Hi! I am the original owner of my 1990 Pilot bought new in 1992. I live in the Los Angeles area. I know it needs another top end as the compression is down to 129psi but it's running so badly its un-rideable. It won't stay running without the choke pulled out and will not idle at all. Must keep it revving and its revving high which likely means it's getting unwanted air somewhere else. It's also not completely combustion the fuel mixture as it's backfiring out the exhaust. I went through the carburetor and it's like new. I made sure the jets were clear. I drained all the gas and put in fresh fuel mix. The spark plug is new and gapped. I made a leakdown tester and I could not pressurize the case. I could hear air hissing inside. After this many years of great service I expect it to need some more invasive work. The unit is stock except for a Wiseco piston. Is there a common failure point on these engines for primary compression? I do not see any air bubbles in the coolant and the balancer oil looks clean. I suppose I should just have everything re-sealed. I'm a bit hesitant to take the whole Engine apart. How complex is a re-seal for someone with average knowledge who is fine with doing top ends? Anyone have a shop in my area they would recommend? Thanks for any advice!

In my opinion I would not even start that machine again because you WILL melt a piston.
The Engine WILL have to come out and all new gaskets put in weather you like it or not.
That's the honest truth.
I don't know your mechanical skill level. I'm a tradesmen with every tool known to man so it's easy for me.
I'm not even sure if some of these dealers even know how to fix two strokes anymore. I would go to your local Honda dealer and ask if you are not comfortable doing it yourself.
It sounds like you have a crankcase gasket leak.
Your Engine needs to be re-sealed.
Try having some one squirt soap water all over the Engine while you are trying to hold some air in this Engine. You may be able to narrow it down. It may even be a simple fix like a cylinder base gasket leak. The Honda FL350 is famous for this.
Also I don't know what kind of "test rig" you are using there. Pictures ??
CO

Here's an update: I took the complete Pilot to a local ATV repair shop. The guy didn't know what this was or that it was a Honda. He asked if this was a Chinese ATV. Then he said it would be a big job to get the Engine out and quoted at least $2,000 in labor. I brought it home and removed the Engine myself. It wasn't that hard to do. Now I'll diagnose and fix it myself. I still need to make the pulley remover tool.

I understand they’re old, but any ATV repair shop that doesn’t recognize a Honda pilot or Odyssey would not be a shop I would ever go to again lol

The problem has been found. The crank seal for the output shaft is bad. I pressurized the case with only breath-blown air while spraying soapy water. I could hear the air escaping there and the soap suds confirmed the leak. I still need to remove the pulley from the shaft. Anyone know if the seal can be replaced without Engine disassembly?

I just want to confirm, is it the right side of the Engine or the left side that is leaking when you are sitting in the machine ?
If it's the right side then it's more of an issue.
If it's the left side then I "think" it can be done from outside.
I don't own a Pilot so maybe someone can chime in.
CO

Edit:
I was just looking at the parts book and it appears it goes in from the inside.
I think you have to spit the cases.
Below I have attached the parts pdf for you to download and have a look at.
Look at page 5.
CO

It's the pulley side. I'm having difficulty removing the pulley. I made the tool for the threaded piece but the part that pushes against the crankshaft created a problem. I don't know if I can save the factory pulley. It won't pop off the crankshaft. I should have made the tool all one piece. The 2nd half is wedged inside and no good way to get it out. I made an extension but that didn't help. Project is on hold while I attempt to figure this out. If I had it to do over I would have tried to get the factory tool.

That does not sound good. I hope you did not damage the threads on the end of the crank. The piece that pushes on the crank is much narrower than the threads. The other part of the bolt is threaded to pull on the clutch. Then you smack it with a hammer and the clutch should pop off very easily.
CO

Post some pictures if you can and maybe a drawing of what you actually made there would help us help you solve the issue.
CO

I'm not optimistic for a good outcome on this. There is metal stuck inside the channel. Unless there is some other way to remove the clutch it may be a lost cause. I was able to put a lot of tension on the piece but I didn't try hitting it with a hammer. I wish I Knew what the back side of a removed clutch looked like.

Please hang in there for a moment as I'll have to go take some pictures for you and post here. It's difficult to understand what you have done there so I'll just show you a few things in a moment.
CO

Ok here are the pictures of what you need.
Please note that I'm not being condescending. I just don't know exactly what you did there or your skills, so I'm just guessing most of the time.

Basically this is a very easy operation.
1) you put the pusher rod into the clutch hole
2) use the correct bolt that will thread into the outer threads on that clutch
3) tighten down the bolt onto the pusher rod until tight
4) give it a good smack with a hammer (it may take 2 tries at most)
It will make a very loud POP ! sound and you think you busted something but you did NOT.

You will also note that the end of the pusher rod is turned down on one end so that it don't hit the threads in the crankshaft. It is also turned down so that it bottoms out in the crankshaft hole and won't touch the threads.
If the piece you shoved down the hole on the clutch is the incorrect size you will destroy the crankshaft threads. This is a serious problem !

