I have a honda pcx 125 2010 model and was looking at the engine (been boring) and I noticed that I had a small leak from a ring/hoop right under the engine just wondered what it could of been and how to stop it
Is it oil?
If so it looks like a broken crankcase.
The loop is the mount hole for he centre stand.
A few options....
Keep topping the'oil up and ignore it
Clean it off and use some type of molecular metal polymer filler
Strip it and get it welded
Strip it and replace the crankcase
Four decades on two wheels has taught me nothing, all advice given is guaranteed to be wrong
Does the bike have a centre stand or just a side stand? It looks like the mount for the centre stand that's leaking. They are a known fault on early 125 models. The stand seizes and the lugs either crack the engine casing or break off all together. The lugs were strengthened on the later ESP engined bikes to fix this fault.
If it's leaking then you would be better to get it fixed as oil loss could lead to engine failure. The oil capacity is only 0.8 of a litre so even a small loss could be a potential problem.
It may be possible to get it welded if there is a decent engineering company close to you but the engine might have to be removed to do this. (Not too bad a job).
If it is a cracked crankcase the labour charge at a Honda dealer would be around £700, if its out of warranty Honda should still supply the parts for free.
I have a friend who could weld it or put the part on would that be better?
But I have found a site that sell the part but it says '1 crankcase comp L' and '1 crankcase comp R' what does this mean?
Left side, right side (of crankcase) but need confirmation on that
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It's hard to tell from the picture, but that looks like a poorly-done weld on the spot where the centerstand used to go. That hoop/ring is where the centerstand mounted, and the weld that is to the left in the picture is NOT on the stock crankcase (the crankcase is a cast part, not a welded one). Someone cracked the crankcase by using the centerstand and sloppily repaired it.
The right way to fix it would be to replace the crankcase, which given the low cost of a PCX in the states, isn't worth it. I'd drain the oil completely, clean up the area as best you can, and slop some JBweld all over that joint around the hoop.