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I have a newbie question for you.

I'm considering buying a 2004 Yamaha TTR600RE- a single-cylinder, air-cooled dirt-focused dual-sport bike. It's perfectly set up for adventure touring, which is what I want it for. The engine has 11k miles on it (not the original engine).

However, the owner has said it burns about a pint of oil every 400 miles on the freeway, which doesn't seem to bode well for any long distance trips in remote places (I'm planning a "RTW"-type trip).

The owner also points out that "The bike sometimes lets out a puff smoke from the exhaust on starting so the valve seals are worn its not a problem did a 1500 mile trip last september."

Are the valve seals the likely culprit? If not, why else could this bike be burning oil? Would a mechanic, upon breaking open the engine, be able to say definitively whether the valve seals or piston ring or anything else are at fault? What would the ball-park cost for replacing the valve seals and piston ring be? (closer to $200 or $500?) How likely is it that the cause of the oil burning would not be properly diagnosed?

If worst comes to worst, what would a ballpark cost for an engine rebuild / new engine plus installation be?

Normally, I'd look for other bikes (and I am still looking), but the bike market where I live is quite small and the TTR is relatively inexpensive and seems to fit the bill in almost every other way (includes many otherwise expensive upgrades for overlanding). So if a valve seal / piston ring replacement would probably do the trick, I'd go for it. I'd appreciate your thoughts.

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    I'm not positive this question is on-topic, mainly due to your asking specifically about pricing. I think there is a valid question in here, such as the why is this bike burning oil portion. Please consider taking out the portions about cost. The reason for asking this is, pricing concerns are very specific to your local and volatile in nature that they may not be the same next week as they are today.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Aug 2, 2015 at 18:34

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The most likely culprit is the piston rings. One way to check before you replace them is to compression test the cylinder, then put a few drops of motor oil into the spark plug hole, and retest. If the compression goes up, it's because the oil is making a better seal on the rings.

Replacing the rings on a single-cylinder motorcycle is fairly easy, search online for a guide if you're interested in doing it yourself. A shop would likely charge $400 - $500.

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  • Unfortunately the piston was scored, so the cylinder is being rebored.
    – bevanb
    Commented Aug 29, 2015 at 8:52

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