Guru
Joined: 11/02/2018
Location: AustraliaPosts: 1911
| Posted: 11:54am 26 Jan 2023 |
The engine looks like a Loncin Industries (China) version of a Honda.
As Revlac wrote if the valve stem is binding in the valve guide it can be freed up with some lubricant (eg WD40 or similar) and working the valve back and forth or rotating it. Easier to do if you remove the rocker but when re-assembling the clearance between the rocker and valve must be set the same as the other valve. You will need a feeler gauge to measure it.
If you can push the valve in but it doesn't return all the way, stopping abruptly 4 mm or more short then the valve seat insert has probably come out of the head. (Note 1)
Repair will require removing the head, getting it machined and a new seat insert fitted.
Note 1
Aluminium is too soft for a valve seat so a ring of cast iron or steel is inserted into the head.
If it comes out it drops and hangs on the valve stem, preventing the spring pulling the valve all the way back.
Edited 2023-01-26 22:13 by phil99