New Set of Carb Boots Failed in 8 Months

When I got my bike ('80 440-A1), the carb boots weren't in great shape and had a hard time sealing against the head, so I bought a fresh set from Z1 in October. Replaced them, got the intakes all sealed up, and (eventually) got the bike running very well.

Fast forward to yesterday. I went to go to work on my bike yesterday morning and it just didn't want to run. Lots of carb puffing, misfires, really uneven, etc. I have a stock airbox/filter, stock exhaust, and stock jetting, so it shouldn't have issues like this (especially since I live in Denver, so if anything I would expect a rich condition, not lean).

I drove instead and when I got home I started working on the bike. Pulled the carbs, cleaned them both out really nice, replaced the fuel line and fuel filter, etc. When I was going to reinstall the carbs, I noticed that the carb boots were split along the bottom, almost halfway up the sides. The split is right along the flange that holds the carb, where the rubber wall is thinnest:



Both boots are split in the same place. I happened to have an older set of boots that I was able to get to seal, and after the cleaning and with the non-cracked boots, the bike was running great this morning, which is what leads me to believe this was the problem.

What would cause the boots to wear out so quickly? They were genuine Kawasaki boots (according to the packaging), so I can't imagine they were just poor quality. Old-stock perhaps? Or did I possibly install them wrong?

What kind of hose clamps did you use on the carb boots?

Perhaps I'm wrong, but I would venture to guess that those "carb boots" (actually carb manifolds) were not Made in Japan.

I was going to guess a missing airbox, aftermarket carb holders, hardtail or a combo of those 3 things.
He said they are new oem carb holders from Z1Enterprises, so I would think they're made in Japan & not old old old.
From his engine tick video the stock carb holder clamps appear to be installed & I guess the airbox is installed as well since the airbox duct clamp springs can be seen. If not a hardtail or missing airbox, the only other thing I can think of is maybe over-tightened clamps?

....

That wasn't my engine tick video. I have fairly standard, but not stock, screw-type carb clamps. They have sleeves between the clamp and the holders. I also have stock (slightly worn-out/dry) airbox boots as well as spring clamps on both of those. And the rear suspension is stock.

Although thinking back, I may have historically overtightened the clamps, thinking that might have been a venue for leakage. I was more than mildly neurotic about the carb holders for a long time. I've since learned not to overtighten them.

I have never seen carb boots splits like this, only hard and brittle.
As martin_csr supposed over-tightened clamps and/or a lot of vibrations can effect this.

Me either, I've run carbs with pods so there is no support the manifolds bear all the weight. Never ever had one rip like that even afer 30+ years. If you are using regular hose clamps you could have created a slit at the edge of the clamp. There are clamps with the edges upturned so they are smooth on the bottom.

The clamps I'm using have sleeves between the clamps and a manfolds, and the edges of the sleeves are upturned. I'll grab a pic when I get home.

Cheap aftermarket get a set of genuine Kawasaki boots I have seen this before with cheap replacement parts.

They were ordered from Z1 and came in a package labelled Genuine Kawasaki.

No eBay APP ID and/or Cert ID defined in Kunena configurationA set of manifolds I purchased a couple years ago have the Kawasaki part number and Made in Japan molded into the rubber edge facing the carbs.
I assumed they were genuine Kawasaki parts, but I think they were just cheaply made aftermarket copies.
I suggest that because the seal to the head would break on each manifold when the carb clamps were snugged up. The rubber was soft; the edges were rough (poorly molded or left untrimmed); and the molded letters and numbers were very distorted and difficult to read.
The new set of manifolds which I recently purchased are all top quality pieces with crisp-straight letters and part numbers, easily distinguished as genuine Kawasaki parts. Each manifold arrived factory- wrapped with a label, and they all sealed perfectly when installed.
I make it a point to buy Genuine Kawasaki replacement parts, with very few exceptions. Scouring ebay for the best prices and quality OEM parts is the only way for me.
Example:

Whelp, don't buy from Z1 then. They sent me junk knock-offs apparently.