I've acquired an old Blackburn frame-fit pump, and however careful I am to connect it to the valve (Presta), I find air always finds its way back out of the tube into the pump, so I can never get it near the required pressure.
Is there a valve in the pump itself, which could be faulty, or might there be another explanation?
Pump question
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Re: Pump question
Perhaps you need to push the pump head further onto the valve, so that the rubber washer does not bear in the little knurled nut.Steve wrote: ↑29 Jul 2021, 9:08pm I've acquired an old Blackburn frame-fit pump, and however careful I am to connect it to the valve (Presta), I find air always finds its way back out of the tube into the pump, so I can never get it near the required pressure.
Is there a valve in the pump itself, which could be faulty, or might there be another explanation?
It's the same the whole world over
It's the poor what gets the blame
It's the rich what gets the pleasure
Isn't it a blooming shame?
It's the poor what gets the blame
It's the rich what gets the pleasure
Isn't it a blooming shame?
Re: Pump question
There's not usually a second valve in the pump, although some have one.
The most likely cause is something is keeping the tube valve pressed open, stopping it from closing while the pump is connected. Possibly the valve core is bent, or possibly there is some obstruction in the pump connector, or possibly your valve core is simply longer than the old pump's designer expected (you might be able to bodge it by undoing the valve nut a little less than fully, if the pump is hitting the nut rather than the post), or it could be something else entirely!
Happy hunting!
The most likely cause is something is keeping the tube valve pressed open, stopping it from closing while the pump is connected. Possibly the valve core is bent, or possibly there is some obstruction in the pump connector, or possibly your valve core is simply longer than the old pump's designer expected (you might be able to bodge it by undoing the valve nut a little less than fully, if the pump is hitting the nut rather than the post), or it could be something else entirely!
Happy hunting!
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
Re: Pump question
I don't know what the Blackburn pump head is like and I hope I'm not teaching you to suck eggs but one push-on pump that I have has (as well as a reversible rubber grommet to convert the head from presta to schrader) a plastic insert behind the rubber grommet that also has to be reversed - could it be something like that? Otherwise, I suspect a bent core, the pump head not pushed far enough over the valve, the pump not being held "straight" or a combination of the last two.
Disclaimer: Treat what I say with caution and if possible, wait for someone with more knowledge and experience to contribute.