Mini Baja buggy snowmobile engine swap!

Kaptain Krunch

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I just picked this diamond in the rough up for almost nothing ($250!). It was built by college kids, back in 2002 for the mini Baja SAE challenge. They were sponsored by polaris, and used many components from polaris ATVS. It was originally powered by a 10hp briggs, per SAE rules. But it has plenty of room for more!

So far i can see the rear suspension is a chopped/re-engineered Polaris scrambler, or sportsman front end. The front suspensions appears to be polaris predator hubs/brakes/ball joints with custom built A-Arms. It has a transmission, also from a polaris ATV with hi/lo/rev/neutral.

My plans are a snowmobile engine swap, most likely fan cooled but i would consider liquid if the price were right.

It certainly needs some work, plans in order:

1: Repair bent RF lower A-Arm
2: free up steering rack
3: Relocate brake and gas pedals (cramped legs, have a few ideas in mind)
4: find a powerplant
5: once its up and running i'll have to replace all 4 tires, and give it a solid paintjob, maybe do some body work.


Few shots of the rear drive setup, unfortunately being hubs from the front of a 4x4 polaris, they have electromagnetic clutches inside that need 12V to engage, im hoping to design some sort of mechanical spool to eliminate that.

Front Hub setup, looks identical to a 500 predator from the early 2000's


AND it passed Tech back in 02'!
 

Kaptain Krunch

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The pink is definitely going to stay! But i may change the yellow to black or green.

As far as a motorcycle engine, thats a hard no. I have a few on hand, but then i lose the hi/lo/rev transmission. A 670cc clone is a boat anchor.

Snowmobile engines are the best bang for your buck, a 440 fan engine makes anywhere from 35-50hp. I may go pick up a cheap 400 liquid sled, which makes about 62hp. Not sure i wanna deal with a cooling system though.


EDIT: going to pick up the 400 liquid sled tomorrow, 63hp@7750rpm.

Sitting here with the springs off the shock 11" of travel at
 

Kaptain Krunch

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Shots from todays progress. I cobbed the bent a-arm bag together temporarily. Eventually i'll have to find someone with a tubing bender to make me a new one.

I measure travel front and rear, 11 and 10.5! The rear cvs have plenty of plunge, and i was a able to spin the transmission with a drill to confirm it could cycle smoothely without binding.

I'll grab some pictures tomorrow once i pick up the sled engine!
 

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Kaptain Krunch

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Scored again! i ended up getting TWO sled engines, for free from a friend. one is a runner, the other is for parts (bad top end). Both are Fuji 488 fan cooled twins, rated at 56hp. They came in polaris snowmobiles from the mid 80s-late 90s.

Today i mounted the engine, using rubber mounts from another sled, and started making the exhaust. since i just couldnt wait to hear it run, i fired it up on pre-mix!

Bolted in place, getting ready to pull right head due to a broken stud. Head off, cylinder has some scoring, and the piston burn indicates a lean condition. it will need to be rebuilt, but for now it'll be okay!
End of the day progress picture! I was able to use the stock exhaust without too much modification. The manifold was chopped and angled up, and the pipe was shortened slightly at the inlet.
I also removed the built in muffler/silencer. a new muffler will be mounted to the back of the buggy. Not much room for an air cleaner!
I "downgraded" the 488's primary clutch, from a p85 to a p90. The p90 clutch is a little smaller, and commonly found on 340/440 sleds, as well as polaris ATVs. Lucky for me, the transmission already has a p90 secondary mounted. I set the Center to center distance at 10", which will allow the use of a polaris 330 sportsman belt.

AND the most important part, a video of it running! as you can see the Right rear axle is bent and will need to be replace. other than that very happy with todays progress!

EDIT: video coming soon, im a little technologically slow...its uploading i think.
 

Kaptain Krunch

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Built an exhaust today! Still just as loud! Next up fuel and oil tank.
 

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Kartorbust

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We had a 1986 Polaris Indy 500 with that Fuji 488 engine, it's pretty bomb proof. Just some advice, we had to run strictly Polaris oil for 2 stroke oil, as our engine was quite picky on that. We had tried 2 different oils back in the 90s when we owned it and it ran best with Polaris oil.

From the bit of reading I've done with members in Baja, a lot of the builds are stupid light weight, mostly for out of the hole running in the endurance race. Awesome score on the Baja and the sled engines. Hopefully dropping in about five and a half to six times the power won't affect it too much.
 

Kaptain Krunch

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We had a 1986 Polaris Indy 500 with that Fuji 488 engine, it's pretty bomb proof. Just some advice, we had to run strictly Polaris oil for 2 stroke oil, as our engine was quite picky on that. We had tried 2 different oils back in the 90s when we owned it and it ran best with Polaris oil.

From the bit of reading I've done with members in Baja, a lot of the builds are stupid light weight, mostly for out of the hole running in the endurance race. Awesome score on the Baja and the sled engines. Hopefully dropping in about five and a half to six times the power won't affect it too much.

I've had a few 488 myself, and used to work at a polaris dealer. They definintely like good quality oil!

As far as handling the power, we'll see. I have faith in the chassis, as well as the transmission, and brakes. I'm skeptical of those hillard clutch equipped hubs in the rear, as well as the steering up front (mostly the rack mounting point). But only time will tell!

Also: ive been off this forum for like 10 years...how do i get my pictures to not upload sideways?
 

landuse

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I've had a few 488 myself, and used to work at a polaris dealer. They definintely like good quality oil!

As far as handling the power, we'll see. I have faith in the chassis, as well as the transmission, and brakes. I'm skeptical of those hillard clutch equipped hubs in the rear, as well as the steering up front (mostly the rack mounting point). But only time will tell!

Also: ive been off this forum for like 10 years...how do i get my pictures to not upload sideways?

The picture thing has been a headache for the last few years. For some reason the forum software turns them around. I normally save to my pc, open them up and orientate them correctly and save again. Then upload them here. It sometimes doesn't help though :D
 

70Cobra

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Get the Tapatalk app for your phone. It's free and you can upload from there. That's what I do.
 

Kaptain Krunch

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So i've been pretty busy getting my shop ready to re-open for no-contact repairs, but i was able to make a little progress today! Its so hard to look at this thing in the driveway and not work on it!

I sourced some free scrap kegs (empty unfortunately) to build a fuel/oil tank. The concept is fuel and oil tank in one, 3 gallons fuel, 3 quarts oil (for the 2 stroke injection pump). Just need to weld some bungs for hose barbs, and make a few filler necks!

I also bought a different p90 clutch off ebay that has a ring gear. Electric start baby!


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Kartorbust

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That's the one thing about the Fuji 488, the oil injection system pretty bulletproof. Though a lot of people do recommend deleting the oil injection in favor of mixing, just to keep it more reliable. When you worked for Polaris, did the oil injection system ever become a problem for people, or does it hold up a lot better than what most think?
 

Kaptain Krunch

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That's the one thing about the Fuji 488, the oil injection system pretty bulletproof. Though a lot of people do recommend deleting the oil injection in favor of mixing, just to keep it more reliable. When you worked for Polaris, did the oil injection system ever become a problem for people, or does it hold up a lot better than what most think?

I have never seen or heard of a pump failing. The only thing ive seen fail was a cable. However these pumps are designed to run wide open in the event of a cable break, so you will actually be getting wayyy to much oil.

Ive taken them apart before out of curiousity, and the design is so simple, i dont see how one could fail unless you ran the pump dry....in which case the engine would be toast anyways.

I'd say its just fear of mechanical advancedment, nobody wanted to ditch the carburetor when efi came out either :idea2:
 
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