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SX 125 2002 serious engine problem!! need help!!

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I rode my bike yesterday, It wos running great!

i rode 6th gear full throuttle for a for about a half a minute and i heard strange "ticking" noice and 5 seconds later as I wanted to stop (still full throttle) the engine just died! now the engine as no compretion and it won't start. I opened the cylinder and the cylinder and piston is clean (the piston has a only a couple of hours on it).

What can the problem be???

Thanks,

Eli.

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So did you pull the head or take the entire cylinder off. IF there's no compression, check the piston rings. Were you running lean? what does the spark plug look like?

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for it to have no compression it has to have a leak some where. rings, piston slop, piston or cyl damage, spark plug not in the hole, head gasket blown, etc.

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I rode my bike yesterday, It wos running great!

i rode 6th gear full throuttle for a for about a half a minute and i heard strange "ticking" noice and 5 seconds later as I wanted to stop (still full throttle) the engine just died! now the engine as no compretion and it won't start. I opened the cylinder and the cylinder and piston is clean (the piston has a only a couple of hours on it).

What can the problem be???

Thanks,

Eli.

I'd say your piston ring was scuffed/galled. Was it fully warmed up when you ran in 6th gear?

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Yea the bike was fully warmed.

So what should I do now?

I toke out the cylinder and it has no damage, same for piston. the base gasket and head o - ring has no damage.

When I toke off the cylinder the piston ring was still comprest on the piston and didn't open back up. could it be a problem?

Could it have anything doing with the power valve?

Does the bottem end has anything to do with it?

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that is your problem, the ring is stuck. Remove the ring carefully and open up the piston ring groove and inspect the ring for damage. You can use the old ring from before the rebuild to scrape out the groove.

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Piston installed correctly? Arrow towards front (exhaust side)? If not, the exhaust bridge (if one) won't get lube through the tiny holes. Other problems too.

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So i toke apart the piston and it the piston was very stuck!! lookes like the side of the piston melt a a littel bet and now the piston has scratches on it!! what could be the reason for this??

(look at the picture).

now the grove of the piston rind is too small for the piston ring in the places it melted. would it be o.k to file up the grove and install the piston? or do i need to change the piston?

img0096r.jpg

Uploaded with ImageShack.us

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No you siezed the piston your main is too small for WFO.

I didn't understand what you sed :smirk:

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Your piston stuck to the cylinder wall due to lack of lubrication (OIL) You can not hold a 125 wide open unless the main jet in the carb is big enough to supply the engine with enough premix to lube the motor.

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Oo o.k thanks!

So can i file up the piston ring grove and install the same piston and piston ring or I need to change them?

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Hmmm... that's borderline. You'd have to do some very careful cleanup ton that piston to use it again. The ring groove can be prepped with a small triangular file, but the piston skirt itself needs to be sanded carefully and evenly all the way around to smooth those scratches. I'd maybe do it, but check the piston every ten hours...

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Oo o.k thanks!

So can i file up the piston ring grove and install the same piston and piston ring or I need to change them?

NO, you need a new piston and ring. From the sounds of it you better take the cylinder into shop and have them look at it, you may need to have it re-plated.

Joe.........

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Oo o.k thanks!

So can i file up the piston ring grove and install the same piston and piston ring or I need to change them?

Lord NO, as Joe said, you will need a piston, rings, wrist pin bearing, and LIKELY a cylinder replate or new cylinder.

To add to what ktmfred said, you also need enough fuel at WOT to keep it from running lean, overheating, and causing the seize. Fuel cools the piston and the added fuel will carry the oil to lube it.

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Well, this is just speculation, but I'd think the cylinder would be fine after that little a seizure. Might just have to clean any little aluminum off of it. I agree that the best course of action is all new parts, but in a world where money is hard to come by, that piston would get re-used in a heartbeat.

I don't think the original poster has the skill to dress the piston properly, so new parts are the way to go...

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Well, this is just speculation, but I'd think the cylinder would be fine after that little a seizure. Might just have to clean any little aluminum off of it. I agree that the best course of action is all new parts, but in a world where money is hard to come by, that piston would get re-used in a heartbeat.

I don't think the original poster has the skill to dress the piston properly, so new parts are the way to go...

when a piston is under a $100, no way would I try to reuse that piston, even on a budget. You can end up costing yourself more money in the long run. There's some pretty deep gouges in there.

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No way that piston would ever go back into anything I work on. That is no little seizure but I guess it is subjective.

Joe.............

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You'll want to get it jetted correctly before running it again. What size main jet is in there?

If you don't know how/where to check the main jet then read the ktm 2 stroke FAQ at the top of this form.

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