Hmm now what (A Rebore!)
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Little off topic, what compression in bars should a healthy dt125 have?
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@Irongamer727 The manual indicates 6.8
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Piston is shagged, looks like something has got in or been in there for a while bouncing about, plus det marks, there is even a low spot on the crown from det. The Head I'm most concerned with hopefully it will tidy up. The bore isnt too sad at all, a light rebore should do it, new piston and see what happens lets hope
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@Pablo13 Yep that looks well fooked for-sure. I would also check the bottom end for any loose fragments floating about, just to be sure. Get one of these and give it a couple of swirls to pick up any debris floating around.
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@Pablo13 I would be surprised if the heavy braking incident caused all that damage, by the looks of it your engine was in decline and had suffered some internal damage most likely from detonation, over an extended period of time. The incident was just the tip of the iceberg and the straw the finally broke the camel's back. You were dead lucky the engine maintained power and you were still able to ride her home. Sadly the price we all have to pay from owning a used bike and not knowing the true history of our pride n' joy.
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@NINJA Yeah I agree. She is a French import, although it was the runt of the litter so to speak, and had expected stuff to go wrong and I guess the mileage is about right for a top end. Just surprised that any plugs I pulled looked fine and it always started first or second kick right up until that incident.
I've run it on super while I've had it, so I guess it must have had some crap French fuel a while back and just managed to hold it together pootling about French lanes until I got my hands on it :grinning_face:
On the upside this may well go to explaining why it wasn't too happy revving over 9k, so if it solves that issue at the same time, I'll be happy. 0.5mm oversize piston, small end and gaskets have been ordered today and the bore and head are at the machinists. Hoping for a quick turnaround :grimacing_face:
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@DTR-NSR said in Hmm now what (A Rebore!):
Hard to tell in the pic but looks like the gudgeon pin circlip is missing? Unless you took it out before pic.
Yeah, and scratches on the side and dome of the piston right about at that point.
Good eyes. -
@Calum it does have those det marks, they are just hidden under the other damage
Dropped the new piston off today, should be back wih the head and bore tomorrow. Gasket set is here too, so if I get a moment I'll get something done on it over the weekend
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Yes, but I suspect that's a result of the engine going faulty and you continuing to run it. Either way, that bike will be down on power now.
If the engine was detonating before the incident, then you will definitely want to sort that out, otherwise you'll just kill another engine.
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@NINJA Piston, small end and bore have already been fitted. Just a new piston and a bit of cross hatching :winking_face:
I got the old piston off and could inspect in light a bit better. Both circlips were still present. Initial diagnosis was correct, and top ring has lost a section around 10mm long.
Looking at the piston, there is more to it than just that IMO. Here is the best pic I can take to give you an idea of the low spot on the crown, to the right side in the picture
mUSgt17pTEhDHzy-QODYJNQ:rk:33:pf:0
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