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Exhaust Valve clearance tight

2783 Views 18 Replies 3 Participants Last post by  Tamir
Hi guys, I recently started to notice tick-tick type noise through engine head. So, decided to check one by one
1. I checked the operation of chain tensioner, working good.

Removed valve cover for further investigation
2. Checked timing chain so check whether it is tight or not. It was tight.

3.So finally I decided to do valve clearance measurements
0.16mm & 0.15mm (requires 0.13mm~0.19mm) OK

0.19 mm & 0.20mm (requires 0.24mm ~ 0.30)
Not Ok
So, I do the math and found that I need to choose thinner shims.

So, here I was little confused that how the hell valve clearance became tighter(usually it wear out so, need to loose).
So, I called the friend who was working in Ducati as Service engineer. He told me, Due to exhaust gas heat, the valve gets heated and the heat is transferred to the top part of the valve called steam And Shims are placed in between valve steam and fingers follower. Due to which shim size gets expanded over the period of time. Which makes the valve clearance tight. He also told me that, due to this problem manufacturers given Exhaust valve clearance is more than Inlet valve clearance.

I thought why not share it with others owners too to make some awareness.

Thank you
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I race in same AFM organization couple years after Ari, he's really cool guy. Thanks for video!!! :)

As a result of abrasion the spacing increases, and then the thickness of the shims has to be increased too. But you ware measuring a smaller space than required, which is weird ???
I have not heard of a case where the Valve Clearance gets smaller, and needs to be replaced with thinner shims. Maybe the measurement did not go well? Something weird here ???
I've adjusted valves on all my bikes for past 38-years and have found clearances always gets tighter over time with wear (I've owned over 30 bikes, well some of them don't have valves). This is area where people need to get out of their heads working with insufficient background experience and get their hands dirty actually working on bikes to understand why this happens.

1. what parts of valvetrain wears fastest? the parts that are hottest

2. what parts of valvetrain are hottest? exhaust valves and exhaust valve seats

3. what happens when valve faces and seats wear? material is removed

4. what happens when material is removed from valve faces and seats? valve sinks deeper into seats

5. when valves sinks deeper into seats, what happens to other end of valve? As in location of valve stem tip? It moves closer to cam!!! Valve clearances decrease over time with wear!!!

Changing shims is to compensate for wear at opposite end of valve where most wear occurs, not for cam-lobes. This is also why exhaust valves gets tighter faster than intake, they face much higher heat during their open time when exhaust flows out. Don't let exhaust valves get too tight as their contact time and pressure when closed cools them by transferring heat to head. Can get fried exhaust valves if they don't have sufficient cooling time. Best to adjust them to maximum end of range.

I've owned this bike since 1986 and have adjusted valves on it over 10x. Ever single time, I've had same experience as Vishal, valves always gets tighter.

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It's not exhaust gases that wear out valves, it's the heat. Temperatures on exhaust valves and seats can get over 750C. This softens metal, causes valve to stick to seat. Some material is lost as valve breaks free. Also softer heated seat compresses causing valve-seat recession.

If you're getting excessive wear on cam-lobes so clearances increases faster than valve-wear, you've got lubrication problem:

  • idle-speed too low... causes
  • low oil-pressure at idle
  • using low-quality oil, always use MA-rated full-synthetic oil. Auto oils are not good enough for moto lubrication

I've got 92K on my VF and it's as strong as when I first got it 35-yrs ago
Speedometer Odometer Tachometer Light Gauge
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