SLVRGHST
Once a tinkerer, always a tinkerer...
Hello Everyone,
This is my first post of maybe a few that I will add in this area of discussion. Hoping to get some support from experienced mechanics about the rebuild work I am doing with the CB750C engine I am working on.
I am doing a complete tear-down of the engine to rebuild it. A compression check of each cylinder revealed to me that there was need of work (90 psi avg.), not to mention engine noise that sounded quite unhealthy. I am hoping to re-use certain parts and replace others.
On the subject of valves, I have pulled all exhaust and intake valves out of this engine. There seems to be the usual wear and tear. The exhaust valves had a lot of carbon build up on the stems and the fillet, all the way down to the valve seats. Not tons but enough that it took a few minutes of careful cleaning with a wire wheel. Once I got them clean, I noticed that on a few, there appears to be some rather concentric bulging in the valve stem. Like a ring that bulges at a height of about 1/16 of an inch and is about 1/4 to 3/8 inch in length along the stem. The bulge does not travel up to where the stem guide starts when the valve is seated. Now, I don't see any damage in the valve faces at all and the rest of the stem is quite smooth. Is this a result of the machining originally done when the valves were made back in the late 70's or early 80's? Is this the result of the engine overheating at some point in its life and somehow the valve stem compressed due to high revving of the engine? Bottom line, should I replace those valves and the guides? Do I just bite the bullet and replace all the guides and valves to get better longevity out of the engine rebuild?? I mean, I have come this far...
Anyhow, I will certainly post some pictures of these valves when I get home today. That should help I hope. Thanks guys!
This is my first post of maybe a few that I will add in this area of discussion. Hoping to get some support from experienced mechanics about the rebuild work I am doing with the CB750C engine I am working on.
I am doing a complete tear-down of the engine to rebuild it. A compression check of each cylinder revealed to me that there was need of work (90 psi avg.), not to mention engine noise that sounded quite unhealthy. I am hoping to re-use certain parts and replace others.
On the subject of valves, I have pulled all exhaust and intake valves out of this engine. There seems to be the usual wear and tear. The exhaust valves had a lot of carbon build up on the stems and the fillet, all the way down to the valve seats. Not tons but enough that it took a few minutes of careful cleaning with a wire wheel. Once I got them clean, I noticed that on a few, there appears to be some rather concentric bulging in the valve stem. Like a ring that bulges at a height of about 1/16 of an inch and is about 1/4 to 3/8 inch in length along the stem. The bulge does not travel up to where the stem guide starts when the valve is seated. Now, I don't see any damage in the valve faces at all and the rest of the stem is quite smooth. Is this a result of the machining originally done when the valves were made back in the late 70's or early 80's? Is this the result of the engine overheating at some point in its life and somehow the valve stem compressed due to high revving of the engine? Bottom line, should I replace those valves and the guides? Do I just bite the bullet and replace all the guides and valves to get better longevity out of the engine rebuild?? I mean, I have come this far...
Anyhow, I will certainly post some pictures of these valves when I get home today. That should help I hope. Thanks guys!