Originally Posted by
peppernick
Re. head clearance Keep On .21s
The stock engine comes with 2x 0.2mm aluminium and 1x 0.1mm brass shims. With all 3 of them used, head clearance is about 0.62mm using the 'solder squish' method. I also noticed the Keep On uses a No.8 plug. Would you recommend removing the 0.1mm shim to make the head clearance closer to the 'generally recommended' 0.5mm ? With a colder plug, I supposed reducing head clearance will advance ignition and make the engine make more lower/mid end power. What are your settings ?
Thanks
I would not take the risk unless you are racing at high altitude.
For better bottom end you can just try the 6-fin header.
if you still want to play with head shims, remember that Keep-on .21 is sper long stroke and the correct head shims are the ones with "XL" in the end of product code.
An actual head clearance of 0.50~0.55mm is usually fine, so make sure your engine has 0.62 and you can try to reduce 0.05mm only.
For the plug stay with 8TGH, it works real nice and is a lot more safer to avoid glowplug failures "from nothing" which can be a common and expensive issue when using 7TGF.
Temperature: do not look at temperature, only as reference, due to the had design and depending on track layout and driver skill I have seen those engines running extremely stable at 160ºC.