takes thirty minutes to start my bike

[McJuggernaut]

[McJuggernaut]

Hi, I am new to this forum.  It's helped a lot already though.  Any how i bought a 1978 cb750k about a month ago. It was in running condition when i bought it.  Had to do some work like change a few seals and replace some cables.  It runs like a champ when it warms up but takes FOREVER to start.  I was wondering if this is just what old engines do or if i have a problem.  Any feedback would be much appreciated

[LukeM]

You would need to determine why it's not starting: no spark, no fuel, no air, no compression. Since it well stay and run eventually, we can rule out the compression issue. That can be tested with a compression gauge if it is a suspect. Checking three air path involves air filter and air cleaner housing and carb boots. Again, since it eventually runs, about all that could be bad here is a dirty air filter. So that leaves bad ignition or bad carb/fuel system.
Check for spark by pulling one plug from the cylinder head, reconnecting the lead  and pressing the hex party of the plug to the posited of the cylinder head. Crank the engine, and seed if there is a good spark. It should need the same for all for plus. Based on what you report, chances are the ignition system is ok. It's possible there's an issue with a coil when it's cold, but the coils for these bikes are usually pretty good.
That leaves fuel. Problems here include a choke adjustment issue, excess vacuum in the tank, petcock filter clogging, cracked fuel links, leaking carb bowls, dirt in the fuel system, or misadjusted carb floats. Check fuel flow by closing the petcock, pulling the fuel line leading to the carbs, and checking the fuel flow into a gas can or boyle. If fuel comes put smoothly and consistently, the tank/vacuum/petcock portion are probably good. If not, check for a dirty filter in the petcock, or a clogged vent for the tank. Another check its to turn the petcock to the ON setting, wait a few minutes, then open the bowl  drain for each carb. If nothing comes out, there's an issue with the float our the fuel line for that carb. Some would suggest using a bit of starting fluid to see if it lights off sooner, but I've read warnings about using it.

I would check your choke setting first, then look at the fuel delivery system.

Sorry if it's a bit long winded, but maybe this will help the next guy. Hope this helps.
L ukeM

[McJuggernaut]

thanks for the tips.  Have checked my fuel delivery system and it seems to be working fine, no clogs and has good flow.  will check my choke and plugs when i get a chance.

[TOOLS1]

These old Honda's are known, for hard starting when cold, but 30 minutes is a bit excessive. The ignition systems on these bikes are not very powerful, so it does not take much, for them to not fire properly. Check your points, and condenser. Also set your timing (a lot of people suggest advancing it about 2 degrees). Also I myself, and several others have had a noticeable improvement using iridium spark plugs.
TOOLS