Topic: Top End Rebuild Issues

[dsharstrom]

Hopefully someone on here can provide some insight into what I'm seeing after my top end rebuild on my 75 550.  I had a blown head gasket so I rebuilt the top end of the engine.  Once rebuilt I reinstalled and cleaned the carbs (bike had not run in over 10 years).  When we went to test the engine with the carbs on the bike there was visible back pressure and gas shooting out the the air box side of the carbs.  Is this normal or what could be wrong?

[seanbarney41]

sounds like you got the timing wrong...either cam or ignition or both.  Might be as simple as spark plug wires to the wrong cylinder/s.  Time to start checking your work.

[wrenchmuch]

Are you sure the cam was installed properly? Are the plug wires going to the correct plugs? Is the wiring correct from the points to the coils? These are the things that spring to mind given your symptoms.
Hope this helps
Mike

[wrenchmuch]

Beat me to it.