I need some Rotax help - Snowmobile Forum: Your #1 Snowmobile Forum

slideways · 12-04-2003, 12:12 PM

Hi guys,
I recently bought a 399cc Rotax 2stroke twin off of ebay. All i was told is that it has a Tilotson Carb and was for a Skidoo.

I need a source for parts. I need the screw on fuel bowl assembly and a wiring diagram so i can get a tach for it.

I also have some general questions for you but those are the important ones. I can get you the serial #s off of it too.

O yea, im putting it on a go kart

G-ForceJunkie · 12-06-2003, 08:04 PM

source for parts = nearest ski-doo dealer

01MXZ800 · 12-06-2003, 08:29 PM

NOT A GOOD IDEA PUTTING THAT MOTOR ON A CART WILL OVERHEAT IN WARM WEATHER

slideways · 12-07-2003, 08:23 PM

Really? See this is why i need your guidance guys. How can i cool it cheaply and effectively?

Will this Skidoo dealer be able to get me parts that are "older". I actually dont know the age of the engine but i do have serials for it. Anywhere online?

Thanks

01MXZ800 · 12-07-2003, 08:57 PM

THEY HAVEN'T PRODUCED A 399CC ENGINE IN PROBABLY 20 YEARS
AND THE FAN NEEDS A SUPPLY OF COLD AIR TO KEEP ENGINE COOL, THIS ENGINE WILL OVERHEAT OVER 40 DEGREES. YOU WILL HAVE BETTER LUCK BY USING A MOTORCYCLE ENGINE.

GOOD LUCK!

slideways · 12-07-2003, 09:19 PM

So you cant run a snowmobile engine above 40degrees? I cant believe that. There isnt anything that i can make to cool this thing?

What symptoms characterize overheating? What harm does it do to the engine itself?

Thanks for the help

01MXZ800 · 12-07-2003, 09:25 PM

SNOWMOBILE ENGINES ARE DESIGNED TO RUN BELOW FREEZING,THEREFORE THEIR COOLING SYSTEMS UTILIZE THE COLD AIR FOR COOLING, IF YOU RUN ONE IN WARMER TEMP. YOU RUN THE RISK OF SEIZING THE ENGINE OR POPPING A PISTON
THE FANS CAN'T PUSH ENOUGH AIR THOUGH THE COOLING FINS
TO KEEP THEM COOL IN WARM WEATHER.

busyfixin · 12-07-2003, 11:20 PM

thats not exactly true. a snowmobile engine may not be set up for warm weather, but they can run fine in warm weather. the biggest problem is jetting rather than cooling. since a sled is jetted from the factory for really low temps (so they dont go lean at 15degrees below 0). they run far too fat when its warm out. too fat is good to a certain extent, as the extra fuel that flows through the cylinder and doesnt burn, and actually cools the engine somewhat. but get way too much fuel, and its hard to cempress all the fuel, which causes a too hot combustion chamber, and this causes overheating. the engine will still need your best efforts to keep it cool. as an air cooled engine develops big time power fade. i would suggest that when you put it in the go kart, make sure there is not much in front of it (seat, clutches, gearbox, etc). i would also make a shroud for it out of sheetsteel, and try not to let it sit still running for a long time.

slideways · 12-08-2003, 07:58 AM

Should i buy and automotive type fan and use it to blow into the side cover of the starter where the fan is? Do the make different carb jets for these or were they pretty much standard?

Do you guys know any online places for parts for this motor?

Thanks again

adrenaline · 12-09-2003, 06:37 AM

see your local Doo dealer for parts. They can still get parts for the older sleds. Or Dennis Kirk may have some parts.

busyfixin · 12-09-2003, 07:08 PM

if you can, id suggest getting a mikuni carb on that thing. tillson or warburo carbs however you spell it, are nearly impossible to tune. at least make sure the intake fan side, has alot of fresh air to it.

