RKTek 858 is LEGIT!

[Jkinzer]

I have 200 miles now on my new sled and can't say enough about the 858 big bore kit. The low end and mid range torque of this motor is amazing and after getting my clutching dialed in it just seems to keep pulling and pulling. I have ran the drop in kits for the past two seasons and i was a little skeptical that the 858 would really be that much better.... but its as big of a difference from stock to drop in if not bigger than from the drop in to the 858. i'm running the 156x3 track this year and pulled right around 50mph track speed tree riding all weekend. This set up has taken my fun factor to a whole new world! Now we just more snow storms!

 

[jerrod07]

I also put the 858 kit in on my 2014. I've got about a 100 miles now and it is a ripper. started with a bikeman tune on my PCV that was super rich but now I've got it pretty close. pulls 8500 fast and stays there


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[Merlin]

I have 200 miles now on my new sled and can't say enough about the 858 big bore kit. The low end and mid range torque of this motor is amazing and after getting my clutching dialed in it just seems to keep pulling and pulling. I have ran the drop in kits for the past two seasons and i was a little skeptical that the 858 would really be that much better.... but its as big of a difference from stock to drop in if not bigger than from the drop in to the 858. i'm running the 156x3 track this year and pulled right around 50mph track speed tree riding all weekend. This set up has taken my fun factor to a whole new world! Now we just more snow storms!

Thanks for the report!

The only thing that concerns me is your statement in bold. Those are the same comments generally used to describe Carl's 900. Top end performance was questionable by some of those offering their assessments.

I've been on the fence between a turbo or one of the RK Tek's 858s for awhile. Having ridden a properly tuned Silber turbo last year I was pretty much sold but the extra coin a guy would save going with the big bore might make the lack of power tolerable if the gap between the 2 wasn't too big.

On paper a guy certainly can't argue with 50 MPH track speed on a 153 X 3 but I'd really like to throw a leg over one of these before I make my decision.


BTW, how are you fueling this set up?


Thanks again,


Glen

 

[nuggetau]

I have 200 miles now on my new sled and can't say enough about the 858 big bore kit. The low end and mid range torque of this motor is amazing and after getting my clutching dialed in it just seems to keep pulling and pulling. I have ran the drop in kits for the past two seasons and i was a little skeptical that the 858 would really be that much better.... but its as big of a difference from stock to drop in if not bigger than from the drop in to the 858. i'm running the 156x3 track this year and pulled right around 50mph track speed tree riding all weekend. This set up has taken my fun factor to a whole new world! Now we just more snow storms!

I sure would like to see you do a direct comparison(same rider, same day) with Carl's 900.......hint.......hint.

That would make my future decision a lot easier.

50 mph track speed turning a 3" is pretty good considering the stock engine will only turn the stock track around 39 mph.

 

[Jkinzer]

Thanks for the report!

The only thing that concerns me is your statement in bold. Those are the same comments generally used to describe Carl's 900. Top end performance was questionable by some of those offering their assessments.

I've been on the fence between a turbo or one of the RK Tek's 858s for awhile. Having ridden a properly tuned Silber turbo last year I was pretty much sold but the extra coin a guy would save going with the big bore might make the lack of power tolerable if the gap between the 2 wasn't too big.

On paper a guy certainly can't argue with 50 MPH track speed on a 153 X 3 but I'd really like to throw a leg over one of these before I make my decision.


BTW, how are you fueling this set up?


