Well, my brother is wanting to do some motor upgrades to his quad, guess hes all pissed off cause I can smoke him now Anyway, he has a 2005 Honda Trx450r and its time for it to have the motor rebuilt. He was thinking of running the 520 big bore kit, but not so sure if its worth all the money. PHIL on the board here told me that doing a port and polish is the hot ticket for more power. I know about the HRC kit and what it does, but a cam is a for sure thing thats going to happen, and then some. It already has an LRD exhaust and UNI air filter, so those areas are covered. What are your guys's thoughts on big bore kits and what sizes do you recommend? He wants to run a Hinson clutch as well. So, what do you all think? Any suggestions, comments, experience with these sorts of things? All help is much appreciated as usual. Thanks!

dude, ask PHIL his specs, he rips me a new one everytime we've raced. then again, i was running dubs. PHIL Im callin' you out for a rematch

Just my .02 cents worth, these motors love compression, that and some good head work, and the big bores will have nothing on you.

PHIL's posting.....

EZ is right, high compression is your friend. Everyones afraid of compression because of common misconceptions about it. Ive ran 2 different 14:1 compression pistons and loved them both. High compression compliments every type of riding style, I think.

Just about any cam other than stock on an 04/05 TRX good. I like the Hotcam stage 2 and HRC cams. Both are awsome for the price. Ive got an extra HRC cam if you are interested, $100.

My current porting is only considered marginal, and it still rips I think. Search around on other websites and you'll see that there are bikes out there that make mine look like a toy, but those 3 items coupled with a good free flowing intake and proper jetting make for a strong reliable motor. I only made 50 on the dyno, but it just plain hauls.

I give all the credit to my suspension though....don't over look it on his build.

Compression and Porting will make a HUGE difference. We are building our shop TRX450 as we speak. Keep an eye on that build. Adam can help you out as well. WE exclusivly run the CP pistons for reliability and power. Our shop bike will receive the CP Race spec piston and our PDR spec porting. THe hot cams run very well in the TRX's, for the price they cant be beat.

PDR

^^^^^There you go!

Send your head to PDR for porting, have him send it back with a shiny new 13.5:1 CP piston, buy my HRC cam, and then add yourself to the list of people that "rips" GWTT a new one at the drags

theres two engine packages i highly recommend, one is the TRX Hot package(look on our site for a full description), by far it gives unsurpassed relaiblity in the industry, the cams work with stock springs (keeps price down) and stage 2 or 3 gives great duning power. that matched with a CP Race piston or a 13:1 shelf piston will bring the bike to life. On the big bore there are several things to consider, just increasing the bore will not efficently make power to money ratio's I like to see and the motor itself is turned into a time bomb in MY personal opinion. If he wants to go big bore I believe keeping the engine as square as possible helps with everything to power, to reliablity and to the extended life of the motor.

Adam

ps Pm me about the second package

I'm with the port and higher compression opinion too.
But if your gonna do some motor work you might wanna look into suspension as well.

ok, so compression and porting. suspension is going to happen to, probably shortly after motor work. The only reason motor is getting done first is because the bike is getting very very tired. It has about 2/3 the power it did when it was new. where is PDR located?

We are located in Anaheim, CA

If you're looking for some good power, the Duncan Racing HP4 kit is great. I have this kit on my 2005 TRX450 and the power difference is great. The displacement has been increased to 470 with a 13:1 compression. Ported/polished, larger titanium valves/retainers, larger CRF 450 carb. With the increaed power, they really recommend a Hinson clutch upgrade. I hear the 520 kit has enough power to pull your shoulders out of the sockets!!!!

The big bores seem to drop like fly's, unless it is the 480 and those have perfomed solid. The HC 2 is hands down the best cam for the normal joe. Hrc is a good cam but the HC2 gives that mid punch. The 04 and 05 trx came with a reliable 10:5 to 1 monster skirt piston that would last forever. If you drop a 12:1, 12.25 to 1, 12.5 to 1 you can run pump gas, 13 and above is race fuel. This will bring that bike to life, I also run the CP piston and they are great on quality, as well as the HC stage 2.

^^^^^^Knows his poop!

ok, so what ive gathered so far, is 520=bad idea, 480 max. get a cam, port and polish, and some better comp. oh and PDR is a good place to go to. at this point, everything is still up in the air, everything might be put off for a little while now too because he has to get a little comuter car.