I checked the compression on my ZRT 800 and found that the cylinder on the recoil starter side has 60lbs of compression, while the other 2 have 110. These numbers are cold, while not pulling the throttle open. The ZRT has about 4000 miles on it.

There does not appear to be any kind of leak anywhere.

I took the sled out for the first ride of the season last weekend - it was running great. The only reason I checked compression was just out of curiosity.

My question is? Can I run the sled for a few trips before fixing the problem? Should I replace all three pistons, or can I get by with replacing only one?

thanks for any advice!

stop running it,,,, you have a problem and it could get worse if you continue. There is another post in here right now about rebuilding the top end of a zrt 600,,,, its nearly the same thing your into. You may have nothing more than a bad o-ring and the pressure is getting out there, you could have a bad ring also,,,, you may have a very very easy fix but could turn it into something major if you continue to run it,,

Yes stop running it. There is a reason its at 40lbs. Although I have had testers read wrong from time to time. Make sure there is nothing holding the little air valve open and not letting the testor work right. I have had this happen when a piece of carbon blows up in there on the last cylinder I checked and I thought the cylinder was bad.. well I went back and tested the other 2 again just to make sure and they were all bad the 2nd time because there was a small piece of carbon stopping the valve in the testor from closing. his is not a common thing to happen but just check it to make sure. If this is not it you have a bad piston, rings, or cylinder or all of them. Could be a bad base gasket.. but unlikely. If your going to end up putting a new piston in you might as well do a complete top end. Have the cylinders checked for clearance as well as making sure they are truely round. Good luck.

I took the cylinder head off the bad cylinder. Both the head and the piston have some markings on them, indicating something foreign was in there. the cylinder walls look pretty good, except the wall just above the exhaust port. It's a little scuffed up. My buddy thinks its minor and can be honed out.

My problem is that I can't seem to remove the cylinder. I've removed the 4 nuts at the base of the cylinder, but I can't get it to budge.

Any tricks to removing a cylinder? BFH?

I took the cylinder head off the bad cylinder. Both the head and the piston have some markings on them, indicating something foreign was in there. the cylinder walls look pretty good, except the wall just above the exhaust port. It's a little scuffed up. My buddy thinks its minor and can be honed out.

My problem is that I can't seem to remove the cylinder. I've removed the 4 nuts at the base of the cylinder, but I can't get it to budge.

Any tricks to removing a cylinder? BFH?
[/b]
be sure to use a RUBBER b.f.h. . :bash:

I took the cylinder head off the bad cylinder. Both the head and the piston have some markings on them, indicating something foreign was in there. the cylinder walls look pretty good, except the wall just above the exhaust port. It's a little scuffed up. My buddy thinks its minor and can be honed out.

My problem is that I can't seem to remove the cylinder. I've removed the 4 nuts at the base of the cylinder, but I can't get it to budge.

Any tricks to removing a cylinder? BFH?
[/b]


Try a rubber mallett first. Tap from each corner all around it. If that does not work, and I have been there b4.. you will need to take a wide screwdriver and find somewhere on each side to pry up on the cylinder away from the base. DO NOT tap the screw driver in between the base and the cylinder as it will damage both. Usualy a "rocking" motion will losten it. keep in mind the cylinder and piston might be STUCK as well so make sure you turn the motor over and make sure the piston is not stuck in that spot. You may have a ring snaging... or worse. Also you cannot "hone" these cylinders out as they are NiCaSIL plated. If there is more then REALLY LIGHT marks you will need to either send it out to have it repaired or purchase another one. Some pics would sure help here.

if its looking nasty near the exhaust port, your gonna want to get it reniked,,,, chances are, when you put a new piston and rings back in there, its gonna catch on there and your gonna have an even bigger mess than what you have now. You will need to get the cylinder and piston out to take a look at the sides of the piston also. If your scored on the walls of the cylinder, your piston is probably shot also. I wonder if the circlip didnt come out and run between the piston and cylinder wall a few times,,,, that will chew up a sled real quick.

Best to pull em all off for inspection, if it's worn through the nic on one cyl chances are the rest aren't far behind.

Best to pull em all off for inspection, if it's worn through the nic on one cyl chances are the rest aren't far behind.
[/b]

I pulled the cylinder off. The piston ring alignment pin had come off. I ended up getting a new cylinder and a wiseco top end kit.

I'm just hoping the other 2 cylinders are ok......

I pulled the cylinder off. The piston ring alignment pin had come off. I ended up getting a new cylinder and a wiseco top end kit.

I'm just hoping the other 2 cylinders are ok......
[/b]

Make sure you take the other cylinders in for fresh crosshatch. The cylinders need to be resurfaced, a fresh crosshatch, for the new rings to seat properly.

I pulled the cylinder off. The piston ring alignment pin had come off. I ended up getting a new cylinder and a wiseco top end kit.