Thanks again,


Glen

If your after the big top end power of a turbo you will never be happy with a big bore. i built multiple turbo'd polaris's from 07-2011 and loved them. i got my first pro in 2012 and started playing with pipes/ drop ins again and this is my first year with a big bored sled since 2000. The 858 kit fills the turbo "void" for me and i don't see myself ever building another one. However, my riding style is tight steep trees chopping throttle all day long, might be wide open for 30 seconds at the most at one time. This sled has way more "fun factor" than any of my turbo's did. the snow was 8-10" of soft with a pretty firm base under it this weekend so my track speed numbers very well could be a little high, but a piped pro with the same track was only turning 40mph track speed when we checked them both on the same up hill run. If you ever ride Mccall or northern idaho let me know, would be more than happy to take you out and let you get a seat of the pants feel.

using the new BD box to for fueling

 

[nuggetau]

If your after the big top end power of a turbo you will never be happy with a big bore. i built multiple turbo'd polaris's from 07-2011 and loved them. i got my first pro in 2012 and started playing with pipes/ drop ins again and this is my first year with a big bored sled since 2000. The 858 kit fills the turbo "void" for me and i don't see myself ever building another one. However, my riding style is tight steep trees chopping throttle all day long, might be wide open for 30 seconds at the most at one time. This sled has way more "fun factor" than any of my turbo's did. the snow was 8-10" of soft with a pretty firm base under it this weekend so my track speed numbers very well could be a little high, but a piped pro with the same track was only turning 40mph track speed when we checked them both on the same up hill run. If you ever ride Mccall or northern idaho let me know, would be more than happy to take you out and let you get a seat of the pants feel.

using the new BD box to for fueling

Would you PM me, I would like to test her out the next time you are in McCall.

 

[nuggetau]

I also put the 858 kit in on my 2014. I've got about a 100 miles now and it is a ripper. started with a bikeman tune on my PCV that was super rich but now I've got it pretty close. pulls 8500 fast and stays there


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The stock motor makes peak HP/torque at 8150, at what rpm does the RK make peak HP?

 

[Kcjepperson]

Good to hear it's running good! I agree with you on the top end, i f you are looking for turbo power on the top end a big bore isn't for you. If you want instant throttle response with a awesome bottom end and midrange torque to play in the tree there is nothing better out there. I could not be happier with my BB. It took a little time to get her dailed in, but I have her rippin now and I couldn't be happier.

 

[Jkinzer]

The stock motor makes peak HP/torque at 8150, at what rpm does the RK make peak HP?

we run them at 8350-8400, they seem to run even better at 8450-8500

 

[beamslayer]

Is the BB using the shim ? Are you running a stock pipe ? Are you guys riding Freeze Out .
When we get more snow I would like to try it out over in the Glover area and compare the drop in kit to my MTNTK kit with 13-1 PAR Head and slp pipe .
The ridge was a tad icy last time not to mention the fog and the guy who went off the saddle to the left and was in a avy . He survived but was real lucky .

 

[Jkinzer]

Is the BB using the shim ? Are you running a stock pipe ? Are you guys riding Freeze Out .
When we get more snow I would like to try it out over in the Glover area and compare the drop in kit to my MTNTK kit with 13-1 PAR Head and slp pipe .
The ridge was a tad icy last time not to mention the fog and the guy who went off the saddle to the left and was in a avy . He survived but was real lucky .

stock pipe, stock can. Yes the Bigbore uses a shim, we ride freeze out all the time. let me know when your going up there and we'll hook up

 

[D8rider]

What shims are you talking about? In my 858 kit all I got was cyl, piston, cheater head, stock base gasket, and exhaust valves

 

[beamslayer]

Can you tell us more about the BB or maybe some pics of the kit ?

 

[Montgom345]

Love to see a video

 

[Jkinzer]

What shims are you talking about? In my 858 kit all I got was cyl, piston, cheater head, stock base gasket, and exhaust valves

The newest kits as of November i believe come with newer style pistons and a cylinder shim.

Can you tell us more about the BB or maybe some pics of the kit ?

big bore kit includes, cylinder spacer, power valve spacers, cylinder exchange, wossner pistons, rk tek billet head and patented domes.

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more information can be found here
858 Big Bore info

Love to see a video

as soon as we get some real snow i will be posting videos after every ride, i don't even think i've taken a riding picture yet this year... i have a couple helmet cam clips from this past weekend i'll see if anything is worth posting

 

[bossman15]

D8rider you have a rev1 kit then.. Rkt has come out with a rev 2 kit that has a shim. All kits this year are rev 2 anything before is rev 1. There are also different fuel numbers with rev2.

