Polaris has these so choked off it's not funny. we are working with a kid right now. we put 38 mm tmx carbs on one. still dialing it in but putting down stupid numbers and speed for a 550. ski-doo had a real good deal on these carbs. as they went injection with there race sled. there all sold now. and i have sold all i purchased from them. so all fuel related stuff really works on these. but yes ufo's made these wake up pretty good. dail'a' jets, quad rings, and ufo's all made these better.

the 550 is running just shy of 600 times. a little pocket porting works as well. this motor is light. so the whole sled is much lighter than a 600 liquid. but these being fan cooled slow done on the second pass. so keeping these cool and not running it much before a run is necessary. shouldn't be a issue on a trail sled? this was on the grass.

 

I am suprised to be honest nobody makes performance parts for those Indy 550s. A performance kit of some kind would be sweet. With the less than snowy winters we usually get a guy could buy one of these for cheap fun. I see leftovers priced under $6000. They are so light that a lil more power and performance woukd make them a total riot on the trails.

 

we use to. but a few guys didn't listen and blew up there sleds. we got bad P.R. on this so we stopped. we had not one issue and had the fastest 550's around that were trail ridden. our kits were even used on some top snow x racers in the day. in the 600 fan class. these always won. these can be made into a rocket. i like the 550 motor the cranks are super strong for that motor. and the thing has huge transfer ports stock compared to other fan cooled sleds. we also worked on putting stator, flywheel, and c.d.i. box from a xc 500 on these. with good results as well. but fuel mod's are the best bang for money spent.

 

What size is the stock carb? I could bore the ID on a lathe at work but I'm not sure I want to screw with the jetting too much. Seems that we go from no snow for testing at home to our first long trip in the UP and we would rather ride than wrench in the hotel parking lot.

We are not going to be racing it, just hoping to wake it up enough to keep the kid happy for one more year.

With the UFO, they say to cut the pilot jet in half. #45 is stock. Should start around #22? Does this sound right?

 

Used UFO on my 97 MXZ when UFO first came out. Worked great. Pilot was at least half. You will know if it is too big. With smaller pilot you need to up the mains at least one size. With the smaller carbs you need to drill a hole in the needle jet tube. Cannot remember specifics. Call Thunder Products. The inventor is full of good info. Installed the on an old 488 FAN. made a huge difference.

 

Interested to hear more about these mods for sure.

 

Years ago one of the guys here built a mod gen2 550 that had cylinder porting, 38mm tmx carbs and a pipe. It was clutched and studded for bear. Sled was geared to run top speed in about 900'. It was a rocket for what it is. Could recall several drag races with the locals it surprised those 99 non ves 500's to the point if they slept it was over. I could remember that sled hosing a lot of stock xlt's and indy 500's to.

 

All I know, they say don't bother, blah blah blah, but they have the most left on the table. Porting, head mods, carb mods, etc. Especially porting. It doesn't have to be radical, as they are much cruder than the.liquid equivalent. Especially the 488 fanners. I laugh every time I see those cylinders. They are very crude.

 

Trouble is once you get into the cylinders and head mods like the one i saw here, you make more heat on these sleds. I remember our guy saying his sled couldn't run just on a diet of pump gas, nor did he think it'd hold up on long rides.
On another note, i had all the rough scale smoothed out on my 81 srv 540 cylinders, transfer ports matched, and exhaust polished mirror smooth. I couldn't believe how much better the sled ran. We had to add heavier rivets to the clutch weights to bring the rpm back down.

 

I am talking conservative, not crazy maxed out head mods or porting. Like your SRV example, but maybe a little more aggressive.. Funny you should mention that a friend of mine I think we were still in highschool, had a 85 SRV.he bought used, not going to date myself, but it was an old sled at the time. We put an 89 Exciter rear skid in it, with fox shocks he bought for it, he put an SLP pipe on it. It was a fun sled.

 

As too slow said, fuel is a concern on the fanners. Todays fuel is not what it once was. Fuel is also part of the cooling on a fanner. Years ago when I had my modded 488 Indy trail it was big fun. Kinda miss it. I have said to freinds, if I lived up north I would have a fanner in the stable for the icey trail days when a liquid has a harder time cooling.

 

Back around 81 i never had an issue with the cooling on my yamaha srv540 even using the lowest octane fuel in quebec. That sled was big fun and a lot better on the fuel range after the cylinder work. Its another sled i wish i still owned. I had an 83 srv 540 that ran well, but was a total pig when it came to fuel...that sled couldn't pass a gas station it didn't like. Never owned another srv 540 after that.

 

Do the Indy 550s need the oil pump mod like the older ones? Anyone know? The newer ones have the CV tech primary clutch also correct? How's the tune ability of the CV tech clutch?

 

That CV Tech clutch was a:buttrock: popular Mod on the Doo 1200 four smoke. Much more power going through it than a Poo 550. Not sure but Doo may have made it oem on the 1200 near its end?

 

Scuba1221, The guy to talk to about UFO is Lonn Peterson at Thunder Products. He is the guy that developed them. Very approachable guy.

