TOPIC:

My current stock carbs on my 1980 KZ440LTD have a tear in one of the diaphragms and ive been having trouble below 3000RPM. Carb kits for the keihnins are crazy expensive for 40 year old parts and I've read about the converison to mikuni slide carbs.

I found a kit for a pair of Mikuni VM30s with a throttle cable and wanted to know if anyone has tried a kit like this and how plug and play it really is. Here is the link: www.speedmotoco.com/kz400-kz440-vm30-mik...z400.30.mikuniop.htm

My initial thoughts are:

• How do you run the fuel lines without a main header like the stock carbs have?
• Will the stock mounting plate work with the mikunis or will the just hang from the intake boots separately?
• Will there be an issue chokign on startup if the choke levers are not connected?
• Will the throttle cable work with the stock throttle?
• Will there be a noticeable hit to MPGs?

The Mikunis seem like a comparably priced way to fix to fix the carbs and upgrade to carbs that are easier to find parts for. Any help is greatly appreciated!

Thank you!

I installed a couple of Chinese replica VM30's on a Kz400 in summer 2019. This thread has some of the details:
www.kzrider.com/forum/11-projects/611489...ling-kz400-s?start=0

We only had time to just start on the jetting, but were able to ride it around on a few short rides and it was a blast.

I'm not sure how much of it will pertain to your Kz440. The intake manifolds are probably a different size than we had.

The fuel line can just be split with a y-pipe or use a filter with dual output.
The VM30's mount without a plate.
I had no problem starting just using the choke on the left carb.
If it was much colder out, then maybe I would play with using the choke on both carbs, but it is a bit of a juggle.
We could not use the stock throttle cable.
We used a Honda CB200 cable that we had to modify to get more travel. It was cheap but not very well made.
That was a bit tedious to modify without harming the inner cable.
You could probably get a custom cable made by Motion Pro, which is what we may do in the future.
We haven't ridden enough to notice a MPG difference. It will depend on how we jet it (needle position, pilots, main).

One nice thing I noticed is that the throttle response is a little more consistent over the stock piston-CV setup (but yours came with diaphragms).

The bolt pattern for the carb boots is the same on both the early KZ400
and late KZ400/KZ440 heads. They are just clocked different so the same
Mikuni boot will work on both.

Nebr_Rex wrote: The bolt pattern for the carb boots is the same on both the early KZ400
and late KZ400/KZ440 heads. They are just clocked different so the same
Mikuni boot will work on both.

Ah, thanks. I wasn't sure if the 440 was the same.
We actually used the boots from the piston-slide Keihin carbs, but it's not a perfect fit. The boots only grab a small area on the carb outlet. It works, but we'll probably look for different carb holders (aka boots, aka manifolds).

Did you have any issues with the petcock on the new carbs? I've read that I will need to run it in Prime to get fuel to gravity drain.

The Kz400's that I worked on have standard off-on-reserve petcocks, so I just used them normally. I don't see any reason why the VM30 would act any different than the stock carbs regarding the petcock.

If yours is a vacuum petcock, then it has "prime" instead of off. You will need to prime the carbs with fuel in order to fill them for the first time, or if you are setting fuel levels. Normally, the bowls stay filled for a few days, so they don't normally need to be primed if you ride the bike every day.