I'm just hoping the other 2 cylinders are ok......
[/b]

Keep in mind that when you use wiseco pistons your re-ring intervals will be allot shorter then with stock pistons. Wiseco's are a higher preformance piston and will require rebuilds allot more then stock. I used to run them in my RM250 back a few years ago when I was racing and I would re ring every 3 weekends. Keep in mind we practiced 3 nights a week as well usualy, however that still does not add up to 3 or 4 200 mile trips. Some will say that Wiseco sled pistons are longer lasting then they used to be, I can not speek for or against that as I have not used them in a sled at all. I just know 3 or 4 people I know refuse to use them in sleds because they say at max you should only put 1000 miles on between top end rebuilds with them. They say you should re ring them at 500 to 700 miles. Again I have no experiance with Wiseco's in sleds so I cant say it is 1000% right but I take what they say to me and my experiance with racing bikes and decided nto to bother to try them in a sled. From what I have heard the best piston to put in a cat is a factory Suzuki piston. *shrugs*

Keep in mind that when you use wiseco pistons your re-ring intervals will be allot shorter then with stock pistons. Wiescos are a higher preformance piston and will require rebuilds allot more then stock. I used to run them in my RM250 back a few years ago when I was racing and I would re ring every 3 weekends. Keep in mind we practiced 3 nights a week as well usualy, however that still does not add up to 3 or 4 200 mile trips. Some will say that Wiesco sled pistons are longer lasting then they used to be, I can not speek for or against that as I have not used them in a sled at all. I just know 3 or 4 people I know refuse to use them in sleds because they say at max you should only put 1000 miles on between top end rebuilds with them. They say you should re ring them at 500 to 700 miles. Again I have no experiance with Wiesco's in sleds so I cant say it is 1000% right but I take what they say to me and my experiance with racing bikes and decided nto to bother to try them in a sled. From what I have heard the best piston to put in a cat is a factory Suzuki piston. *shrugs*
[/b]

How will I know if I need to re-ring? Will the compression get lower and lower Or will it just go out one day? Last year was my first year sledding and I put about 750 miles. I'm guessing that I will put about 1000 this year.

How will I know if I need to re-ring? Will the compression get lower and lower Or will it just go out one day? Last year was my first year sledding and I put about 750 miles. I'm guessing that I will put about 1000 this year.
[/b]


You can check your compression every 500 miles or so. We used to re ring every 3 weekend s or so just because we knew how hard we ran the motors and after a while of doing it you kind of get to know when you were losing power. Again I am not 100% sure as to how they work in sleds as I have not used them in a sled before. Also keep in mind when racing moto x there is allot more dirt and dust in the air that the motor takes in. No matter how much you oil your filters on a bike there are still tiny parts of dust that make it in your motor so that may have something to do with rings being worn out faster. I thought of putting wiseco's in my zrt9 but after talking to a local race motor builder I decided against it. He said they are awesome for drag sleds as you only put 8 or 9 miles on every race. So they can last you a while that way. He figures every 500 to 700 miles you should re ring wiseco pistons in sleds. Is he right? I have no idea if it is a fact or his opinion. But I do trust his opinion. And if I have to re ring every 600 miles or so, on a good season I will have to rebuild 2 times or maybe 3. No thank you. lol. I dont mind doing it every fall if I should... but Idealy I would like to get 2k on a set of rings without having to even check compression. I actually went with a set of stock cat pistons and had them coated by a friend of mine. He did the skirts and the domes. They looked damn pretty !! So pretty I didnt even want to use them ! lol

I have used Wiseco in my race and trail sleds and have NEVER experienced the type of wear or frequency of ring replacement as mentioned above; ever.

Install them correctly (by that I mean with the correct piston to cylinder clearance and ring end gap) and they last just like OEMS. I have had engines with over 3000 miles on a set of Wisecos with zero issues.

Re-ringing every 3 weekends?? Something wrong here. I beat the living hell out of my 250+ HP race sled and ran SEASONS with the same pistons and rings (running a solid 145 LB compression each and every season, no loss). I'll give you the dirt scenario for moto, but not on a sled.

If you follow directions CAREFULLY, don't be afraid of Wiseco. They have benefits that the OEMS do not have.

I have used Wiseco in my race and trail sleds and have NEVER experienced the type of wear or frequency of ring replacement as mentioned above; ever.

Install them correctly (by that I mean with the correct piston to cylinder clearance and ring end gap) and they last just like OEMS. I have had engines with over 3000 miles on a set of Wisecos with zero issues.

Re-ringing every 3 weekends?? Something wrong here. I beat the living hell out of my 250+ HP race sled and ran SEASONS with the same pistons and rings (running a solid 145 LB compression each and every season, no loss). I'll give you the dirt scenario for moto, but not on a sled.

If you follow directions CAREFULLY, don't be afraid of Wiseco. They have benefits that the OEMS do not have.
[/b]


Again I am going by my experiance with racing my RM 250's and not sleds and from what I have been told. I have never used wiseco's in a sled because everyoen I have asked alwasy tells me the same story. Your the 1st who has gave them a rave review that I have seen. Maybe I shoudl try a set n see for myself. i did like them in my bikes. I loved the fact that they are very softer then normal pistons in case of a melt down. *shrugs* Glad to hear you have had good experiance with them. Maybe the people I have asked are idiots. lol

i have 4,000 miles on my wiseco`s . they have the same comp every year

I finished the top end kit last night. Installed new wiseco pistons and had the cylinders honed. I have 125lbs of compression on all three cylinders (using my old pos gauge).

I'll keep an eye on the compression and will post back any changes.

thanks for all the help

i have 4,000 miles on my wiseco`s . they have the same comp every year
[/b]
Mine did also on the old 711 till a ring broke.......put new slugs in a save a replating bill
wiseco `s are not as good as oem`s so don`t think that they are.....ring lands were wore
caused slack which in turn hooked by the exhaust port and caused $350 us damage to a good cylinder. My next wiseco`s were changed out at 2000 miles .......anyway to each there own.....
Cape Breton Stock.....................

Mine did also on the old 711 till a ring broke.......put new slugs in a save a replating bill
wiseco `s are not as good as oem`s so don`t think that they are.....ring lands were wore
caused slack which in turn hooked by the exhaust port and caused $350 us damage to a good cylinder. My next wiseco`s were changed out at 2000 miles .......anyway to each there own.....
Cape Breton Stock.....................
[/b]

Things like this are what I have heard over and over. Ill stay stock as well.