i have a 1987 polaris trailboss 250 4x4 and im in the process of rebuilding it now one question i have is cooling! i know its a air cooled motor but when im crawling through my forest im not going to be able to get fast enough to cool the motor has any one out there done any cooling mod to the 250 im thinking maybe a fan blowing rite at the motor! any ideas will help!

 

seems some a lil bigger had a oil cooler,..might be easier to add on but idk,...a fan with ducting to the cooling fins might work too....good luck!

 

since it is a 2 stroke (no oil in engine)an oil cooler couldn't be applied. you could maybe hook up a fan as you mentioned to help cool. kind of needs to be protected form debri and mud and what not. imo

 

ya im think off putting the fan likes 6 to 12 inchs in front of the motor and i am going to be making a tunnel from the front of the quad to the fan with some thick plastic to keep mud and stuff out of the fan with a screen at the front, and i was thinking of trying to make a heat sheild for the exhuast pipe up front so my fans not just blowing hot air from the exhuast!

 

might be able to reverse it and have it suck the hot air away as well. just a thought.

 

Don't block air flow to the head cooling fins! You can place a fan with a screen to help with dirt ,bugs,etc and either mount a sensor on the head fin(or just a toggle switch) to turn the fan on when your down low in creeks with little air flow. On the most part the little 250 did ok with out a fan and even the 300 fan motor rarely came on (mainly because they mounted the sensor on the top engine bracket instead of the head!) and quite a few of both of these machines are still running around! OPT

 

Thanks OPT, ya im just going to put a fan on and then use some sort of plastic to make a tunnel have the tunnel open up front were a raditor normaly would be then have the tunnel go rite to the fans facing the head! basicly just going to make wheel wells so no mud gets into the fan or on the motor! And the only reason I'm worried about cooling is I plan on buying 30" silverbacks for my scrambler so I'm going to take my 28" mudzillas off and putting them on the trailboss!

 

Is there anyone on here that has setup a trailboss for mudding if so do you have pictures
or just pictures of a trailboss with mud tires I wanna get a idea of how to do mine!

 

another thing that makes me think is needs a fan is when i plow after about 20 or 30 mins i kinda sounds like it starts to knock so ill shut it off and put some snow on the cylinder head and wait a min or two and then
start it back up it sounds good again but im really hard on it when i plow and it only really happened when i was plowing alot of snow making me have to full throttle it alot!
just let me know what you think it is causing it i was running a lean oil mix
of 40/1 and rite before this last snow i did a 32/1 and it seems to have gotten better! i did a compression test and its has the same as when i first rebuilt it 125psi

 

40-1 premix ratio should be plenty enough oil,(injector pumps are usually set up close to 50-1) we only mixed 32-1 on our race bikes! 125 pounds is fair compression,but I usually got closer to 140-145 psi when I bored them. Could be a little piston rattle when it gets hot,cylinder expanding,etc. You might try a good synthetic "smokeless"(not really smokeless,just a little less smoke) oil and see if it helps if you're using a conventional TCW3 injector oil. OPT