440 kit on 97 Explorer 4x4
$1650.00 total

Blew up after 35 minutes. Cylinder broke at base.

Aaen welded cylinder for free and suggested stud girdle kit. Oh now you tell me.
this time it worked for 6 months, then the piston was worn out.
Bored and new piston kit, its running.
But it doesn't have the power Aaen said it would.
A stock 2001 400 Scrambler will out run it.

Any one had any luck with the 440 Kit. I'm not satisfied at all.
The 650 Prairie will smoke it !

 

PRAIRIETWIN,

Generally you won't get a lot of top end with the 440 kit. The larger you make the bore the lower the ports become and thus the lower the machine will rev. The best thing for it would be to have kept the bore size stock and had it ported, put a bigger carb on, better reed valves mid or top end pipe, a Swaintech coated Wiseco piston, cool head and air box mods.

Big bore generally doesn't make more hp than the standard bore/ ported, carbed and piped motors as with most four strokes. The Polaris motors are vastly under tuned to make them safe for the average rider. These motors have tons of potential in them if you leave the bore size stock. Also, you have to leave the motor warm up quite a bit when using forged pistons to keep them from mating to the cylinder walls.

 

If it wasnt ported, the ports are so far from specs now it wont make any top end power. When I went .140 over I had to grind alot to get it back to where it needed to be. Also you need to raise the transfers to get the filling of the top end. Without good porting, the bottom end cannot deliver enough air and fuel to fill the top end good. The big bores make more grunt for pulling hills and what not, but sounds like they should have covered the bases with you a little better. By the way, it is really not a 440, it is only a 411cc. Bubba

 

He said "mating" [img]i/expressions/face-icon-small-smile.gif[/img]

 

Heh,huh huh. He said grunt and fill the top end, huh huh.

 

You guys should be ashamed of yourselves. This poor man has problems.

 

The cylinder was ported by Aaen to their trail specs.--- Revs out to 8200rpm----most of time 7800rpm
Bore was 88 mm---------now 88.5 with .008 piston to bore clearance. cylinder so thin allows for flexing(vibration of cylinder).
head was stock but opened up to accept new piston.
Compression ratio was 12.5 to 1 comp. 92 pump octane
Aaen top end pipe
42mm taper bore carb. 430 main jet
V-force reeds.
All new air box system--------then open K/N filter only.
Aaen clutch kit----Green or orange spring(which ever you prefer) Weights(53g?) new helix, blue driven spring
63 to 65 HP kit.

Oh it gave the quad more power, almost to much power to trail ride. but when stock quad out runs it, what a waste of money. Unless you like wheelies all the time at take off. then buy clutch kit !!

 

Nothings wrong with a little Beavis and Butthead humor.[img]i/expressions/face-icon-small-smile.gif[/img]

 

Well, the info you gave gives a real concern. Sounds like your revving and not going. The first thing that really bothers me is that you shouldnt have that kind of piston to cylinder wall clearance. The max clearance that I run with the big bore is only .0045-.005. Any more and it really isnt too good for piston skirt wear. I can see why it would eat a piston quickly. The other thing that concerns me is that Aaen shows their full mod kit with the modified top end pipe to only turn 7250rpms. HPD's race pipe only runs 7200-7300. CPI's pipe runs at 7500rpms. If your turning 7800 all the time and sometimes more, you have clutching issues BAD! You need to get on the phone with Olav Aaen and tell him exactly what you've posted and see what he says. Something is not right. Remember, all the power in the world means NOTHING if the clutching doesnt match. Hope this helps,Bubba

 

Base cylinder bolts must be retorqed after intial warm up and then rechecked frequently thereafter. If the base bolts are loose movement will occur possibly snagging a ring, premature wear and maybe even breaking the base as it did on yours. The lack of power is probably in the clutching like Bubba said. If Aaen says peak hp is at 7250 rpm with your set up and your at 7800, your not where you need to be. 200 rpm either side of the powerband when shifted out will rob hp in a hurry.