I have a 1998 ZRT 600 triple with 4400 miles. Based on general knowledge when should I consider a rebuild? The sled has been mostly ridden on groomed trails or on lakes. I had it over 100 mph on many occaisions. What are the indicators or when its time to rebuild or should I just "if it aint broke dont fix it"? Any information is appreciated.

If its runnin good leave it alone, do a quick compersion check - that can tell you alot as to how worn the cyl/rings are

our 2001 zrt is at 3500 and this will be the last year before a rebuild...

magic number for twins is 4500-5500 after that the rings are too worn into the pistons they push back then its piston on cylinder direct contact and well its all down here from there, learned this all from charles at fast track performance who did the motor on the jag, he had a couple sleds there that he was rebuilding, and showed me the pistons to prove it....apparently triples you can go a bit further but presonally for about $130 a piston, or even less for just rings, its worth it, ya blow a jug or worse the piston does like above and seizes well then you can take out not only a jug but your entire bottom end.... preventative is always better in my opinion...

as above compression check tells alot to, nothing beats a good tear down however, tear it down if its good throw the new gaskets in and go, if it needs rebuilding rebuild it.....

My 1997 600 went 9000 miles before the crank shaft broke.But I think being under water for a week didn't help,but it still lasted another 2 years and 1500 miles after that.Last year I put in a new crank,pistons rings ect.I plan on keeping it for a long time.

I've got 8200 on my 2001 ZRT 600, runs strong, cylinders are in great shape, and compression is great across all 3. I've got the rebuild kit, but I can't bring myself just to rebuild it, when it doesn't need it. Run good oil (amsoil interceptor here), and keep it off the lean side, and it could last a good long time.

If the compression is good, leave it. You will need it sooner if you are running pipes and turning higher RPM (more wear and tear).

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yours is the 6th crank I`ve heard of giving up the ghost in the 9,000 mile range . mine did at 9,250

I think what I will do is look for the rebuild kit. Then next spring I will tear it appart and rebuild it. One thing that worries me about my machine is the oil usage is pretty low. I am in no position to upgrade so I am going to have this sled for a long time. I do love it however! Good thing.

Where did you find the rebuild kit? How much was it? How do I keep it off the lean side. I appreciate any help, Thanks!

1996 thru 2000 are prone to the pistons breaking.
What you need to do is pull the carbs and the reed cages, roll the engine around and look at the intake corners of the pistons through the reed opening.
Look at both corners as the crack at a diagonal angle toward the center.

The cracks will continue up to the lower ring groove and that piece will fall off and wipe the entire engine out.
I am a mechanic at a snowmobile shop and have seen it happen several times.
Suzuki "beefed" up this area on the powervalve engines and they will go a lot farther.

Give it a look, If they aren't cracked, leave it alone.
I have put several of them back together with the cheaper SPI pistons at 60 bucks each. May be something to consider?????
Mike

60 BUCKS EACH???? WHY YOU CHARGE ME 120.00 ?????????

About what mileage do the cracks start? See my 99ZRT question thread.

I have seen them start to crack as little as 1500 miles. I had one fail a wipe out the entire engine at 2200 miles.
It only takes about an hour to inspect.
Mike

You can get them from your dealer. When I say rebuild kit I mean, I've got the rings, I've got an extra set of pistons, I've got an extra set of cylinders and powervalves. Shopping the forums during the summer is your friend. Keep it off the lean side, means to properly jet it throughout the whole rpm range, don't run on the edge, if your plugs look closer to lean then rich, jet up.

rebuild it. its cheaper than a new motor. then u dont have to worry about whether u need to rebuild it or not. if u are worrying about it, then its time. those pistons see alot of rpm and temp changes and alot of general wear. took my 96zrt 6 about 8000 miles, then the pto piston caught a port. it had good compression, but that doesnt tell everything. bye bye engine. i just built another engine for this season. good luck

I have a 01 1000Tcat. my advise is at the start of every season do a compresion check and see where you stand. Theysay you shouldn't have more than a 10% differance between all sides. And while you have your reeds out take a look at the exhaust side of you head off and look at the pistons on that side as well as you intake. Check for any scratch lines running threw the ring areas and wear at the top edge and look for piston sleave wear or scuffing. Take will tell you if you are getting piston slop. Use good oil and you should be able to get 5000 miles, like a few have said stay a tad on the rich side is better than poching in the middle of the season. I had to rebuild mine last year at 5200, Lost a screw in my read cage and spit it you, but got it in time before it went any futher! Good luck!

