Billet cylinder head design for cg 125. ..HELP..

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

hidrojen

Member
Joined
Nov 13, 2023
Messages
6
Reaction score
0
Location
tr
Hello, I have a CG125 motorcycle. I am looking for a billet cylinder head design that can withstand high revs. I will have it made by CNC. Is there anyone who has a ready-made design or can you find it for me on the internet?


like the example in the picture
 

Attachments

  • 110000079706559.jpg
    110000079706559.jpg
    26.8 KB
Why would you think the original head design would not 'withstand high revs'?
If the engine RPM is too high, I would expect the rod to be the first thing to fail.
Higher RPM may require higher valve spring preload, but that would not impact on the head design unless it became so ridiculously high that it deformed the ports.
 
Orijinal silindir kapağı tasarımının yüksek devirlere dayanamayacağını neden düşünüyorsunuz?
Motor devri çok yüksekse, ilk arızalanacak şeyin rot olacağını düşünürdüm.
Daha yüksek RPM daha yüksek valf yayı ön yükü gerektirebilir, ancak bu durum, portları deforme edecek kadar gülünç derecede yüksek olmadığı sürece başlık tasarımını etkilemez.
The material of the original cylinder head is bad, anyway, when a performance camshaft is installed, the engine goes to high speeds and produces excessive power. When the original valve springs are not strengthened, valve float occurs. This damages not only the cylinder but also the cylinder head, so I was planning to remove the cylinder head from the CNC machine with a different material.
 
If you have an original Honda engine, the material of the head should be good for some heavy use.
The CB125 (overhead cam) heads may be limited, but the CG125 is notoriously bulletproof.

The rest of the engine will not hold together at such high RPM as would require valve springs so strong that they would damage the original head.

Valve bounce will damage the valves and the valve seats, but the engine will stop before it damages the head.

I have been involved with drag racing engines which use original cast alloy heads from the 1950s, running with alcohol fuel and nitromethane. It's not easy to damage the head casting!

I suggest using the original head until you break it - then see what broke and think about what to improve.
 
When you install a large piston in the engine, it starts burning oil because it cannot completely scrape the oil off the cylinder surface. How can this be solved? in addition, the engine scratches the surface by sticking to the cylinder piston at high rpm, so how to solve this?
 
Reduce the tangential pre-load on the piston ring. as it helps a bit. Reduce the side clearance of ring in the piston groove, which helps minimise the gas pressure behind the piston ring, providing the ring does not seize in the groove.
Use Molybdenum in the oil - After running-in! It helps prevent scuffing.
Use a finer grade of stone when honing bores, 1000 grit instead of 600 grit, or whatever is one grit finer than your current stone grade.
Increase cylinder cooling, if you can.
I heard of water spray onto the cylinder being used by a bloke racing an air cooled single, supposedly to help keep the Standard finning cool... to avoid it seizing with the high compression piston and larger intake and carb used for racing, with well advanced ignition. But hearsay isn't always reliable...
K2
 

Latest posts

Back
Top