Hey guys,
I bought a 1996 Polaris trail boss new in 96 for my kids and they are grown up now and I needed to do something with it. A buddy had a small dune buggy frame and said I could have it .. sweet. I broke out the sawzall and hacked the trail boss up keeping the engine,transmission and rear suspension in tact to keep it simple. I mounted the front steering and suspension and fabricated a steering wheel. Everything came together nicely and the finished buggy was slightly lighter than the original ATV. I experimented with the carb jetting until it was dialed in and when I test drove it it topped out at 42mph.
As any speed loving off roader I got bored with it and wanted to put in more HP . . that's where buddies are so cool they seem to have what your looking for and the price is always good. I got a call from a buddy who had a 96 Polaris sportsman 400 4x4 that had over heated a bit and scuffed the piston he said come and get it and see if it will work in your buggy. The jug wasn't in bad shape just little aluminum stuck to the cylinder wall so after some muiratic acid and a scotchbrite pad it was ready for the Weisco piston and rings.
With the motor back together i'm ready to start the swap so my questions are (Both units are 1996 trail boss 250 and a sportsman 400)
1. What ignition and wiring problems will I face?
2. Can I use the 250 transmission?
3. Can I put the primary drive clutch on the 400 motor ?
4 Will the carb off the 250 work on the 400? (they appear to be the same size)
5. How can I post pics so you can see what Frankenbuggy looks like?

I'm sure I will need to post more questions as I encounter them but this should get me going.
Thanks
Leadfinger
"watch for the finger"

 

You'll need the 400 stator,cdi,wiring harness,etc. You'll need a radiator,hoses,fan,etc.
Trail Boss gear case is h/n/r 400 4x4 has low range and to use this transmission you'd need the 400 shift box. Clutches can be swapped around as basically all non ebs clutches were the same except for weights and springs. 250 engine used a VM30ss carb,the 400 used a VM34ss carb. Plus I'm sure there's several more things I'm missing,but shouldn't be any big deal after what you've already done.

 

I have the cdi and wiring harness for the 400 but was hoping to just use the one from the 250. I also forgot to mention that I have both the gear cases but will be trying the 250 H/N/R case first to see how it performs since it is already installed. As for the radiator, hoses, fan I will be installing those as soon as i get the rest figured out since they will just be in the way.
I am finding subtle little differences that are slowing me down like the screws that hold the retainer for the inner cover seal are smaller diameter on the 400 and I had to drill and tap to accommodate the larger screws . . little stuff that are easy fix but you cant just ignore.
Aligning the engine to the gear case and maintaining the correct 10" center to center and left to right position is proving to be a challenge any thoughts or tips I could use to help with that task?
I'm the type of guy that doesn't discourage easily and as problems come up I find a way to knock em down so one way or another Frankenbuggy will live.

Mr Old Polaris Tech your knowledge of these machines is priceless and your willingness to share that knowledge with others is worthy of Sainthood and I want to thank you for the help you have given me and others.

 

You need the 400 harness because the connectors and modules aren't the same as on the 250 as well as the stator itself. It really needs to be a complete 400 including the carb in this case.The rest you can fabricate to your heart's desire. Plus plenty of videos and details on youtube that can give you ideas.If they can stab high power snowmobile and car engines in atvs,anythings possible.

 

Finished the alignment of the engine to the gear case. Now I'm working on the wiring since I have the CDI and all its pretty much plug and play. I don't have the pipe from the 400 so the 250 pipe will have to do for now. I don't have the thermal switch for the cooling fans so until I have time to buy some parts I don't have off ebay I'm gonna just put my own switch in for the fan.
When I open the throttle should I see oil squirt from the oil injection hose?
I haven't hooked that up yet I want to make sure its working before i do

Can anyone tell me what kind of power I'm looking at with this motor . . is it a long stroke beast that is slow to make power? or a quick revving screamer?
I'm hoping for a noticeable increase in "ohellyes"! performance

 

Compared to the 250,yes more power.Don't know if the 250 pipe is going to help or not..You wont see oil squirt out from the injector hose at the carb. More of a dribble according to how much throttle is given.The pump is calibrated along with the throttle cable,more throttle,more oil. Based on a 50-1 ratio from the factory as long as the pump marks are aligned.If you have the line disconnected to check,make sure you install a bolt in the intake manifold and I'd also premix the first tank at 50-1 to insure you have a good supply of oil if you're check the pump out. One way to fool the pump into thinking the engine is running wide open is to remove the three screws on the pump cover,lift the pump wheel up all the way at an idle and oil should increase from the line.Look at this chart,can give you some ideas on stock hp rating along with increases that can be made with a little $$. Aaen Performance - Polaris ATV Scrambler 400
Plus here's a view of the pump. You can barely see the mark on the pump body.Pump is set a little off the mark(richer)

 

While inspecting the oil line to the intake manifold I sprayed carburetor cleaner thru the check valve that bolts (banjo bolt) to the intake and wasn't satisfied with the results. It acts like its plugged, can I poke a thin wire thru it to clear it out? I know its some sort of check valve but shouldn't it be easy to blow thru? What is the function of the valve? to keep the oil from draining back when the engine isn't started for a while?
I would feel better if it was cleared out so oil would flow better but maybe its like this by design. Maybe I just ask too many ridiculous questions . . lol

 

Just pull the check valve off and blow it out with air or any spray carb cleaner.Easier also just to replace the 3/16" vinyl tubing if it's cracked and worn.No wire through the opening.

 

Do all the 96 Polaris 400's (scrambler, sportsman, xplorer etc)have the same engines?
Do they all have reed cages? what are the differences if any?
I have a Mikuni TMS 38 flat slide carb I want to try but cant find a boot that will fit. The only carb choices I have are Makuni VM 26 and VM 30 and then this TMS 38, would it be worth trying to find a boot for the flat slide or just get the stock VM34 off ebay?

 

All 400 engines are basically the same over the years with minor differences.VM34 was the stock carb for the 400.The 250 used the VM30 carb. Just me,if you have access to the right carb I'd get the blame thing running first,then if you're serious about more power there are several places like this one online you can check out and can spend some money at.Aaen Performance - Polaris ATV Two Stroke - Top End Pipes