VERY SLOW to warm up No idea why???

I have a 79 KZ650. It starts fine with the choke on. However it takes at least 10 mins running with the choke on before its warm. Once its warm it runs like a champ, idles fine, everything great. Just wondering if anyone has the same problem or if this is normal. The bike is bone stock with about 10k miles. Even after riding for hours, it sits for 20 mins and then it takes a while to warm back up. The choke has to stay on for it to idle. Any suggestions???

check your pilot jets, sounds like they could be a little bit plugged. you should be able shut the choke off within seconds of firing up.

Is it true that the 10% ethanol in gas can cause it to run lean?? Would that effect warming up the bike?

Could also experiment with slight enrichment of the carb pilot circuits.

If carbs have side located pilot air screws, turn each screw in clockwise 1/4 turn.

If carbs have bottom located pilot mixture screws, turn each screw out counter-clockwise 1/4 turn.

If performance degrades, return screws to original settings.

Good Luck!

I had similar symptoms when I got my bike. The WG Coil Re-powering Mod eliminated most of this for me.

Best of success.

Plug wires were my problem.

amele7 wrote:

I have a 79 KZ650. It starts fine with the choke on. However it takes at least 10 mins running with the choke on before its warm. Once its warm it runs like a champ, idles fine, everything great. Just wondering if anyone has the same problem or if this is normal. The bike is bone stock with about 10k miles. Even after riding for hours, it sits for 20 mins and then it takes a while to warm back up. The choke has to stay on for it to idle. Any suggestions???

I had that problem with my 750 when it was new because Kawi put 40 pilot jets in the Kali engines and they were WAYYYYY too lean. With 50 pilots, I only have to use the choke for maybe a minute at most and then it runs pretty well.

thanks for the advice. Im gonna start with putting an electronic ignition and have the carbs cleaned out and see what happens

Changed the ignition, coils, wires and runs much stronger and smoother but still having the warm up problem. We figured out that way too much air was getting in through the carbs on the engine side. The black carb holders/gasket must have leaks, dry rotted or not sealed. Too much is getting through them. Has anyone had this problem?? Tried to get new ones from Z1 enterprises but they're out of stock

amele7 wrote:

Changed the ignition, coils, wires and runs much stronger and smoother but still having the warm up problem. We figured out that way too much air was getting in through the carbs on the engine side. The black carb holders/gasket must have leaks, dry rotted or not sealed. Too much is getting through them. Has anyone had this problem?? Tried to get new ones from Z1 enterprises but they're out of stock

Am doubtful that intake air leak is reason for slow warmup because bike is reportedly otherwise performing well and would not do so with such leak.

Thinking either pilot circuit fuel passages and/or pilot jets remains partially ostructed, or needs larger pilot jets, or both, all toward enrichening fuel mixture in the pilot circuit (and presupposing that an attempt has already been made as earlier suggested to enrich by turning in side-located pilot air screws or turning out bottom-located pilot mixture screws -- as that's what these adjustment screws are designed for).

Could also check service fuel level (clear tube method) to assure float levels not being too low and causing a lean condition.

Good Luck!

I am having this same issue. I have a new dyna coil, plug wires, fuel filters, vance and hines exhaust, plugs, .... Mine looks to be running rich and takes forever to warm up. Once running it pops a bit and sounds like it is missing?? It idles and runs great when warmed up under 6000rpm anything above that:dry: it seems to fall on its face. Any suggestions? I am in Nebraska about 1100ft above sea level with a mild climate.

richen up your pilot circuit a size or 2