Topic: Carb insulator options

[rhinoracer]

Mine are hardened and it was a pain to take the carbs off, I guess it'll be even harder to put back on since there's no place to hook the breaker bar.

I don't want to spend about a hundred bucks for new insulators and air box tubes, so are there any options?

I know you can't bring rubber back to life, but are there any mods or tricks to make them fit better without them losing any sealing?

[MRieck]

Mine are hardened and it was a pain to take the carbs off, I guess it'll be even harder to put back on since there's no place to hook the breaker bar.

I don't want to spend about a hundred bucks for new insulators and air box tubes, so are there any options?

I know you can't bring rubber back to life

You have answered your own question. Old stuff, especially that which has seen a billion heat cycles, is worn out. Nothing lasts forever. Unless you want to chase vacuum leaks etc for eternity....instead of riding....get new boots. They are not that much.

[754]

This may or may not apply.

When those materials age they sometimes oxidize.. like a tire that may spin easy after sitting. One trick I learned is some car guys restore their rubber door mouldings by putting them in a hot tank at an engine shop.  Might be worth a try, it may get the oxidized layer off..

[MRieck]

This may or may not apply.

When those materials age they sometimes oxidize.. like a tire that may spin easy after sitting. One trick I learned is some car guys restore their rubber door mouldings by putting them in a hot tank at an engine shop.  Might be worth a try, it may get the oxidized layer off..

No it isn't. Hot tanks DO NOT EXIST ANYMORE It costs more to get rid of that solvent then to use the equipment ( about $1,000.00 per gallon.....at least). Step into the 80's..and I am not attempting to be condescending..that crap is banned in all enlightened contries. Wash tanks using hot H2O and detergent is the norm. Pony up and get new boots. Chasing never ending vacuum leaks for 10 years......sounds like constructive use of time to me.

[BobbyR]

The rubber was compounded with plasticizers to make it supple. These chemicals  leave the rubber through age and heat along with other factors. Once they are gone, they are gone, you cannot put them back in. You can heat the rubber  10 different ways and it will get softer for a few minutes and it will harden again. As mike said you will get air leaks. If you are tight on cash just replace the airbox to carb set first. In my industry rubber air springs and bushings have a maximum lifespan of 7 years. You will hear about ATF soaks. I have some I found that have been soaking for a year, still hard. New rubber boots actually pulse with the engine like little hearts.   

[MRieck]

The rubber was compounded with plasticizers to make it supple. These chemical's leave the rubber through age and heat along with other factors. Once they are gone, they are gone, you cannot put them back in. You can heat the rubber 10 different ways and it will get softer for a few minutes and it will harden again. As mike said you will get air leaks. If you are tight on cash just replace the airbox to carb set first. In my industry rubber air springs and bushings have a maximum lifespan of 7 years. You will hear about ATF soaks. I have some I found that have been soaking for a year, still hard. New rubber boots actually pulse with the engine like little hearts.   

Bobby....you deal with big......real big air but your words ring true no matter what.

[MRieck]

The rubber was compounded with plasticizers to make it supple. These chemicals  leave the rubber through age and heat along with other factors. Once they are gone, they are gone, you cannot put them back in. You can heat the rubber  10 different ways and it will get softer for a few minutes and it will harden again. As mike said you will get air leaks. If you are tight on cash just replace the airbox to carb set first. In my industry rubber air springs and bushings have a maximum lifespan of 7 years. You will hear about ATF soaks. I have some I found that have been soaking for a year, still hard. New rubber boots actually pulse with the engine like little hearts.   

Bobby....Like I was told a long time ago...old shi. is old shi.

[rhinoracer]

I still think there is/should be a better way to mount those carbs without having to rely on prybars every time you want to take them off or put back on.

Or are new boots so soft they go on like butter?

[MRieck]

I still think there is/should be a better way to mount those carbs without having to rely on prybars every time you want to take them off or put back on.

Or are new boots so soft they go on like butter?

Yes!! They are. You don't know how graet they are until you try them. You will say....damn....that was easy.

[rhinoracer]

I guess I'll give them a try then. Do aftermarket ones (i.e. cheaper) work the same as Hondas?

[Deltarider]

It's clear that insulators between carbs and head should be airtight. How about the insulators between carbs and airfilterbox. Does a hardly visible crack there really affect carburation?

[Raul CB750K1]

Time is money too. The time that it takes to install the boots is worth for me more than the new boots -I recall they costed me about 60 bucks or so-. I doubt there are aftermarket boots either. Aftermarket companies normally specialize in "consumables", you know, brake pads, cables, filters etc.

If you install the engine sides first, you will have four mouths for the carbs. Dont' tighten anything. Squirt a little WD40 in the carb throats and in the rubber boots, twist the boots until they are aligned, with the bike on the centerstand -it helps if you tie a strap from the centerstand to the front wheel-. Put the carbs facing the boots, tilt the carbs slightly downwards, and once the four mouths start to enter the boots, make a big press with the carb setup. Once all four mouths are in it is a matter of evenly pressing them. Don't tighten anything. Do the same with the airbox-to-carb, bolt the airbox in place, and once everything is in place start to tighten the clamps.

[754]

 
Wow Nice responses on here!!..

 re the isulators.. I have maybe 3 or more sets that have not seen sunlight or an engine in 20 years or more, I am wondering if they might be allright. I will check them out soon., not that I really have a need to use them..

I dont think that I  have used them  or stock carbs since the early eighties..

[754]

Well I asked that guy today if he did indeed put the rubber parts in a hot tank, he said yes. I asked if he still used the hot tank he said yes.
 I then told him that someone had posted that  you are not allowed to use them and disposal costs are huge... he laughed and said "Is the guy from California?"

