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Discussion Starter · #1 ·
Hi guys,
Here's my problem. I have a 1976 kz400. It has just under 30,000 miles on it but was rebuilt around 15,000. While riding it back to school yesterday (it's about a 3 hour trip) it started dieing like it was running out of fuel. After sputtering along for a few minutes it died. I let it cool for a minute then started looking around and saw steam coming from the air box. Upon further investigation I found that it had blown oil backwards through the carbs into the air cleaner. Now I've been riding and maintaining this bike for over 10 years but I don't know what to do for this one? Do you think it is just a stuck valve or did a ring go and it's blowing oil past the valve? Please help, my transportation and my hobby is not looking good.

Thanks to all,

Mike
 

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Discussion Starter · #2 ·
Update:

I pulled the breither tube and it has no obstructions. I pulled the engine plugs outside of where the valves sit on the left side (this is the side that is no longer firing) and they move up and down when I turn the bike over by hand. When started it is blowing white smoke (bad I know). If somebody could tell me if it's time to start looking for a newer bike or if maybe it can be repaired without major cost involved please let me know.

Thanks
Mike
 

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did you remove the spark plugs for inspection? if so, are they oil soaked? if there is oil from the crankcase breather tube, and oil on the plug(s), you most likely have a broken oil ring or worse. check compression (but beware, sometimes compression will be o.k. if only the oil ring is broken). also perform a "leak-down test" this will tell where compression is leaking ie into crank-case, exhaust or intake. hope this helps.
 

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Discussion Starter · #4 ·
Bad News

Well guys, I pulled the plug and shined a flashlight in, there's a whole in the piston about the size of a quarter :( , guess my riding is done for the year, maybe it's time to learn to rebuild an engine, any suggestions?

THanks

Mike
 

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Mike, first thing you need to figure out is why there is a hole in the piston. Once you open up the top end, determine if it was caused by a mechanical failure, ie ingested nut or bolt, broken valve seat, etc. or by heat from a lean condition. if it is heat caused, the first item that comes to mind is a loose spark plug. A loose plug will allow the cylinder to have extra air that causes a lean condition and piston "melt-down". Keep us all posted on your progress, and once you get it back on the road, check the spark plugs regularly and get a "read" on them as far as how they look for heat. Tan color is good, white isn't.
 
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