Topic: Post Top end rebuild

[ChrisG13]

I recently did a top end rebuild on my 1978 honda cb550k four. I am curious as to what I need to do afterwards to ensure it to turn over.

The bike tries but wont turn over, Not too sure if I need to rebuild the carbs as well.

just looking for some insight or if anyone could direct me to another post, that would be great.

Thanks for the help

[70CB750]

Turn it over slowly by hand.  If it does not turn over, chances are there is something wrong with degreeing the cam or timing.  Dont force it, it can lead to bad things.

[strynboen]

think the cam are 180 deg ,,its easy to do it vrong..and then the valvets hit the pistens..on mine  i put the ignision sentifugal regulator one half turn vrong..it dont make harm...just fustrasion...

[ChrisG13]

I took extra time to make sure that the timing was set properly, knowing that being even a little bit off can cause major damage.

The crank rotates and the starter turns over. I think that I am either not getting the proper fuel to the carbs causing it not to fire properly.

I have spoken to my local honda shop, he instructed me to try adjusting the carbs fuel to air ratio. by adjusting the brass screws located at the bottom of the carbs. just  make sure that i adjust them all equally.

[disco]

Like Cal said.....verify that you've got the cam timed properly first.

When you're certain that is OK, I would then spray some starter fluid into the spark plugs. If it will run briefly on that then you've narrowed the problem down to a fuel problem. Similarly, if it won't fire on the starter fluid go & look for spark related issues. 

[strynboen]

have you then thekked that the ignision sentifugal regulator..not are  put a half rotation vrong in..

[Bodi]

Hmm. You took the carbs off a running engine and set them aside. Then you did a head rebuild and remounted the head: it won't start.

A mechanic told you to fix the carbs??? That makes absolutely no sense.

As a rule the problem is what you worked on, not stuff you didn't touch. Make sure the carbs are getting fuel and forget them for now. Disco suggests starter fluid to diagnose fuel/spark - good idea. Resolving a head problem - presumably leaking valves or smoke due to worn guides - doesn't require changing the mixture radically: the carb setup that ran before will run now.

Cam timing may be a problem and I would confirm that first. More than a few teeth wrong, and valves hit pistons - so if it's far from spec you should check that there's no valve damage. This happens on the first turn of the engine and afterwards may not be obvious.

Valvelash adjustment went normally?