Carb holder gasket/sealant to cylinder head?

This is on my KZ750 but figured I'd ask the group here as well. Putting it back together for the season and have tracked down a leak between the carb holders and cylinder head while tuning. I know it's best to replace but mine are unobtainium part number 16065-1046. Took me a year to find NOS intake ducts but no luck on these whatsoever. Any suggestions on what I can use to seal these up to the cylinder head? I removed them without an issue when I redid the head and they are in good shape but hardened on the head side therefore causing them to leak when installed and torqued dry. I searched but got varying answers on it.

 

Just so I understand, the rubber of the intake boot itself is the only thing that seals it to the head? No o ring or gasket? Or is that gasket the unobtanium that you mention? I think I would use some right stuff gasket maker, or maybe the ultra copper permatex as it has a higher temp rating. Would soaking them in wintergreen oil and rubbing alcohol to soften them help the situation at all?

 

Yup, no gasket. Every KZ I've owned was this way but this is the first one with super hard to find parts. Not sure that soaking would help as they are fairly soft and pliable on the carb end but pretty hard on the head side and has an indent from the port. I'm thinking about trying this as it's high heat and fuel resistant but wanted to see if anyone had any real world experience.

https://www.permatex.com/products/g...uel-resistant-gasket-dressing-flange-sealant/

 

i don't understand, need a picture.
if you need to soften up the rubber, i've had good results with the stuff they sell for cars, rear main seal leaks.
it takes about a week but it works. it took the choke plunger cap from granite back to rubber

 

Would making a gasket to go in there help at all rather than using a sealant? The only benefit to sealant is it will fill in any imperfections better than a gasket. Just throwing ideas out there

 

I'll get a pic. Gasket might be possible but I'm not even sure what I would make one out of for this application.

 

Those carb holders should have a "O" ring that seats in the boot and fits to the head? As mentioned above, we need a pic of this. I have been using the Valco brand black all in one silicone for boot cracks and questionable "O" rings. Seems to be working great so far. Keeps its pliability when it dries.

 

Back of holder. Looks like there may have been a slightly raised area at one point but hard to tell:



Port on cylinder head:



Carb side. As you can see it's still pretty flexible and in good shape. Hoping a smear of fuel resistant sealant will do the trick to reuse these:

 

You can make a gasket out of gasket material or a cerial box.
In either case I like to use permatex 80697 copper gasket spray to dress the gasket for a better seal, and it won't look messy.

 

that sure looks like a o-ring groove to me

 

Nah, they are flat when new with a raised lip around the inside opening where it sits on the cylinder head port to seal. You can kind of see the raised part still on the holder along with the impression from the cylinder head.

Cereal box hold up to the heat? I have three kids so that material is pretty common at my house

 

Thanks for the pic, really helps out. Those do seem to be well worn and the ridge is not raised as it should be. I would add some type of gasket silicon on each of those. Up to you if you put the silicon on and then put them on wet or let it dry.

 

Yep. Cardboard won't catch fire until just shy of 500ºF, so you're good with using it as a gasket material (except on the exhaust).
I've used it on chainsaws and the intake of my old garden tractor.

 

I was able to clean up the backsides well with a soft brass brush and wiped down with a rag sprayed with carb cleaner. Looks I'm not the first one to try and seal these up as there was some other sealant on there. I got some of the Permatex Permashield as it's comparable to Hylomar and I had a 25% off coupon. Big difference in my carbtune readings and I can actually see the carbs "dancing" a little when I start the bike, the vacuum created in the holder causes it to suck the carb in towards the motor.