Uncorking your 450R on a budget...

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El Mamito USMC

Zorros Racing Team..
Staff member
Apr 11, 2012
ok guys thanks Sredish for the great info... and this works better or for the most part for 04-05 TRX

Just spend $6500 on your R ? --- Are you broke now ? --- But you want to get your "Politically Correct" TRX450R running like it should have off the assembly line ? --- (Honda being very conservative on horsepower and the industry's shifting to "quiet power" in ATV's, have really bottlenecked the new R, but luckily in ways that don't cost too much to square-away... And most times keeping it at or under the magic 96db noise limit ... If you don't care about noise, you should consider it because we owners can tend to create issues with "race bred pipes" EX: Where last year it was OK, a new elderly couple bought a cabin in tim-buk-too and doesn't like your thumper noise even though you have been riding there for years ... Complaints reflect negatively on our sport and since the whole market is shifting, our minds should be prepared for "quieter pipes" ... Ok enough about that ...)

Here we will teach you how to un-cork your R for the least amount of money possible the right way ... There are many ways to un-cork the 450R, but this thread discusses how to do it the most inexpensive way ... Read On --

The TRX450R comes from Honda pretty corked-up as far as power output goes and this is for many restrictions that government puts on new ATV's sold in this day in age ...

But un-corking your R is pretty cheap and simple ... All you need is some basic parts and some basic motorcycle know-how and you're set ...

STEP ONE-----------

Opening up the Airbox:

You can simply remove the Lid or cut the rear section out of your stock lid ... This is a free mod ... (Cutting the rear half of the lid in the perforation is very similar to the HRC lid without the water deflector flap and provides enough air to feed a 180-190 Main jet so removing the whole lid seems to not be necessary) ... *** In most cases the bike will rev better off the bottom by not totally removing the lid ...
When you remove the airbox lid, you'll see a white intake snorkel that extends down into the airbox and connects to the carb inletting ... Remove this piece and cut the whole rectangular shaped part off ... Deburr and smooth the piece inside diameter and outside diameter where you cut ... The part to cut off looks like a vaccum cleaner attachment ... Replace this piece the way you took it out ...

Finally, there is a 3-way breather T on the right top side of the engine case right behind the header pipe ... Remove this, and look down inside ... You will see a reduction about half way down that is smaller in ID than the rest of the large part of the T ... You will ream this out with about a 1/4 to 3/8" drill bit making it the same size as the rest of the ID of that part of the T ... And replace securely after cleaning out all shavings ... Done

Total Cost: FREE

STEP TWO------------

Re-Jetting the carb ...

www.450RHQ.com highly encourages you buy either the HRC jet kit to re-jet your R ... The reason for this is these kits come with a much steeper tapered needle and this is imperative to a linear mid-range fuel metering ... The stock needle is designed to support the stock R and simply moving the clip to the 4th or 5th position (stock is 3rd) is not optimum and you may experience a bog or improper jetting ... All I can say is: USE THE REVISED NEEDLE WHEREVER YOU GET IT, THIS IS IMPORTANT ! ... Now some are doing an alternate measure to this requirement by bumping the 48 stock pilot jet to a 50 pilot and dropping the clip on the stock needle to the 4th position ... Now I don't have any issues with you trying this, but as I have said before, if Honda has us replace the needle as part of the HRC power-up kit, rather than replace the pilot, I'm sure there's a reason ...

Total cost: $25-$50

Sparks Jet kit: $50
(comes with HRC needle, and an assortment of main jets)
HRC Jet kit: $25
(comes with HRC needle and a 185 Main Jet)
DynoJet kit: $45-$50
(comes with revised taper needle and an assortment of jets and a block-off device to aid in low end fuel metering)

STEP THREE--------------

Opening Up The Exhaust:

This is simple ... The stock arrestor is removed by removing 3 allen head screws and is replaced with a bigger end cap ... You have a couple choices ... There are HRC End Caps that sell here on our site for $25-$35 by members at times, and also on eBay (recommended over generic due to Honda engineered part, spark arrested, and quality sound!) --- There are also inexpensive 2" end cap inserts on eBay that cost about the same ... These are simply 2" stamped and butted tube inserts that go between the stock trim ring and the muffler ... SOME OF these that are on eBay are NOT spark arrested !

Total Cost: $25-$35


STEP FOUR (Not required but worth it's weight in gold)

Upgrading the stock flame arrested air filter:

Hands down the best buy we here at www.450RHQ.com feel is the Sparks Racing filter kit ... It comes with a foam high flow filter, billet aluminum verturis ring and clamp ... This billet ring allows for a much more reliable and rigid mount and provides for a smoother transition from filter to boot ... You could buy a W Bros or UNI for a little less, but they either come with a arrestor cage, or no billet ring ... Spend the extra $15-$20 and buy this filter ... If you already have a pro design or sparks ring, the replacement filters are $27 ... (This mod is not mandatory but rounds out out budget hop-up package in a big way) ... Any foamie comes dry so you will need air filter oil ...

Total Cost: $45


$50 to $85

Adding the sparks filter you are at $130 ... *** If you buy the sparks Jet kit and filter combo you get a price break by the way ...
Likes: grtrat1


Active Member
Oct 31, 2012

A few years ago I saw the dyno results of the HRC Kit vs Stock, and all of these things definitely wake the 450 up. If my memory servers me correctly, stock 450 is something like 36hp off the showroom floor, and with the HRC kit it brings it to 44-45HP, granted this is with the HRC cam too, but still a huge difference.

Its funny cause I just cleaned my garage and went through my old TRX box and pulled out all of the HRC kit stuff Ive had for a few years collecting dust. I guess I should get these things over to the classifieds to help another member out...