TRX 450 exhausting out the intake

[oldred95]

My dad bought a well used TRX 450 (yea its not an ATC but its still a honda) and we got it running but it was blowing the exhaust out the carb. and it had a lot of crankcase pressure too. Took the exhaust off and it seemed to run a lot better so we figured the muffler must be plugged. Cut the muffler open and it was clean. Ok so we pull the rockers so the valves would be closed, pressured up the cylinder with air and no leakage out the intake or exhaust but there was a slight hiss of a leak somewhere. So we pull the head off and the head gasket (metal shim gasket) has been hot and warped and fubar'd in general and was leaking. Roll the engine over and notice the huge ridge at the top of the cylinder so we pull the sleeve and now its getting bore and a valve job done. Anyway what we still can't understand is why it was exhausting out the intake. We checked the timing chain and its tight but we did not check the cam timing. If the cam timing was off enough for it to exhaust out the intake I wouldn't think it would even run. Other then needing a little throttle to start it seemed to run ok other then no compression and exhaust out the intake. It makes no sense. This is the first 450 we've been into and I was just wondering if any of you guys knew what might cause this.

[motoman110]

cam timing was off

[Dirtcrasher]

BOO, BOO, BOO, BOO - No quads allowed here!!

Remove one tire and I'll bet it will fix itself.

[oldred95]

Do you think timing chaing stretch could throw it off that much? The guy said it had a "carburetor problem" but otherwise ran fine. Once we started tearing into it we found a motor mount bolt almost all the way out and the owner said they had done some "work" to it. I doesn't appear have been torn down to the cam chain but we may have to. Guess we'll check the cam timing and go from there.

[oldred95]

BOO, BOO, BOO, BOO - No quads allowed here!!

Remove one tire and I'll bet it will fix itself.

LOL

Yea they aren't my favorite but still. My 125 3 wheeler was originally 4 wheeler and when I got it they had ridden it until the entire RF wheel assembly fell off and they kept on riding it after that. I rode it that way a few weeks before chopping it back down to a 3 wheeler frame and putting on a 200S frontend.

[RedRider_AK]

The timing is off. I think that yes, the timing chain could have stretched, but it's more likely that it got loose (stretch) and skipped time, changing the timing very seriously. I had a TRX125 that my friends rode so much/hard/didn't maintain, that it did the same thing.

[oldred95]

We tore the engine on down a couple weeks back and the cam tensioner was bad and backed clear off and the chain had a boat load of slack in it and was just plain shot. On top of that the cam was advanced a good 20-30 camshaft degrees because it had jumped a few teeth on the chain. 122 bucks later a new chain and a 91 dollar tensioner fixed it. It runs like a demon now for a 450 and it actually sounds pretty good to with the reworked stock exhaust. I'm thinking about giving my 200x exhaust the same treatment rather then spend 200+ on an exhaust system.

[RedRider_AK]

On top of that the cam was advanced a good 20-30 camshaft degrees because it had jumped a few teeth on the chain. 122 bucks later a new chain and a 91 dollar tensioner fixed it.

So basically, exactly what I said. :) You're :welcome:

[oldred95]

So basically, exactly what I said. :) You're :welcome:

Yea pretty much.