Exhaust Valve clearance tight

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

Tamir said:

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 ???

Click to expand...

Tamir said:

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 ???

Click to expand...

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.

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.

https://www.ms-motorservice.com/en/technipedia/post/valve-damage-and-causes/
https://www.motorcyclecruiser.com/valve-adjustment-simplified/
https://journals.sagepub.com/doi/abs/10.1177/1350650119872093

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