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XR 400 Top End Noise

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Hi,

Does anyone have any experience fixing XRs with a noisy top end?

I recently rebuilt my motor with new stock piston, cylinder hone, and new timing chain and valve stem seals etc.

Since then it has made significantly more engine noise that sounds to me like valves/top end noise.

So far I have done the following to try to find the source of the noise:

Checked valve clearances (lots of times!) following the correct procedure to make sure the auto decomp is not active

Replaced the timing chain tensioner with a new factory honda one

Installed four new valves and guides

Replaced the factory cam with a stage one hot cam in order to remove the auto decomp system in case that was making the noise

About the only thing I have not replaced now is the rocker arms and shafts.

The sub rockers have very slight wear marks where the clearance adjuster studs bear onto them. Could this be the source of the noise? Has anyone had a similar problem and found new rockers to be the fix?

The bike runs great and I have done about 5 hours on it with no apparent increase in the volume of the noise.

Any help would be greatly appreciated. Cheers.

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Well, I was hoping that someone else would take this one on... but, I'll bite.

Mine is also making a little extra noise since I rebuilt it. However, It is my understanding that XR's are a little rattley when the valves are adjusted properly.

Without listening to your bike we can only make guesses ? :bonk:

Perc

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Cheers Perc, I can apppreciate what you are saying re not hearing the bike. I realise it is very dificult to diagnose a problem from half way around the world via the internet!

What I was hoping for though was to hear from someone who has managed to fix the rattelyness. From what I can work out it is very common for these motors (XRs and TRXs) to get noisier after having valve type work done. Surely there is a reason for this and also a cure.

Anyways, I've got some new rockers on order now so I shall re-post once they turn up and I get them installed. Shouldn't take long. I'm getting really good at taking the top off the motor now!!!

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the bikes are just noisey by nature, there is a lot of valve train movement with rocker arms, sub arms compared to modern 4st. most if not all modern bikes are bucket on valve design, which is much more quiet.

best advice just ride it, you know the sound your bike makes and you will know when it mkes a new noise and when that happens, fix it. uintill then pin it to win it. and besides its an xr they never die.

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Are you pretty certain it is the valves that are causing the increased noise? From what you say about your work I might guess that something else may be the cause. Were all your measurements good on the hone/piston replacement? I am also assuming that it is more noisy after the work than it was before correct?

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I thought that when you swap the stock cam for the Hot Cam they tend to make a bit more top end noise. I'm still running the stock cam with decomp. removed, but I'm sure I've read that several times here. :bonk:

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