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Tappy XR400

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OK I'm out of ideas now, recently my XR440R has started making a loud tapping sound from the top end.

I have had the entire engine stripped by a mechanic friend, everything appears to be FINE. I've changed the oil, had the auto decompressor system removed, valve clearances.. even done exhaust gaskets and replaced bits of the clutch including the basket guide as the basket appeared to wobble a bit.

The bike on the whole is quiet and sounds fine, except for the tapping noise!

It runs REALLY well, it rides REALLY well. But it taps.

As said I've pretty much ran out of ideas and have replaced random stuff that probably didn't need replacing, so I've uploaded a video of the bike idling, any ideas??? much appriceated!

Video is here

http://s241.photobucket.com/albums/ff19/sparkscw/?action=view&current=IMG_0431.flv&newest=1

Please excuse the fact its a bit dirty, needs a good clean but have been tryng to fix it first hehe.

Slightly bent valve?

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...........

Slightly bent valve?

Pop the top.... sounds horrible. Could be a multitude of things, Either way... best to look into before next ride and more damage.

And it's too hard to diagnose without pulling the top end, which is really pretty easy (do you have a service manual?).

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Pop the top.... sounds horrible. Could be a multitude of things, Either way... best to look into before next ride and more damage.

And it's too hard to diagnose without pulling the top end, which is really pretty easy (do you have a service manual?).

sounds like the valves or may be a bent rocker to me.

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Sloppy bearings on the connecting rod? My 650R sounded like that. Valves and cam were OK, but the bearings on the rod were junk. Changed the rod and everything was purring like a kitten again...the bad news is that's it's a bitch of a job to do!

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It sounds like an exhaust leak to me.:banana:

How's the compression? If it's good, this would eliminate the head gasket. Do you have any way to blow smoke around the head and exhaust to look for leaks?

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I had an xr6 that sounded like that even though it ran great. What ended up happening is the cam chain had stretched causing the valves to slightly contact the piston. It eventually stretched enough to cause it to not start.

Luckily I replaced the chain and put it back together and all is good.

AKM

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I only got the bike yesterday (copied and pasted the bit above tha my friend had wrote on another forum) I bought it off him with the idea of breaking it but am just looking into what it could be before I commit. I'm also not sure how much it would be worth. I've got a XR600 aswell so I have no real need for it.

It's fitted with gadget sump guard, mikuni pumper carb, excel rims, talon front hub, wp rear shock, tag t2 fat bars,trail tech computer, gripper seat, acerbis front disc cover, Full FMF exhaust system and probably bits that I've forgotten. I'm guessing some of these bets shuld fetch ok money.

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It sounds like an exhaust leak to me.:banana:
+1

I also wonder if the cam timing is off.

Really? I disagree.

But hope for the guy it's as easy as that. "Wouldn't that be nice easy fix"

... sounds like Cam, Valve train, or similar with the web video. It'd help to cover the exhaust with a mitten/glove and listen again. And see also if the noise ticks more with more RPM. That would help too.

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You can't help but wonder about this one. mr-Jrod opened this thread up with... "I have had the entire engine stripped by a mechanic friend, everything appears to be FINE."

Something got missed? If the cams & bearings looked good, then the timing had to off more than 1 tooth going back together if the valve train is making this noise. If the engine was making this noise when they "stripped"... wait a minute what exactly does "stripped by a mechanic friend" mean? Was the engine taken apart?

If the engine was taken apart, inspected okay and put back together properly... this is why I thought exhaust leak. :banana:

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Originally the headgasket failed.

It was taken apart and replaced, He said while apart the valve stem seals were replaced(I'm using car terminology and im not sure if you call them the same thing on the bike :banana:) It was put back together and shortly after it started tapping.

He then had it taken apart to try and cure this, small end, cam tensioner etc were all checked and the auto decomp was removed.

I'm sure its not the exhaust as with a screwdriver to my ear i can hear the tapping from the top left of the engine. This is why I suspected a slightly bent valve as its not easy to see and can cause tapping.

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Originally the headgasket failed.

It was taken apart and replaced, He said while apart the valve stem seals were replaced(I'm using car terminology and im not sure if you call them the same thing on the bike :lol:) It was put back together and shortly after it started tapping.

He then had it taken apart to try and cure this, small end, cam tensioner etc were all checked and the auto decomp was removed.

I'm sure its not the exhaust as with a screwdriver to my ear i can hear the tapping from the top left of the engine. This is why I suspected a slightly bent valve as its not easy to see and can cause tapping.

Okay! :banana:

I don't think it would be running with a bent valve. Multi cylinder engines can get away with this, but single cylinders just won't make compression and won't run.

What does your valve clearance check at right now?

When you pull the valve plugs off to check, you can see if the tappets are damaged.

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Okay! :banana:

I don't think it would be running with a bent valve. ...........

I'm not sure that's (100%) correct... I had a 650R that ran with a bent valve, but soon died some miles later. And during that time frame, it would only start by being pulled, and later... no more start (it was Ka-put!) ...and was rebuilt.

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I'm not sure that's (100%) correct... I had a 650R that ran with a bent valve, but soon died some miles later. And during that time frame, it would only start by being pulled, and later... no more start (it was Ka-put!) ...and was rebuilt.

Well, thats my point... it would need to pushed off a tall hill or pulled to start.:banana:

If this bike kick starts, I don't think it has a bent valve.

He He. mr-Jrod, your input on our assumptions?

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Well, thats my point... it would need to pushed off a tall hill or pulled to start.:lol:

If this bike kick starts, I don't think it has a bent valve.

He He. mr-Jrod, your input on our assumptions?

I got'cha.... and I was just enlightening the comment a bit. Ya know... "outside the box" kind of stuff :banana: ...just ignore me. :banana:

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The bike is a real pig to start when cold, once warm its fine.

In cars I know a slightly bent valve can cause tapping, I guess with a single this would effect it more which is why it might not start.

I think its getting to the stage where I either start pulling it apart or just break it (but then I might aswell pull it apart first! :banana: )

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It sounds like an exhaust leak to me.:banana:

How's the compression? If it's good, this would eliminate the head gasket. Do you have any way to blow smoke around the head and exhaust to look for leaks?

Kinda what I was thinking when I first saw the video.

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The bike is a real pig to start when cold, once warm its fine.

In cars I know a slightly bent valve can cause tapping, I guess with a single this would effect it more which is why it might not start.

I think its getting to the stage where I either start pulling it apart or just break it (but then I might aswell pull it apart first! :banana: )

Absolutely, when you get my age you have to say... what else was I gonna do today anyway!:lol:

I really am a little surprised buy the fact that I still enjoy working on the bikes more than riding (Almost like therapy). I know it sounds a little off, but my son (17) got me back into dirt bikes after about a 30 year hiatus, and I can spend all day in the shop with a pot of coffee and the stereo. This is real satisfying for me!:banana:

My point is that pulling this bike down to find the problem is a good excuse for "therapy". Not a problem!:banana:

Perc

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