Exhaust tappet gets tightened when engine reved at idle

[Lkhangee]

Hi
I am using 163ML liquid cooled 200cc engine in my street bike.
While I don't Rev bike at idle. But people Rev it out of curiosity when the see liquid cooled engine in this frame.

I noticed many times that when i Rev it while idle it would die out and the kick would become super soft indicating no compression.

I checked the valve clearance and there no clearance on the exhaust valve only. No such issue is observed if I m riding full throttle on highway at its tallest gear.

Noticed that disappearance of clearance 3 times at least.

Regards

[Weldangrind]

Please tell us more. Are you saying that if you rev it at idle, the exhaust valve clearance somehow disappears? Do you have to adjust the valves before it will start again?

[Mudflap]

Could be valve seat recession.

[Lkhangee]

Please tell us more. Are you saying that if you rev it at idle, the exhaust valve clearance somehow disappears? Do you have to adjust the valves before it will start again?



Yes to both questions.

[franque]

The valves should be adjusted cold, after the engine is at room temperature for a day. When the engine heats up, the clearances will tighten, due to thermal expansion. Assuming you aren't suffering extremely severe valve seat recession, and the valves are adjusted to the proper clearance, the perceived zero clearance isn't an issue. What clearance are you adjusting them to now? Also, I should add, I've never seen any motorcycle engines that ask you to check hot clearance, so the readings you're getting right after the engine runs are basically irrelevant.

[Mudflap]

On every CG engine I've checked, the valve lash increases as the engine heats up.

[Megadan]

On every CG engine I've checked, the valve lash increases as the engine heats up.

My 167FM, aka aircooled CG250, after 1000 miles I intentionally checked my valve lash hot after setting it cold, and it shrank by .001 to .0005 once hot - like I just shut it off after riding for 40 minutes hot.

There is a reason the minimum lash is .002", and even at that adjustment spec the valves are pretty tappy.

[Lkhangee]

Valves clearance is set to 0.08mm cold engine after one day rest.
As cold as anything in its surroundings.

After full throttle at idle for hardly 2-5 seconds bike shuts off and when I Chek only exhaust valve clearance is gone the tappet was so tight that it leaves the valve open and no compression is there. Nothing as such on intake side clearance remains same.

[franque]

I'd pull the head then and see what the exhaust valve seat looks like.

[Lkhangee]

I'd pull the head then and see what the exhaust valve seat looks like.

Yes I will pull the head and see how is it.

[Lkhangee]

Here is how the head cylinder and plug looks like.

Bought replacement cylinder and piston, replaced valves and valves guides, and lapped valves. Will tie it together to see how it turns out

[Lkhangee]

For 163ML class engines what are the specs of valves? The replacement valves that arrived are 2mm shorter and the valve stem place is also 1-2mm shorter.