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2007 trx400fga Rancher 400AT exhaust chirp

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My other halfs Rancher 400AT is making this weird high pitch chirping out of the exhuast I'm concerned it may have a bad exhaust valve.  Mainly because I just finished a top end job on it (like 5 or 6 hours of break in time and 1 oil change already).  It doesn't do it at idle its when giving it throttle.  

Valve lash has been checked and is at spec

Compression is at 90psi which is down from 105 stock spec... (not happy to see...)

tried leakdown test couldn't managed to hold crank and perform test and check for leaks need an extra hand lol. 

tried dollar bill trick on exhaust and if I bring it flat up to the exhaust I can actually let go of the dollar bill and it will sit there against the exhaust just moving to and from the exhaust.  If i just dangle it it blows it off the exhuast and it doesn't suck it back.

 

whats been done:

Piston (next size up from stock, not a big bore) and rings. wrist pin. cylinder bore and hone

head was Cleaned up new valve seal guides and valve and seats cleaned up and lapped.  don't believe any new valves were installed.

new gaskets

new cam chain and tensioner  ( the one thing I didn't look at was when I did the chain I actually pulled the cam out and I didn't check the auto decompression lobes)

Carb rebuilt with new jets same size as what carb had before for my altitude.

I did the cam chain and engine assembly using honda shop manual.  

 

The head and cylinder work was done at a pretty reputable powersports / machine shop in a city not to far away basically thats the type of work they do on the regular.  they sourced the piston and rings (all Honda)  and all gaskets (not Honda lol).  

If anyone has some input I'd appreciate it.  just trying to narrow it down before I pull the head and have a look.  I haven't even really finished breaking this thing in since all the work was done put like 5 or 6 hours break in ride time on it already did an engine oil change.

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Welcome aboard. 

 

My kid's 300 does that.  It's the muffler on hers. 

 

You sure it's an engine problem and not a loose/ rusted baffle in the muffler?

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I suppose it could be I was concerned cause compression is low and it's a new piston and rings and valves were done.  Also it only started after a couple hours of riding so concerned maybe it was running a touch lean and caused an issue.  

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Not the same noise as the kid's 300.  That almost sounds like a dry bearing to me. 

 

@shadetree @Fishfilesand @toodeep seem to be pretty good at diagnosing noises over the interwebs.  See if they have any ideas

 

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Well managed to leak test.  Pulled off the rocker box and tested and valves are sealing.  Guess I'm just going to let it ride like that for now and keep an eye on it.  

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Still sounds like a dry bearing to me.  That doesn't help much though.  Lots of bearings in that engine.

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Ya I put a stethoscope on it can't even track it down.  And don't think any bearing is going to translate that noise out the exhaust and not be heard in the engine.  

 

 

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Sounds normal to me since about everyone of them I'm around give that chirp sound. Some are a lot worse than others but most have it. Most all of them are higher mileage machines so I just figure it's baffles inside getting a little restricted or maybe even came loose in a few spots. I just revert to the old saying "if it ain't broke, don't fix it". lol

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Thanks toodeep.  I was thinking exhaust baffle.  It's really the first engine I have been internal on since I went to tech school so just a little anxious lol.  It's at 6500km 4200mi and 580 hours not sure how that rates for lifespan.  You can see what I did in the top post, just a light overhaul trying to get a little longer life for the wifey.  So plan is run it and if it spits out a part number worry then lol.

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