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Valve clearances over time

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I am curious whether valves tend to tighten or loosen over time. I just checked my 2018 350 exc-f. Everything is at the high end of the tolerance range except the left intake which is .0178 (max .015). The bike has 20 hours on it now and the clearances have not changed since the 1 hour check. 

My uninformed opinion is that having something a little loose is not a problem, things tighten with wear, and .028 out of tolerance is not serious enough to hassle with shimming since it is just a little loose. 

Anyone care to comment particularly whether I should shim the one loose valve?

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Posted (edited)
1 hour ago, pmckenna said:

I am curious whether valves tend to tighten or loosen over time. I just checked my 2018 350 exc-f. Everything is at the high end of the tolerance range except the left intake which is .0178 (max .015). The bike has 20 hours on it now and the clearances have not changed since the 1 hour check. 

My uninformed opinion is that having something a little loose is not a problem, things tighten with wear, and .028 out of tolerance is not serious enough to hassle with shimming since it is just a little loose. 

Anyone care to comment particularly whether I should shim the one loose valve?

I have the same bike...my first 4 stroke in 10+ years.

When I owned them back then, the clearances would tighten up, due to the valves cupping. So its my belief that this still holds true, with only the rare exception will they loosen. 

It seems like once the valve train is broken in, there isn't much movement. Mine was recently at the dealer for a warranty issue, so I had them check the clearances while they had the cover off...18 hours and still in spec. Unless something funny happens, I don't think I'll check for another 20 hours or so.

To answer your question, if I had one valve slightly loose I don't think Id mess with it.

Edited by Hammy-56

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My 350 valves did not move for the first 275 hours and when they did it was the shim that wore down to make them loose so new shims and still good at 500 hours quite impressed with this motor and valves. Del west makes great valves.

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Posted (edited)
7 hours ago, pmckenna said:

I am curious whether valves tend to tighten or loosen over time. I just checked my 2018 350 exc-f. Everything is at the high end of the tolerance range except the left intake which is .0178 (max .015). The bike has 20 hours on it now and the clearances have not changed since the 1 hour check. 

My uninformed opinion is that having something a little loose is not a problem, things tighten with wear, and .028 out of tolerance is not serious enough to hassle with shimming since it is just a little loose. 

Anyone care to comment particularly whether I should shim the one loose valve?

Japanese, shim under buck tends to tighten only, by the design

The ktms,  because of the quality of valve, Ive not seen tightening issues(also on a light leaded diet ), those who have seen movement has normally been on the opening side of things. the shim, the rocker arms, and the valve stem collets can wear.  I just recently adjusted 3 shims, each 1 size larger at 870 hours, that's the first shim size change the bike has ever had., Im set on the mid to tighter end of the spec.

If you are actually tightening on the ktm design, its a strong sign of dirt ingestion, especially the intakes. So your intake gap is likely to widen, unless you get some valve face wear, but it could also stay where its at, for hundreds of hours.

Edited by Spud786

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It's not that far out if you want to run the bike 10-15 hrs and check again. Loose is okay, better than tight. Fairly easy to do on the 500. Dot goes up on the threaded intake shaft. Check both rocker shafts for clean condition, Exhaust shaft has no directional mark in the manual or on the part.

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Thanks fellas.
Just to be clear, these are 2 of the 4 bolts that are to come out to remove the shafts on a 2017’-19’ ?
57740103524__F1BC8A66-A028-4685-A838-2D9FA87CA76E.JPG

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That's it. 

Bike in 6th turn CS bolt CCW with 17mm socket til the dot is at TDC. If both rockers have slack-TDC. If not rotate 360 and check for slack. That's TDC and the shafts slide out. I don't lock down the crank, some do.

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Some more guidance if you dont mind.

Math was never my strong point. Not even close.

Any tips on what size shims ill ask for tomorrow to bring these into the middle of the range?

IMG_4423.thumb.JPG.ec12727cda6e69f4d20151144044baf1.JPG

 

How I measured

57741086957__7A782433-FB89-42B8-BFFF-C016D7772207.thumb.JPG.10e291c577e74eb8630a4e148f2bb670.JPG

57741065659__CB6AA391-1E72-4F4E-8A4D-2A7B11856E74.JPG

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Posted (edited)

You need a 2.20 on that right intake and that's it, but dealers rarely have new shims, you are either 10mm diameter or 8.9mm depending on year model.

 

2019 would be 8.9mm diameter

Edited by Spud786
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In case someone else is facing their first attempt at shimming, I found this video on youtube which seems to be rather well done.

 

I don't think this is necessarily definitive but it makes the process seem rather transparent. We'll see what happens when I attempt it. Good thing is that is applies more closely to my 2018 350 than some of the other videos I have seen.

If you are knowledgeable about such things and want to comment on the video that would great.

Thanks for all the comments above.

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