Indy 500 speeds?

[Doc Madison]

I have two Indy 500's that I just started using this year and noticed a big difference in performance. A '99 500 XC SP had the speedometer pegged at 100-105 and a '97 500 EFI would only do 78 mph on hardpack. Are these consistent speeds for stock sleds and if so, why the marked difference in speeds between the two? Both seemed to run smoothly. Thanks!

[The_Duckslayer]

Only 78! That would be zipping right along for a snowmobile. Probably some government rule that says they can only go so fast. Designed to keep the younger riders a bit safer I suppose. Good thing that the governmnet is always lookin after our interests

Take care and N Joy the Hunt././Jimbo

[SledNeck]

actual speed= under 100 on gps.

[Shack]

78 or a 108, its wheel chair time when you hit that tree.

I would say its the speedo head. On a sled, they can we way off (+ or -) or very close.

I would check with GPS, like sled neck said.

[hanson]

I am not a Polaris guru but I believe those sleds have major differences in their engines.

The 97 500 EFI more than likely has the Fuji engine which is a piston port motor. This was the same engine in my 89 500 Classic and is the same engine in the newer 500 Classics as well. I don't think I ever got my 89 500 Classic over 85mph.

The 99 500 XC SP I believe has Polaris's USA built Liberty engine in it which is a reed valve motor. 500 XC SP was also Polaris's high performance model in their 500 class. Could be other slight engine differences such as compression and carburetion that are making it run faster than your EFI.

[Shack]

Throw in what Hanson said and then it also comes down to clutching.

You can have a great variation in speed from the same sled and motor if you change clutching. In the hole or out of the hole, bottom end or top end, clutching is a major factor on acceleration and speed.

Plus throw in the EFI verses the Carb thing; many, many factors could be the result of a difference in speed between two sleds with same CC index number. I would not say this is start of a concern.

I would not worry about it, they run good. Just ride them and be happy the are running good . Some posters on this forum would love to have the concern you are posting about, verses the concerns they are going threw right now

[Black_Bay]

No those aren't typical real world speeds. The current stock 500cc world record is only 102 mph. That is on a race only sled tuned for the conditions, clutched for top speed, speed tracks with a lot of studs...you get the idea. My guess your '99 was closer to 90 to 95 mph. Still plenty fast for a 500 cc sled. The '97, on the other hand, sounds like it needs some work. You say it runs smooth so I would look at the clutching and gearing. Both sleds should be running about the same speed with the nod to the '99.

[Doc Madison]

The EFI still goes faster than I'm usually comfortable going so I'm not disappointed with it, given I initially bought it for my wife, but I was just curious about the vast difference in speed. When the two go side by side, there seems to be at least 10-15 mph difference. Thanks for your responses.

[fishingforester]

Hanson is right on the money, here's a little more info. I used to run a '97 Indy 500 (carb'd), and I recall the rated power output of that engine was 78 hp. On one perfect glass trail and brutal cold morning temps, I got the speedo to read 90, but was only able to do it once.

The Liberty 500 has considerably more power; if memory serves me, the '99 was somewhere in the 90-100hp area.