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Mtntk full mod vs Rktek 858

I have talked to a few people and they found that the poo 800 dosent have enough case volume to support a big bore. Twins pipes will help but there just isnt enough volume to work they way they should....
Compression and porting are the way to go....
 
Reddragon800 said:
I have talked to a few people and they found that the poo 800 dosent have enough case volume to support a big bore. Twins pipes will help but there just isnt enough volume to work they way they should....
Compression and porting are the way to go....
Click to expand...

The kit i run uses a spacer between the block and cylinder ( added volume ) , cylinder and block are ported , i run and data log the pipe pressure , right now i run the single SLP pipe with the thing can, may do some testing with the stock pipe.
 
Big bore with twin pipes

So here is what I have found out. I'm running the RK TEK kit. It also came with a spacer for the added crankcase volume. The kit runs so much better with the twin pipe setup on it. The missing piece to this kit all along was just upgraded pipes. We added 2-3% to mid range 5% fuel to the top end and I've got all kinds of power and track speed. I was grinning from ear to ear all day long. I put CPI racing twin pipes on and all I can say is wow! The power band is huge and it pulls like a bastard. Just a little more tuning on it tomorrow and I'll have it dialed in. I'm seeing 47-49 mph track speed now and I'm a big guy. With my gear on I weigh in at 310lbs. So if you can budget for pipes with your big bore do it. I'm throwing more weight on my primary than I've ever ran and added more to the end of the weight too. So the twin kit has solved all of my problems I have been fighting all along. I'm happy! Enough said I guess.
 
Clarifying

The track speed I'm referring too is while climbing a 60% grade in the mountains at 7500-9500 feet ASL , harder base with 12"-18" of powdery conditions. I know there are a lot of factors related to track speed. Went from barely beating my buddy with my big bore and no pipes to adding twin pipes and putting like 12 sled lengths on him. So I am just relaying that this was the best improvement I have ever done to any sled I have owned.
 
The CPI pipes were actually not as loud as just the super-s can I had on the stock exhaust pipe. They were surprisingly quiet. The power has been great. The CPI twin kit is the way to go. They fit well, no extra heat issues, no plastic melting or hot areas, no rattle, just flawless. Mike gave me some pointers from CPI and he was spot on. A little clutching will make this even better. I have the sled I've been after finally. Have two rides on the new twins and I like them.
 
Are the cpi twins for a big bore only or stock 800 aswell?

2 of 3 of my edge chassis' run twins and i have no complaints, curious if the pro 800 can benefit from them aswell.
 
Last edited:
glad to hear the pipes helped, just want to make sure these r the set you r runnning? i dont see a pro rmk specific set of pipes

cpi racing polaris 800 rmk 2002+ twin pipes??
 
So my MTNTK kit and 3" X3. managed to get it ll installed for my trip to revelstoke and wow does that thing go. hard to tell if its because ov the track hooking up the snow conditions weren't the greatest but the motor felt strong and held its own with the turboed yamis that were with us. would recommend this kit to anyone a sled you can't wait to ride. Brought it up to Kitimat bc hoping to get a few more days in this season since its done back home. will update more if i get out again.
 
I am running CPI twins on my 910 pro and love them. Mike says twins can be made for the stock sled. I am not sure what the benefit would be on a stock pro, but on my 910 it really woke up the top end.
 
I've been trying to be in contact with CPI but hard to get a hold on them with email.

Kcjepperson could you take a picture on the pipes? would like to see how the fitment is on the sled. Hard to imagine two pipes will fit :eyebrows:

Happy with the build quality of it? Did you run your 910 with stock pipes before?

Really like to get my hands on a setup for my 858! :face-icon-small-coo
 
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