|.: HRC kit for the TRX :.
Well, it's in and the TRX is running again, so I thought I'd include a report of what I found out:
The kit is very complete, it's not just a camshaft and muffler end cap. It comes with a camshaft, new needle, new main jet, new crank case breather, new airbox cover (with a splash guard that can be used or not depending on owner's choice), new airbox snorkel tube, a totally different end cap and spark arrestor for the muffler, along with a new gasket/seal.
The camshaft is visibly different, no need to measure this one to see the higher lift and longer duration, it's obvious.
The stock carb needle is a C55d, the new needle is a C51b. The stock main jet is a 118, the one in the HRC kit is a 185. Big difference!
I wondered why the crank case breather needed to be changed, since they looked identical.....until you take the old one out and compare: inside diameter is almost double on the new one. Ditto for the new airbox snorkel: half the length, much larger diameter.
The new airbox lid has almost half of the top gone, but there's a splash guard that covers some of it, at an angle to keep water from going directly into the air filter: it directs air or water to the bottom of the box. I'm thinking you can get more air without the splash guard, but water and dirt can also get in easier without it. It seems well thought out.
The new muffler end cap replaces a strange, long, small diameter tube with holes drilled in to let the exhaust out. I can't believe this motor could even run under that restriction, you gotta see it to believe it, and there's still more turns and twists inside that huge stock silencer. The new end cap is simply a chrome cap with a huge hole and a spark arrestor screen. Much better, not a complete fix, but good flow and still quiet.
Easy for anyone with standard mechanical ability, but time consuming. There's no easy way to turn the motor except for the kickstarter, so you spend some time getting the marks lined up for TDC while installing and timing the cam. At least it's only one cam.
The top end on the TRX/CRF is simpler than the 400EX; direct operation of the intake valves means no hardware like rocker arms to fool with, and the exhaust valves actuator is very clean. The only thing you DON'T want to disassemble is the decompresser cam assembly on the end of the camshaft, unless you have excellent manual dexterity, lots of patience and enjoy working on Swiss watchworks.
You'll either have to buy or make a tool to hold the cam tensioner to replace the cam. The 400EX shop manual had a description on how to make one. The TRX450 manual has you buy the tool instead, but you can make one, since it'll be identical to the one used on the 400EX, except for a bit longer length/reach.
One warning, being off by one cam gear tooth on this motor means no running motor. No forgiveness there. Ask me how I know?
I thought it would be too rich, and that Honda was playing it safe with the slimmer needle and enormous main jet, I also wondered about air jet or pilot jet changes. No need, it started on the second kick, idled smoothly, and responded very well to throttle blips, no hesitation.
It now makes a much cleaner sound. I have no doubt it'll pass noise regs at Silver Lake: at least it never went above 98 Db on my meter. The sound is more pleasant, more like a hi-performance motor, instead of the strange noises it makes when stock.
I had gotten a 13 tooth front sprocket from Hondapartsworld when I ordered the kit, because I felt 1st gear was too high, I've now changed my mind. The amount of torque it gained from the installation of the HRC kit made 1st gear feel just fine: you can pop the clutch on level ground, it won't stall.
I had cured the wheelie problem with suspension tuning, but it's back: every shift at full throttle means the front end reaches for the sky again, all the way to 4th gear, even if I have all my considerable weight forward. LOTS more torque, and LOTS more acceleration. Blip the throttle in mid of RPM band, you get wheel spin or a forward lunge, like right now. That's using 18" Turf Tamers in rear and grooved car radials in front.
I'm very satisfied with the HRC kit: it was simple, complete, gave a very obvious performance increase, and there was no guesswork and hours of tuning like it's sometimes encountered with the purchasing of some aftermarket cams, or exhaust systems.
It saved me the time I'd normally spend experimenting with different jets to compensate for the exhaust system change, experimenting with airbox lid off, on, holes, wondering why the crankcase isn't breathing right, which cam and exhaust combination, etc.
I'm satisfied with my TRX450's motor. It's plenty fast and responsive now, so I'll spend my time and the rest of my money fine tuning the suspension, riding, and adding BLING-BLING
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