Going to try a big-bore kit on my 2016 YZ250F ... any setup suggestions?

Rider 5280
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2006
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11/9/2011
Location
Denver Metro, CO US
3/6/2021 11:34am
Hey guys, I'm going to try a big bore kit on my 2016 YZ250F. Here's my build list so far. Any suggestions to make this thing run really well and be as reliable as possible?

Parts list I plan to install at next top-end rebuild interval (already have all parts listed below, but open to going a different route):
(1) Cylinder Works 269-cc big-bore kit
(2) Hot Cams stage 2 intake and exhaust cams
(3) Vortex ignition mapped by Tokyo Mods (with map switch)
(4) GYTR larger intake boot
(5) Lightspeed carbon fiber velocity stack installed in the the GYTR boot
(6) Twin Air PowerFlow billet intake system/air-filter conversion
(7) Yoshimura ful titanium exhaust system + Dubach Racing full exhaust system (going to try both)
(8) Cycra Powerflow plastics (for lessened intake resistance)
(9) Rekluse Core EXP 3.0 clutch system + Rekluse Torque Drive clutch system (going to try both)

So, given the above ... any setup recommendations to get the most out of this configuration?

For example, do I really need to port the cylinder head to make it run right? Do I need better valves/springs? Is a beefed up crank assembly a must?

I always love all the inputs, so THANK YOU in advance!

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walent215
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Ridgecrest, CA US
3/6/2021 12:50pm
Highly recommend ;
Vortex ECU
REKLUSE Torq Drive system
Dual injectors
U4.4 or MR PRO6

Do not recommend ;
Hot cams
Big bore kit
Exhaust system is preference
Not much gain at all to be had with one . If I remember right the Yoshimura gave the best gains and the others were almost nil .


We own a 2016 Yz250f and have run a vortex Ecu, Aftermarket cams , Reputable builder I prefer not to name , U4.4 .
We haven’t run a Torq drive on this bike as the Yamaha clutches have been great but have run them on Crf 250/450 and they are probably one of the better mods of any ive ever tried.
I don’t recommend the cams because the stock Yamaha cams have proven worthy to the aftermarket we’ve tried. The Big bore reviews are far to unpredictable for me to get behind. I would definitely update the crank assembly to atleast a rebuilt oem with your choice of rod. I believe the Prox rod kits are sufficient and a Carrillo or Cwi aren’t really “ necessary “. We also have not ran the dual injector kits but after a quick search of reviews I personally would spend my money on that setup before experimenting with a big bore kit.
Porting would be beneficial for sure but that is a narrow window of power gain also , bottom- mid , mid - top etc.
I would also look at cryo treatment , isf treatment , polished/tumbled transmission work as another mod before some of the others you have listed . We have only owned one bike with tumbled/polished transmission and I will say it was very noticeable and I would spend my money there as well.
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Rider 5280
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2006
Joined
11/9/2011
Location
Denver Metro, CO US
3/6/2021 7:19pm Edited Date/Time 3/8/2021 7:52am
I have 1 bike that I ISF'd the transmission on and I was very pleased (450F). Good reminder - thanks!

Tell me more about the cryogenic treatments ... noticeable improvement in parts longevity?
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yzf162
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6/23/2020
Location
Grant Park, IL US
3/6/2021 8:14pm
Actually getting read to do the same build with Tom zont.
18 yz250f
Big bore cw 270 kit, rocket exhaust, no toil screen, flat dimpled valves, dlc rappers, piston coating, polished and blue printed bottom end, ported head, copper seats, cwi pro rod with the crank balanced to the rod and new piston weight.
Gytr air box, get ignition and a dual injection.
It will all be dyno tuned in for what ever fuel i choose by zont
Im likely using stock cams. As was said. The stock cams are really good. I have pc cams to try for fun but of all the cams I've seen even hot cams,yoshi and crower. It just seems to move the power and not really create power.One can that i know works well is Williams motor werx vari cam is good but expensive.

If your looking for the dual fuel injection on that bike if you go with get ignition i can get you the air box and injector set up used from a great builder cheap. You would just need the ecu. Witch i believe i can get you a deal on that as well. If you went with a tom zont head you might even be able to piggy back the dyno tune off my bike. Just spit ballin ideas.

I strongly recommend the CWI pro rod Its what im ordering this week. I worked there during the r&d and early production runs. Im all about strength and longevity. I still have a pro rod from 09 in a 08 built kx270f big bore with over 150 hours and the rods still good. If your building a motor up a high end rod is cheap insurance.


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walent215
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Location
Ridgecrest, CA US
3/6/2021 8:59pm
Rider 5280 wrote:
I have 1 bike that I ISF'd the transmission on and I was very pleased (450F). Good reminder - thanks! Tell me more about the cryogenic...
I have 1 bike that I ISF'd the transmission on and I was very pleased (450F). Good reminder - thanks!

Tell me more about the cryogenic treatments ... noticeable improvement in parts longevity?
I spoke with Robby Bell about it years ago and he said it wears unbelievably ... Even mentioned treating sprockets and other hard parts just because of the wear characteristics.
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The Shop

Rider 5280
Posts
2006
Joined
11/9/2011
Location
Denver Metro, CO US
3/8/2021 7:50am Edited Date/Time 3/8/2021 7:53am
This was a great suggestion walent215.

I'm not at a point I can readily cryogenically treat the transmission, etc., but I can treat some critical items during my next top-end rebuild like:
(1) timing chain
(2) cylinder
(3) piston
(4) wrist pin
(5) piston rings and circlips

Thanks for mentioning this!
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