I have to disagree with this. The stock cat pistons arent prone to breaking. There are alot of well known zrt600's that have run untouched for 5,000+ miles zero problems. The zrt600 engine is probably one of Cats most durable engines to date. When they are taken care of they go and go and go. As far as pistons go, the break in every 2 stroke hi performance engine I have ever seen or know of, its not unheard of. But the zrt600 breaking pistons, not even an issue on the grand scale, not like some sleds out there. I do know for whatever reason the piston design changed over a few times but it want all due to breakage problems. There are a ton of zrt's running around untouched engines with lots of miles on them.

What I have found is they break at the circlip grooves when somebody has messed with them and taken out the circlips before and sometimes they break when you reinstall the clip. That I have seen, same thing on the 440 zr's and sno pro's. Same thing. Seems when somebody has been into an engine, there lies the biggest problem as most dont know what they are doing and overlook too much stuff.

I wouldn't run anything besides a factory piston or a wiseco as long as you properly check clearance and warm it up properly. I'd stay away from the cheap shit pistons.

Here is a picture of a piston off a untouched EXT 600 2 up that belonged to a 60 year old man that I rebuilt the engine on.
He bought it brand new and it had 2400 miles on it.
If you look at the intake side of the piston.. you can see the crack angling toward the center of the piston.
It is just starting to crack on the other side.
When the cracks meet in the center on both sides and breaks off, it drops down in front of the "pork chop" of the crank and there is no clearance for it and it breaks the rod and blows the front out of the case... and the engine is junk.
As far as the comment on the Tawain "SPI" pistons, I bet I have sold a 100 of them and installed 25 of them myself.
Never had one problem with any of them and never had a engine failure due to them.
Mike

I dont doubt that you never had a cracked piston but fact of the matter is they arent known for cracking pistons or piston problems. There is always a sled out there that shouldn't have a problem but did and that sled obviously had a problem. When I think of sleds or particular engines in sleds that are prone for piston problems I think of the zr600 twins or the doo 600's and 800's(for example) with piston problems with recalls.

Back to the zrt piston, that could have been just a bad casting. Who knows, or just bad ass luck.

Useing the SPI pistons is just prefrence. If thats what you like thats cool. Id personally have no problem installing them on a lower hp sled but anything of mine I stick OEM or Wiseco.

the "dot" on the stock zrt 600 piston goes towards exhaust, correct?????????THANKS HAWK!!!

Yes

I just rebuilt my 96 ZRT 600 motor. It had around 5,000 on it (I think, I forgot). I had a TON of snow get into the carbs and pack them solid even. I had snow scoring in one cylinder. Compression was slightly low.

I just put SPI pistons in it and reassembled it. Should get it started this week, hope all is well with it now.

I measured my jugs according to spec (have high tech measuring equip at work), they were in spec still.

SNOW800! THANKS!!!!!!HAWK!!!!

On one of my 900s around 6000mi I noticed cracks forming on all three pistons exactly at the same spots near the skirts. Put in SPI ones about two years ago and haven't had a problem since...

I aslo run the SPi's and have had no problems, that crack on on bottom skirt is a common thing but I would only check it after the 5000 mile mark, then keep an eye on it. My zrt engine has about 15000 miles on it. (2 1/2 rebuilds and its a 96 600 motor)

Its been solid for the most part I have shaved the weights reved that engine past 9000 rpm, and it will still pull the new sleds hehehe!!!

Warning 9000 rpm is very hard on the crank and because of that I have gone through 3 cranks. I have toned my sled down since then. (just to get more life out of the engine)

Still a really good motor and fast for its class..

I ran my 1997 600 to 5000 mile mark amd was told that I should check the pistons for cracks.I pulled all 3 jugs off and low and behold the centre piston had a crack in the skirt on the exhaust side.I replaced all 3 pistons and ran it to the 11000 mile mark and pulled the total engine apart.The only thing I replaced was the crank seals.Put it back together and sold it at the 12000 mile mark.Ran nothing but castrol oil in it.I had all the crank bearings checked and were still excellent.I also made sure my primary clutch was top notch at all times .I beleive this is very important to crank life.