Author Topic: 376 monobloc on 1955 A7SS  (Read 223 times)

Offline Terryb

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376 monobloc on 1955 A7SS
« on: 02.06. 2020 09:36 »
Anyone had a stay up float sticking down and fuel pouring out of the tickler?

Online berger

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Re: 376 monobloc on 1955 A7SS
« Reply #1 on: 02.06. 2020 11:13 »
yes many times when I was a kid with abused field bikes, tapping them with anything at hand sometimes stopped it. when the float bowl cover was eventually taken off to clean the crud we caused more leaks from the bowl cover gasket *bash*

Online bsa-bill

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Re: 376 monobloc on 1955 A7SS
« Reply #2 on: 02.06. 2020 11:17 »
yes, took me a while to get it fixed, I think it was catching on the boss in the float chamber for the cover screw ( looking at it from the drive side it's the screw at 7 o clock ish) I filled a bot off the boss and it hasn't done it since.
Just why it decided to start this I have no idea - one of life mysterys

All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online Black Sheep

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Re: 376 monobloc on 1955 A7SS
« Reply #3 on: 02.06. 2020 14:36 »
With brass floats they could spring a leak and sink causing flooding. I have heard tales of stay up floats expanding slightly with modern petrol and catching on the float chamber cover. Worth a check.
2 twins, 2 singles, lots of sheep

Offline Terryb

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Re: 376 monobloc on 1955 A7SS
« Reply #4 on: 02.06. 2020 15:28 »
Thanks Bill, I'll check that out. The Carb was new in 2006, but it has o ly done 8K since then and most of those miles have been in the last 5 years. It started playing up on and off recently. I have tried to use an older copper one, but then the tickler becomes less effective. The float  chamber is spotless, so it's not dirt. I'll check to see if its fouling on anything. Thanks

Online groily

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Re: 376 monobloc on 1955 A7SS
« Reply #5 on: 02.06. 2020 16:41 »
Also had exactly the same problem recently (on a 389 but same difference), after no hint of trouble for several years. I put a brass float in, using the same tipped needle, same seat etc, and the problem went away. Could be the raised moulded letters maybe causing jamming in certain circs - they do say to have them on the outside face I think  . . . but mine got stuck when being tickled whichever way round. And could well be another modern fuel thing I suppose.
The workaround was 'tickle till drippy, turn fuel off, start, turn fuel on again after about 20 seconds'. The vibes etc sorted it every time and it never happened with the engine running.
Bill

Online RDfella

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Re: 376 monobloc on 1955 A7SS
« Reply #6 on: 02.06. 2020 17:13 »
In similar vein to bsa-bill:
For years I’d put up with one of my monoblocs pouring out fuel when fuel turned on. A sharp tap with a spanner always cured it and it wouldn’t recur until the next start up weeks later.
I’d looked inside the carb but never found anything wrong. Eventually I did a closer examination, spurred on by comments on this forum regarding a similar situation. And so I found the problem. At last!
Now every time I use my bikes, I turn the petrol off (can’t on the Honda) before I reach home, thereby ensuring there’s no stale fuel in the carbs for the next time I use it. What I discovered was that the plastic float was getting jammed on one of the cover mounting screw bosses (near the bottom – where it would be resting when the carb was empty). Hence why it flooded on first use but was OK thereafter. Now the float is made in two halves, presumably heat welded together, which in turn leaves a small ‘flashing’ on its circumference. It was the flashing which was jamming on the boss and I was able to solve the flooding problem by shaving that flashing flush. Must be 20 yrs I’d always gone to the bike with a spanner in my hand ready!
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Terryb

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Re: 376 monobloc on 1955 A7SS
« Reply #7 on: 13.06. 2020 17:09 »
Hi All, I've taken the plastic float and smoothed the flashing off of the side and so far it's behaving itself. So hopefully job done, many thanks Guy's *clap*