Can't install carb boots

I recently found new (old) BS-38s for my KZ750B after fighting with the VM34s for over a year and not getting the bike to run properly. Plug after plug got carbonized, bike was running too rich, tried everything single pilot out there with every float height and setup and nothing did it. My next step was, let's try the original carburetors this bike was designed for. I finally got them and got the new (old) boots as well, but they’re an incredible tight fit. I can only get the carbs half way in, can’t go over the rubber 'ring' that's in the middle that I’m guessing is was fully holds them in place. Is it suppose to be this difficult to get them in ? Also do I use a gasket between the boots and the engine or just screw them in without any gasket?

THANK YOU

The lower one in the picture looks used. If the rubber is hard, there is a good chance they will leak. A picture or two from the side might make it more clear to forum members if the boots are fully seated.
No gasket should be used. If the rubber is hard, they will not seal. Some Three-Bond or Hylomar may help for a while, but they will only work if the rubber is supple.

I've found that a little swirl of Vasoline in the carb holders helps things along.
And if you can get a wooden 2x3 or I think I used a 1 1/2 x 1 1/2 square piece of wood to gently pry on each carb in turn they'll suddenly plop into place.
I'm about to do the same in a couple of days once the weather warms up. I'm not looking forward to it but at least I have new supple carb holders.

Just wipe a bit of oil or grease around the inside and they should pop on.

Make sure the clamps are floppy loose.

Theres a bunch of videos on youtube about softening and restoring rubber parts.

' Wintergreen' is the stuff to use,apparently. Mix with water and boil them. Makes a terrible smell. I wanted to avoid this,so I just wiped them down,sealed them in a bag and put it somewhere safe! That was about 5 years ago. Still haven't found them. I ended up buying new ones for my build.I think they were only about euro10 each on ebay. One day,the originals will turn up. And they better be super soft!!

I haven’t found what works yet but I know by accident what definitely doesn’t. I wanted to clean up some rubber parts. Just knock the funk off. So I dropped them in kerosene with the intention of it only being long enough till I found my degreaser brushes... Well oldtimers kicked in and I lost track and two days later I remembered. I pulled them out and initially thought I has found a hidden secret. They were super soft but then I noticed they were swelled up about 1 1/2 times normal size. I thought cool they just need to dry up. Well about a week later they we hard as a rock and smaller then normal. I guess the kerosene drew out all the oils from them... they quickly when in the garbage.

Kerosene is recommended to clean o ring chains. But then again you don't leave them soaking.

I managed to snap them in place using a little bit of red n tacky but that was with the boots not installed of course, would’ve been impossible if they were mounted on the engine. Getting them screwed to the engine was another challenge. The rubber is definitely rock hard, no way they were made that tight of a fit. Looking for a better solution for boots though if i find one I’ll post.

I have good luck with a blow dryer (or, even better, a heat gun) for all of my hard rubber parts. Might be worth a shot!

Rather than fight the problem and not find a good solution, why not just replace them with new ones? I know new ones are a little expensive on eBay, but it's not like you will need to replace them frequently. Once every 25 years should be about it. Ed