840 Big Bore W/stage Iii Cams, Done!

Finished with it today and am still breaking in the new top end. but i can tell you that this thing is a beast. haven't given it more than half throttle and my vdi has not come back from Velocity yet, so there is a lot more power coming still. The low end torque is crazy and the top end is supposed to be even better. I will post some pics of the crank case breather setup that is required with this motor and if anyone has any questions on the install you can pm me.More to come!

just to clarify, this kit is from Four Stroke Tech and i don't do motor work, except my own. so if you are a do it yourselfer and have questions on this i may be able to answer them. by the way Mickey Dunlap at FST was great to do buiseness with both before and after the sale, i would recomend him to anyone, on top of that he usually has these kits in stock ready to ship!

Good to hear Chase!! What are you running for exhaust, did you make a custom one? These kits are awesome, once setup right with a VDI and good exhaust, it will most likely double your horsepower. Im trying to decide between the standard bore kit with stage II's or the 840 with stage III's. I do all woods riding so I think the standard bore with II's may be the way to go for me. Keep us posted on the beast.

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2 time GNCC Utility Unlimited Champion

Current Rides: 08' Team Green Teryx LE, FST 840, Muzzys, Dalton, VDI, Pro Armor, Douglas Spiders, Bighorns 2.0's (mine)

08' Red Teryx, VDI, Trail Tech Vapor, ITP 212's (wifes)

I fabbed up a 2" stainless flowmaster hushpower II for now and made mounts that use the stock frame mounts, it sounds real good. will get something else as soon as something good becomes available. my vdi will be back from Lyle this week sometime, so for now i'm using the stock cdi

got any pics of the build?

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SUNBEAM RED LE TERYX
msa nukes,28" bugs,audiopipe,belt snorkels,dyna cdi,billet shift knob,extreme lift,HW carb kit,rear bumper,k&n filter kit,Night owl hids,overdrive plate,grant wheel

That great to hear give us a full report when its dialed !!!!

here are some pics, the first one shows were you have to drill a hole in the rear cylinder for a return line for the new crank case breather setup. i used a 1/2" brass nipple, JBed it in place then drill a hole through the cylinder. the hose is from a yfz 450 it is the perfect length and has a 90 on the other side just were you need it. the second picture shows the box you have to use for the crank case breather, it also is off of a yfz 450. i fabbed a mount for it that attaches to the shifter frame and it fits perfectly inside the engine cover like this, you can also see were i extended the hose coming from the crank case, it then gos into the second nipple on the yfz box. the top hose on the yfz box is the open air vent it just go's down to the bottom of the skid. i may end up rerouting it up and putting a small filter on it, we'll see. the third and fourth pics are of the exhaust i made, it mounts in the stock locations and there was no need to cut off the stock head pipes either. it seems to work very well for now. the merge collector was made from a piece of 2" stainless and a couple of bent 1.5" stainless, shaped and tigged together. then the inside was cleaned up with a die grinder to remove all edges and smooth out as best as possible. the last is of my teryx for those who have not seen it yet.

Man looks neat,how close are you too glamis? There is a fellow bench racer named michealtom401 that loves to outrun Teryx's.. He is in the dune reports thread. If you close please go and ride with this dude and show him how the teryx performs...LOL

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09 850XP Browning LE
Deluxe front/rear bumpers
HID headlights
Polaris Front storage box
K&N filter

08 Camo LE (SOLD)

I like where and how you mounted the breather should work good. For those of you getting ready to build a V-Twin motor this is something you want to make sure you do or you will end up with oil in your air box. Even if you start reving the stock motor with a VDI this can be a problem.

One thing I seen with these motors is you need to warm them up a good 15min. before you run them hard or you will damage the rings seal by blowing hot gases past the rings washing the cyl. Ring seal is the main problem we see with these motor from not taking your time warming them up and breaking them in.

As of today we will be building some new high compression 800 kits for the close course racers on the west coast for their cc rule limits.

How would you suggest break in on a new engine? In the past I have rode them pretty hard from the get go and mine have all ran strong.
Hopefully I'll get my teryx this week and I can practice it again just want your opionion.

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09 850XP Browning LE
Deluxe front/rear bumpers
HID headlights
Polaris Front storage box
K&N filter

08 Camo LE (SOLD)

The key is get it warm so the rings seal. It's OK to run them somewhat hard, just be on and off the gas, this is what seats the rings. Holding it wide open down the road is hard on them if the rings are not seated yet. You only get one chance to do it right or you will be calling me for a big bore before it's timelol

I cant wait to hear some more feedback on these motor kits! Im planning on doing one, but just waiting to hear some more results. Please keep us posted!

Lookin sweet. Make sure you post some video of it beatin a Rzr! Do you have access to a dyno?

So following Mickey Dunlaps recomendations on building exhaust headers that would work good with this motor, i finished them today. I used mandrel bent mild steel that i will end up having ceramic coated when all finished and tested. I started with vw exhaust flanges and gaskets cause they are an exact fit, then came of the head with about 12" of 1.5" tubing then steped it up to 1.625" tubing. the front header i made go over the flywheel instead of under like stock, to make it as short as possible. finished header length is
40.5" and both front and rear are exactly the same length ( some said it would be impossible). I don't believe the front one can be made any shorter than this i did every thing i could to try. Tomarrow i will fab the merge collector and the pipe mounts and give a report on how it runs. the pipe i am using is a hushpower II shorty with 2.25" in and out. here are some pics of the headers, you can see the difference between the stock one and the ones i made.

Excellent work Chase, that should free up HP on that beast! Keep us posted on the results.

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2 time GNCC Utility Unlimited Champion

Current Rides: 08' Team Green Teryx LE, FST 840, Muzzys, Dalton, VDI, Pro Armor, Douglas Spiders, Bighorns 2.0's (mine)

08' Red Teryx, VDI, Trail Tech Vapor, ITP 212's (wifes)

Oh Man, go with the duals. Better top end and on most pipes, 2 more horses.

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Hatfield-McCoys Rider
Piney Rider