Apparently he said they had banned them there quite a while back, one of the first places. But here they are still in use. I asked him about disposal and he said they are paying  abut 1% of what was mentioned on here.. actually it was less than that even.

Interesting, I forgot to ask him about if he figured it would work on the intake rubbers after talking about the other.

So I guess its a matter of where you live.. I seriouslly doubt that  we are an unenlightened contrie ( spelling is copied verbatim from a previous poster)

[MRieck]

Well I asked that guy today if he did indeed put the rubber parts in a hot tank, he said yes. I asked if he still used the hot tank he said yes.
 I then told him that someone had posted that  you are not allowed to use them and disposal costs are huge... he laughed and said "Is the guy from California?"

Apparently he said they had banned them there quite a while back, one of the first places. But here they are still in use. I asked him about disposal and he said they are paying  abut 1% of what was mentioned on here.. actually it was less than that even.

Interesting, I forgot to ask him about if he figured it would work on the intake rubbers after talking about the other.

So I guess its a matter of where you live.. I seriouslly doubt that  we are an unenlightened contrie ( spelling is copied verbatim from a previous poster)

Right...I live in Massachusetts.  In Canada anything is possible though it takes 14 months to get bypass or hip replacement surgery. Hey....that process is illegal all over the USA pretty much....at least on the books. If you are living a Jack London novel out in the Yukon you can do anything you want I guess.

[Jerry Rxman Griffin aka MuthaF'er]

$65.80 for a new set of insulators on their way from Service Honda. After 32 years I finally broke down. You'd think I work for them as much as I mention their name  . I'm just one of their biggest fans.

[754]

Re last page..

 Oh YEAH!! Well I bet my sled dogs can beat your sled dogs..in the 1/4 mile!!!                    

 And I think everyone should get to run their CB 750  at over the ton on the ice ... .. at least once!!



  actually dozens of times was even more fun...

[rhinoracer]

 And I think everyone should get to run their CB 750  at over the ton on the ice ... .. at least once!!

  actually dozens of times was even more fun...

Mine can hit the ton on ice laid on it's side 

They're breaking me down too. $65 bucks isn't much if that's all you need to get your bike running, but what most don't get is that I'm rebuilding the bike almost from scratch. Engine internals, engine cases, wheel hubs, spokes, rims, tires, gas tank, and on and on. So any part I can reuse is cash saved for other parts that it needs, like a seat, battery, gauges, turnsignals, etc.

So if there's something I can try for less than the cost of OEM I'm willing to give it a try.

[jonbuoy]

I wondered about using neoprene hose fittings, its a quite a sharp angle to the carbs so I think it has to be molded to fit.

[MRieck]

Re last page..

 Oh YEAH!! Well I bet my sled dogs can beat your sled dogs..in the 1/4 mile!!!                    

 

Well...you got me there. Hillclimbing is the closest I've come to ice racing using a CB engine.

[azuredesign]

In Canada anything is possible though it takes 14 months to get bypass or hip replacement surgery. Hey....that process is illegal all over the USA pretty much....at least on the books. If you are living a Jack London novel out in the Yukon you can do anything you want I guess.

Hey Man,
I grew up in Canada, and the Jack London quote is priceless. Not too many things I read crack me up before 8am.

Without being elitist, fixing up a bike, or just keeping an old bike running can be an expensive proposition, especially when it's really a conveyance for recreational purposes. I know an expense for one guy is not the same for somebody else. However, I think all of us want a bike that runs well and strong.
If you can get the old boots on, and you're happy with the way she runs, all great and good. But if your bike is surging or running lean on some plugs, and generally pissing you off, $65. and an hour of time
is a really good investment.
Just my Canadian $.002

[nteek754]

Hey all . just a heads up  I for the past 20 years or so    put the boots on the carbs leaving the clamps loose put them in front of my space heater Ive only melted one set  JUST KIDDING for a few minutes then walk over to bike and boom they slide right on. I use pod filters so I dont have the issue with the stock airbox good luck have fun Craig in Maine

[andy750]

I bought new rubbers for engine-carbs and carb-airbox and believe me everything slips right on and off so easily its worth the $65. It takes 10 mins from start to finish to get on, clamp down, airbox back on and ride away. Try that with your "re-conditioned" boots 

Some corners you can cut but I wouldnt cut this one.
cheers
Andy

[BobbyR]

 And I think everyone should get to run their CB 750  at over the ton on the ice ... .. at least once!!

  actually dozens of times was even more fun...

Mine can hit the ton on ice laid on it's side 

They're breaking me down too. $65 bucks isn't much if that's all you need to get your bike running, but what most don't get is that I'm rebuilding the bike almost from scratch. Engine internals, engine cases, wheel hubs, spokes, rims, tires, gas tank, and on and on. So any part I can reuse is cash saved for other parts that it needs, like a seat, battery, gauges, turnsignals, etc.

So if there's something I can try for less than the cost of OEM I'm willing to give it a try.

OK, I see your point in a pinch you can probably rig your old boots to seal. You can heat them to get them on then use some hi temp sealant if they leak. When you get a few bucks you can replace them with new. The advice you get on this forum will always strive to give you the correct answer. How much money you have in your pocket is only known to you.

[obnoxshuz]

I have been wrestling with my carb boots too and found that boiling them in a pot softens them up and makes installation easier....But, I can't wait to replace them. I've seen aftermarket ones on ebay but are not for my 78 750K...

http://cgi.ebay.com/ebaymotors/NEW-HONDA-CB750-CB900-INSULATOR-CARBURETOR-INTAKE-BOOT_W0QQitemZ280168116265QQihZ018QQcategoryZ35597QQssPageNameZWDVWQQrdZ1QQcmdZViewItem