01MXZ800 · 12-09-2003, 07:21 PM

I WAS JUST GOING TO SAY THAT THE THE TILLOTSON CARBS ARE IMPOSSIBLE TO FINE TUNE BUT BUSYFIXIN BEAT ME TO IT. I WAS NOT SAYING THAT YOU COULD NOT A SNOWMOBILE ENGINE IN THE APPLICATION THAT YOU WISH TO YOU JUST NEED TO OVERCOME THE COOLING ISSUE. I WAS JUST SAYING THAT THERE OTHER MOTORS OUT THERE BETTER SUITED TO YOUR PROJECT
THAN A SNOWMOBILE ENGINE AND WOULD GET YOU THE RESULTS
YOU SEEK WITH LESS WORK AND EXPENCE. I HAVE DELT WITH THESE ROTAX MOTORS FOR 25 YEARS AND THAT THE VINTAGE OF THAT MOTOR RAN PRETTY HOT IN COLD WEATHER AND THE RELIABLITY IS NOT WHAT YOU WANT, FIX FOR 2 HOURS AND RIDE FOR 10 MINS AND REPEAT THE PROCESS.

Maverick · 12-09-2003, 10:44 PM

who has a rotax engine and doesnt need help, lol. sorry guys, was too tempting i had to say it before anyone else started busting balls.

good luck fixing it man.

Michael_in_AK · 12-10-2003, 04:39 PM

good luck man i would try a 450 dirtbike motor then it would hall ! lol well i need some rotax help to lol umm it is a 583 l/c and its over heating and it aint the htermostat and i thot it was the head gasket well the hoses were leaking so i tightend them up and took it for a spin it was not even worm yet and it lost some power it would rev up but it would not got verry good... any info? thanx........

good luck with the cart man!

busyfixin · 12-10-2003, 05:14 PM

a bike engine is hard to use also though, since you have to build really weird engine mounts, and it will probably vibrate all funny, its also hard to get the shifter and clutch to work in a kart. it can be done, for sure, but sometimes its an even bigger pain to get a bike engine to work. with a sled engine you may have tuning and cooling problems, but with a bike engine, it may never get built in the first place, as alot of people have a real hard time with fabrication. also a bike engine isnt counterballanced, and the mounts are solid. a sled engine uses a mounting plate, and rubber mounts to soak up the vibes. with a sled engine though, you must be very careful to get the clutches aligned, or else you will throw belts all the time.

slideways · 12-10-2003, 09:30 PM

Crap, Crap, Crap.

I thought this was going to be much easier than this. I got the engine for $200. I wasnt going with the bike motor because of $$. Believe me i would love to have a transmission on the thing but being a broke college kid i cant put that $up. I figured that 400cc's would make up for all the low end i would need.

Junk? Geez it seemed really nice while i had it running. Of course that was only for like 5 minutes.

I really would hate to go swapping carbs etc, since i was meaning for it to be a bolt on installation. I was going to have a keyway machined in the crank and run a double pulley system to the axle. One with a low range and the other a high range run by idler/tensioners on a shifter handle. I can dump the clutch slowly in torque mode and then smoothly transfer to cruise by popping the handle out and pulling the other in.

The tilly has the 2 screws on it that i dont really understand but i had it running smoothly but it seemed like it wanted to die if it idled too low (which seemed high to me). What kind of rpm does this run at WOT? It didnt appear to have any type of governing system it seemed like it was just running on the most amount of fuel it could dump into it.

Thanks for the interest guys. Its helping me

slideways · 12-20-2003, 10:29 PM

Anybody?

Is there any other forums out there that might know about Rotax's?

Thanks

Snowsk5054 · 12-20-2003, 11:35 PM

Dont know of any other forums.

palmrose2 · 01-01-2004, 10:38 PM

Quote:

Originally posted by slideways
Anybody?

Is there any other forums out there that might know about Rotax's?

Thanks

Yes.

The 503 air cooled Rotax is popular for ultralite aircraft. Do a search. And I wouldn't junk the tillotson to soon. They aren't perfect but at least you can do a lot of adjustment with the screws without thinking about idle air jets and throttle cutaways.

The cooling shroud is a good idea. You need to draw air from a cool dust free area.

Julien · 03-06-2006, 08:05 PM

I don't know why did you say that the motor will overheat, because it have a fan that cool the engine while running!