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2017 Polaris sportsman 450 HO help

13K views 5 replies 2 participants last post by  lateburd 
#1 ·
I would appreciate some help. I am currently working on a 2017 Polaris sportsman 450 HO. Cam broke so replaced it along with gear. I cannot find info on timing this bad boy. I see 2 horizontal marks on the gear which i assume would be parallel to the head. I'm guessing the little tab on the cam that goes in the notch on the cam gear lines up with a mark on the chain, I see only 1 mark. I took out the sensor and don't see any distinguishing marks on the crank positioning. And is it the typically top dead center alignment or I read somewhere about a bottoms dead center alignment. Also what are torque specs on the head? Thank you. Or if someone can point me to an e manual for this beast I would appreciate that also. Thanks!
 
#2 ·
Put the piston at TDC - install the cam so the lobes are pointing down (about the 8 and 4 o'clock positions) - install the cam sprocket - the pin in the cam should be in about the 10 to 11 o'clock position and with the sprocket installed, the two horizontal marks on the sprocket should line up with the surface of the cylinder head
 
#4 ·
Do it by the book or do it my way - after several rebuilds, I determined the head bolt torque to be 45 to 48 ft lbs - I no longer do it "by the book" - I wet the threads of the bolts and the washers with diesel fuel to achieve the "film of oil" the manual calls for - I tighten the head bolts in a criss-cross pattern in 3 stages to 45 ft lbs - when tight, I loosen them to about 20 ft lbs (about 1/4 turn) then retorque them to 48 ft lbs and call it done. Make sure you have an accurate torque wrench - I use a Snap On TECH2R100 $499.00 or less depending on how much your Snap On guy likes you
 

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#6 ·
I don't know where you heard the reference to BDC unless they just describing the two positions of the piston in relationship to the crankshaft.

Anyway - it makes no difference to the camshaft whether it's installed TDC of the compression stroke or the exhaust stroke - in one instance the cam is simply 180 degrees opposite of where it is for the other stroke. However, engineers do some stupid shit! An engineer could have you set the engine to BDC to install the cam 90 degrees away from TDC if the cam was located on the side of the cylinder. But is just a difference in the timing marks in reference to crankshaft position. That's why manuals are an invaluable tool. The timing of a special use engine could be anywhere the engineer designs it to be. Where do you think the cam timing for a radial aircraft engine would be? Which cylinder would you set at TDC or would it make a difference. NOTE: radial engines always have an odd number of cylinders (3, 5, 7) due to the complexity of valve timing and the firing order is all odd followed by all even in sequence. There's something to think about when you don't have anything to do.
 
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