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Discussion Starter #1
I had this idea of teaching my kids to ride so I bought small dirt bikes for them, both hondas 50 cc and 80 cc. They have been riding at local off-road place where I take them regularly. But they became bored riding the same circuit where I can watch them. Now I want to buy a bike for myself so we can ride farther together. don't want a big bike but just big enough so my daughter can transition to it after she grows from her 80cc. so, I found this Yamaha yz85 two stroke. but this is more of motocross racing bike. I've never owned 2 stroke. What are the considerations buying one for a long term? are they capricious? need a lot of maintenance? what is reliability like? and what to look at when buying used one?
 

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Two stroke engines fire every time the piston approaches top dead center. Twice as often as a four stroke. No valves. Very simple, extremely light, and they produce a lot more smog than a 4 stroke. No valve train means the engine is much more compact. Power is very roughly equivalent to near twice the 4 stroke displacement.

The fuel\air mix is pulled in through a port in the cylinder wall, and exits another port. That's two fairly large holes in the cylinder wall. That beats up the rings much more quickly than a four stroke does. Also blows a lot of rich mixture out the exhaust....

Because the cylinder gets doused in the un-burned fuel, it rinses away the crankcase oil that would lubricate the rings. 2 strokes require oil in the fuel to lube those rings. Some bikes do this automatically, metering oil for you. Many more require you to pre-mix it before you fill the fuel tank.

All that fuel washing away oil films is tough on plain pressure fed bearings.... 2 strokes by and large use roller bearings instead. Roller bearings wear more quickly than plain bearings will.

All of that means long term ownership should include learning to replace rings and roller bearings -- not anywhere near as critical for a kid's tiddler mini bike as it would be on a full blown race bike.
 

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Two strokes also tend to foul out spark plugs often if they are not ridden wide open.
 

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If you plan on getting her into motocross riding/racing, get the yz85. If not, a crf150f would be more user friendly and easier to transition onto for trail riding.
 

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Discussion Starter #8
I know how 2 stroke works just never owned one. my daughter is not getting into motocross for sure, I'm just teaching kids to ride so they know how, but we don't share the same passion for motorcycles, on a long run I don't think they will continue. I get the point about yz85, it could be too much. I wanted ttr125 just nothing comes along on local graigslist
 
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