I'm not quite following your question. The #415 chain that comes with most engine kits goes on the left side. It is the drive chain from the engine to the rear sprocket.
If you're talking about the chain tensioner...oh wow. There is about three days worth of reading here on that subject. Use the search feature at the top of the page, type in 'tensioner' and get ready to see what all the options are for that device. You'll see people who swear you need it, people who swear you don't and every option between those opinions. Way too many threads to link here. Try the 'search' and if you can't find an answer, come back, we'll help.
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