125-200cc Top end questions

I have a 2008 cr125 that I'm thinking about rebuilding this coming winter as it has 20 hours on the top end and thats only since I installed a trailtech vapor and I bought it second hand so the top end time is unknown but I estimate it to be around 50+ hours. anyways I took the head off to inspect the bore and it has some vertical dark lines on the intake side and I'm wondering is I should be concerned and am curious about if it looks healthy or not. Also should I go with an OEM ABCD size piston or a Wiseco 54mm one?
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Personally if you cant feel any groves then i would run it.
I would do rings and check piston at the same time.
Could do a light hone too.
The bore size determines what oversized piston you need.
Usually stamped on the underside of the cylinder below reed block.

Thanks I don't know if I'll hone the cylinder as I can still see the cross hatching but I'll have to wait for winter anyways

i did run my oem piston for approx. 70hours, sometimes i was doing mx, some of the hours i was doing 2hour racing, and also i was up climbing mountains in romania.
make sure your piston has got the 2 holes on the exhaust bridge- i didnt notice when i changed the piston to a vertex one which caused my engine to seize in minutes...

+1 on the Vertex lube holes.
I have also seen a 125 seize within 5 minutes after being fitted with a none holed Vertex while being ridden gently from the owners house to mine, A distance of around 2 miles. One exchange jug later and plenty of replacement pistons all with holes the bike has done hundreds of hours and has been 100% reliable.

Do the 165 pistons have thses holes? Didnt check/notice when did recent top end

that looks fine if the grooves aren't too deep then just run it, or peace of mind hone it for a few seconds before rebuilding. You should have a stamp somewhere on the cylinder stating if it's a size abcd, if you can find that I'd go for the size stated or the one above it, ie, if it says d, go for the d, if it says ''a', for an ''a'' or 'b'' piston, as the cylinder wears it allows a tiny bit more space anyway. Wiseco are good but pretty sure they're forged to be made, they're not as good for cold starts, but are better for negine failures, tend not to break apart as much as cast piston, but then cast pistons don't need as much clearance when started cold so if you don't warm up before riding for the cheaper cast piston. Don't worry about 50 hours unless you're riding it flat out everywhere, I've had pistons go on for well over 200 hours without issue [on the road anyway, not hooning round an mx track ]

I Hope this will help some of you guys... I do run Yamaha YZ125 2005 on Pistons as they are easier to get and they have already the holes on the exhaust side.
But as i m always trying something different i also found out that i can use gasgas 125 pistons as an direct replacement... just have a look at the pictures...

which one is less expensive?

Spot on miezzie now find me a cheaper piston to the wossner for my 360.
They cost me £156 each throw..

whats the bore?

Think std bore A is 77.94? Im using D size max overbore
Think the deck height is 27mm that may be a lie will measure with calipers in the morning.

Yeah and free freight to Australia!!!

Nah been there mate, sa or usa next babe.

I bought a Wössner kit for 20€ on amazon...
I m not after the Best price, i was looking for compatibilty and maybe a more durable piston as the vertex pistons dont have the lube holes and the yz pistons require the sqiush to be modifiyd slightly.

can you share a link please?

Thats sold out... you have to be very Quick at amazon.

i don't get, all i can find is cost approximately 100$. With whom i have to sleep, to buy it for 20 euros?)

I think you are to late, there are thousands of good Deals you just have to find. I bought clutch plates for the 250WR for only 8€- another day they have been back at 35€...

Its a case of first come first serve i think.
Gotta be quick.