Yes the slack at the thumb throttle should not be more than 1/8" or the etc contacts in the switch can touch and die.Several good videos on youtube about this and other repairs/maintenance. Plus I'd pull the reverse limiter module black wire to defeat it as these modules fail.Eliminates having to push the override button in reverse to get full power.It's the module on the left under the front panel. 1100-1200 rpms at idle is about right.Never been a fan of jet kits as most manufacturers remark the jets so you really don't know what size they are and in most cases you're paying mostly for the titanium jet needle. I'd install the carb kit for this engine. Shindy makes a good one made in Japan.Then at least you can rule out any carb problem.The 335 and 400 used the same #40 pilot jet,but the 335 used a 150 main jet versus a 167.5 for the 400.Could make a differnce.http://www.ebay.com/itm/2001-2002-POLARIS-SPORTSMAN-400-CARB-CARBURETOR-REPAIR-KIT-03-412-/360494309042?pt=Motors_ATV_Parts_Accessories&hash=item53ef229eb2&vxp=mtr

 

That sounds exactly like what the problem was, because I was thinking there's no way that tightening the slack in the cable is doing anything in the carb. The jet I put in was a 160 out of the jet kit, It seems to run okay but I'll see if I can find something closer to 167 in the kit. I am running a k&n filter also. I set the e-clip on the 4th setting down from the top, although the kit said to run it the 3rd down. I figured with the bigger motor it couldn't hurt. I'll get some pictures and videos up of it running once everything is buttoned up. Again thanks for all your information!

 

K&N is less restrictive than the stock filter even with a sleeve. Could be part of it. Plus did you have the K&N on the 335 when it blew up as you said?? Just my two cents,never been a fan of em as I had to rebuilt two 500s because of them. Partially owner negligence I know,but in sandy areas they give me the ******* even with outerwear.Again each to their own preference. Like to see some pics and a video of this Frankenstein atv..

 

Got a video of it running before all the plastic went back on.


And heres some pics

 

And I gotta say, what a power difference. I think the 335 was tired, so it was a very soggy power. She gets up and goes now

 

They never should have made a Sportsman 335. That's not enough engine for so heavy a quad. Congratulations on a successful upgrade.

 

Think that's why we only sold about 3 of em. Just no power. Wasn't impressed at all when they first came out. Looks like a good engine transfer,but have you run it long enough to see if the fan kicks on or not?

 

Not yet, I don't have the temp gauge that I ordered from ebay yet. I did let it run for about 10 minutes and it never came on, but it didn't seem too hot either. I have am IR temperature gun somewhere that I'll have to use to try and get a temp to see if it kicks on. When I get time tomorrow I'll check that ad let it run longer, if not I'll just hard wire a toggle switch.

 

Cool . Good work.

 

Got the fan wired up to a switch, for now. I parked it up on car ramps again with the radiator cap off to bleed the coolant system. I ran it for about 35 minutes letting the air bubbles come out, while squeezing the coolant lines to burp the air out. I never got it to overflow like Ive had happen with cars (tons of bubbles come bursting out, then top off the coolant and call it good).. and there were still some small bubbles coming out when I put the cap back on to call it quits for the night. Should I be concerned about this?

Also, I have done some browsing in other threads and have run across something else im not sure about, which is aligning the clutch, or motor. I can see the belt spinning with the vent off when its at idle, and it does clunk a little bit when going in and out of gear. I assume I just have to loosen the motor mounts and move the motor to align the belt on the sheaves, but what is the actual process of doing this? I replaced the belt back when it had the 335 motor in, and the belt was in for about 3 hours of riding until the motor blew, and I noticed there was some rubber dust in the belt cover, and a couple times through riding I did smell rubber. Im assuming I should replace the belt, again, and maybe try to get it aligned correctly. I am just trying to get everything squared away 100% before I start taking it out in the woods.