Rk tek 925 clutching questions...

[Brutus]

My new to me sled is here. Coming off a 2009 m8 cutler turbo and jumping into a 2013 PC with the rk tek 925 big bore. It's already set up pretty well IMO. I'm wanting to take some extra measures with clutching to prevent any issues others may have had with the PC. I've read a ton of threads on here about clutching suggestions and have talked myself in a full circle twice now, so I'm reaching out the experts to see if anyone out there has run this setup at similar elevations.... What's worked, what hasn't. Ok so here's what I got...

- 2013 pro climb m8 925 rk tek big bore with boonie box
- full jaws pipe kit
- c3 belt drive (I believe the 19 tooth top gear)
- 162 3 inch ce track stock drivers
- I ride above 6,000 ft and rarely get over 9,000 ft western Montana
- I ride varied terrain.... But I don't climb big hills any more so no long wot pulls. Im after short quick bursts and like the grunt on the bottom.
- I'm about 170 pounds (not to concerned about spending $$ to cut sled weight)

Currently the sled has the stock 36 helix and stock secondary along with a little stiffer spring. The primary has a set of cutler adjustable weights and a 140/280 spring not sure of brand. I rode it a few miles last year and it was a blast of a sled, but it did seem revy or peaky at times. It would hit 8700 rpms for a blink then pull down to 8400 - 8500 at wot. I believe with that pipe setup those revs are the target. The sleds not a belt blower by any means. All that may be normal and the answer may be leave everything alone in regards to angles and weights. If that's the case should I spend some money beefing up a few of the clutch components including the shaft, helix, and primary cover to compensate for higher hp numbers and torque? Or should I spend the money to replace them all together? I've looked at and considered products from team, thunder, bike man, cutler amongst others. I've got an extra $1000 or so I'm wanting to put on this sled and have it pretty much earmarked for clutching, venting, and air intake. Outside of boost where would you put it? Sorry that was a lot of info but too much is better than not enough. Thanks for any advice you can lend.

Bru

 

[madmax]

The problem with clutching is it's very personal to the rider. What one guy loves, another hates. You'll get 20 " snowest experts" (lol right there) respond with 20 different answers. I'm waiting for my 925 cylinders to be done. Going on a 2015 162 with a belt drive and a three inch powerclaw, so we will have the similar setup. I like adjustable clutching so I can fine tune on the hill. Going to try the shockwave adjustable helix, used it on my XP 860 and really liked it. Probably CPC adjustable weights. If you are not a "tuner" adjustable components are a waste of money.
BTW, do you know if a timing key was installed in your sled?

 

[Brutus]

Definitely going to stick to the adjustable weights myself. I like that on the fly ability to clutching. Leaning towards the team secondary with the heavy duty shaft from STM. I'll end up playing with primary springs and weight til I get what I want. I may do the 911 cover also.

We tried the 2 deg key last year in this sled and kept tripping det so it came back out. I think Kelsey recommended it so I'm sure he's had some luck with em.

Bru

 

[madmax]

On the dyno they much much better power with the timing advanced. Do you have the billet or stock modified head? Do you think you are bouncing off the rev limiter?

 

[Brutus]

It's got the RK Tek Billet Head with 13.5 domes. I've got his head on another m8 and am running the 13.7 domes with 91 octane no issues same riding areas. Note sure if Higher Octane would have helped out with the key but..... Didn't try just took it out casue it ran so well without it in. Wasn't hitting the rev limmiter it was det for sure. I'd be interested in hearing more about the key working or not...

Bru

 

[boondocker97]

You might want to try a bit steeper initial angle helix. I'm running a 42/36 in my 900 pro-lite 162 in deep snow at 9-10,000'. I think it would even pull a 44/38 in spring snow conditions. Exta initial load might help with your rpm spike.

 

[Johnsdevil]

Clutching

In my personal opinion I would run a stock primary spring.

