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Dirt tracker
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No worries. Take compression test and leakdown test and relax. These things will run a long time on a top end. It will usually give you plenty of warning when it's getting tired. This way you can compare compression and leakdown readings and calculate service interval to your next top end job. She'll be just fine lad. No worries
 
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Discussion Starter · #26 ·
That's quite a bit of carbon in that exhaust port to claim 5 hours run time. Reckon it could have been rich oil ratio and perhaps they were telling stories about the hours. It's hard for me to accept that story. I wouldn't be the one to call your seller a liar, but that picture looks more like 40-60 hours run time for those piston scratches and carbon deposits. None of your pictures should discourage you. You still have an awesome bike. Your seller may have given you a bit more of a story about the hours but the bike still looks like a keeper.
I also put oil in the cylinder and did the test again and no change. And am I supposed to hold the throttle open when I do the test? I didn’t.
 

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Yeah, those are sweet bikes. The motor, as you have seen, has two drain bolts. One on each side. Put the drain bolt in the right side and leave it there. They are notorious for stripping. Just snug it in and leave it there. Do all your oil changes with the bolt in the left side.

I also agree that that seems like more shavings than I would be comfortable with. Change your oil regularly and keep an eye on that.

I also agree that that looks like a ton of oil build up for only 5 hours on a "fresh rebuild." Can you get a better picture through the exhaust port? Not that any of that really matters because if it is getting good compression and it runs well, just run the thing! Those are great bikes!

Do yourself a favor and safety wire the shift lever bolt. It is a taper-spline fit and when that bolt gets loose your shifter just instantly disappears. That can ruin your day.
 

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That oil looks way to dark for 5hrs in a 2 banger.
Bike could've been rebuilt and they haven't cleaned the cases properly which could be why there is more shavings on your magnet.
I would go with Auggie's idea of doing a couple short oil change intervals and see if the filings clear up.
With the oil being that black in a 2 banger, they might've rebuilt it and then poured the old oil back in.
"Don't laugh, I've seen idiots do it"
 

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Discussion Starter · #33 ·
That oil looks way to dark for 5hrs in a 2 banger.
Bike could've been rebuilt and they haven't cleaned the cases properly which could be why there is more shavings on your magnet.
I would go with Auggie's idea of doing a couple short oil change intervals and see if the filings clear up.
With the oil being that black in a 2 banger, they might've rebuilt it and then poured the old oil back in.
"Don't laugh, I've seen idiots do it"
Man I just can’t comprehend how much of an idiot someone has to be to put old oil in a freshly rebuilt engine!
 

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Discussion Starter · #34 ·
That oil looks way to dark for 5hrs in a 2 banger.
Bike could've been rebuilt and they haven't cleaned the cases properly which could be why there is more shavings on your magnet.
I would go with Auggie's idea of doing a couple short oil change intervals and see if the filings clear up.
With the oil being that black in a 2 banger, they might've rebuilt it and then poured the old oil back in.
"Don't laugh, I've seen idiots do it"
But yeah I’ve gotten some more oil and gonna change it in a few hours again.
 

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hey there Kranjack19... after seeing the exhaust/piston picture, i got bad new for you my friend... i been running bikes since 1980 and am a mechanic by trade. your 125 needs to come apart soon or it's going to blow up and your going to need a cylinder for sure.

why?... both 2 strokes and 4 stroke pistons survive cycling inside the cylinder at 8000 RPM because of a thin layer of oil between the piston skirt and cyl. imagine putting two flat pieces of glass together on the table with a few drops of oil between them. you would be able to slide the top plate around with ease. now imagine one of the glass plates being made with long grooves that go from side to side. the oil would escape out these grooves. the plates will bind. it would take hot grease or a ton of oil to get the two plates to float and slide in the same way right?

it is common for guys with the older steel bore snowmobile engines to put a new piston into a scratched up bore. then they wonder why the piston seizes in the bore within 10 hrs. in that case the cyl groves will let the oil escape. in your case it may be just the piston that is scored, but the result will be the same. it is only a matter of time till an engine in your condition will blow up.

when we change out pistons in our bikes due to high hours, they should still look completely new. I have kept all my bikes maintained with grease at the air filter face and proper gas and jetting and i have never had a failure. every time i replace a piston it still looks new. this includes running a 250 2T piston for over 200 hours. I have seem nikasil cyls wear out beyond their max ID bore dimension and not have a singe scratch. so you get the picture, you have a problem.

on a side note, cross hatch in a cyl bore helps the oil hang out there in the micro groves properly. so if a cyl is so worn the cross hatch is gone, it is at risk of failing.

it does not matter if the guy lied to you, though i assume he did, a bike can be abused quickly. leaky air filters, bad jetting, cold start ups etc and a bike can be shot in hours.

next time you are holding a new piston, borrow a vernier calipers and note that the top is a lot smaller then the lower skirt. this is because the piston needs to heat up to be the same size. the dome is more dense and thus expands more than at the skirt, about 10 thou more (.010"). the skirt expands too. as does the cyl. if you don't give all this time to happen the piston will "swell" in the cyl to the point that the film of oil can no longer protect the piston, it will bind slightly and get scratched up. you wont tell for a long time, but just once like that and the damage will wreck havoc eventually.

i cant tell you how often i see guys unload their bike and cold scream it to warm it up. so wrong. they often fowl a plug too because a 2T leaves a pool of oil at the bottom that needs to heat up again, or it will get pushed up to the plug while its thick, but i digress.

changing the gasket at the ex pipe will not stop that oil leak. that gasket is not made to stop oil. the oil is from the crank bearing opposite the magneto leaking case-oil into the crankcase from the gearbox. it may also be jetted too rich and have ex valve issues.

as others have said, don't panic as you have a nice bike. but none the less, here is what i suggest you do... pull the carb and remove every jet including the carb slide needle and tube that the needle drops into. compare all the jet numbers to the book for a 2009 and replace anything that does not match (unless you can find updated info to support the changes). you will need a good magnifying glass to read the numbers. the best one for the job can be ordered from a nearby Caterpillar dealership part # 8S-2257 called a Loupe.

next reseal where the rubber boot meets the airbox as dirt can suck in there. may have to replace rivets and put it back together with some top quality sealant. some models sell a rubber gasket for that spot but it still needs sealant. use a new air filter unless you're sure there are no holes, and also use grease at the mating face. dump out the gas tank and rinse it well. now when your rebuilt motor goes back in, it shouldn't get messed up.


for the engine... take it to a reputable shop and ask for a strip and assess and repair-cost quote. tell them it needs crank seals. show them the picture of the drain plug magnet. ask them to inspect for chipped gears. make them show you the cyl once the engine is apart. if you can feel any scratch with a seal pic, it is no good. if they say it is worn out, as for micrometer specs and stats to prove it.

keep in mind they will likely quote you for a new KTM cyl and wont likely sell you a repaired one, which is half price. once you know if you need a cyl you can exchange yours at US Chrome in Wisconsin by way of the mail. mail yours in and you wont have to pay the core fee. they do top work. no problems at all with their stuff. most shops say they will only source their own parts. as for the service manager and tell him your using US Chrome. he will likely comply even though they loose money from the parts mark up.

anyway, sorry to bear the bad news, but hope this helps!
 

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hey sorry, but with that much scoring on the piston... it needs to be rebuilt before it blows up and wrecks the cyl.

also the ex gasket will not stop that oil. the oil is from the crank seal leaking gearbox oil into the crank case. when you get it rebuilt, makes sure every jet and needle in the carb is stock. or an ok size as per a mod. also look for how dirt got in past the air filter, including that rubber boot where its riveted to the airbox. those joints need sealant,

as for the dirty oil and the piston scoring etc... there is no way the thing was just rebuilt. lastly, keep in mind that cold starts are the hardest thing on an engine. the piston needs time to expand at the same rate as the cyl bore, or it will squeeze out the thin film of oil, bind the skirt to the cyl, and start that scoring process. long warm ups at lower revs is a must. the good side is you wont fowl the plug like guys do during hi rev warm ups.
 

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NICE! KlimbThatMountain. You know your stuff. Just a few comments (added in to your post below where relevant)
hey there Kranjack19... after seeing the exhaust/piston picture, i got bad new for you my friend... i been running bikes since 1980 and am a mechanic by trade. your 125 needs to come apart soon or it's going to blow up and your going to need a cylinder for sure.

why?... both 2 strokes and 4 stroke pistons survive cycling inside the cylinder at 8000 RPM because of a thin layer of oil between the piston skirt and cyl. imagine putting two flat pieces of glass together on the table with a few drops of oil between them.you would be able to slide the top plate around with ease. now imagine one of the glass plates being made with long grooves that go from side to side. the oil would escape out these grooves. the plates will bind. it would take hot grease or a ton of oil to get the two plates to float and slide in the same way right?

COMMENT: KTM 125sx bikes rev up to 12,000 rpm

it is common for guys with the older steel bore snowmobile engines to put a new piston into a scratched up bore. then they wonder why the piston seizes in the bore within 10 hrs. in that case the cyl groves will let the oil escape. in your case it may be just the piston that is scored, but the result will be the same. it is only a matter of time till an engine in your condition will blow up.

when we change out pistons in our bikes due to high hours, they should still look completely new. I have kept all my bikes maintained with grease at the air filter face and proper gas and jetting and i have never had a failure. every time i replace a piston it still looks new. this includes running a 250 2T piston for over 200 hours. I have seem nikasil cyls wear out beyond their max ID bore dimension and not have a singe scratch. so you get the picture, you have a problem.

COMMENT: Based on all this I recommend a new Nikasil coating for the cylinder. That would then mean that you can fit standard pistons and you know what you are working with.

on a side note, cross hatch in a cyl bore helps the oil hang out there in the micro groves properly. so if a cyl is so worn the cross hatch is gone, it is at risk of failing.

it does not matter if the guy lied to you, though i assume he did, a bike can be abused quickly. leaky air filters, bad jetting, cold start ups etc and a bike can be shot in hours.

next time you are holding a new piston, borrow a vernier calipers and note that the top is a lot smaller then the lower skirt. this is because the piston needs to heat up to be the same size. the dome is more dense and thus expands more than at the skirt, about 10 thou more (.010"). the skirt expands too. as does the cyl. if you don't give all this time to happen the piston will "swell" in the cyl to the point that the film of oil can no longer protect the piston, it will bind slightly and get scratched up. you wont tell for a long time, but just once like that and the damage will wreck havoc eventually.

i cant tell you how often i see guys unload their bike and cold scream it to warm it up. so wrong. they often fowl a plug too because a 2T leaves a pool of oil at the bottom that needs to heat up again, or it will get pushed up to the plug while its thick, but i digress.

COMMENT: Make sure the fuel/oil mix is correct. I struggle with the later recommendations of 60:1... We have ridden KTM's for close to 14 year and never had a seized piston. Partly I put that down to us using 40:1.

changing the gasket at the ex pipe will not stop that oil leak. that gasket is not made to stop oil. the oil is from the crank bearing opposite the magneto leaking case-oil into the crankcase from the gearbox. it may also be jetted too rich and have ex valve issues.

COMMENT: Often the issue is a worn crank seal on the r/h side.

as others have said, don't panic as you have a nice bike. but none the less, here is what i suggest you do... pull the carb and remove every jet including the carb slide needle and tube that the needle drops into. compare all the jet numbers to the book for a 2009 and replace anything that does not match (unless you can find updated info to support the changes). you will need a good magnifying glass to read the numbers. the best one for the job can be ordered from a nearby Caterpillar dealership part # 8S-2257 called a Loupe.

next reseal where the rubber boot meets the airbox as dirt can suck in there. may have to replace rivets and put it back together with some top quality sealant. some models sell a rubber gasket for that spot but it still needs sealant. use a new air filter unless you're sure there are no holes, and also use grease at the mating face. dump out the gas tank and rinse it well. now when your rebuilt motor goes back in, it shouldn't get messed up.


for the engine... take it to a reputable shop and ask for a strip and assess and repair-cost quote. tell them it needs crank seals. show them the picture of the drain plug magnet. ask them to inspect for chipped gears. make them show you the cyl once the engine is apart. if you can feel any scratch with a seal pic, it is no good. if they say it is worn out, as for micrometer specs and stats to prove it.

COMMENT: 2 stroke KTM's are not rocket science. If you are handy with tools and have the time you can save your self money. Get a good service manual for your bike. Then if you get stuck come back on here and ask questions and we will help. Go to the category: "Tips And Tricks" where you will find many of the KTM manuals. Some free, other for a small amount.

keep in mind they will likely quote you for a new KTM cyl and wont likely sell you a repaired one, which is half price. once you know if you need a cyl you can exchange yours at US Chrome in Wisconsin by way of the mail. mail yours in and you wont have to pay the core fee. they do top work. no problems at all with their stuff. most shops say they will only source their own parts. as for the service manager and tell him your using US Chrome. he will likely comply even though they loose money from the parts mark up.

anyway, sorry to bear the bad news, but hope this helps!

COMMENT: Thanks for taking the time to write all this down KlimbThatMountain!!
 

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NICE! KlimbThatMountain. You know your stuff. Just a few comments (added in to your post below where relevant)
Hey @KlimbThatMountain I reckon ye better give @Axzon a bit of writers credit on your novel there:LOL:
I write most of mine without help. Good that you showed up here.....my finger gets tired writing these damn novels:)
 
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