My cousin has a 400cc two stroke polaris it is four wheel drive and has two chains to run the wheels it is not a scrambler I think it is a explorer maybe? anyways he can't beat a 600 grizz his dads and I told him I could get a 400cc engine to scream im familiar with sleds but after looking at the clutches I see that the secondary apears solid and only the primary seems to be variable is this right? I suppose it's possible it has siezed up or is there a heavy spring in there? what mods are the best bang for the buck so he can beat that grizz and still keep a decent low end I would start with pipes personnaly but he has a limited budget. so I was thinking Blue primary spring drop two teeth on back sprocket and maybe a K&N am I on the right track or is something else better for a decent price? any help is appreciated sure I could figure it out on my own but your help will save a lot of trial and error. by the way I drove it and I was impressed by how sporty it was everyone who drove it was saying a 400cc two stoke should have way more power I think this model was very detuned from the factory. the front chain looks like an engineering nightmare and we didn't check the chain it was loose and it broke the case open a bit on top luckily im a skilled welder and that was no problem. It ate up the chain it had on it pretty quick but we should have checked it out first the guy that had the quad had the chain way too tight. other than that it has been pretty reliable we buried it in mud and rode it pretty darn hard and it has not failed us yet. One other problem is the fuel petcock has to be shut off or it leaks gas is that a cmman problem?

 

Sounds like it needs a carb cleaning or the needle and seat cleaned/replaced or check for debris to solve the leaking problem. As far as the clutching. Be very careful on replacing the primary springs. The ATVs are not like the sleds at all. Without a pipe change about all you want to step up to on spring would be a white primary spring stock from a 2wd scrambler or sport for the primary clutch. The secondary clutch does move apart or else the bike wouldnt go. They can be fairly stiff to do on the bike. If you put the bike in gear and lock the brake then you should be able to push and turn CC the inside secondary sheave and get it to go apart. You should buy an HPD violet or Aaen blue secondary spring. The belt should ride right above the secondary clutch about 1/16 of an inch. If it doesnt then it is worn out or needs adjusting. You need to blow the clutches out with an air hose and lightly sand the faces with some 320 grit and clean with brake cleaner or carb cleaner. That will pretty much get your clutches serviced and along with the 2 spring changes and belt check will improve performance and acceleration a lot. A k&n filter with some jetting will also help it make a little more power.Hope this helps,Bubba

 

oh...though you meant 400-stroke engines, [img]i/expressions/face-icon-small-confused.gif[/img]