Afterfire Flames Help?!

[Sphinx536]

Hi, so I have a Cb350 1971 twin and I just did a top end rebuild to check rings, valves, clean, and replace gaskets. It wasn't running before I tore it apart and now after some replacements and repairs its still having trouble. It is backfiring/afterfiring flames out of the exhaust (super cool but not good) I thought I timed points correctly but may not have, (valve gaps are good) But also have read it maybe a fuel/ carb issue? carbs are stock... so anyone have experience or advice for this what is the main cause of afterfire or backfire?

 

[goldy]

Sounds like carbs to me, may have some blocked passages/ jets.

 

[Tim]

Before bothering with your carbs, be 110% sure about your ignition timing, valve lash and cam chain tension. All of these have to be spot-on before touching your carbs.

Sounds like your exhaust ports are opening perhaps a bit early. Are you sure you got the cam aligned properly when reinstalling? Could it be 1 tooth off?

 

[Sphinx536]

I think its my points... I had the cam sprocket with the L at the top the whole time. I really hope its my points. Can you explain valve lash? is that valve clearance/timing?

 

[teazer]

Are the complete exhaust pipes on or are you running it without pipes?