SOHC.co.uk Forums > CB500/550
CB550k1 US Import - UK registration
K2-K6:
Yes, the squish band as Sesman notes.
It's there from original casting mould and not really machined generally.
Function is to "squirt" the unburnt combustion charge towards the spark plug site just as the piston comes up to compression. The spark has already fired (btdc) the mixture, the flame front should be making it's way out radially from that point, the squish accelerating the unburnt towards that front to improve combustion speed/complete burn.
It notably should not have any sharp edges in that critical zone as they may go over temperature and promote pre-ignition firstly.
In reality here, the area will be reduced slightly as the head will move closer to the piston after skimming, meaning that you can gently "dress" this area to clean it up with a rotary abrasive as you've got a little excess material to play with after that skim. Technically you should do the same to each one to match across the four cylinder to keep equal combustion.
juitz:
Made it to the camshaft - ok or not ok?
Pitting on the valve lobes?
Laverdaroo:
I'm no expert Dave but I'd be looking for a new one if it was me but like I say, I'm no expert. Thats quite excessive in my book but somebody should be along soon with a bit of 'better earnt knowledge'.
K2-K6:
That first photo of peak load site seems to scupper it if left that way.
Some here have had good repair and regrind by Newman cams that may be an option for you. Thats if a decent replacement is not readily available.
Some used one's will equally have problems, it's by no means certain that you'll be able to buy one that's perfect.
juitz:
--- Quote from: Laverdaroo on February 19, 2023, 12:47:58 PM ---I'm no expert Dave but I'd be looking for a new one if it was me but like I say, I'm no expert. Thats quite excessive in my book but somebody should be along soon with a bit of 'better earnt knowledge'.
--- End quote ---
Cheers Roo - I'm leaning towards a replacement but any second hand ones seem to have the same issue.
Did peruse other threads and seems like some people have not had issues with pitting as long a sit doesnt get worse.
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