[jarrod.mason86]

Ok, so same old story. I bought a 2004 trx400fa on Thursday, admittedly I did not do my homework. It shifts perfectly through all the gears in manual and accelerates to the 50mph range, which seems right. Reverse works perfectly also and i have no error codes blinking. I already did a fresh oil and filter change with GN4 10w-40. When in auto mode, if i am at a stand still and fully accelerate, it takes off and shifts throught the gears just fine, however when i slow down and re-apply the throttle it fails to downshift and will just rev. If I let off of the throttle and come to a complete stop, it again seems to shift fine, the problem only seems to exist at slow speeds and when coming to a rolling stop as opposed to a complete stop. The bike has 233 hours and 1200 miles on it. It is in very nice condition and seems to have been taken care of. I've taken the winch off to get the VIN number so that I can give it to honda today to see if the recalls were done, thats the best idea I have for where to start. I know hundreds of guys have asked these questions, and I've also read the stickies posted by people like melsman. Given the details, would anyone have an idea of where the best place to start would be? Is this going to cost me a small fortune to fix? Im somewhat mechanically inclined, and feel safe doing certain maintenance on my own, but Im not sure that I would be comfortable tearing an engine apart. Someone PLEASE help.

MELSMAN
TTWHEELSQUAD

You guys seem to be pros with this quad, any input would be greatly appreciated

 

[SamUK]

Autos aren't my forte but is GN4 10w 40 a Wet clutch oil? Is it specifically for ATVs and motorcycles?
If not, then drop the oil and change immediately.

That's as far as my auto knowledge goes unfortunately, hope you find a simple fix.

 

[jarrod.mason86]

Yeah it is. I verified on here and with service tech it is one of th recommended options. Thanks for the thought

 

[jarrod.mason86]

Nobody? no shifting issues out there for the 2004-2007 trx400fa's?

 

[wheelsquad]

Hey Jarrod. Welcome to the forum and sorry you plunked down hard earned cash on a turd of an ATV. Hopefully you got a great deal. BUT, if you don't abuse it, and get through the initial quirks you can get years of use out of it.

We established over PM that you aren't running oversize tires, and the ECM did receive the recall update since it was a 2004 model year. And since it doesn't have any error codes and is working great in manual (ESP) mode....it's doing EXACTLY what mine was doing when I had my issues....And the cause of my problems was a barely noticeable slipping clutch, confirmed by having zero issues after replacing the clutch. I fought believing Melsmans theory on it being the clutch for a couple years. But he was right and I eventually became a believer.

It doesn't seem like that should be causing your lack of downshifting while slowing down, and premature upshifting (especially under a load) problems in auto, but that was the fatal flaw in the logic in Honda's ECM programming, even after the recall. All was good if no clutch slip occurs. But once even a tiny amount does, the ECM tricks itself into thinking it's going faster than you are, and upshifts.

And to make matters worse, part of the ECM initializing steps included a stall test. Well that stall test was enough to glaze the centrifugal clutch enough to cause just enough future slipping under a load to mess with your auto shifting.

So my recomendation to you....keep running it in auto in the easy cruising and other riding without being under load...and then run it in ESP all other times, or all the time if you like it. If that isn't a problem, just keep doing so until your clutch actually wears out enough to be a probem at all times. If it's working fine for you as-is, just keep running it that way. But if you really really want to use auto all the time now, then put a new centrifugal clutch in it now.

Don't take that advice as gospel. I'm just one guy with one experience. But yours lines up exactly with mine. Good luck.

 

[jarrod.mason86]

so is the best route an entire clutch replacement or a rebuild of sorts. Also, how hard is it to replace the clutch on this, something i could do myself or do i need to take it to a shop.

 

[wheelsquad]

so is the best route an entire clutch replacement or a rebuild of sorts. Also, how hard is it to replace the clutch on this, something i could do myself or do i need to take it to a shop.

Download a copy of the factory service manual. It goes through the whole procedure. There are threads here that explain how to download one. The centrifugal clutch is under the front crankcase cover and I'm going to rough estimate say $200 in parts.

But like I said before, if you don't mind ESP, just run it that way as there is nothing major wrong with the bike still. Or count your losses now and sell it.