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1979, CX500, Z, shaft drive.
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Discussion Starter · #1 ·
Hi. I have a problem with my front tyre (CX 500 1979). The last couple of times I have been out to it the tyre has been completely flat. There is no evidence of a puncture i.e. nails etc in the tyre and I have checked the valve isn't leaking. I was wondering if it is possible to put an inner tube in the tyre to stop the leaks. The tyre is a new Avon Roadrider Mk2 tubeless. size 3.25 x 19. What size of tube do you recommend to get. Thanks in advance.
 

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1979, CX500, Z, shaft drive.
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Discussion Starter · #3 ·
I would find the leak first before even considering a tube. The leak could be a cracked wheel in which case you definitely want to replace it.
Thanks - I have checked all round the rim and there are no cracks - the wheel is in great condition and the tyre is brand new - I will check al round the valve again to see if that's at fault.
 

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1983 cx650c
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1,308 Posts
A spray bottle with water/dish soap is good for checking for leaks, or a tub large enough to immerse sections of the wheel so bubbles are visible. The bead seating area gets corroded so new tire won't seat on irregularities. I change valve stems when changing tires on old bikes.
 

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I had this issue years ago (and several sets of tyres ago too...) - corrosion on the rim caused both tyres to very slowly deflate, like a slow puncture. Tyre shop removed the tyres, cleaned up the rims and refitted the tyres. No problem again with those tyres, or with any new ones since.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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It could be the valve itself. Sometimes, a little grit or corrosion gets in there and prevents it fully seating. There's a simple tool for cleaning the stem and valve seat. Or the valve insert could need replacing.
The soapy water will show if that's the fault.
 

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1979, CX500, Z, shaft drive.
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Discussion Starter · #8 ·
Thanks for the help. It's definitely not corrosion on the wheel rims as they are very clean and tidy. I will get the soapy water out and check all round and immerse the rim bit by bit in a trough of water to see what I can see.
 

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It is not visible with a tire mounted so I don’t take much time trying to polish it and making it pretty, but some people do and that is fine. I use a wire wheel in a 4 1/2” peanut grinder and give it a quick go over. I’ll have one cleaned up in 15-20 seconds.
 

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Cx500 1978 engine probably later
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27 Posts
First check if that is where your leak is with soapy water brushed where the tyre and rim meet.
If you see bubbles that's your problem.
The tyres are tubeless so you'll probably need to take it to a tyre fitters to get it removed.
My local tyre fitters removed the tyre, cleaned the rim bead seat and refitted and balanced the wheel for about £20.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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It is not visible with a tire mounted so I don’t take much time trying to polish it and making it pretty, but some people do and that is fine. I use a wire wheel in a 4 1/2” peanut grinder and give it a quick go over. I’ll have one cleaned up in 15-20 seconds.
Is that a brass wire wheel? Stainless steel might be a little harsh on the aluminum.
 

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No I didn’t use a brass and I agree a brass would be safer. Like I said, I am not worried about looks, just cleaning where the bead seats. I hit it fast and gentle, just enough to clean it. You definitely don’t want to sit there with the grinder and actually remove aluminum material from the wheel. Maybe it takes a touch. I worked in the tire business for several years in my younger days, both passenger car tires and big truck and commercial tires.
 

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1979, CX500, Z, shaft drive.
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Discussion Starter · #17 ·
So I've just tested it with soap solution and there are fine small bubbles coming out all round the bead seat rim - there's the problem!!! So I've taken the wheel off and let the tyre down - broke the bead off the rim and there is a bit of corrosion on the rim - as I haven't got a little wire wheel can i clean it up with some we/dry paper to take the corrosion off? How much will I have to clean it back? Thanks in advance.
 

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1983 cx650c
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I had the tires off when cleaning the bead area and used two grits of sandpaper,, one fairly coarse (100-120grit?)and finer wet/dry for finishing. Blowing debris away with compressed air after sanding is important. Possibly some large c-clamps would hold the tire away from the work area if done with tires on wheels? They need to be free of the corrosion or it will continue to create air leaks.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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I usually go over a rim with 220 paper when I change tires. It's not so course as to gouge the surface, but is enough to remove corrosion and old rubber residue.
 

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Discussion Starter · #20 ·
Thanks for the advice. I used some fine grit paper and cleaned all round both sides of the rim. There was quite a bit of oxidation but it cleaned up nicely. I made 2 small blocks of wood to hold the tyre bead away from the rim and worked my way round. I pumped up the tyre to see how I'd done and found although it was massively improved there were a couple of bubbles on each side. I have ordered some tyre bead seal to sort these little areas out. Thanks for the help guys.
 
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