Okay. So ive had this 2001 polaris scrambler 400 2x4 for,over a year now and it curently wont start and back fires when trying to start. It has a top end and bottom end with around 24 hours. And ive checked the plug and it comes out all black amd oil. Ive tajen the plug to a wire wheel to clean it and it still wont start. My electric start spins but wont crank but ive been,using pull start. I want to convert out to pre mix so help with the plug fouking. What do i need to do. Thank,you.

 

Check and see if the boot is on the carb all the way little air in the head will cause this to back fire i had this same issue or if its 2 stroke check the reeds.

 

If it's sat for over a year pull the carb and clean it and may need a new carb kit if it's gummed up enough. As far as the oil pump,just disconnect the line leading to the left side of the intake manifold,drain the oil tank and install a small 6mm bolt and washer in place of the injector bolt. I'd premix 40-1 with a good oil.http://www.ebay.com/itm/Polaris-Scrambler-400-1997-2001-Carb-Carburetor-Kit-/380717280350?pt=Motors_ATV_Parts_Accessories&hash=item58a484ac5e&vxp=mtr

 

Yes its 2 stroke and it never sat forvover a year. Im ginna pick up a plug today and done prrmium and try that

 

Oh and my psi is at 125

 

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Low compression,probably why it's back firing. Might be time to take the top end off and see if it just needs a fresh top end or complete rebuild. Check the rod for any up and down play. If there is any a new rod kit and crank bearing,seals will be needed. Don't go for any short cuts on a two stroke as it can just cost you more in the long run.

 

I checked my reads today and looking insidd,the head and the piston appered to,have some,scrathces on,it. But,it didnt seem,to,have any play

 

You really can't tell by just looking through the intake manifold at all the damage to a piston. Could have damage on exhaust side also,plus could just have too much slack between the piston and cylinder wall. Plus piston needs to be off the rod to really be able to feel any small amount of up and down play on the lower rod bearing. Best to bite the bullet and just take the head and cylinder off as 125 psi is on the low end for the 400.

 

Does ghis explain why it bacjfires