The pictures in this thread are FL350 engines with a 94c comet clutch.
It don't matter because it's the same sequence and procedure for a pilot.
The only difference is the specs on that pusher rod.
CO

Reading this thread slowly it appears you have rammed a rod down the hole that was the wrong size ------------ ohhhhhh I could have fun with this one LOL.
All may not be lost.
If the piece you rammed down the hole was big enough and did not go into the threads then that's a bonus.
Maybe you can still get it out because the end of it was mushroomed a bit by that pusher bolt.
Can you get at it ?
Could you drill it and then tap a few threads into it ?
You can make an extension bit to get the drill bit down the hole.
Same for the tap ----- braze weld a tap in a rod and thread that drill hole. Take a piece of readyrod and thread it in. Pull out.
CO

All that holds these clutches on is a taper.
Taper on the crankshaft and a taper on the clutch.
The center bolt holds it all together.
Once you break loose the taper clutch just falls off.
You can see it in the pics. Pilot is the same.
CO

Thanks for the photos! I used a long 3/8" thread bolt with the top cut off and the threads ground smooth as the center pushing tool then got an M14 1.5 bolt and welded an extension piece to avoid removing the greasy cover (which I ended up removing anyways). I didn't expect it to get caught under the lip past the threads. There's no getting it out. It's under too much tension. I regret adding more pieces of round metal until I could build pressure with the bolt. It's all stuck in there now. The only thing I didn't try was hitting with a hammer. I made a mistake and it's going to set me back. I appreciate the advice.

Let me think about this for a minute
CO

I'm thinking the crankshaft threads are probably okay since the part I inserted was thinner than the threaded bolt that holds on the clutch. It may be just that I didn't hit it with a hammer. I built a lot of pressure using an electric impactor since a socket wrench wasn't enough to pop it.

I think that if you put the pusher bolt back in and tension it up and smack it with a hammer it will come off like it's suppose to. It's all jammed in there now so whats to lose ?
If you damaged the threads in the crank then the damage has already happened but 3/8" is .375 and that clears the threads in the crank.
I use an air gun to tension this up before I smack it with the hammer.
If you don't have that tool then it may take more than two tension tries and hammer smacks to get it off.
I think you are still good here.
CO

It WON'T come off with just an impact. You WILL need to smack the pusher bolt head with the hammer.
You'll hear a loud POP ! but that's how they come off.
I think you are good.
CO

Get back to me on this so I can log off. Thx.
CO

I'll try again tomorrow!

Ok.
I think you're good.
CO

Just another opinion here but I see that the Engine is out and sitting on a concrete floor in your shop.
When you take that clutch off tomorrow it may come off violently and land on the concrete floor. I would put the whole thing on a piece of plywood when you do it.
I busted the lip on the moveable shiv one time because it hit the table and fell off.
That Pilot clutch is gona cost 5 franklins if you have to buy another one.
Just my opinion.
CO

Go here viewforum.php?f=25 page through the Pilot CSI articles I and others cover just about everything you will want to know about a Pilot Engine.

You will also find how to change the clutch side crank seal viewtopic.php?f=25&t=5597

I made my own clutch remove tool http://pilotodyssey.com/PO/viewtopic.php?t=3324

In the future use the search here or google search, make sure when using google to include fl400 or you will get automotive answers.
Example fl400 pilot clutch removal

I think you will find the answer to every question asked about Pilots and Odysseys on this site, locating the answer might be tricky, never hesitate to ask.

TAKE and POST too many pictures each step of the way so we can see what your doing more pictures the better we have trained eyes and can pick up stuff in the pics, other problems not even relevant to what your working on, its why I named so many of my post CSI because each part that fails on ANYTHING should have a CSI and or Autopsy, your on your way you found the ROOT CAUSE of your problem the crank seal failed, most likely the lips on the seal wore out, its a dual lip seal the outer lip of the seal is to keep the dust out the inner seal seals the crankcase.

Once you get the seal out take detail pictures of the seal inside and out, is the metal spring on the seal inside missing? Show the wear on the lips of the seal. Show the crankshaft where the seal rides is the crankshaft worn from the seal?

Thanks.

149-153 PSI is the stock compression range.

Any guess how many takes of gas or how many miles you have on the Pilot since last rebuild?

Show us the inside of your air box including the the air filter, since the Engine is out take detailed pictures of the inside of the intake and exhaust openings, I also want pictures of the inside of the intake boot, the boot that goes between the air-box and the carb, DON'T CLEAN IT I need to see the as found condition. It does us no good if you wash parts then take pics.

While your getting photo happy take pictures of the carburetor inside and out I want to see how much wear is on the carb slide.

Whilst the Engine is out drain the oil in the transmission and take pictures of the oil I want to see how much metallic hue is in the oil. Try taking the pictures in lighting that best represents the actual things your seeing, another words take a pic of the drained oil, look at the pic, does the pic look close to what you see in real life? If not change lighting or camera setting try to be accurate.

Thanks.

Hint http://www.pilotodyssey.com/intake-mod.htm and http://www.pilotodyssey.com/prefilter2001.htm