Author Topic: Cb750 f1 rear cowl rubbers  (Read 1685 times)

Offline Coppertop1234

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Cb750 f1 rear cowl rubbers
« on: August 24, 2026, 08:00:07 AM »
Presently trying to source 2 rear cowl rubbers
It seems the were discontinued several years ago and I have a cowl with no rubbers

Tried everywhere I can think at moment
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Ken4004

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Re: Cb750 f1 rear cowl rubbers
« Reply #1 on: August 24, 2026, 10:30:37 AM »
What do they look like ? Is it a type of grommet ?

Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #2 on: August 24, 2026, 10:34:59 AM »
Thinking of trying to make my own at moment Ken
Thought of making a mold using silicone as filler with a bolt in centre to strengthen and allow fixing
Or buy a cowl with them on hoping they haven't perished

Here's a pic of what they are
« Last Edit: August 24, 2026, 11:05:53 AM by Coppertop1234 »
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Ken4004

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Re: Cb750 f1 rear cowl rubbers
« Reply #3 on: August 24, 2026, 07:31:26 PM »
I wonder if it’s worth trying to make one out of a solid piece of Rubber and cut it with a sharp knife.

I did have an idea of making rubber parts using rubber sheet and  building it up in layers and using vulcanised rubber adhesive to bond the sheets together.
As you’re not actually going to see them it doesn’t  really matter what they look like.

I did think about making the fuel tank rubber mounting using this method, what gave me the idea is was a repair I did on a pair of diving fins I repaired using an inner tube to repair the split which didn’t look great but it make a very good repair.
I used Black  witch adhesive to bond it together which is used to repair wet suits and is a really strong bond.
« Last Edit: August 24, 2026, 07:34:21 PM by Ken4004 »

Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #4 on: August 24, 2026, 07:50:41 PM »
No problem in trying these ideas out Ken .it keeps it interesting and satisfying if you can adapt
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #5 on: August 25, 2026, 07:10:10 PM »
First attempt of making some rubber stops for rear of seat.

Dong think wife will notice her ice cube trays has gone
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #6 on: August 26, 2026, 07:16:22 PM »
Don't think plan a will be a success ,but waiting for silicone to set.
Marvelous if you put it down when your using it day after nozzle is set solid.

I have spotted air holes around mould so it can cure,but we will see how it goes.
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Ken4004

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Re: Cb750 f1 rear cowl rubbers
« Reply #7 on: August 27, 2026, 07:57:54 PM »
I have seen videos concerning making rubber parts and after mixing  the rubber solution the next step is too get any air bubbles out of the solution.

This is done by putting the filled mould into a vacuum which over half an hour or so draws all the bubbles out of the rubber solution in the mould.

Offline exvalvesetdabbler

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Re: Cb750 f1 rear cowl rubbers
« Reply #8 on: August 28, 2026, 09:57:01 AM »
I have used polyurethane  rubber for making the T shaped rubber grommets in the Speedo bowls, tail light brackets.  I used shore A 50 and the black pigment additive.  It's not so prone to entrapment of bubbles.  You have to work quick though.

I have also seen articles of people using the stuff they glue car windows in with for repairing suspension bushes on classic cars.

Regards
Dave

Offline exvalvesetdabbler

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Re: Cb750 f1 rear cowl rubbers
« Reply #9 on: August 28, 2026, 10:05:31 AM »
First attempt of making some rubber stops for rear of seat.

Dong think wife will notice her ice cube trays has gone

Hope you used a good mold release agent in those ice cube trays otherwise you're in deep trouble when your wife sees them.


Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #10 on: August 29, 2026, 10:09:35 AM »
Failed miserably.

Back to searching for standard fit rubbers

Found some in Germany cheap enough  at a tenner each but 40 quid postage on top
I could buy a cowl cheaper which may be an option

I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline exvalvesetdabbler

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Re: Cb750 f1 rear cowl rubbers
« Reply #11 on: August 29, 2026, 12:58:30 PM »
If you want small rectangular molds have a look for 'potting boxes' used for encapsulation of electronics. The come in all sorts of sizes.  For mold release I dissolve  a half teaspoon of Vaseline in about 50ml. white spirit and paint the inside of the mold generously and wait for the solvent to flash off.  Works for both silicone and urethane resins.   To get any kind of deep fill to cure, it needs to be a two pack resin where the hardener and resin are mixed and used immediately.

This is the kind of stuff I have used. https://www.mbfg.co.uk/polycraft-fc-3680-black-polyurethane.html

Last time I bought some you had to buy the pigment separately I guess things have moved on a bit.



Regards
Dave

 

Offline neat street

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Re: Cb750 f1 rear cowl rubbers
« Reply #12 on: August 29, 2026, 01:32:47 PM »
Have you tried dk motorcycle spares... also know as two wheel spares. I have brought a few things from them in the past via ebay, maybe worth contacting them https://twowheelspares.co.uk/
CB500 1975
CB750F 1976
KLX250 1983
Lambretta SX200 1979
Mini Mayfair 1984

Offline Coppertop1234

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Re: Cb750 f1 rear cowl rubbers
« Reply #13 on: August 30, 2026, 09:42:00 AM »
All Sorted Thank you

one of the sohc4 members had a set he is kindly sending me.
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration