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200 SX meltdown

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We had our last race of the season. Saturday I was on my last lap of a 7 mile course with the finish line in sight and the engine seized. This weekend I will tear it down and see how bad the damage is. I am very interested to find out what the root cause was. The bike ran great at the 24 hour race under the same temps / jetting. I could hear a squealing then up the face of a jump and the seize bog sound that I know so well. Kicked it over a couple times and could hear the grindage gong on inside. I checked coolant and it was fine. The engine was very hot so it must have been a little lean for as hard as I was pushing it.

Joe........

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Hate to hear it Joe,

What main jet were you using? needle?

Float level too low?

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check plug for signs of detonation (flecks of silver on the insulator, or pot marks on the head piston) when two strokes get real hot they tend to detonate(ping) they die soon after that.

didn't grab the wrong gas can at a gas stop? Seen that happen.

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I do not remember at the moment the jetting I am running. I just pulled the plug and did not find what I expected, it looks fine. No aluminum flakes at all. I turned the engine over with the kick starter and it sounds fine. Now I am puzzled. I will pull the jug this weekend. Too damn sore to do much at the moment. Sooo odd I run hours at the 24 hour yet I am mega sore after a 1.5 hour race;) Then again I didn't have any get offs at the 24 hour.

Joe.........

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check the big end of the rod, they have been known to tighten up too. Good luck.

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With all that mud/water at the 24 hour race just prior, I wonder if perhaps a little leftover dirt stuck in the carb/jet caused a lean condition?

You said it ran great for the 24 hour. Did it run great right up to the point of squealing/seizure in your 7mile race?

I'm no expert, just brainstorming.

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50:1 Dumonde Tech, been running that for years. Why I suspect a lean condition is the last time I jetted it was at Eddievile and it was 100+ degrees. With the colder weather I may have needed to fatten up my jetting but the bike has been running great so I was reluctant to change anything.

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

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jetting was allitle off, it seized, happens to the best of us, rebuild it and move on, aint no mystery to be solved here :busted:

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Wish it was that simple. I pulled the engine today and took the cylinder off. While the piston does have some minor scoring it is nothing like I expected it to be. Things look pretty normal. The top end needs to be done but nothing that explains the squealing and sudden stop. I pulled the clutch cover and still found nothing bad. Looks like I will be splitting the cases just to be sure. I know what I heard and it was not good so something has to be wrong.

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

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Wish it was that simple. I pulled the engine today and took the cylinder off. While the piston does have some minor scoring it is nothing like I expected it to be. Things look pretty normal. The top end needs to be done but nothing that explains the squealing and sudden stop. I pulled the clutch cover and still found nothing bad. Looks like I will be splitting the cases just to be sure. I know what I heard and it was not good so something has to be wrong.

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

I thought I had done the same thing on my 05 during a HS earlier this year. Climbing lots of hills on the gas. Heard a squealing like I had never heard before and the bike didn't want to go. So, luckily I was on top of the mountain and took the most direct logging road down to my truck. Ended up I overheated the clutch....cranked it up and it sounded normal again.

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hmm, if that is the case I have never done that. Strange shizzle. I was pushing the engine hard that day and it was hot as hell when it stopped. Regardless, a new crank and piston kit is going in;) I will split the cases and check all bearing just to be sure.

Joe..........

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Wish it was that simple. I pulled the engine today and took the cylinder off. While the piston does have some minor scoring it is nothing like I expected it to be. Things look pretty normal. The top end needs to be done but nothing that explains the squealing and sudden stop. I pulled the clutch cover and still found nothing bad. Looks like I will be splitting the cases just to be sure. I know what I heard and it was not good so something has to be wrong.

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

was it like somebody hit the killswitch then all compression was gone ? :lol: you ran it to lean. cylinder doesnt always look like hamburger, sometimes they just have a small amount of scoring.

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was it like somebody hit the killswitch then all compression was gone ? :lol: you ran it to lean. cylinder doesnt always look like hamburger, sometimes they just have a small amount of scoring.

Must be what happened. I've just never seen it happen so light. In the past when I smoke an engine it has been ugly.

Joe......

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We had our last race of the season. Saturday I was on my last lap of a 7 mile course with the finish line in sight and the engine seized. This weekend I will tear it down and see how bad the damage is. I am very interested to find out what the root cause was. The bike ran great at the 24 hour race under the same temps / jetting. I could hear a squealing then up the face of a jump and the seize bog sound that I know so well. Kicked it over a couple times and could hear the grindage gong on inside. I checked coolant and it was fine. The engine was very hot so it must have been a little lean for as hard as I was pushing it.

Joe........

Do you have digital images?

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The last time I heard a squeeling before a sieze it was a crank bearing. Lots of hours on the crank? aftermarket crank? Some have had issues with new aftermarket bottom end kits.

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This engine was Austin's (my son) 2007 125 SX that I installed an 08 200 crank and top end on so this OEM crank has been around. The crank and top end was out of Ty Peterson's 2008 200 XC that he kept grenading trannies. Crank life,, who knows.

I have two complete 200 engines at the moment. One will get a new Hotrod crank. The other will get a rebuilt OEM crank. Both will be in Andrews hands for truing etc.

Time to put the HotRod crank to the test;) I'll have the spare engine for a backup.

Joe.........

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