xr 70 not running well

i have an xr 70 that i put a new big bore kit but after installation it only starts on choke and backfires constantly. the bike runs for a few seconds then dies. while trying to start it the bike made a popping sound and spit smoke from the air filter. someone please help!!

Timing is off.

how do i change the timing becuae i checked all the marks and everything lnes up correctly??

First thing to check is your valve clearances.  If that's not it, I'm thinking you might be a tooth off on your cam chain and sprockets but it's been ages since I have performed that check or timed a machine like this so I'll let the rest of the community guide you on this.   Good luck, I'm sure it's a minor issue.  See if you can get hold of a service manual, that will guide you.


Edited by HondaRacer37

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