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Exhaust Valve clearance tight

2784 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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1. How many Km's have been past since the last tensioner replacement ?
Bike is running 23,000km odo. Not changed the tensioner yet. Checked the operation it thoroughly. And even though it was giving false reading, timing chain should be loose.

2. Was the Valve Clearance test done with a cold engine?
Yes, bike was complete rest since last 10days.
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That's why asked to the Ducati mechanic, and asked the reason. He said what I have written above and shared with you guy's.
To confirm the fact here's some videos from YouTube
and another one from MC Garage
both which have exhaust Valve clearance towards tighter side.
OK, I able to source new shims, I will update results. Currently I was facing two issues
1. Exhaust gas smells was different (like mixture is rich). Which makes sense now that due to tight clearance exhaust Valve was opening earlier and closing late (which result some unburn mixture escape out).
2. This tick-tick noise which is confusing here, as noise should only be there when something is loose.
As sourcing such part is task in India. let's see what happens after new shims.
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!!!
Thank you sharing the valuable information about the tighter valve clearance, as I was thinking that if shims worn out evenly, the clearance has to increase not decrease. Thanks adding the missing points and sharing the experience of doing it, as for first time starter we need confirmation even if is small things.

Thanks @Tamir for lots feedback, as even though we are are from different parts of world, only few people are interested to share their experiences and knowledge.
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I've got 92K on my VF and it's as strong as when I first got it 35-yrs ago
View attachment 44978
It's really great to see that some one is keeping the bike running for such a long. I wish I could keep min Lil bird too.
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Vishal, do you ride on GP tracks, and are usually on the red RPM's?
No, I even not crossed the 110kmph mark on bike. Using the bike only for touring purposes.
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@Tamir whatever results i will find out, I will update it. Please don't make diagnosis thing as personal agenda to share he is wrong and I'm right. We are here to share help, feedback and experience.
Even for your pressure drop test we have shared knowledge(as thing was new), and followed process to get results.I have a FAST Pressure Drop in the Fuel Hose 2 sec...
I personally learned few new things too. So please calm down and relax @DannoXYZ and @Tamir, we most probably newer meet to each other so please at least maintain a friendly discussion.

Thanks again for valuable information
Hi guys, after long time. Following are the conclusion of my observation after long time.

1. After shim replacement, the noise was not completely gone. But i was in town where I don't have option. But noise was very less, so i continue to ride.
2. After talking with few local Honda mechanic I found that Cbr250r don't have this shims issue, and only by replacing the chain tensioner will short out this issue. I know they are not completely right, still I have checked the tensioner thoroughly and found no issue with tensioner.
3. After riding the bike city traffic found loss of power and engine sound is Lil louder, even engine rpm climbing to 1800-1900rpm from 1600rpm every time I start it (even engine is hot).
4. So figured out to replace the chain tensioner and see, after replacement all the above niggles gone and engine sound become smooth and rpm was settle at 1400rpm instantly. Rode it few kms and found bike performing really good:).

So, to conclude please change the chain tensioner as a preventive maintenance. As it is the weakest member from engine assembly (herd from most of local Honda mechanics) to avoid this kind of issues.
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