Top of my NS125R piston looks like a rat has nibbled it???

[the rides nsr]

Hi everyone,
i was having problems with my ns125 were it would stutter through 5000 to 6000 rpm and then would be ok again , i then was riding home from work one night and the bike just lost complete power and boged out and then died. when i got the bike home it wouldnt start by the kick start so i tried bump starting it and that worked but you had to keep the revs on other wise it would just die. i then took the engine out and took off the the cover of the cyclinder head and there was a a deep groove in the cyclinder bore and at the top of the piston it looked like a rat had nibbled the edges of my piston there was three little bits missing. Can anyone tell me why this has happened thanks phil
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The roads of the world need to have rubber burnt on them !!

[stinkwheel]

Sounds like your engine seized. Usually happens because it is running too hot.

This can happen for several reasons (list not exhaustive):

An air leak in the area of the carb causing it to run lean.

Fitting of a high flow air filter without re-jetting the carbs.

Fitting a sports exhaust or tampering with the standard one without re-jetting the carbs to suit.

A coolant problem.

Ignition too far advanced (shouldn't really be an issue as it'll be keyed).

Wrong grade sparkplug.

Insufficient oil feed.

Some pictures wouldn't be a bad thing. Also a picture of the sparkplug electrode.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

As above, but can also be caused by debris from some failure damaging the bore and then bouncing round in the combustion chamber. For example a bit of a piston circlip or the end of a ring.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[The Shaggy D.A.]

Your profile says the bike is "semi derestricted", and in another thread you said the airbox was standard - what derestriction has been done?
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Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[arry]