 

I've put UFOs in a dozen sleds over the years. Had very good results with fanners - along with any piston-port type and old school rotary valve motors. I usually dropped the pilot jets 1 less than half like Rick said and usually had to just do minor changes to the primary clutch for basic economical performance increase. Lonn @ Thunder is a super nice guy and will help you with any questions. Easy to install if you have a drill press. They work really well with an oval bore on the carbs. I had sent carbs to Dakota Performance back in the day and they would oval bored and install the UFOs. Good improvement through the entire power band after I weighted the clutch to bring the RPMs back down.

 

For what its worth bout a year or so ago I did read where a guy said he put a GGB can on his Indy 550 and said it gained a nice increase in tnrottle response...

 

Was the guy about 12 years old?

 

Im not afraid to admit I know zero about snowmobile performance mods. Now atvs I have done lot of mods but with sleds Im clueless. Can you add like V Force reeds or other aftermarket type reeds to these for a boost?

 

nope. there a cylinder reed motor. it's still a piston port motor with a small reed assist petal at the bottom of the cylinder intake side. it allows earlier intake into the crank case before the piston skirt clears the intake port. which is weird. why they choked it off with 34 mm carbs but have big crank case volume? i'am thinking it was a fuel pig with 38's on it. they were probably going for better fuel mileage with the 34 carb's? no one makes any aftermarket reeds for this. and probably wouldn't see a gain here.

 

I would leave the motor, pipe etc alone. You'll probably be asking for trouble on the trail with those motors. Rick knows these sleds and see if he can do the work and help with the parts you need ? I would bore the carbs, UFOs and tune the clutch, jet to ride in all temps so you can leave the hood down and just ride. May be rich in the warm weather, but rip in the colder weather like stock jetting. I have a 440 fan and a Gen 2 550 we ride every year sitting in the stable, but the reality is if you really want much more power, then go to a 600 liquid. That 550 can be woken up for sure and it will be a fun sled if you do.

 

I can tell you the old gen2 ves 600 i had was faster than those 00 700 mach 1 triples. Raced a slew of them that were clutched and studded. Only could really one that was close.

 

I snow-checked a 2000 600 xc sp. Loved that sled. I studded it, put a RB Industries clutch kit in and back then we sent our secondaries to Goodwin to have them machined into a roller secondary. Sled was a rocket. My buddy on his 98' CK3 700 Mach 1 and my other buddy on his 98' 670 MXZ w/ dynoport pipes knew what my taillight looked like. Except that Mach has long legs on the lake runs. I got a huge kick out of that. We couldn't believe how fast that sled was with studs and clutch work. That's about when we stopped donating our money to the Crank Shop and Dyno Port etc and tuned the stock sleds. dependable and fast.

 

You didn't need these aftermarket clutch kits imo. I ran ground down sides on 64 weight to 63 an almond/ gold spring with slp slippery brute buttons, epi purple secondary spring and a hsp 34x helix. 23/40 stock gears. I ran a 2 degree timing key with hsp reprogramming the cdi unit. 120 chisel studs using all 3 belts along with air box mods. This worked well for 1000' runs. Used different gear/clutching for 660'
A buddy of ours had his carbs oval bored along with the stuff i did on his 00 600 ves..that sled was about 2 sled lengths faster than mine. Both of were able to beat 800 sleds, his more often.





a purple epi

 

Darn I thought there was a new post on 550 performance.

 

back to sorta the topic...any hop up an EVO 550 Fan? seems that sled chassis might dominate the widely popular fan cooled racing class lol.

 

I think theres an ecu upgrade that gives you full power for the evo.

 

same 550 motor. ufo's first. these respond to fuel mod's very well. yes get the tune or what ever Polaris does to get it over 50 mph. we have got as much as 85 mph out of the 550.

 

Years ago one of the guys here ran 91 mph on our stalker gun on ice with his gen2 550. I think this was around 1 mile run.

 

Put a fresh top end from MCB (SPI pistons?) in this weekend as well as new crank seals. Indicated the crank when I had it out and the mag end was out .004". Put a c-clamp on the counterweights and easily got it turning true. Sanded the exhaust ports smooth but not to a mirror finish. The kids fingers got sore pretty quick and I didn't see the point in spending all day on it for a 550F.

I called Lonn at Thunder Products and he was very helpful and informative. Hopefully the UFOs arrive before Thursday so we can install them next weekend.

Stock gearing is 18/42. I'm thinking we could get away with 18/40 and I have a 40T gear lying around. Rider weight is 90 lbs soaking wet.

Do you think clutching changes will be required or will gearing taller compensate enough with the UFOs? It is just a trail sled, he's not racing anyone but his mom.

 

I would think it's going to pull more RPM and may need a couple more grams to start. I wouldn't crank up the engagement with a new primary spring unless you can hook up. Should be a fairly easy test and tune.

 

Exhaust ports should end up a mirror finish...its the intakes and transfers that don't.

 

No. It does nothing to make them mirror smooth. A very BIG misconception for porting. It's the shape and size, not the shine that makes power.

 

What is the target RPM on this engine?

 

Guessing for a fan, 7K rpm