Author Topic: Honda CB fender rust - how to treat?  (Read 1394 times)

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Offline Rayzerman

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Re: Honda CB fender rust - how to treat?
« Reply #25 on: January 21, 2026, 08:02:05 AM »
I may have posted this elsewhere... I used a rust remover gel and various brushes to get rid of much as possible.  Painted the underside of the fender with silver paint (didn't want black), then applied two coats of Flex-Seal clear.  It feels like a thicker rubber coating when dry, looks grey, doesn't draw attention like black would, and seals all the joints/edges.  It's going to last longer than the rest of the bike, lol.




Offline PeWe

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Re: Honda CB fender rust - how to treat?
« Reply #27 on: January 21, 2026, 08:27:27 AM »
My K2 got black stuff under the fenders as shown earlier. Not visible with wheels and tires on.

My K6 had bitumen under the rear fender when I bought the bike used January 1979.
Sand and pebbles did not hammer the fender. I'll fix front fender at next front wheel off.

The K2''s spray sill stuff is hard and "rubberish" at the same time. Sand and pebbles silencer. ;D

The grey Hammerite must be good for the chromed headlight ears inside that can rust.
Steel rims have usually sharp edges where welded together and roughly grinded. Paint it.

Where sold which explains. Maybe possible to find on eBay and Amazon.

EDIT: link corrected

https://www.hammerite.com/countries/
« Last Edit: January 21, 2026, 08:46:10 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #28 on: January 21, 2026, 05:46:45 PM »
Rear fender now installed  :)

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #29 on: January 21, 2026, 07:01:58 PM »
Old photos of the rear fender ;)
« Last Edit: January 21, 2026, 08:00:28 PM by kyle750 »

Offline ozm29c

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Re: Honda CB fender rust - how to treat?
« Reply #30 on: January 26, 2026, 05:22:39 PM »
Just to add my take on rust removal. Attached photos better tell the story on how I sorted my 350 rear mudguard/fender. Chrome surfaces protective taped, glass bead blasted, etch primed and then painted in a dupli-colour engine enamel.

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #31 on: January 26, 2026, 05:50:56 PM »
^ ^ ^ WoW ^ ^ ^

Your rear fender turned out looking fantastic.  Did the bead blasting remove most of the rust?  With etch priming and good quality paint it should be good as new. Another fender saved -  excellent work!

Offline ozm29c

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Re: Honda CB fender rust - how to treat?
« Reply #32 on: January 26, 2026, 06:26:37 PM »
kyle750 - It certainly did. The bead blaster left a very clean finish which in turn was a perfect surface for the etch primer to key into.

Offline grcamna2

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Re: Honda CB fender rust - how to treat?
« Reply #33 on: January 26, 2026, 08:25:27 PM »
^ ^ ^ WoW ^ ^ ^

Your rear fender turned out looking fantastic.  Did the bead blasting remove most of the rust?  With etch priming and good quality paint it should be good as new. Another fender saved -  excellent work!

 8) :)  ;)
75' CB400F/'bunch o' parts'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #34 on: January 27, 2026, 06:48:44 AM »
Slightly off topic but still about rear fenders.  This K1 rear fender showed up for sale on YJ.  Already bidding has pushed the price to over $200 USD  :o I'm quessing its the JDM sticker.  Condition also looks very good.  I would love to have this fender for my JDM K1 but it's out of my price range. 

Offline MauiK3

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Re: Honda CB fender rust - how to treat?
« Reply #35 on: January 29, 2026, 07:08:17 AM »
Looks to be in great shape, maybe never really used. Price is pretty high, agreed.
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline PeWe

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Re: Honda CB fender rust - how to treat?
« Reply #36 on: January 29, 2026, 08:21:31 AM »
A new rear fender is not cheap
https://ebay.us/m/F5pqEC

I paid half from DSS UK for maybe 10 years ago.

I bought another NOS Honda for  about 2/3 of that price a few years ago from Germany. +300€

Vietnam fender
Rear
https://ebay.us/m/BQ2ll9

Front important to order right. Early fork or later. Late K2 got later fork used on K6 too.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline M 750K6

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Re: Honda CB fender rust - how to treat?
« Reply #37 on: January 30, 2026, 02:01:35 AM »
I was initially happy to use a re-polished original. But as my rolling restoration neared completion, the mudguard was too shabby. I used a rear from Vietnam. Was a b1tch to fit. But looks stock and it's still looking clean.

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #38 on: January 30, 2026, 02:40:11 AM »
Someone got a bargain with this CB500 fender

https://www.ebay.com/itm/167972975190


Offline newday777

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Re: Honda CB fender rust - how to treat?
« Reply #39 on: January 30, 2026, 05:43:22 AM »
Someone got a bargain with this CB500 fender

https://www.ebay.com/itm/167972975190

That says 1969-1970 CB500.
CB500 1st year was 1971.
Buyer beware.....
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 1 K2, 4 K6, 1 K8, 1 F1, 1 F3
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline PeWe

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Re: Honda CB fender rust - how to treat?
« Reply #40 on: January 30, 2026, 06:06:29 AM »
When you have got a new tank with side covers from Yamiya or a recently re-painted old set.
Everything will look shabby if not replaced with new looking parts. ;D

I had done all, bike still looked shabby until I ordered a new licence plate.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Online kyle750

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Re: Honda CB fender rust - how to treat?
« Reply #41 on: January 30, 2026, 06:14:11 AM »
Someone got a bargain with this CB500 fender

https://www.ebay.com/itm/167972975190

That says 1969-1970 CB500.
CB500 1st year was 1971.
Buyer beware.....

Perhaps a mistake by the seller. Sellers love to include Sand Cast in the item description. 

Offline jonda500

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Re: Honda CB fender rust - how to treat?
« Reply #42 on: January 30, 2026, 05:00:06 PM »
The early 500 and 750 rear fenders are almost completely identical - the only difference is in the wiring tunnel and the wire pass through hole location. When mounted to a bike there is no visible difference!
John
Remember that an ignoramus is only someone who doesn't know something you just learned yesterday!

A starter clutch thread:
http://forums.sohc4.net/index.php/topic,122084.0.html
1972 CB500K1 original 4 owner bike
1972 CB500K1 returned to complete/original condition
1975 CB550F built from parts - project thread:
http://forums.sohc4.net/index.php/topic,149161.msg1711626.html#msg1711626
197? CB500/550 constructing from left over parts
1998 KTM 380 (two stroke) recent impulse buy, mmmm...