1995 zr580 efi and exr 580 efi - Snowmobile Forum: Your #1 Snowmobile Forum

chevette_boy · 09-18-2006, 11:32 PM

looking at these sleds both 95's hows the 580 motor and efi system clutch etc ?

**RJ Gleason** · 09-19-2006, 12:12 AM

EFI is much better than a carb. No messing with jets and it adjusts to elevation and temp automaticly. 580's are strong and the clutch is made by Comet.

BC_Dan · 09-19-2006, 02:13 AM

580s (especially the ZR) of that vintage are known for breaking piston skirts at around 2500-3000 miles. Both mine did. If the pistons have not been replaced and it has that many miles, that's something you will want to do...

The ZR engine is the more powerful engine, the cylinders for the ZR are ported differently for more power. The ZR engine sits lower in the chassis which helps in cornering. ZR's corner absolutely awesome. The EXT has a higher engine mounting position, to allow the rider to lean the sled easier for deep powder riding. The 6-post Comet clutch requires frequent rebuilding, sometimes as soon as 1000 miles. It's often better to replace with an AC 9-post clutch, which are more durable. If you do that, you will have to get the proper clutch puller to go with the 9-post; the puller for the 6 post won't work.

The battery-type EFI on the 95 requires a good battery. If the battery is failing or won't hold a charge, you are dead in the water. If the battery is fresh, my 95 EFI started on the second or third pull, every time.

If the ZR has the stock plastic skis on it, adding dual carbides, such as Woodys, makes darting almost disappear. It's not too bad with the stock single carbide, but the 2-runners made a very noticable improvement on hard-pack trails.

If you ride a lot of trails, the ZR is a great sled; if you ride the trails to the powder, choose the EXT. Both will give you a LOT of fun!

chevette_boy · 09-19-2006, 02:17 PM

thanks so both the ext and zr may have clutch issues ?

BC_Dan · 09-19-2006, 04:08 PM

That era of 6-post ac/comet clutches was not as durable of a design as the newer 9 post, or the new AC 6 post. To keep 'em running right, rebuilding about every 1000-2000 miles is pretty important, especially if you want optimum performance. I have 4 AC snowmobiles and all of them came with 6-post. I have replaced all but one with 9 post. When the last one needs work, I will replace it as well. I figure if I am going to have to rebuild something, I may as well rebuild a more updated clutch that will last longer.

chevette_boy · 09-19-2006, 06:16 PM

is the 580 a piston port motor ? it looks to be that way

although i guess the efi solves part of the low throttle spit-back problem

BC_Dan · 09-20-2006, 10:11 AM

Yes, the 580 is a piston port. You do get some spit-back in the EFI, not as much as the carb version, though.

chevette_boy · 09-20-2006, 07:52 PM

how is the 580 pretty powerful ?

BC_Dan · 09-21-2006, 09:39 AM

I think the stock ZR version has about 95 hp, there is no mention on HP in the repair manual... Arcticchat.com has a TON of Cat-specific information and some guys that really know their Cats... ZR's really wake up when you add twin pipes, they get scary fast real quick! That's not as easy to do with the EFI; you have to get an upgraded "chip" to run the fuel control to prevent burndown...

chevette_boy · 09-21-2006, 01:24 PM

figured as much do alot of efi tuning with cars but wouldent know where to begin with making a chip for a 2 stroke would u know where i can buy a chip ?

BC_Dan · 09-21-2006, 04:19 PM

best guess for that age AC would be ebay.. usually, the company you buy the pipe from will also sell the chip for their pipe so you don't burn down... chips are pipe specific, one brand chip won't work properly with another brand pipe...

motopimp · 10-19-2006, 01:44 PM

Quote:

Originally Posted by BC_Dan

That era of 6-post ac/comet clutches was not as durable of a design as the newer 9 post, or the new AC 6 post. To keep 'em running right, rebuilding about every 1000-2000 miles is pretty important, especially if you want optimum performance. I have 4 AC snowmobiles and all of them came with 6-post. I have replaced all but one with 9 post. When the last one needs work, I will replace it as well. I figure if I am going to have to rebuild something, I may as well rebuild a more updated clutch that will last longer.