Running a stiffer spring would increase your RPMS but might make them more consistent. I personally didnt like the two stage helix that was far appart because I like instant rpms. If you put too much of a load on your clutching you have to get the track spinning before you start to pull max rpm. I found that when I was in the trees i was constantly working the throttle trying to get everything going to pull max rpm when i wanted it... (too much work) I would rater pinn it and pull full rpms asap. I ran a 39/37. Still load but still pulled strong rpm. Thats with a softer secondary spring too. One thing to remember if you are having belt issues its usually in the springs. If your springs are too far appart the clutches will be busy chasing one another. if you get springs to "match" one another you will get better results. The clutches will work in unison and not be fighting one another.

Just my 2 cents.

 

[Johnsdevil]

clutching / gearing

Another note:

if you are looking for torque, number one thing to do is gear for the speed you are looking for at a 1:1 ration on your clutches and then throw as much weight as possible into your primary. The more weight, the more torque.

 

[madmax]

It's got the RK Tek Billet Head with 13.5 domes. I've got his head on another m8 and am running the 13.7 domes with 91 octane no issues same riding areas. Note sure if Higher Octane would have helped out with the key but..... Didn't try just took it out casue it ran so well without it in. Wasn't hitting the rev limmiter it was det for sure. I'd be interested in hearing more about the key working or not...

Bru

Look on the Dynotech research webiste. They dynoed an RKT 925 and got 190 hp with the stock pipe and stock reeds. With 10-15hp coming from just a timing advance. It will still run good without it, but there is more power to be gained.

 

[Brutus]

Good info guys thanks. I'm definitely going to explore the timing key further. I'm wondering if a higher fuel octane would eliminate det with the key. Or I call rk tek and get lower comp domes? That's one big reason I'm going back to big bore from boost... The race fuel for me was a pia to deal with all around.

After a lot of reading and asking questions of friends I'm pretty sold on the hercules helix, 911 primary cover, and abc kit from thunder products coupled with lots of venting. I'll be changing primary springs out as well until I get a combo that works for me. Thanks guys.... Snow is close. I'll post (for what it's worth) the combination I end up with along with the results of the timing key.

Bru

 

[Brutus]

Some good reading here thx madmax I'm definitely going to explore the key further.

http://www.dynotechresearch.com/file_upload/page_files/dtrrktek925cat.pdf

 

[carlc]

I think you should leave the sled alone for at least one ride Cory! I have personally ridden that sled quite a bit as you know, and it is honestly the best setup big bore I have ridden. We blew one belt in tog while riding over 80 down the trail for a long amount of time. I have held the sled wide open for over 30 seconds on a long pull in deep a'' snow in Seeley, with zero problems and could hold my hand on both clutches. Also, Kelsey told us that every sled is different, and he has sleds make more and less power with the timing key, so be careful there. I will tell you that a detonating sled is no fun to ride. And it always happens in Seeley on a deep day ! IMO if it ain't broke don't fix it. At least ride it once so you can have a baseline before you start changing things.


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[Brutus]

Definitely going to put a few miles on it this year before I get to changing things. I'd like to find a dyno in town and run some tests similar to what dyno tech did in that article. The hp ranges are crazy, one can't help but be intrigued. :face-icon-small-win. I agree that sled is amazing as it sits.... The only thing noted when I rode it last year was the blink of an over rev. At this point I'm more interested in primary and secondary longevity and preventing some sort of catastrophic failure down the road that costs me $$ but more importantly a deep day in seeley.... I missed plenty last year while waiting for parts to arrive. At least we got a cat dealer in town now!

Bru

 

[carlc]

The only dyno I know of is dyno tech in Belgrade. But it is a track dyno and involves a track swap. Plus, dynos are extremely hard to replicate a load similar to riding a mountain. They are great for making power numbers, but very hard to get clutches and computers tuned. We found that out with the 09 m8 push. And some of the vipec tunes. Time will tell on the dealer, but they have a lot to learn, I can tell you that


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