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bcaskey08

Rode With No Coolant And Now My YZ400 Won't Start! HELP!

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So after hours of searching over the FAQ and various threads on this site I have resorted to making a new thread. This is my first post on TT but I am quite familiar with forums as a whole so here it goes:

 

I recently bought a YZ400f with a 426 top end on it and I took it out to the desert and went on a group ride with some more experienced riders than myself. Needless to say the took me on one hell of a ride and I dumped my bike twice. The first time was a soft landing and the second time was a little harder but iI was uninjured in both. the problem is that on the second drop one of the lower coolant hoses came loose and started a slow leak. once I started riding again, the pressure built up and dumped all of my coolant out without me knowing. the bike kept running for a while, then i stalled it (let the clutch out too fast) it became harder and harder to start each time i shut it down (using the killswitch). we ended up bump starting it to get it back to camp (10 miles) then I put it on the trailer and went home.

 

The next day I tried to start it and nothing. I still have what feels like a lot of compression (the TDC lump is still hard to push through without using the decomp lever) so I changed the spark plug thinking that I fouled it when it was on its side but that diddnt fix the issue, so next I dropped it off at a local shop in Vista, CA to have the carb cleaned and re jetted since the previous owner had it set for 3000- 6000ft above sea level and I live at sea level.  So the shop cleaned the carb and rejetted it but they said it still wont start. I told the tech that it had overheated bad and he said that the piston rings were probably fried and it would be $600 to redo the top end.

 

What do you guys think? is that a reasonable assumption and if so is that a reasonable price? I'm new to riding so I'm struggling a little. Any help would be appreciated. Thanks!!

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Overheating can do much more than just fry rings. Probably needs all new top end. 

 

Sorry.

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Could be a lot worse than $600. I've seen the heads start to melt between the exhaust valve seats when they're run with no coolant.  Figure a new or replated cylinder, piston, rings, gaskets, and probably at least two exhaust valves and seat refinishing. 

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Damn. That's what I was afraid you guys were going to say.

So if there is still a lot of compression does that mean that the rings are still intact?

Also the tech said that he doesn't do compression tests on one cylinders because it's only a test of how hard you can kick it over.

Is there a way to test to see if the rings are infact fried or not?

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The only way is to take the engine apart, its not that hard, just take your time and everything will be fine, look at tutorials it shows it in a very detailed way :) best of luck

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Is there a way to test to see if the rings are infact fried or not?

 

Yes.  You can have a leak down test done.  It will show you if it leaks, how much it leaks, and what's leaking.

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Yes. You can have a leak down test done. It will show you if it leaks, how much it leaks, and what's leaking.

So I called my local autozone, pep boys and oreilys auto parts store and nobody has a leak down tester. I did see this one online:

http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

How much does it normally cost to have a leak down test done?

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Also I tried hill-starting it and I got it to run for 5 seconds then it cut off when I gave it gas which leads me to believe the piston isn't seized in place

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might not want to try to run it anymore until someone does a teardown, leakdown test , or at least a compression test.

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might not want to try to run it anymore until someone does a teardown, leakdown test , or at least a compression test.

That seem like good advice to me. I just wanted to make sure that I wasn't kicking it wrong and it really ran the whole time. I did all of the research about the "magic starting process" and I think I've got it down except for the part where the bike starts haha

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