Starting / warming up engine trouble-help!

Hello everyone, I'm new to this site/forum and I need some help with my KZ650. Ok so I have a 1978 KZ650 and I have a little problem with it . So when I start the bike I start it on full choke and you know how you're suppose to set the choke down gradually in a few minutes or seconds, well with my bike that damn thing has to warm up for 10, 15 or sometimes 20 minutes. I had a friend clean the carbs and it at least seems to start up better , but it still warms up for a really long time. I have a new battery and plugs in it and they are gapped to the specs in the manual . Any sugestions on what may be causing this?
Thank you.

Its the nature of the beast. They are cold blooded bikes. 10 minutes should get her warmed up. How does she run when warmed up?

She runs fine. Nature of the beast...hmm someone has told me that before , but I had more people say that this is not normal ( I can't say that I know since I'm no mechanic ), but its also a little inconvenient. I'd like to get on the bike and be off in a couple of minutes . Do all KZ650 's do this?

It could be a jetting issue if you have to run on the choke like that. Usually when it starts cold it takes a couple of minutes to get up to operating temp. If you want it to run from the get go with out warming then you need a fuel injected bike

I'll have to look into the jetting issue then and see if it helps. I dont mind waiting a few minutes till it warms up , but I think 15 minutes in summertime weather is way too long 2 min or even 5 minutes I can live with and no I don't want another bike , I like this one )) thanx for your help

you do realise you can drive away on half choke right?? welcome to kzr by the way...steve

Hello, David, and WELCOME to KZR!
We're glad you're here!

As to the lengthy warmup ---

Might experiment by enrichening the carb pilot circuits by using the pilot adjustment screws.

For example, side-located pilot air screws could be turned in 1/4 turn each, test run for effect, and go another 1/4 turn in for an even richer pilot mix test run.

The carb pictured below has a side-located pilot air adjustment screw.

If bottom-located pilot mixture screws, turn out to enrichen.

May also adjust idle thumb screw if necessary to maintain desired idle rpm.

Good Luck!

[Click on image to enhance view]

It would help if you gave a little more info. Is your KZ650 stock or does it have a 4 into 1 pipe or (Lord, we hope not) pods? Ed

Guys I can't thank you enough for all your replies with all the help info.
My KZ650 is as stock as it gets . Nothing has been done to it , except for the paint job ( I had painted it myself a couple of years ago ). I will try to carefully use your all your advice to see if I can solve this problem once and for all, starting with the pilot adjustment screws.
Thanx again.

I suggest you try the following. Get the engine running and idle it down as low as it will idle. Spray carb cleaner around the carb holders, especially where they mate with the cylinder head. If the engine dies or seems to react to the carb cleaner, you need to replace the carb holders. This may seem unrelated to the engine taking so long to warm up, but consider the following. If there are tiny cracks on the mating surface of the carb holders (where they seal against the cylinder head) the engine will tend to run lean at idle because air is being sucked in between the carb and engine. This occurs at idle because with the throttle closed not much air can come through the slides and this creates higher vacuum within the carb holders. Opening the choke enriches the fuel mixture which may compensate for the unwanted additional air. Once the engine gets good and hot (like after your 15 minute wait) it’s possible that the mating surface of the carb holders, which is rubber coated, becomes a bit more pliable and seals better or possibly the heat induced expansion of the cylinder head and carb holders tighten the seal a bit, and at this point you can shut down the choke because the engine doesn't need the enrichment. My ’77 KZ650C1 is totally stock also, and I’ve owned it since new. Over the years, the idle became less than smooth (not horrible, just not very smooth at 1000 and lower RPM) and the bike took forever to warm up. A mechanic did the carb cleaner test (above) and the engine died. The carb holders looked like new on the outside, but when I removed them there were numerous tiny hairline cracks in the mating surface. These could not be seen with the carb holders mounted on the engine. I replaced the carb holders and now the engine idles very smooth at 900 – 1000 RPM. But I noticed I can now shut down the choke MUCH sooner than before replacing the carb holders even though I changed nothing else. It may be just a coincidence, but it’s worth you doing the carb cleaner test. Ed

i know this may not be much more help, but i recently changes my carb holders, and WOW.
my bike went from having to run with the choke partially on full time, to starting w/half choke, imeddiatley shutting down, then riding off on a warm day, choke off within about 30 secs on a cold morning. i would check into that first thing, especially if you think they are original, or over 10-15 years old, even if the carb cleaner has no effect. you will be pleasantly rewarded.

My 77 KZ650 Starts up on full choke and once it starts I have to move choke to half and shes ready to head out. I allways start bike setting on it so its level.Fuel on, full choke ,clutch in, push start button, let out clutch ,choke to middle ,let it idle, fasten hemet, gloves on ,check mirrors, clutch in, down to first gear, clutch out ,throttle on ,brake first stop sign, choke open all the way and veeeerrrrooooooooom About 2 1/2-3 min. Winter takes 5-6 min.