Topic: 77 cb550 just finished rebuilding but won't start

[clayherget]

Just finished rebuilding 77 cb550.  It won't start.  I initially tried to start it without the exhaust and noticed flames shooting out of the head.  I put the pipes on because of the flames.  I have tried spraying starter fluid in the airbox and almost got it going.  Because of the flames I am thinking maybe i have the cam chain off by a tooth or so.  I did put the chain on with the notch in what I thought was the right spot and spun the engine by hand several times and it seemed to line up everytime.  Anybody have any ideas?

[TwoTired]

So, I take it the starter spins the motor but it won't catch and run itself?  (Or, maybe the starter isn't engaging?)

When you put the cylinder cover on, did you heed the shop manual warning about keeping the rocker arms on the top of the valve stem rather than hitting the side and bending valves as the cylinder cover is torqued down?

The adjusters usually need to be backed off all the way and then rubber bands used to hold them up during installation.

Have you checked the compression yet?

When you pull the plugs what conditions are on the tips?  Sooty, gas wet, dry?

If you are getting flame, there is likely spark.  Have you dismantled the spark advancer?  If so, maybe it's 180 out when reassembled.  Correct wiring of Blue and Yellow from coils to points?

What condition are the carbs?

[clayherget]

Yes starter spins but won't catch and run itself.
I did put the valve cover on with rubber bands and I gapped them when I put them back on.
I have not checked compression yet but will do that today.
I have not pulled the sparks since trying to start it but will do that today.  I am using the original sparks so they're not really in great shape to begin with.  I may just replace them with brand new but I was with you thinking that there is spark if there is fire.  The sparks did work before I took it apart.
I think by the spark advancer you are talking about the points plate and I did think about that so I may check that today also.
The carbs were cleaned by a professional about two years ago.  When I took them out I did shake all the gas out of them (as opposed to draining them properly) and the gas that was in it was ethanol free. 

Ok some good suggestions here to begin with I'll go through all of these things and we'll see what happens.  Thanks

[bryanj]

If these are the pd carbs the pilot jets and pathways are blocked and i know you said they were cleaed but if sat for a month they clog up

[TwoTired]

The choke knob/cable needs an adjustment in order to make sure the butterflies are closing completely.  Something to check.

The advancer is behind the points plate. It's what the points cam sits upon.  If unchanged from last run, unlikely a problem unless frozen.

Do check compression.  The valves bend easily with side loads.  Might even turn the motor and watch each valve go through its full cycle through the inspection covers.

If the carbs have dried out with gas remaining there could be things blocked by residue.  That's why you check each plug tip for wet immediately after a few revolutions with full choke applied.  Each cylinder has it own carb for fuel delivery.  If pilot jets/adluster tips are blocked, it will never idle, may run with a bunch of choke and throttle midway open as the jet needle and main seldom block.

Oh, and make sure your battery is strong.  Low voltage means low spark.  And the starter motor can drag down the voltage when engaged.

If the points have sat more than 6 months, they may have a film on them stopping current flow.  You have a points dress file/burnisher, right?

Cheers,