Hard Cold Srart

My 79 KZ400 LTD is notoriously hard to start when cold. Once it warms up it lights off instantly. I’ve read here that there is a mixture adjustment, which was pre-set lean from the factory so that emissions would meet US standards. According to the posting there is a cap over the mixture screw, which can be removed to allow access to screw. Once adjustments are made to slightly richen the mixture it suppose to cure the cold start problem.

Is this the definitive cure for cold starts all other things being equal? My valves are properly adjusted, carbs clean, good spark, hot battery, etc. Any advice would be appreciated.

I don't mean to make light of your pain, but there is no cure.

All my bikes are "cold-blooded", too, and I think most people here would corroborate that about their bikes. It's a common frustration... :S

NO CURE?? In this age of enlightenment? We can put a man on the moon and there's no cure for hard cold starts? Surly you jest.....

Anyone else? Please? Someone?

My "cold" starts might not equate to your "cold" starts as I'm in North Central Texas, but I have ridden to work several days where it was in the low to mid 20's this winter and my bike always starts on the first touch of the starter, especially when it's cold.

If the carbs are sync'd and the pilot and idle are adjusted correctly, at least on my bikes, they went from hard to start to amazingly easy to start after syncing and adjusting air mixture and idle. I've only owned two bikes so my experience is limited, but it was night and day with my two bikes, both of them 4 carb bikes.

Please list your bike year and model, and your location in your signature.

Post edited by: fergyfer, at: 2006/03/17 10:26

I would definatley have to agree that it is the settings, I live in New England and te settings do make all the difference. I run different setup for when it is 10 degrees out then when it is 60. So I would think that syncing the carbs and having the settings for your weather/altitude would make a tremendous difference in the way your bike starts up.

Doug, while you have a 4 cylinder, these twin carbs work very similar to yours. You can ease starting woes a tad IF you can find some larger pilot jets... they are hard to find... none are available in the aftermarket. The other thing that would help is to richen your idle mixture some by turning out your pilot fuel mixture screw. It is located on the engine side top/center. There is a cap covering it from the factory. These screws may have been set a bit lean but I can never see much rhyme or reason to their settings if I am the first to uncap them after many years of metering fuel. On most models, they can have one screw all the way shut and the other 4 turns out... If you DO decide to mess with these screws, I would buy new ones via some rebuild kits (that is about the only thing in a KZ440 rebuild kit other than a float needle and bowl oring. Take care to replace the little rubber washer under the needle. When you remove the needle, you will need to get out the small metal washer and old oring from beneath. The 440s idle really is poor without a good seal for the mixture screw and a new oring is the key. The other thing you can do is make sure that gas flows through the small hole in your float bowl where it goes through an internal check valve and through a hole in the bowls upper edge (I think... but it does have a hole in the bowl's bottom which is not the drain). This is where gas for the choke is picked up... in fact, a brass tube on the bottom of the carb sits in this hole. Make sure that the little hole in this tube is clear as well.

Please forgive. I here am new. To your world, welcome. I’ve added my location and type of ride to my signature.

Great information WiredG. It sounds like you are referring to the same type of tuning process I mentioned at the beginning of the thread. You directed your comments to Doug concerning his 440 but I gather it applies to my 400? So there IS a plug on the carbs that hides the mixture screws, and they DO need to be tweaked more to the rich side? Cool.

Also, do you have any idea if new screws come in an OEM carb kit for a 400, and will I still need to increase the size of the pilot if I adjust the mixture as you recommend?

He referred to my comment about having 4 carbs (KZ1000P) and syncing and adjusting working similar to your 2 carbs (KZ440), so his suggestions were directed to you. WG is definitely the carb expert on this forum, and his is always a voice you want to learn from!

Good luck!

Thanks Doug. WiredG does seem like a very knowledgeable individule and I appreciate his, and everyone's input.

I have a few more questions and I'm sure I will have more as I attack the cold start problem.

Balancing carbs sounds like an important part of the cold start equation and the only experience I have balancing carbs was with Corvairs. That was a pain in the #$%^. I think I know where I can borrow a manometer. Where on these diaphram carbs do you connect the vacume lines, and is there a satisfactory way to balance them without a meter?

Thanks again for everyone's input.

Hopefully WiredGeorge or someone else with experience with these carbs will be able to tell you where the vacuum ports are. My BS34's have vacuum ports on each intake manifold that are all capped except when the carbs are being balanced. I have a non-vacuum operated petcock so my #2 carb's vacuum is capped as well, and I removed the smog/vacuum stuff and capped it off.

Something I'd suggest would be to pick up a clymer or KAW service manual. They are lots of help.

Ridge Runner wrote:

...Balancing carbs sounds like an important part of the cold start equation and the only experience I have balancing carbs was with Corvairs. That was a pain in the #$%^. I think I know where I can borrow a manometer. Where on these diaphram carbs do you connect the vacume lines, and is there a satisfactory way to balance them without a meter? ....

Looks like your definition and my definition of "cold start" is different. I just meant I have to leave the choke on for a few minutes of riding. Maybe have to kick it 2 times (no elec. start on mine).

Anyway, there should be a little hose that connects the two rubber intake manifolds at the bottom. You disconnect the rubber hose, connect the manometer hoses, and you're off to the races.

As for balancing them without a manometer; the manuals all seem to suggest that you can do it by feel. BWAH! Maybe you can, I couldn't. I got a Morgan Carbtune because I don't like mercury, but there are tips here on the site to make one for soooper cheap.

Good luck...

You are correct Sir. Our definitions of “cold start” do appear to be different. When I first try to start the bike in the mornings it may take 30 or 40 seconds of cranking for the motor to even hit. That sequence may happen several times. As the cylinders get warm from shear friction it will finally light off and cough and sputter for 10 or 15 seconds. After that it slowly starts to smooth out and about then is when I flip choke lever off. A minute or two later and away we go.

It’s much worse when it’s really cold. “Really cold” in Arkansas means 50 degrees or colder and I have found that the problem is greatly diminished if I spray a quick squirt or two of carb cleaner into each cylinder through the spark plug holes. After initial start up, no worries. She runs strong throughout the acceleration band and will start almost instantly for the rest of the day.

I’ve been told proper valve adjustment is crucial but then everything works with everything else. All systems need to be properly adjusted and functioning including having a hot battery. I believe I have covered those bases and still it is really hard to start when cold.

I am looking forward to adjusting the mixture this weekend as described by WiredGeorge under those hidden screws. I’m going to tinker with the balancing too. I’ll let everyone know how it goes.