Hello, I'm John Talley with partzilla.com.
Today we're going to be looking at our Honda TRX 400EX and we're having to diagnose a little
bit of a problem here.
We had adjusted the valves in one of our other videos, and what I've noticed is this on is
spitting out just a little bit of smoke, so we need to start diagnosing to see what's
going on in there.
One of the first steps we need to do is go ahead and check the compression.
That will give us somewhat of an indication of what's going on inside of the engine.
Once we do that then we can make a determination if we need to go ahead an pull the head and
possibly even go down and look at the piston and rings.
So, that's just a little bit of an overview-- this is going to be a pretty intense investigation
so if you're ready let's dive into it.
Alright, before we get started I just want to show you some of the tools you're going
to need to get this project done.
For the most part, it's going to be covering a pretty wide range of either sockets and
or wrenches as well as different sized Allens.
You want to make sure you've got a full set of metrics going from at least eight up to
14mm on your sockets. and you need to go from vie up to about 10 for your Allens.
You're going to need a couple of screwdrivers, typical pliers, some cutters, different extensions,
and you want to make sure in your tool kit if you still have it you have this little
gadget right here.
This is what you're going to need to pull your spark plug out because there isn't a
lot of clearance in there.
Other than that, just a decent ratchet, a magnet, little pick tool, and then a Sharpie,
some plastic bags because you're going to need to write down by section the different
nuts and bolts as they come off the machine.
So that's a general overview of what you're going to need.
Okay, to perform a compression test your engine needs to be at operating temperature.
So what I need to do now is at least go ahead and set the fuel tank back in the position,
connect up the hose and let it run for about two or three minutes.
If you're in an enclosed space, make sure your doors are open where you've got some
kind of ventilation going because as you know exhaust fumes-- they're poisonous.
Alright, so let's get that tank back on there.
Doesn't have to be bolted back in, just set her up there, reconnect the hose, turn it
on, and start her up.
Alright, so we've got the machine warmed up, and this is a pretty simple procedure.
All we have to do is pull the spark plug, then using a compression tester with an adapter
like this one, go ahead and screw it down in there.
You want to open your throttle all the way up, crank it over about seven or eight times
and you'll see the needle start going across the scale there.
What we're looking for is something in between 100 and 128 PSI.
Anything below that would indicate we probably have a problem.
So let's get that spark plug out and get this connected up and see where we end up.
Alright, our engine is warmed up, so all we need to do is just get our spark plug out.
Once we get it out, we'll put in the compression tester adapter.
Boy was she running rich.
It shouldn't have been that black.
May explain why we may be burning some oil in there.
Alright, go ahead and get your adapter in.
Put on your compression tester.
Like I said, you want to open up your throttle, spin her over about seven or eight times till
the needle stops moving.
And you get a high point for your reading.
Alright I said we needed between 100 and 128 PSI?
Well, we're about at 85.
So that tells me there's a problem in there.
Where that's going to be I'm not quite sure yet.
So what we're going to do is go ahead and pull of our intake system-- our carburetor,
take off our exhaust, header pipe.
We're going to go and pull the head and take a peek in there.
What we're going to be looking for is possibly a worn valve, a valve that's not seating correctly.
And if all that checks out, we're going to have to go a little bit further and take a
look at our piston and rings.
So I'm going to pull the rest of this plastic off so we've got full access all the way around
the motor and we'll start breaking it down.
So, away we go.
First thing we need to do is go ahead and disconnect the battery terminal.
Go from the negative side.
Next we're going to need to go down there and set the machine to top-dead center.
And we actually already did a video that shows you how to do that when we were checking the
valve adjustment.
So you can reference that one.
Alright, we've got our plastics out of the way, and I want to go ahead and give you a
bit of a tip here.
As you start diving into this and the bolts start coming off, it all makes a lot of sense
at that point, but when it's all split down, you've got a whole bunch of nuts and bolts
and then you're not going to know where they go.
So my advice: get you some plastic bags, a little Sharpie.
As you take off a certain piece, whatever nuts and bolts were associated with that,
write it down.
Your carburetor, head, or intake, whatever.
Just something where you can get back and say "oh, okay, those are the ones I need."
It'll save you a lot of time in the end, so trust me on that.
