Camchain and tensioner seen up close in a cutaway bike engine

Home Repair And Restoration

Leaky Bead - Again

Job Date 10 December 2019

By Ren Withnell

Waaaaaaay back on May 2016 (them's were the days) regular readers may recall I had a leaking bead on the front tyre of the CBF125 - Leaky Tyre Bead Repair. In the intervening years I have since learned this is actually a well known and established issue with the venerable CBF125. 

The issue is corrosion of the alloy. This corrosion if left unchecked becomes thick enough to allow air to pass between the rim and the tyre. It could be argued that the front wheel's paint isn't very good or even the alloy, but from the number of forum posts and YouTube videos this happens to car alloys too. I guess for most other motorcycles they just ain't doing the miles in the winter like my poor CBF does.

I've never had the same issue with the rear. I suspect this is due to the rear being regularly dosed in an anti corrosive layer of chain lube whereas the front enjoys no such luxuries. I am pondering whether or not to put chain lube on the front rim from time to time... ahem.

It's been leaking from the bead for a while now. It's not a problem I just need to remember to re-inflate the front twice a week. Then this Monday when I left work I noticed the front end was worse than usual. A check at home revealed I was down to 7psi. I'm surprised the bike was still rideable. I pumped it up to 30psi (25psi is the standard setting) and left it overnight. It went down to 10psi. That, that is unacceptable. 

In fact I was sure I had a proper puncture but I could find nothing in the tyre. I filled a tub with water and the only leaks I could find were bead leaks. I, oh dear, I guess I'd better take the tyre off and clean the bead. 

The front wheel off Ren's 125 partially submerged in a tub of water to look for leaks
"I'm forever blowing bubbles!"

Luck is a funny thing. Luckily I have the day off work as I'm using up the last of my annual leave before it resets in January. Unluckily it is raining and the wind is up, perfect weather for messing with motorcycles.

I get the tyre off using my patented "bits of plastic with tyre levers". I sit for half an hour to put my fingers back in their sockets, stem the bleeding and to dry off a little. I spend a happy hour with a wire wheel in my electric drill polishing off the corrosion and old paint as the rain gently brushes my face. I wonder - at what point is the rain too heavy to use a 240v drill? I spend another happy hour sanding and scraping the paint off the tyre too, you know, just in case.

Breaking the bead on the motorcycle tyre using a g-clamp and some wood
DIY bead breaker.
Close up of the rim showing poor paint and some corrosion
It doesn't look much at all, but it's enough to leak air.
Where the tyre bead touches the rim a lot of paint from the rim is stuck to the tyre
The paint is now mostly stuck to the tyre, not the rim.
The tyre with the old paint and corrosion scraped off, looking clean now
Some scraping and scrubbing got the tyre clean.

The rim after cleaning with a wire wheel in the drill
That's the worst of the rim sorted out too.

I can now refit a tyre with nothing more than my bare hands and a 3 foot length of stout wood. I now have a compressor with a small tank to re-seat the beads. Re-balancing is a doddle with the DIY balancer. Refitting the wheel is a faff as always, so many spacers, so few hands. I'm already black from head to toe with oil and grease so while I'm here I'll re-re-re-re-re-re-re-re-re clean the front brake again too. I must check to see if I can get stainless pistons for the front.

The wheel up on a DIY balancing tool
This is the easiest part of the whole job.

I have put the bike to bed. Tomorrow I shall check the pressure and if all is well take myself off for a shakedown ride. 

Will this be the last of it? Oddly - hopefully not? I did consider repainting the rim but as the last bout of paint failed I would need to do some serious research to discover the ultimate CBF125 alloy wheel anti corrosive long lasting paint. Without paint the corrosion will return sooner or later. So why did I say "hopefully not"?

The last time the rims were done the bike had about 50,000 miles on it. Now at 86,500 that means I've covered 36,500 miles since then. I do rather hope I can get another 36,000 miles out of it and get the chance to clean the rim again! Or, well, perhaps I should just clean it when I fit a new tyre. That means it'll get done every 20-odd thousand miles. 


If you've a tale of life on the tools to share contact ren@bikesandtravels.com

Reader's Comments

Upt'North said :-
I thought at first you were describing an age related health issue our Ed, phew, we dodged a bullet there.
Fingers crossed Rene that your bead is leak free. I'm just surprised the air could get past the dirt.
Well done for not electrocuting yourself and sending Manchester into a pre Christmas black out, imagine the shame, the headlines, "motorcycling buffoon switches off Manchester Christmas lights".
I didn't doubt you for a second.
Upt'North.
12/12/2019 1:49:46 PM UTC
Ren - The Ed¹ said :-
So you worked out I'm too tight to pay for eleccy so I'm wired into the Christmas lights in Manchester? I tell ya, that was a *HUGE* extension lead from here to town, 16 miles of cable. I've buried it under the trash that lines the grimy streets so no-one will find it.

You know, I can go to better blogs than this to be insulted.

