Author Topic: Softening hard carb boots (Read 18487 times)

grumburg · « **on:** April 08, 2009, 08:03:43 AM »

After removing the carbs on my 750 Hondamatic, found the rock hard boots are unavailable. Wrapped them in a wet towel and put them in the microwave for 2 minutes (or until steaming hot). Kept them in the towel until ready to slip them on. Slipped them on the head and carbs snapped right on.

BobbyR · « **Reply #1 on:** April 12, 2009, 10:50:02 AM »

That is one of the 100 ways people have used to soften old rubber. It is at best a short term fix and when you are finished you will have hard boots which are not very good for sealing. I have a set that has been soaking in ATF for two years and you can crack walnuts with them. OEM new boots are still available. That may be a good long term investment.

grumburg · « **Reply #2 on:** April 12, 2009, 05:34:55 PM »

Any help in findng 77 750 Automatic carb boots would br appreciated. Have been looking for 2 months with no luck. $:-\$

BobbyR · « **Reply #3 on:** April 12, 2009, 06:01:30 PM »

Where have you been looking, should be the same as a K model

Spanner 1 · « **Reply #4 on:** April 12, 2009, 10:25:42 PM »

Bobby the 750A carb boors are 24mm, the K bikes are 28mm..i.e. the A has smaller carbs...

grumburg · « **Reply #5 on:** April 13, 2009, 10:29:51 AM »

Not only are they smaller, but #1 and #4 cylinders are curved since carb bank is smaller. Also, 77-78 are not interchangable with '76. Part numbers for 77-78 (#1-#4) are 16211-393-020, 16212, 16213, and 16214.

BobbyR · « **Reply #6 on:** April 14, 2009, 04:39:28 PM »

I am sorry I did not realize they are that different. I guess you have to do what you have to do.

Steve F · « **Reply #7 on:** April 15, 2009, 08:37:43 AM »

A while back, someone posted about this using some home made concoction that included "mint oil" or something like that. I tried to search for it last night and came up empty. Who posted this?

BobbyR · « **Reply #8 on:** April 15, 2009, 09:36:10 AM »

That is Oil of Wintergreen they are talking about. The two problems with old boots is installing them and creating a seal. If new ones are not available, you have to do what you gotta do.

goon 1492 · « **Reply #9 on:** April 15, 2009, 11:33:21 AM »

Man bobby I was thinkin' about if an atf bath would do any good, guess not. $:-\$

mystic_1 · « **Reply #10 on:** April 15, 2009, 11:41:22 AM »

I can confirm that Wintergreen oil does the trick. I have some pics and data from when I did some last summer, I'll try to dig it out.

The only side effects are that the boots will continue to smell strongly of wintergreen for a long time afterwards. I have my intake boots sealed in a ziplock to keep them from stinking up the garage, and I can smell the wintergreen right through the plastic.

mystic_1

Steve F · « **Reply #11 on:** April 15, 2009, 11:54:20 AM »

Quote from: mystic_1 on April 15, 2009, 11:41:22 AM

The only side effects are that the boots will continue to smell strongly of wintergreen for a long time afterwards. I have my intake boots sealed in a ziplock to keep them from stinking up the garage, and I can smell the wintergreen right through the plastic.

mystic_1

Now you can say your bike is "mint".

goon 1492 · « **Reply #12 on:** April 16, 2009, 11:17:45 AM »

Where would one find this oil at? I feel silly asking this becasue I have probably seen it in the store already and wondered " what the heck is that for?"

BobbyR · « **Reply #13 on:** April 16, 2009, 11:30:29 AM »

You can get it at a real Drugstore. Remember all of this is very temporary.

Gordon · « **Reply #14 on:** April 16, 2009, 12:03:39 PM »

Quote from: BobbyR on April 16, 2009, 11:30:29 AM

Remember all of this is very temporary.

How existential of you... $:-\$

BobbyR · « **Reply #15 on:** April 16, 2009, 03:01:24 PM »

Quote from: Gordon on April 16, 2009, 12:03:39 PM

Quote from: BobbyR on April 16, 2009, 11:30:29 AM
Remember all of this is very temporary.

How existential of you... $:-\$

Thanks, I try

When rubber compunds are mixed it is decided how elastic the part is intended to be. A certain amount of "elasticizers" are added to the mix. These chemicals are unstable and will literally evaporate out of the rubber. You cannot put them back in. What you are doing with heat and solvents is breaking down the rubber and making it temporily softer.

I went through this and Mike Reick suppled me with a new set of manifiolds. When i start the bike with the tank off you can see them beat like little haerts so they are sealing well and are that pliable.

If you are stuck because a part is not available, you have to make do. If you are a victim of this economy, soften the boots as best you can and keep food on the table and roof over your childrens heads.

If you have the $50 or so bucks to buy new ones, it is a good investment. that is all I am saying.

Have a Blessed Day Y'all

Bobby

mystic_1 · « **Reply #16 on:** April 16, 2009, 03:05:59 PM »

I agree completely. New boots are best. That said, the wintergreen trick can squeeze out a few extra miles while you save up for the new ones.

mystic_1

6adan · « **Reply #17 on:** April 21, 2009, 08:14:12 PM »

I put some in mineral spirits to try and it did nothing,all other rubber I put in it would swell and get soft but these thing stayed hard as a rock.

BobbyR · « **Reply #18 on:** April 21, 2009, 08:52:37 PM »

Quote from: 6adan on April 21, 2009, 08:14:12 PM

I put some in mineral spirits to try and it did nothing,all other rubber I put in it would swell and get soft but these thing stayed hard as a rock.

That is because it is a fuel proof rubber the petroleum oil will not have ant effect.

swan · « **Reply #19 on:** June 04, 2009, 02:07:17 PM »

To soften hard rubber boots with xylene and wintergreen oil read:
http://forums.sohc4.net/index.php?topic=29707.0

Toxic · « **Reply #20 on:** June 05, 2009, 07:36:38 AM »

[/quote]
If you have the $50 or so bucks to buy new ones, it is a good investment. that is all I am saying.

[/quote]

Where do you get them for $50? got a link?

swan · « **Reply #21 on:** June 05, 2009, 02:55:52 PM »

K and F models carb insulators

Z1 Enterprise
set of four carb insulators for CB750 K and F models: $76.21

Honda Parts Direct
$76.88 for set of 4 insulators A and B

$40.98 CB750 A model sets for Grumberg from Honda Parts Direct if they are still available.

I have been using my Wintergreen and xylene mixture for 2 years on 4 bikes and all are running and idling fine with no vacuum or air leaks. $10 worth of ingredients saved me over $300. Why throw something away if you can make it work again?

Toxic · « **Reply #22 on:** June 05, 2009, 08:03:46 PM »

That's great, thanks for the links.

I'll check them out.

grumburg · « **Reply #23 on:** June 12, 2009, 04:59:16 PM »

Went to Honda Parts Direct. Web states: "We are closed and not accepting orders" WTF?

noisebomb · « **Reply #24 on:** June 12, 2009, 07:49:50 PM »

They (probably) have them here.

http://www.cyclepartswarehouse.com/fiche_section_detail.asp?section=124873&category=Motorcycles&make=Honda&year=1977&fveh=2978

If Honda doesn't make them anymore, they will refund the purchase price. I have ordered a lot of parts from them (78 750K), and haven't had any trouble.

News:

Author Topic: Softening hard carb boots (Read 18487 times)