My RKT 858 experience

[IQRIDR]

First off, I want to make it clear- I am not bashing a product here. I am posting my objective experience with a product. Lots of people are asking and contacting me regarding how the kit ran and I, as a long time member here on Snowest and a shop owner I feel obligated to set the drama aside and simply post the facts.

When the 858 motor first got out on the snow, it ran great once the fueling was dialed in. Pulled massive track speed, motor sounded very healthy, everything was good. Then, I lost a rod bearing after about 50-60 miles. Crank was done. At this point, the sled needed a new piston on the mag side (mag rod bearing scored it up) but already had some scuffing on the PTO piston as well. This concerned me but I was assured that it could be run again once it was cleaned up a little with a scotch brite pad.

The cylinder also had some interesting scoring...I have my opinion about it, RKT has theirs, I suppose the cylinder plating company would have one also. I will let you form your own.

I then rebuilt the motor with a new crank and 1 new piston. It ran great, again, for about 5 rides or so, then started losing power and compression slowly. I dissembled the motor to find 2 heavily scuffed pistons and the cylinder looking and feeling worse than before.

I believe that there are some problems with this kit that can most definitely be solved, but it has been brought to my attention that people are being informed that the sled ran great for a lot of miles and is still running. The 858 kit got a total of just under 350 miles on my sled the 2 times it was installed. I have since reinstalled a stock cylinder and pistons with my previous head and pipe setup. I do not want people to be misled or under the impression that the kit had no problems. I will be sending the pistons back to RKT for inspection.

Normally I would have continued to keep all this to myself but I feel morally obligated to the industry and my shop's reputation to put the facts out there and let them speak for themselves. This kit DID RUN GREAT but it does have problems that need to be addressed and to be honest I am sure RKT will address them and have a good running, cost effective bang-for-the-buck kit. This was a one-off kit.

I want to make it clear that there is nothing wrong with the sled as far as snow ingestion, belt dust ingestion, oiling, etc...a picture of my stock piston with 2438 miles on it will attest to that..no significant scuffing or wear, in fact they looked pretty decent and still made perfect compression.

Stock piston, intake side (STOCK 2011 PISTONS, THESE ARE NOT THE 858 PISTONS)

Stock piston, exhaust side

RKT 858 cylinder

Inevitably there will be people bashing me or disagreeing with my choice to post this here...but I got into this business for a few reasons with a set of specific principles and morals and I do not want to be responsible for people being misled or misinformed. Flame away.

 

[AKSNOWRIDER]

Chad, thanks for posting this..questions, how tight was the bore clearence when you first assembled? (hard to see in the pics but looks like it was a little tight?) also did you monitor egt's and did it hold consistent? thanks..

 

[KAWGRN]

A breath of fresh air!!!!Honesty,morality!

 

[beamslayer]

Thanks for the reply. Like you said it was a proto type and I hope Kelsey gets it fiqured out I for one would like to have affordable BB.
No flame from me.

 

[wellfed777]

IQ
x2 thanks for the report !
i don't see any questions in you post it was a proto test situation
you explained your test of said product . the info will help rktec build a better product then we all win

 

[RKT]

it has been brought to my attention that people are being informed that the sled ran great for a lot of miles and is still running.

Normally I would have continued to keep all this to myself but I feel morally obligated to the industry and my shop's reputation to put the facts out there and let them speak for themselves. This kit DID RUN GREAT but it does have problems that need to be addressed and to be honest I am sure RKT will address them and have a good running, cost effective bang-for-the-buck kit. This was a prototype kit.


Inevitably there will be people bashing me or disagreeing with my choice to post this here...but I got into this business for a few reasons with a set of specific principles and morals and I do not want to be responsible for people being misled or misinformed. Flame away.

This really interests me.. (the red highlighted parts above)

Where is this "informing" coming from and who is doing it?

 

[knifedge]

--Thanks for testing the prototype kit so that the final kit will be reliable. That is what
prototype testing is for. --Looking forward to a Cat 925 BB myself.


--BTW -- what were your coolant and EGT temps? AFR ratio? --The Pro is a little lacking when it comes to the cooling the motor
in stock configuration, then add a bunch more HP and possibly a fuel ratio tuned on the lean side with marginal snow(not in
AK), and SQUEAK.
Now with factory OEM piston/cylinder clearances, you might still be running the kit, like your stock cylinder setup. But who
wants to blow a skirt(although yours have lasted, just the rod bearing blew up).

--OK, so clearances got too tight with the BB kit -- Question is why?

--Just thinking-- based on the lack of information given in this thread, only more questions are raised concerning
engine operating conditions during the 350 miles the BB was tested. Maybe the BB Kit needs more clearance, maybe
it does not. Under the operating conditions that you subjected it to(whether proper or improper), obviously, more
clearance is needed.

--I would imagine that RKT has run and tested this kit in other sleds as yours would not be the very first one. If that is true,
I am sure they would not send out your kit out of tolerance relative to what they have successfully tested themselves.

--One more thought-- Assuming your testing at low elevation and all engine operating parameters are correct, you would be
making substantially more HP(heat) at low elevation than at elevation where BB kit originated. Maybe slightly more clearance is
necessary( if all engine operating parameters were correct). --If I was RKT, I would have had you sign a confidentiality agreement before I sent you a prototype kit. Testing is testing.