So far, there is still air in the tyre. It remains to be seen just how much.
12/12/2019 4:43:12 PM UTC
Christopher said :-
This too has been an issue with my CBF125 over the past 18 months or so. Seemingly a common 'fault' then, I hadn't realised, and was unsure if this was due to a (very)slow puncture, or the beading on the rim.
The current tyre has little mileage left, thus, i am fitting a new replacement this weekend.
The rim is in good order, with no corrosion, and i wonder if the paint used on the rim is a factor?, In any case i shall get my trusty wire brush to work and carefully remove it, which will (hopefully) make a difference.
13/12/2019 10:49:20 AM UTC
Ren - The Ed¹ said :-
When you say the rim is in good order is this the rim as you can see it or have you looked at the bead where it meets the tyre? I suspect you'll find some corrosion there. What age and mileage does your CBF have? Also let us know how you get on.
13/12/2019 10:56:40 AM UTC
nab301 said :-
Ren , on other bikes, I've used alloy etch primer which as its name suggests , etches into the alloy... . Works well once you clean and degrease properly. Available in aerosols . ordinary paint won't adhere to alloy.
It's not too bad with tubeless tyres , if you had an Enfield (with tubed tyres ) the chromed rims rust so badly that if you don't include them in preventive maintenance you can suffer punctures / blow outs which can be more painful than "tyre changing pinched finger syndrome"
Painting though is more of a summer job ( for the paint to cure properly) unless you have a nicely heated work area or preheat the surface with a heater/ blow torch.

Nigel
14/12/2019 3:42:49 PM UTC
Ian Soady said :-
My wife's previous car was plagued with leaky wheel rims. The tyres would stay up for weeks then suddenly (usually when she was in a rush to go somewhere) one would go flat.

The local tyre place cleaned the rims up with a wire brush and used sealant which seemed to do the trick. Something like the link below.
http://www.tyreconsumables.co.uk/product-xtra-seal-heavy-duty-bead-sealer.html...
15/12/2019 10:14:39 AM UTC
Christopher said :-
Ren, I will give a progress report in due course. Having cleaned up the rims today, removing the black paint etc, they appear okay. There were a few, albeit small 'spots' of corrosion in places, now removed via 400 grade wet and dry, and i am now ready to fit my new tyre
The CBF was registered in early 2012, I bought it September 2015 with 4000 miles recorded. The current mileage is 41,500 miles. It is used 12 months of the year, for 'leisure' use. Incidentally the previous keeper had an inner tube in the rear, due to the same 'issue', Since cleaning the rear rim,with the same paint removal etc (when that particular tyre had worn out) and reverting to its tubeless original intent, it has since been fine, (though i do make a point of checking the pressure before each ride).
15/12/2019 7:02:39 PM UTC
Ren - The Ed¹ said :-
nab301 - The first time we "did" the wheel to stop the bead leaks my friend Latchy sprayed the inner rim with grey etch primer. I believe the "etch" part means the paint is slightly acidic, the reaction somehow allows the paint to grip the metal better. Beyond that we left the rim with just the primer. This primer too has come asunder from the rim so either the etch didn't or my lack of knowledge on painting things has become exposed.

I've seen the bead sealer products Ian. My question is - is this a gloop to aid sealing that over time I would expect to wash out or is it like a varnish to treat the alloy rim to prevent future corrosion. I expect it's more the former than the latter.

You're doing some healthy miles there Christopher! Leisure miles too, you must like to get out and about a bit. It's good to see it's being used properly. Which tyres are you using? I found the Conti-Go! to be fine but the Michelin City Pros feel better in the wet and winter.
16/12/2019 9:05:05 AM UTC
Christopher said :-
Ren. The new front tyre fitted is the Michelin City Pro. This replaces the Pirelli Angel City, which i have used for two years or so.
The rear has had the Michelin on since August, and feels fine, again, this replaced a Pirelli Angel, which was potentially a good bet for longevity, with the previous one going to almost double the mileage of the previously fitted Conti-Go. Tyre life actual mileages are though, somewhat subjective, no two of us ride the same, along with differing power to weight ratio's, etc, etc. The 'problem' with the Pirelli rear was they were punture prone, e.g the last one had to be replaced some 4000 miles early,I had fitted a 'plug' which held for 6 months, but began leaking again, no way to seal it, hence in the bin it went, so to speak. Michelin claim these City Pro's are 'punture resistant'.....We shall see!!
16/12/2019 9:18:05 PM UTC
Ren - The Ed¹ said :-
To quote from Michelin's own website "Extremely robust MICHELIN City Pro tyres that provide great puncture resistance in any conditions and are long-lasting too." Note - puncture resistance, not puncture proof.

Again from their site - "Thanks to MICHELIN OVERLAP TECHNOLOGY (MOT), it is unlikely that these tyres will get a puncture. Across 48 motorcycles that had covered a total of 400,000 kms, only 4 punctures* were reported." 4 punctures in 400,000 kilometres is 1 puncture in 100,000 kilometres or 62,500 miles. It sounds great but in my experience, meh, yeah that's about right. If you're visiting engineering shops with turnings across the car park and builders yards with nails everywhere then it's very good.

I just find in the cold and wet conditions they aren't particularly grippy but they do have a better feel and stability than other tyres, that's why I've stuck with them.
17/12/2019 9:18:04 AM UTC

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