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Blown up or what?

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My 02 CR 125 was running really good ever since i bought it. The other day i started it and went to take off after it was warmed up, and it died. I just thought that i fouled the plug, so i put a new plug in and nothing. I have tried every plug i have, even bran new ones. You can see a spark. And i can push down the kick start with my pinkey finger even when the plug is in tight. But for some reason the plug isnt wet, so do you guys think that it is blown up or needs a head gasket or what?

Thanks for all your replies!!

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ur ring is probably shot, you might be able to get away with just replacing that, but while you're in there just do the whole top end, buy a kit (piston, ring, pin, circlips, bearing, head gasket, base gasket)

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If you can easily push the kickstart down with your finger with the plug installed, you don't have much (ie, any) cranking compression. I doubt it's just rings if the engine was running then suddenly died. It doesn't sound like reeds because the engine produces at least some cranking compression as the piston closes off all the ports, even with the reed cage removed. Unfortunately, the last time I saw a total loss of compression was when a friend broke a piston in his CR80. The plug that came out was coated with aluminum, so it was obvious that something bad had happened. I'd say it's time to pull the top end and perform a major inspection. BTW, how many hours do you have on the current top end?

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If it was the top end, you would feel a loss of power for a couple hours then a blow up, i think you should tear it down to be sure.

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If you can easily push the kickstart down with your finger with the plug installed, you don't have much (ie, any) cranking compression. I doubt it's rings if the engine was running then just died.

:thumbsup: That'd be my guess! I have seen holes in the top of pistons do the same thing.

Take the spark plug out, cut a piece of cloths hanger wire (Make sure its long enough not to loose in the cylinder) and gently put it in the spark plug hole until you touch the top of your piston. Now very slowly move the kick starter, does the piston push up the wire, if so, does it follow it down? If not, than Skipn8r is on the right track about serious damage.

GOOD LUCK :ride:

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I bet it's your carburetor, because my CR125 did the same thing yesterday I thought it was the plug but it was firing and no gas was coming out when I would crank it with the plug out so I immediately new it wasn't getting gas so I went to the carburetor first and if you look on the bottom of the carburetor there is a bolt about a 3/4 I think and If you unscrew it about 1 and a 1/2 turns(don't unscrew all the way) and shut your gas off it will let what gas that is in the carburetor run out bringing any dirt out with with it and that dirt keeps the bike all clogged up and that was my problem so give it a try if it doesn't work then it won't hurt anything it will just clean your carburetor just make sure you screw the bolt back tight and turn your gas back on. I'm pretty sure that is whats wrong with your bike it's nothing major you just need to do that to your bike every now and then I do it every 10 rides to keep my bike healthy.

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I bet it's your carburetor, I'm pretty sure that is whats wrong with your bike it's nothing major you just need to do that to your bike every now and then I do it every 10 rides to keep my bike healthy.

Uhhhh.... Did you read his post? :thumbsup:

"i can push down the kick start with my pinkey finger even when the plug is in tight"

Carburetor? I think NOT! :ride:

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I took my head off, and there is no hole in the piston, but it is really black on top. I looked at the rings through the exhaust port and they looked ok to me. I will probably just put a top end in it anyway now that it is apart. But still not sure exactly what the problem is.

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Have you checked the exhaust/ power valve. Are you sure it's not stuck open? They will gum up and stick . This will cause low comp.

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Uhhhh.... Did you read his post? :thumbsup:

"i can push down the kick start with my pinkey finger even when the plug is in tight"

Carburetor? I think NOT! :ride:

Ohh my bad i thought he said he put his pinky finger over the spark plug hole and pushed the kicker down and didn't get any gas. Sorry but but it wouldn't hurt to clean your carburator out with the advice i gave him

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Uhhhh.... Did you read his post? :applause:

"i can push down the kick start with my pinkey finger even when the plug is in tight"

Carburetor? I think NOT! :applause:

Ohh my bad i thought he said he put his pinky finger over the spark plug hole and pushed the kicker down and didn't get any gas. Sorry but but it wouldn't hurt to clean your carburator out with the advice i gave him.

ANd our XR70R is doing that is it like not firing I know you said its sparking but is it firing because I can push the kicker down on our XR70R and it will drop and barely come back up I think something is wrong with the crank or the fuel valve because i kick it and it lets out exhaust so the exhaust valve works but makes no noise at all when cranked but if you crank it once and stop you can here like the piston or crank or something still rotating for a good three seconds and then it slowly stops if in our case it is the valves it wouldn't be yours problem because you don't have valves you have reeds so unless it is you fuel reed or crank then I don't know :ride: we have our XR70R in the shop trying to figure it out now. See if your gasket isn't on right or something which would result in no compression. ohh and try and see if your oil drain bolt isn't in or your dipstick which would mean no compression but don't laugh I've seen it happen. :thumbsup:

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