oil cooled systems using the thermistor sensor in the oil cooler and hooked to the thermistor modules were set to kick on at a hotter temp(260 degrees) than water cooled machines. This is the main problem area I'd be concerned with.That along with hoping your 335 electrical system is compatible with the 400 engine. Really curious as to how this turns out.

 

Soooooo....
Got the coolant filled, changed the oik, cleaned the carb, and hooked up the fuel tank. Turned it over, thing fired right up. Has an exhaust leak where the head pipe connects to longer pipe, but seems to run good at idle / slightly revving it. I'm going to bleed the coolant system before I try it out but so far it seems good.

 

Hope the fan kicks on before it gets hot so you don't have to toggle it. Enjoy your 2000 model Sportsman 400 which technically doesn't exist...

 

Thanks! I primed the oil, and as you said a gasp of air came out. I parked it up on some ramps and let it run for about 10 minutes with the coolant cap off, the fan never came on but it didn't boil over either. One thing I did run in to that maybe you can shed some light on, OPT, is that it idled beautifully, then as I would Rev it up or blip the throttle it would randomly idle down to the point of shutting off. There was a tad bit of free play in th e lever, and when moving the lever within that free play, it would bring it from wanting to die, back up to a smooth idle. Note: it never did this before the jet kit instal, but did after the jet kit install with the 335 engine shortly before it blew up. I do have a new throttle cable but a closer inspection shows I don't think that's the issue. I'm wondering if a seal is worn out and I should buy a carb rebuild kit. The engine runs and revs great, and I tightened up the free play in the throttle lever to almost nothing aND it seems to have gone away, so far. I have also adjusTed the idle on the carb to where it starts nice and smooth aND idles close to 1200 rpm. Any ideas?