 

[beamslayer]

I see or do not see any pics of the 858 piston ??? Is it scored on four corners ?How did the rings look ? What did the inside of the piston look like ?
Kelsey who said this or who said that I am not concerned about the only thing I am concerned about is having a wicked running reliable pro. I hope you keep us posted on the 858 kit . Chit happens
P.S. I have a chance to go to Revy in may to ride with some guys if you want to donate a kit I will use my sled as a test mule and in July we put on the grass drags here in ST. Maries ID another good test.

 

[hyperduc]

Wow, this is a shocker. Are you telling me that having people pay to be beta testers for a product DOESN'T work? But yeah, go ahead and insinuate that he's a liar before you exercise even the smallest bit of customer service and admit that you might be wrong.

 

[Matte Murder]

IQ how was the kit fueled that you ran? Did you have gauges on the sled? Air/fuel and exhaust temp? If so what did they look like? Did you turn up the oiling before or after you installed the kit? I am just asking questions. I don't have any ax to grind, I just own a Pro and am interested in all forms of performance upgrades. Thanks for posting.

 

[Super Dave3]

Can you post some pics of the pistons?

 

[camocat1000]

why no pics of 858 pistons ?

the pics of the 858 cylinders do not look ported..correct me if I'm wrong and I could be aren't the 858"s ported? they look like factory ports IMO

did you use a boondocker box and his setting ?

what shop do you own?

 

[IQRIDR]

Sled was run on 93 octane fuel. EGT's not over 1250. PC5 fuel box. I did not post pictures of the pistons yet because it's not everyone's right to see his piston design but I will edit the pics and post them to show the scuffing. Heavy scuffing on intake and exhaust side with random 360 degree scuffing also.

The operating conditions could not have been better for testing. Deep snow. Oiler was turned up last year to about 35:1 ratio.

I didn't post pictures of his pistons or the underside of the cylinder where you can see his porting...those are the kind of things each builder has put a lot of time and effort into designing and I wasn't going to put pictures of it all over the internet. I will post pictures of the pistons at my discretion after a little editing so those questions can be answered though.

Let me reiterate- there was nothing improper about the running, building, or tuning of this sled. I have tuned and built plenty of big bores from all different manufacturers, many of the initial kits have hiccups, it happens. Plenty of happy customers here in Alaska to vouch for my credibility and knowledge, no need to toot my own horn.

 

[AKSNOWRIDER]

thanks chad....

 

[pura vida]

i saw both the cylinders and pistons. luckily i'm uninformed enough i don't have the ability to know or relate proprietary piston or porting design...

but i've built, blown up, and rebuilt plenty of motors and these pistons and cylinders looked incredibly bad. completely wasted. and they felt just as bad as they looked. i've seized motors before that looked better than these cylinders and pistons looked. my first comment was, "good lord, those look worse than pistons out of a bad cfi-4 800 motor".

there was clearly a motor issue. what that issue/s was i'll let those with more expertise and experience than me to figure out. it's a bummer b/c it showed some tremendous potential at first and was quite impressive. but later on, after watching it have its *** handed to it by stock sleds, it was clear something wasn't copacetic. and the pictures clearly show that...

hopefully kelsey (sp?) gets it worked out. could be a really nice setup.

pv

 

[Hardass]

How many other 858's are out there? are they having issues?Maybe they should have a close look at there top ends.

 

[indydan]

Sled was run on 93 octane fuel. EGT's not over 1250. PC5 fuel box. I did not post pictures of the pistons yet because it's not everyone's right to see his piston design but I will edit the pics and post them to show the scuffing. Heavy scuffing on intake and exhaust side with random 360 degree scuffing also.

The operating conditions could not have been better for testing. Deep snow. Oiler was turned up last year to about 35:1 ratio.

I didn't post pictures of his pistons or the underside of the cylinder where you can see his porting...those are the kind of things each builder has put a lot of time and effort into designing and I wasn't going to put pictures of it all over the internet. I will post pictures of the pistons at my discretion after a little editing so those questions can be answered though.

Let me reiterate- there was nothing improper about the running, building, or tuning of this sled. I have tuned and built plenty of big bores from all different manufacturers, many of the initial kits have hiccups, it happens. Plenty of happy customers here in Alaska to vouch for my credibility and knowledge, no need to toot my own horn.

I respect you trying to protect something but there is nothing to protect.

Its a piston............ not a rocket ship part, and by the looks of the marks in the cylinder its a forged piston. And your pictures already gave away whats going on you can tell by the ring travel area where they stopped well short of the OEM rings.

Not really a big news flash, As I said nothing to hide.

You can put any piston you want into this motor and nothings going to change. There is a dynamic reason its hard on pistons.

I'll bet 20 bucks the pistons are hard lined and the skirts are collapsed at least .003 to .005 thou already.

 

[INDEEP]

Why did it go so quickly? Is it possible the cylinder goes out of round at operating temp? Especially since it's been overbored. If it's true Polaris is adding another 2mm to it's cylinder skirts in 2013 maybe there's something to this. This is the second time they've beefed them up.

 

[AKSNOWRIDER]

pretty much all cylinders go out of round as you heat them up...normal practice is to put deckplates on to pre stress them(simulate being bolted togeather on the motor) before finish boring/honing is done...also ..the cfi motors have very marginal coolant flow on the exhaust side due to the compact design and powervalves..means the already high heat exhaust puts even more heat into the cylinder..piston/bore clearence becomes evenmore critical...a thousanth to tight and she can squeak a piston..especially on a real long full throttle pull..or being a tick to lean, or...well you get the idea....

 

[INDEEP]

I'm talking more out of round than normal. A properly fitted piston (not a loose OEM) would just exasperate the issue.