1978 kz1000a renew and revenge project

bry195 wrote:

Hi all — first off, thanks for the help and the knowledge here. I’m grateful for the experience this forum brings.I’ve tuned a lot of carbs (and done plenty of EFI builds), so I’m not expecting carburetors to behave like EFI. I’m using a single wideband to guide changes with a simple goal: a bike that starts, runs, and travels reliably. Power and efficiency are secondary. Ive tuned inline 4 motorcycle engines with carbs and oxygen sensors many times over a 15 year period. It wont be like efi but it will be as good as anything else. The point isnt to pursue perfection. The point is to run in it in the cold/warm/altiitude/fuel grades and find the best compromise or middle ground. But most of all I will be making changes based on the experiences ive already had and combining them with specifics I learn from you on the kz1000.

On jets: my mains are close to what’s been suggested. I’m currently experimenting with non-Mikuni jets. I don’t recommend that route for most people, and I only went there because I’m comfortable measuring/machining and accepting the risk. For anyone not wanting that risk, please follow the standard recommendations from the folks here.

On the choke plunger: I really appreciate the documented fix — totally agree it’s a common, under-diagnosed issue. Regarding “rubber rejuvenator,” I want to be clear: I’m not proposing it as a general solution. I’ve experimented with removing oxidized outer layers and re-plasticizing rubber (background in race-tire prep), and I’ve seen temporary improvements that are impressive (from full loose to full push). Longevity is unknown and likely limited; I’m treating it as an experiment on my own bike, not advice. For what it’s worth, I verified every circuit, including the choke, with a leak-down test before and after. 

Big picture: I’m not trying to upend KZ best practices. I respect the established guidance here and wouldn’t tell others to do what I’m doing. Some of us enjoy pushing the edges and owning the consequences — that’s on me, not the forum. If my path earns an “I told you so,” that’s fair.Thanks again for the continued guidance.

By the way, has anyone used the BS series carbs? inexpensive, for oil cooled, and one of the best carbs ever.

bry195 wrote:

Those BS carbs were really good in the transitions from mid to wot. Really good at elevation too.


He has a stock 76 kz900 with 4/1 and pods. still running points and has 120 main jets. plus the last time he actually did more than start it was 10 years ago. I dont think it will be too much of a problem. My bike is the same except it’s a 1000, carbs will be dialed in (air correction jets too) and electronic ignition with hot coils. All new tires and bearings . 

Is the 1000 faster than the 900 in a quarter mile?

 

• 1976 KZ900 (903 cc): ~12.2–12.4 sec @ ~110–112 mph ¼-mile; top speed ~130–132 mph.
• 1978 KZ1000A (1015 cc): ~11.7–12.0 sec @ ~114–117 mph ¼-mile; top speed ~133–136 mph.