 

[Norway]

Credit where credit is due.

nuggetau, Merlin, others: Check out the words of Erik Woog, aka VOHK, in this thread: http://www.snowest.com/forum/showthread.php?t=360405

NB! DISCLAIMER! Don't let me put words in Eriks mouth! This is what it is, nothing more.

Quote:
"I rarely chime in on threads like this, however feel there is a bit more to talk about here. First of all anyone who knows me knows I am a fan of power, period, it matter less who or how it comes as long as there is a ridiculous amount of it. That said, the Carl's build turned out great, the motor pulls with authority right off the bottom and got along well with the GTX 2860 at 11k'. It does however fall a tic short on the big end, which is consistent with what find on the natural aspirated units as well. Its a nice motor, and if it were a 1/3 the cost it would be a home run. The trouble starts and ends with the numbers, at more than double the cost of the RKTek 858 one would expect more, bottom line even the RKTek drop in will out leg the Carl's 900 and its less than $800. Generally budget is an important consideration to most riders considering any level of build, if one were to equate horsepower per dollar the choice is pretty clear... As Austin mention the RKTek 858 turbo with a GTX 2863 at a half pound less boost was MUCH faster than the 900 with only a minor sacrifice in bottom end punch due to the application of the larger turbo. For those wondering, the RKTek motor did not like the 2860 at all, it flows way too much air, we will be testing even larger turbos soon to explore the ceiling on this package. More on that later...Hope this helps to clear things up on this matter."

Yes, this is a turbo application, but you get some serious points in there. People have not complained out loud about Carls 900, on the contrary. It seems they have made a good kit and coupled it with good clutching.

Having researched pro 800 + big-bore myself, I am never the less left with a consensus on a motor that is just physically to small to begin with for big-bores to work (crankcase volume, transfer volume).

Proof is in the pudding and now more and more people tell us they liked Kelseys pudding. Seems he found a way for some cc's and aerodynamics to work together, making a package that works for the pro 800.

Well done Kelsey.

 

[bossman15]

Jkinzer I just put my 858 kit together this weekend but have not hit snow with it yet.. Was wondering what elevation ur at ? Did u use his fuel numbers or have take sum off the top? What clutching tied or TSS? Helix?Roster weights? Where do you have them loaded? And last lol how is the fuel consumption compared to stock? Will I have bring gas along to ride all day?


Thanks in advance

 

[Jkinzer]

Jkinzer I just put my 858 kit together this weekend but have not hit snow with it yet.. Was wondering what elevation ur at ? Did u use his fuel numbers or have take sum off the top? What clutching tied or TSS? Helix?Roster weights? Where do you have them loaded? And last lol how is the fuel consumption compared to stock? Will I have bring gas along to ride all day?


Thanks in advance

We ride 4-8k feet, Kelsey has new numbers up on his site as of Saturday, use those numbers they are working well, i'm not a fan of the Tied it just doesnt seem to work as good tree riding, we run a 62-42-40 helix with h5 alloy speedwerx springs and epi adjustable belly busters right now running 66 adjustables with the adjuster all the way in the heel. Fuel consumption is about 10-15% more than stock. Still good enough that we're not packing extra fuel.

 

[Merlin]

nuggetau, Merlin, others: Check out the words of Erik Woog, aka VOHK, in this thread: http://www.snowest.com/forum/showthread.php?t=360405

Thanks,

I read that the day it was posted & found it somewhat interesting that his findings were the same as some of the other forum members who posted their results with the 900 last year. Bottom line appears to be "lesser return for the investment".

The RK Tek drop in kits have a fairly impressive track record with only a handful posting with complaints of detonation. Having personally ridden one last year I can attest to their noticeable bump in performance & being a relatively "good bang for your buck". If the 858 can maintain a similar reputation with proven durability(those skirts are getting real thin after the over-bore ) it should be a winner.