What we're going to do here is pull the entire intake system as an assembly.
You've got a 10mm in the back, a 10mm bracket on either side, and then just a hose clamp
up at the carburetor itself.
A couple of turns on the screwdriver and that'll loosen it up.
Now this entire section will lift out.
You need to kick off the breather hose right here on the side and it'll just pop right
out.
Now this entire assembly will just lift out.
Next you want to loosen up the clamp on the front of the carburetor.
A little bit of a wiggle and she'll pop right out.
Next you have your exhaust where you have a 10mm up at the top, an Allen, and then there's
actually a 12mm down under the Allen on the frame.
Once you get that 12mm removed, she'll slide right off.
Remove your head bolts.
There will be four of them.
12mm socket will do the job.
And now with a little bit of wrangling, she'll end up sliding right out of there.
Get around that clutch cable and off she comes.
Next, you'll need to remove the top motor mount.
It's basically a bolt that goes all the way through with a couple of rather large spacers.
Now there's going to be several 8mm bolts all the way around the perimeter of the head
itself.
We're going to go around and pull every one of those.
Now don't forget this 12mm right in the very dead center.
With that last bolt removed, she will just pry right off.
It may take a little bit of wiggling, but there she comes.
We need to remove the cam chain tensioner, but to do that we have to get this bracket
and the negative cable, which is mounted to a bolt on the starter itself.
We need to remove those two things so we actually have access to get to the two 8mm bolts that
hold the cam chain tensioner in place.
Now with the bracket and the negative cable removed, we can get to those two 8mm right
here.
Still a little close, but they'll come out.
Now with the tensioner removed we'll have enough slack on the chain to actually pull
it off the sprocket.
What we want to do here is go ahead and remove that top Allen head bolt.
We're going to rotate it 180 degrees and then remove the other Allen bolt.
With both bolts removed, the cam gear will actually slide off and then allow you to remove
the camshaft itself.
We want to reach down in here and pull out the decompression pin.
Now be careful not to drop this.
It's a tiny little pin and there's actually a spring that's under it that we can remove
later when we get the head all the way off.
Now we can get out the cam gear itself.
To keep the cam chain from falling down in the engine, I'm going to use just a length
of wire to hold it up in place.
With the chain held up in place we can go ahead and start removing the head bolts.
There's going to be four of them, 14mm.
There's a fair amount of torque on these so you'll have to put some effort into it.
Once they're all broken loose, remove all the nuts.
And keep in mind that there are still washers that need to be extracted.
The last thing you want to do is have one of them fall down inside the engine.
So we're going to cram this shop towel to make sure that doesn't happen on this particular
one because it's right on the edge where it would just fall straight into the engine.
Here's where that magnet comes into play.
Make simple work of this.
Reach down in there and actually grab each washer just like that.
And with that, the head will just lift right off.
Just feed the wire through still attached to the cam chain and just let it hang to the
side.
To remove the cylinder, We need to get these four 14mm bolts here and then there's two
8mm bolts on the side of the block.
the cam chain guide just pulls straight out.
It takes a little bit of force but it will pull straight up.
Next we can remove those two 8mm bolts on the side of the cylinder.
You may need to use a swivel joint to get it in there.
Now your 14mm.
A fair amount of torque on these.
Get those broken loose and removed.
Use your magnet again to remove the washers.
And the cylinder will just lift straight off the piston.
Feed that wire that's holding your cam chain through and there it is.
Now with the bottom end of the engine completely exposed, we need to go ahead and get a couple
of shop towels and fill in the voids so nothing falls in there.
Make sure you go on both sides of the connector rod.
Next we're going to reach in with our pick tool and remove the piston pin clip.
It'll just pop right out if you pick at it from the bottom.
Now see what happened?
It would have fallen straight down in the engine if I didn't have those rags there.
Next we just push out our wrist pin.
And then the piston is just going to lift straight off.
Alright guys and gals, there it is.
A TRX 400EX top end completely disassembled.
Alright, this is going to conclude video number one.
In video number two we're going to evaluate each piece: the cylinder, the piston, the
head, looking at the valves to see if we can figure out where this smoke is coming from.
Once we figure that out, we'll make the necessary corrections and then video three we'll get
it put back together.
So come on, let's get to the next video.
Thanks for watching.