Help No Spark below say 50 degrees!

[chomer]

Use my 1977 620 to go to work but past few months its been below 50 degrees in AZ! I get no spark so no start.

When I get home from work it will start right up. I've replaced the battery, Alternator, Voltage Reg, Ignition mod, (its a 1979 dizzy)

Igniton switch, some wiring, resistor, coil, cap, rotor, battery cables and even new tires!

What can affected by temperature like this. At wits end....

[DISLEXICDIME]

Choke.

[datzenmike]

How are you testing for spark? Or is it just not starting? As DYSLECTIC says. Temps drop you need a functioning choke.

 

When the motor is dead cold take the top off the air filter and then pump the cas. The choke plate should snak closed on top of carb if working correctly.

[banzai510(hainz)]

how about when cold take the center coil wire and put to chassis and hit the start key. or your friend if you got one hit the key.

See if the coil wire sparks. if not ir very very weak you might have a HOT START wire proplem or coil to much resisitance or soemthing of that nature.

I would ck the connections at the coil.

I seen a previos owner hoot up the Hot start wire on the wrong side of the ballast resisitor and it wasnt getting the FULL voltage. IN START

 

also I had this before and it was a loose intake manifold. start when warm engine fine

Cold it would be hard to start. so ck the carb bolts and intake bolts if loose.

 

 

I wouls also do a valve lash ck. as your valve might be starteing to getting on the tight side

 

put a timming light on this also.

Maybe do this 1st once you get it running and see where your starting from

[chomer]

Did spark check at lead wire and plugs. Also by passed the solenoids on carb thinking they are tied in somehow. My wife made me put a blanket on it last night to keep it warm! Got down to 39 degrees ....didn't help this morning.

[slayer510]

My 510 has over the last 2 weeks gotten harder and harder to start especially cold starts in the morning'any how yesterday it finnaly became a no start. I was thinking a carb issue(mikuni's no choke)but it been starting before no prob so I strted with ignition using an inline spark checker at the plugs,no spark'then at the coil'no spark. I then grabed my powerprobe III(every one shojld have one) to verify 12v and ground at the coil,its ok.next while engine is cranking watch for the ground at coil to pulse'if pulse is present the distibutor and ign module are working and leaves you with a bad coil witch is what I had. Replaced coil and problem cured. Hope this helps.