2008 700 RMK time to replace top-end, suggestions?

[windsock]

Thinking that it is time to replace the top end on the wife's 700RMK 2008. We'll have probably 2700 miles on it by the end of April and hope to do the work in May/June when we have the time. Any suggestions on pistons? I think I've heard that it is best to use the OEM pistons but perhaps I heard wrong........ ?

 

[F-Bomb]

The only time I'd use aftermarket pistons is when OEM isn't available especially on something as consistantly reliable as that application. The stockers are not out of line either price wise. Did you compression test it? 2700 in 2 or 3 seasons isn't that many. If you ride 1000 ish a season I'd keep going. Maybe have them bought and on the shelf just in case. Takes a short evening for most to do this service. Once again if all is well I wouldn't mess with it. Run premium syn oil and do your other maintanance and it should keep on jugging a lot longer then 2700.

 

[dub]

I agree, I would run a stock 7 to 5K with good compression easy!

 

[windsock]

I'll check the compression then. Thanks for the advice. I just remember having to replace my pistons on my 2003 800 doo at every 2000 miles or there was hell to pay.

 

[mtnsledder]

6300+ miles on an 07 600 155 RMK and 4500+ on an 08 700 155 RMK , haven't touched the motors on either.

They both run great, engine compression was 120 psi on the 07 last time I checked a few hundred miles ago.

Two of the best sleds we've ever owned and we've had quite a few.

 

[clutch man]

6300+ miles on an 07 600 155 RMK and 4500+ on an 08 700 155 RMK , haven't touched the motors on either.

They both run great, engine compression was 120 psi on the 07 last time I checked a few hundred miles ago.

Two of the best sleds we've ever owned and we've had quite a few.

It is not a good to run any 2 stroke snowmobile motor over 5000 miles with out repalcing the crank seals. There is too much of a load on them and no oil gets to them to keep them sealed. Plus the heat from the clutch on the PTO side gets that seal to hot and brakes down the rubber. As far as the top end POLARIS has the best pistons and do last longer than the seals.

 

[wyodragon]

2008 700 blown

Made 2099 miles when piston skirt broke,took out cylinder and all of that dropped in the case and took out the crank. $3540.00 for a new engine. Compression was fine in November. I am going to be a lot more pro active about the top ends on both of my 700's now. Dont hear of a lot of problems but it seems like when they go it is usually more than a piston. Upside is its new now

 

[SnoKing]

Thinking that it is time to replace the top end on the wife's 700RMK 2008. We'll have probably 2700 miles on it by the end of April and hope to do the work in May/June when we have the time. Any suggestions on pistons? I think I've heard that it is best to use the OEM pistons but perhaps I heard wrong........ ?

Just a little FYI.

In 2008 the 700 RMK engines were furnished with 2 styles of pistons.

The early production had 2 rings and the later production had single rings. I thought there was a difference so I just looked it up.

 

[95RXL]

Made 2099 miles when piston skirt broke,took out cylinder and all of that dropped in the case and took out the crank. $3540.00 for a new engine. Compression was fine in November. I am going to be a lot more pro active about the top ends on both of my 700's now. Dont hear of a lot of problems but it seems like when they go it is usually more than a piston. Upside is its new now

My 08 700 has gone down twice now. Once at 1500 miles and again at 2400 miles. Both times was because of broken piston skirt and both times it took out the cases, reeds, and cylinder on the side that broke. It has been each side now. I checked compression within 200 miles of the last break and it was near 120 each side. Mine has the single ring piston. I have little faith in my 700 even after hearing all the good things about them. Anyone looking for an 08 D7 with a fresh motor????????? I'm scared to run it. The warranty comes off this October.

 

[sledneck_03]

my 08 has 4000 trouble free miles........

 

[SnoKing]

my 08 has 4000 trouble free miles........[/Q


DO YOU KNOW IF YOU HAVE DUAL OR SINGLE RING PISTONS?

I'M INCLINED TO THINK YOU MAY HAVE THE DUAL RING.

WHAT IS YOUR SLED'S DATE OF MANUFACTURE?

 

[sledneck_03]

my 08 has 4000 trouble free miles........[/Q


DO YOU KNOW IF YOU HAVE DUAL OR SINGLE RING PISTONS?

I'M INCLINED TO THINK YOU MAY HAVE THE DUAL RING.

WHAT IS YOUR SLED'S DATE OF MANUFACTURE?

its also a rental and so i think it has a few tricks done to it to keep it alive. i know it uses a good amount of oil..... i also have no idea whats been done to it the first year so it could have had the pistons updated.

it says on the tunnel 09/07/2007 manu date.

 

[SnoKing]

its also a rental and so i think it has a few tricks done to it to keep it alive. i know it uses a good amount of oil..... i also have no idea whats been done to it the first year so it could have had the pistons updated.

it says on the tunnel 09/07/2007 manu date.

O.K.

I'm going to find out what the mfg date break is between the dual and single ring units.

 

[Pownar]

I had some problems with the single ring. I did a precautionary top-end using the double ring just in case. I think I will throw in wiseco pistons this summer and have the jugs re-nicked and see how they do.

 

[95RXL]

Can you just replace the single-ring piston with the dual ring or is there anything else that you have to do as well? What actually causes skirts to break off? I thought it was from piston slop but like I said, I had good compression prior to it happening and my sled uses more than enough oil too.

 

[Pownar]

You can just put the dual ring piston in with just a cylinder hone job. It has to be the hone from polaris though. I have been told that the single rings tend to get more piston slap that can lead to skirts breaking. Too much oil is not good either. I would think that anything under a 40:1 ratio is too much. If there has been a lot of cylinder wear, you might want to check your ring end gaps.

 

[95RXL]

Thanks. I think my oil pump arm got a little sluggish last winter and wasn't returning all the way to it's resting position when I'd let off the throttle. Gonna attach an extra spring to the arm and mount it somewhere to help it return as it should this summer. I was using 3/4 of my oil in one tank of gas. I had it looked at at a shop and they said everything looks fine. Next day..........bam!!!
Just got it back at the beginning of March and won't be able to test it until the warranty is off next year.

 

[95RXL]

700 double-ring pistons.

I looked up the double-ring pistons used in 08 and there was 2 different part numbers. 2203512 which was used in the 07's and in the early production 08's.
Then 2203707 which was used in the 08 switchback and the short tracks. Anyone know which one I would put in my 08 D7 155 if I were to switch it to the double-ring pistons?

 

[SnoKing]

I looked up the double-ring pistons used in 08 and there was 2 different part numbers. 2203512 which was used in the 07's and in the early production 08's.
Then 2203707 which was used in the 08 switchback and the short tracks. Anyone know which one I would put in my 08 D7 155 if I were to switch it to the double-ring pistons?

The Switchback and the LATE production (single ring) RMK both use the same cylinder 3021866 so I would think the 2203707 would be the one.

 

[95RXL]

I think you're right. The 08 switchback has all the same part numbers for the crank, the cylinders, and the cases. Just the pistons are different so that should work. Thanks. That'll be a good summer project.