1977 KZ650 Cold Start Issues

I just picked up a 1977 KZ650 and it is hard to start when cold. Once the bike is warmed up it runs fine. Just hard to get started when cold.

I am going to do a carb clean as sink, new plugs and check the points. The only this is that it runs good once its warmed.

Any ideas?

Still have ignition points? If so, gap and set them to the specs. New sparkplugs of a slightly hotter range may help along with new sparkplug caps(they have a resistor to limit the RFI of ignition systems) and may be wearing out.

If it were me, I'd be pricing ignition coils too as even when new,the spark was marginal. Dyna makes a good replacement coil, so does Accel. Z1 enterprises sells replacement sparkplugs,caps,sparkplug wires and ignition coils.

I'll "pull a Patton" here and suggest the first thing in the service manual - check the valve lash/gaps, as this is SUPER important and should deffinately be done first to avoid chasing problems all over. + the whole rest of the maintenence chapter. :laugh:

I you do change to a hotter plug, don't ride it super hard in cold weather, you can hole a piston - seen it done!

I agree with the suggestions others have posted, but I would add to make sure when you clean the carbs that the choke / enricher circuts are clean and that the plunger is working correctly.

And of course in case you don't know..... DO NOT touch the throttle while trying to start! Otherwise the choke system will not work properly.

Also KZ650s are always a pain to start cold. All the miles I've done on KZ650s since new they were all hard to start cold, particularly after sitting for more than one day. I don't think the enrichener circuit in combination with the small bore pulls in enough mixture when cold. At least this is my theory. All KZ1000s no problem starting cold, all KZ650s pain in the ass. I ride all winter and have since 1978 on KZ650s and they are hard to start cold, every one of them. Thank the lord for a kick starter and a leg that works, it's needed all winter.

RonKZ650 wrote:

Also KZ650s are always a pain to start cold. All the miles I've done on KZ650s since new they were all hard to start cold, particularly after sitting for more than one day. I don't think the enrichener circuit in combination with the small bore pulls in enough mixture when cold. At least this is my theory. All KZ1000s no problem starting cold, all KZ650s pain in the ass. I ride all winter and have since 1978 on KZ650s and they are hard to start cold, every one of them. Thank the lord for a kick starter and a leg that works, it's needed all winter.

+1 - seems to be a 650 thing. my 78 is just cold blooded in stock form

TeK9iNe wrote

"pull a Patton

"

I love that phrase. Good one.

If enough use it we might see it in the Oxford English Dictionary some day

I have a similar problem with the 1980 750 but the choke seems to actually make it bog down worse. It sounds like it(and eventually does) has no battery but I haven't been riding long enough to know if that's what it would sound like starting cold.

Haven't had a whole lot of time to go through it and work on stuff... my boring indoor job is keeping me away from the old girl