2011 Prom RMK top end rebuild- just pistons or fix it kit?

[Juicebronco]

I'm sorry if this has been beat to death, but I've been searching and reading for days, and still don't know what to think. Many of the posts I find are older, and so I'm thinking maybe things have changed over the years.

I have a 2011 pro rmk 800 with 3000 miles, and my compression test says 120 PSI on one side and 90 PSI on the other, so I clearly need to tear down the top end. I've never done it, so I found a buddy who will help me, and he is a mechanic, so we should be good on the work.

But now I'm at a loss on if I should be just doing new pistons or get one of those kits with the spacer and taller pistons. Now that the sled is nearly ten years old, I'm guessing people will have better info on how each have held up over the years. Just the pistons are cheaper, but I don't want a shorter lifespan just to save a couple hundred bucks.

I'm in the Upper Peninsula of Michigan, and I put 300-500 miles a year, most of the time is off trail, but most of the miles are the occasional weekend I trail ride with my old man or something. If that is a factor.

Thanks for any input.

 

[1madbird]

I would tear it down first and see why you have low compression on the one cylinder. This will help you decide since you may need more then just pistons. Any scratch's in the cylinder wall that you can feel with your finger nail will require the cylinder to be repaired. With that many miles you will want to measure everything including the bore and the pistons to make sure the bore is not out of spec and needs redone anyways. You can do a fix-it kit with new pistons and the spacer. There are a number of different companies doing them. MTNTK is one that I have read a lot of people have had good success with. You can do a search about Fix-it kits and find other options. Sorry don't have any personal experience with the fix-it kits. I choose to do a long rod from Indy Specialties along with his HG7 cylinders and stock pistons. Now I have a new motor that I can trust for many more miles.

 

[Juicebronco]

Yea, I plan on inspecting prior to ordering parts, well having my buddy tell me how things check out, haha. I was just hoping to have a game plan if the cylinders and what not checked out. Thanks for the response though.

Anyone else with personal experience.

 

[TDR]

MTNTK fix kit regardless of what you find. 11-13 were notoriously bad if you didn’t do this.

 

[05rmksteve]

I've had good luck with the bikeman durability kit and the spi fix kit not such good luck with rktech kits (wiseco pistons). I try to stay away from kits that use wiseco pistons. Make sure to check your crankshaft run out and thoroughly inspect your lower connecting rod and bearings. If you want a guaranteed motor go with indy specialties.

 

[Juicebronco]

OK, so just go with a kit either way. I appreciate the advice.

 

[05rmksteve]

You could also install a set of 15 pistons.

 

[dheida6]

I did the top end on my 12' this fall with the RK TEK drop in kit and couldn't be happier. Truly pull and go and much better power and throttle response. People who have problems with their topends after rebuilds generally do not measure clearances and just throw the parts in and hope for the best. Measure ring gaps and bore to cylinder gaps, you are always better on being a little too loose than a little to tight. Closely inspect the cylinder for cracks and sharp edges and deburr them a file. Make sure you use a factory cylinder base gasket, the aftermarket are junk paper and lead to leaks.

 

[sledtahoe]

If you need a new block , cylinders go with Indy dan

 

[sledtahoe]

I've had good luck with the bikeman durability kit and the spi fix kit not such good luck with rktech kits (wiseco pistons). I try to stay away from kits that use wiseco pistons. Make sure to check your crankshaft run out and thoroughly inspect your lower connecting rod and bearings. If you want a guaranteed motor go with indy specialties.

Many weisco kits here no problems.

 

[Norway]

Mtntk uses Wisecos, and while that name does have a sketchy rep. on here, they changed their alloy before this whole pro thing started.
Mtntk has literally thousands of kits out now, so they are certified.

But like said, you must know how to measure and check for fit. Ring end-gap may need some massaging and its critical!

Indy Specialty is a little more coin, but you WILL be happy you did!

Luck.

Sent fra min S60 via Tapatalk

 

[diamonddave]

Mtntk uses Wisecos, and while that name does have a sketchy rep. on here, they changed their alloy before this whole pro thing started.
Mtntk has literally thousands of kits out now, so they are certified.

But like said, you must know how to measure and check for fit. Ring end-gap may need some massaging and its critical!

Indy Specialty is a little more coin, but you WILL be happy you did!

Luck.

Sent fra min S60 via Tapatalk

Bingo. MTNTK fix kit only. They were the pioneer of the cylinder shim and taller piston. It works, it runs, and it lasts.

I do recommend replacing fuel injectors when doing a top end. Especially in an ‘11

As for the comment above, The piston RK Tek uses is not the same as the piston that MTNTK uses.