Hi, I have rebuilt the carbie today. Bike isturning over ok, but is backfiring thru the exhaust and wont start.

Any suggestions what it could be and what i could do?

thanks

It's a 92 883 sportster hugger. We got a new carbie kit. So we have replaced all the gaskets, even the manifold gaskets. Got a new vacuum piston. Have put everything back together and the carbie seems to be fine. It got tuned up a month ago and was told I needed to get a carbie kit and replace everything. Think he mucked around with the timing as well. So not sure if the timing is out now.

 We removed the timing plate and found this melted. Can that affect the bike from starting? Carbie is fine so we are moving onto everything else.

that just looks like the glue the factory use when putting it together if the bike was running before you pulled carbie apart  ? go back in to it , have you turned the fuel tap back on ?, did you have the spark plug leads off are they around the right way ?

+1 leads 180deg out. or wrong way round. which ever way you want to look at it.

Normally back firing and carb farts are due to bad timing.
Worst carb can do is give the wrong mixture, too rich or too lean.
Lean gives more heat and rich more deposition.
Check your spark plugs for the right color.
Since he has been fiddling with the timing, i think the prob lays there.

If the ignition has not been modified you'll have a dual fire system so switching spark cables makes no difference since they both fire at the same moment. (2 connections on coil)