Does that "era" include a '98 ZR580 for both the clutch and piston skirt issue's ??? Thanks.

IndianRvrShiver · 10-19-2006, 03:16 PM

Quote:

Originally Posted by motopimp

Does that "era" include a '98 ZR580 for both the clutch and piston skirt issue's ??? Thanks.

AC didn't make 580's in 98!

BC_Dan · 10-19-2006, 03:22 PM

If the clutch is a 6-post Comet, it's a weaker design than the 9 post AC, and may need rebuilding as early as 1000 miles if ridden aggressively.

I thought that AC went to a 600 ZR in 1998; if it's a ZR580, I would think the same issues would be present with the pistons as the design did not change. You don't hear near as much about piston problems with the ZR 600 as the 580's had. It's not a death knoll for an engine; you just have to keep an eye on it. Changing pistons before they break is pretty easy and not terribly expensive. Changing after the piston skirt breaks is a LOT more difficult and way more spendy, especially if parts end up in the crankcase and toast the bearings.

BC_Dan · 10-19-2006, 03:24 PM

There were EXT's and Panteras in the 580 engine in 1998.. but no ZR that I am aware of...

bm250r · 10-31-2006, 09:25 PM

BC_DAN, i just picked up a 96 ext 580. What pistons would you recommend i look into? Where can i read more about this clutch upgrade? I did a few google searches but i cant find much for the older sleds.

BC_Dan · 10-31-2006, 11:53 PM

I have weiscos in both my zr's and like 'em a lot. The big issue with long life in the 580 was piston skirt wear resulting in breakage of the skirt. OEM pistons are a cast piston, weisco's are forged, which are stronger. They also require a bit more clearance in the cylinder, which makes them pretty perfect for me, as I did nothing to any of the cylinders with the exception of running a hone to break up any glaze. Older Weiscos had a bad reputation for cold seizing, mostly when someone would fire the sled up and go zooming off; the cast cylinders heated at a different rate than the forged pistons, and the pistons expanded too fast, resulting in seizure and damage to the cylinder and pistons. If you go to a forged piston, you should ensure that the engine has ample time to warm up before you hit the throttle hard. Newer Weiscos are less prone to that, but the issue still exists between dissimilar metal types and expansion rates.

OEM pistons work fine too, but you may have to do more checking on the cylinders to make sure they are ok to accept the pistons.

The clutch on the mid-90's AC was a comet clutch with an Artco number. Artic Cat had a lot of pretty premature failures with the 6-post Comet with the higher hp and torque of the engines of that era, and came out with the 9 post as an Arctic Cat design to overcome that problem. The taper and offset is the same so the clutches are interchangable. You can use the same weights, but the springs are different; for the AC clutch, use AC springs, as the AC springs have a smaller inside diameter.

If you were to go order a new clutch from your AC dealer to replace your 6 post clutch, you would get a 9 post (did that). If you go to the 9 post AC clutch, you will need a different puller as the 6 post and 9 post are different threads on the end where the puller engages the clutch.

In 2002, AC also introduced a new clutch, which is also a 6-tower, but TONS stronger than the old Comet design. I dont' know if they make the new 6-tower with the correct offset for a 580, but it is a brute of a clutch!

bm250r · 11-01-2006, 08:50 PM

WOW, thanks for all the info.

The sled i picked up has a burnt piston and it scored the sleeve very bad. Im gonna try and pick up another cylinder instead of messing with the one i have and put some wiseco's in as you recommended. Since mine is a 96 ext do i need another cylinder from the same year or are all the 580 ext liquid motors the same? And are they the same from side to side? Thanks for all the help.

BC_Dan · 11-02-2006, 12:09 AM

The part number for the cylinder is the same for both sides. It's also the same cylinder that the ZR used, so you may find one pretty easily. Check Alpha Sports - Arctic Cat Snowmobile Catalog for parts.