I recently ordered the Ultimax UA483. A lot of research looking at "high performance" belts... On the 400/450 I found no reason to use a more expensive belt.

Ok. The only kit I've found is the Airdam kit and Mainstreet Cycle(only retailer I've found) is currently out of stock. I toasted the belt over the Memorial Day holiday after trying to pull a buddy out of MS sticky icky following 2-3 weeks without rain. I'm set to replace the belt and reclock the secondary.

That event, my 26" tire upgrade and my need for speed out of corners was more than the stock belt was ready for over 3 days. 

Anyone using a Dr. Pulley weight/slider on their Primary w successful performance improvement?

I have. Very noticeable. Not only do they slide better and react to shifting needs and back shifts faster, but the range is a little better which means for us with wet clutches, a hair lower ratio on take offs and a little farther to full shift-out which a hair more top end. Yeah...worth it. I'll never go back to the rollers.

I'm having a difficult time finding the proper slider. Any idea what fits the primary on the '21 400S?

Anyone using a Dr. Pulley weight/slider on their Primary w successful performance improvement?

There's a local shop (MSC in Tishomingo, MS https://www.mainstreetcycle.com/shopping/item/10/LIFTKITFREESHIPPING) listing a 2" kit from a Canadian manufacturer, Perfex https://perfexind.com/collections/cforce Although the manufacturer lists it as a 600 kit, MSC currently shows it available for my 400 (unless they're passing off the highlifter 1.5" kit via the listing) I'll update as I gather more info from MSC.

Join us in the 400/450 group.

There's a local shop (MSC in Tishomingo, MS https://www.mainstreetcycle.com/shopping/item/10/LIFTKITFREESHIPPING) listing a 2" kit from a Canadian manufacturer, Perfex https://perfexind.com/collections/cforce Although the manufacturer lists it as a 600 kit, MSC currently shows it available for my 400 (unless they're passing off the highlifter 1.5" kit via the listing) I'll update as I gather more info from MSC.

There's a local shop (MSC in Tishomingo, MS https://www.mainstreetcycle.com/shopping/item/10/LIFTKITFREESHIPPING) listing a 2" kit from a Canadian manufacturer, Perfex https://perfexind.com/collections/cforce Although the manufacturer lists it as a 600 kit, MSC currently shows it available for my 400 (unless they're passing off the highlifter 1.5" kit via the listing) I'll update as I gather more info from MSC. 

It's come to my attention that some or many are seeking performance upgrades for their bikes so I'd like to share my discovery and encourage others to do the same.

There's a highlifter lift kit available but not truly fit for the U.S. model(Front bracket doesn't sit flush on the A-Arm). https://www.ebay.com/itm/274448411060  I'm running it ATM and have zero issues after 3 days of rough MS riding.(hope to fabricate a better fit in the fall) Advertised 1.5" but truly adds an inch of ground clearance. Rear hub simply flips on that bike to lift the rear an inch.
Airdam Clutches has a clutch kit http://airdamclutches.com/clutches/cfmoto/# , available from https://www.mainstreetcycle.com/

If you're interested in exhaust, check out whiskey bent tips https://whiskeybentmetalworxandmotorsports.com/shop/ols/products/xn-c-force-performance-exhaust-tip-90-degree-cf-moto-cfmoto-cforce/v/XN-C-FRC-PRF1-1-5 or an RJWC exhaust is available for the 400. https://invidious.tube/watch?v=J1-FAPdwurY

Also, there's a warrior risers snorkel kit available, https://www.snorkelyouratv.com/product-page/sya-warrior-riser-snorkel-kit-for-cfmoto-cforce-400-500-2016-2020

What you'll find is that there's one, possibly two manufacturers for any mod you look into and most are in the Euro or Canadian market but they're out there. 

Also, there's a warrior risers snorkel kit available, https://www.snorkelyouratv.com/product-page/sya-warrior-riser-snorkel-kit-for-cfmoto-cforce-400-500-2016-2020

Yes, Sir!!! Doing the same. There's a highlifter lift kit available but not truly fit for the U.S. model(Front bracket doesn't sit flush on the A-Arm). https://www.ebay.com/itm/274448411060  I'm running it ATM and have zero issues after 3 days of rough MS riding.(hope to fabricate a better fit in the fall) Advertised 1.5" but truly adds an inch of ground clearance. Rear hub simply flips on that bike to lift the rear an inch.
Airdam Clutches has a clutch kit http://airdamclutches.com/clutches/cfmoto/# , available from https://www.mainstreetcycle.com/

If you're interested in exhaust, check out whiskey bent tips https://whiskeybentmetalworxandmotorsports.com/shop/ols/products/xn-c-force-performance-exhaust-tip-90-degree-cf-moto-cfmoto-cforce/v/XN-C-FRC-PRF1-1-5 or an RJWC exhaust is available for the 400. https://invidious.tube/watch?v=J1-FAPdwurY

What you'll find is that there's one, possibly two manufacturers for any mod you look into and most are in the Euro or Canadian market but they're out there. 

Bruno, do you find it more unstable with brackets installed? Did you install also spacers in front and/or back?

I'm contemplating on whether I should wait until I can source a set of spacers before installing the brackets to make it more stable.

Yes, the highlifter kit includes 1.5" spacers for the rear (to clear stock 12" wheels after rear hub flip, to which I can't say necessarily is required on the '21 Cforce 400S U.S. model) I placed those on the front and bought a set of highlifter 1" spacers for the rear.
TBH it's my opinion the stability concern would be determined by height of tires. I upgraded the 24" tires to 26" and the ride, comfort and stability improved drastically.
Currently running Tyre Guider Maxx Plus 11" REAR and 9" FRONT on ITP SS312's and I'm extremely happy but I'm sure my old shoulders would appreciate me removing the spacers. Give and take on a non pwr steering bike if you ride aggressive 

I went ahead and installed the front brackets and gave her a few laps around the property. So far so good but I won't be hitting the trails hard for another two weeks. I'll update after I return from my memorial day fun

Thanks Roja. I'd watched that video at least 6 times prior to receiving the kit but I'd never noticed that. After viewing it again, I believe you're correct.

So the HiLifter bracket kit definitely does not fit the front. 1" wheel spacers do allow the rear hub assembly to flip and lift the rear, without any rubbing inside the stock 12" wheels. I bought those separate. The kit included a set of 1.5" wheel spacers which I've placed on the front in hopes of somewhat evening the stagger when I install 11"W & 9"W tires (Back & Front respectively).
I've decided to eat the expense and retain the brackets to use as templates for the fabrication shop (unable to deliver the bike to the shop atm). I've taken some rough measurements and believe they'll be able to produce an adequate bracket.
If you were to buy the highlifter kit you'd find the plates are approximately a qtr inch too short to rest on the A Arm on the front-side of the shock mount and that the mount is too close on the back edge for a plate to rest there at all.

I'll update as progress is made. 

Just made the purchase. I'll let ya know how the install goes