Fuel level in Monoblck

[Barnsey]

Does anyone happen to know, can you buy a transparent cover to go on a Monoblock reservoir, so that you can see what is going on inside while the engine is running?

  I reckon that either the float needs adjustment or else it is still sticking in the down position.
(I thought that I had fixed that).

  Having tweeked the timing to get it to run smoothly, it was revving hard, so I wound the tickover screw down to an idle speed,  but then I spotted the fuel dripping from around the air intake. 

If necessary, I know that I could make one from Perspex/ Acrylic,  but Acrylic isn't fuel proof.  OK for debugging but not something I could leave on the bike.     

[JulianS]

If your carb has a stay up float the moulding line on the float may stick on the rib for the cover fixing screw causing flooding. You can usually scrape enough of the moulding line away to solve the issue.

[JulianS]

Another possibility is that has been wrongly assembled - if it is an original monobloc, the type which takes the thick O ring not the thin concentric type no washer should be fitted between the carb body and the float needle seating. It raises the seating and the float needle can rest on the tickler before it cuts the fuel supply causing flooding. The later monoblocs take the washer and have a recess machined in the carb body for it.

[Rupert]

Doesn't help you see the actual level of fuel but the small pimple on the cover between the AMAL logo and Made In England indicates where the fuel level should be.

[Mike40M]

In this link is a hint how to fit a plastic tube
https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=424598

[Barnsey]

Thanks Chaps!

  I've already filed down the seam on the float for that reason, and cleaned off the oxide on the body casting.  I thought that I had fixed that problem.

  I've ordered some tubing and a piece of acrylic sheet from Amaz@n. 

    BR,  Ian

[iansoady]

This is my solution: a spare bottom plug tapped 1/4" Cycle and a spigot made up.

[Barnsey]

That is a neat solution!   

  This morning I found fuel dripping out of the air intake, so I am pretty sure that it is overfilling. 

  It also says that the fuel tap is leaking. 

  Can anyone recommend a good vertical fuel tap with a built in strainer? Also  a brand of transparent fuel hose to match? 

   Ta,  Ian

[Barnsey]

I thought, maybe something like this: https://www.ebay.co.uk/itm/385248028317?_skw=BSA+fuel+tap&itmmeta=01JAMM9KRSMGRTVQ0YC1DK69HK&hash=item59b292669d:g:LsUAAOSwd4VjWnfd&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKlPor6Fqtb4HP7NhlWG4M0rIekOq7Ie9%2BEY1P5z5oHyk3mN3LyAKeqr0XoJUNhbRyaf%2B4juF6FnoZiVpdy133SA24N6Btn%2BST2CIMQ3l5QE3SGK0tywI5gbybgCUyigQzbovM9Zp0dMdobv7Tq0Gui9MRCSuvQobnC%2BSzJx5kgUmiNpNbsJQZ3DgTCpdlwpcgzNJqNn1FlTGpXTs1ABJfvQVk5ZoGyHUYgJTJIzZvTFJiZAwygRGKTIKldPEGsm7HRu%2BnXJqwd37MrnVzEPQhue%7Ctkp%3ABFBMvrymlNVk

[scifi]

I don't think the level of petrol in any float chamber makes a jot of difference to the richness of the mixture.   The reason for this is that it would take a column of petrol 46 feet high to make 1 bar (1 atmosphere.)  so a change of height in the float chamber of a few mm does not change the pressure on the jet very much.
You can see this in practice if you shut your fuel valve off at the end of a run, the bike does not change it's tickover until the fuel is exhausted.
So unless your float valve is malfuctioning, the level is not important, just as long as it is not overflowing or not flowing at all.

[Barnsey]

I hear what you are saying,  but isn't that why we operate the tickler?  To overfill the bowl and enrich the air fuel mixture?

     Ian

[DAVE BRADY]

Hi,

There is probably some complicated physics at play to do with the draw of the induction stroke which creates a depression in the carb which causes fuel to come up through the jets to mix with the air being sucked in etc.
The height of the fuel will influence this effect
If the fuel is too low the effect is reduced leading to weak mixture but if it is too high the mixture will be too rich.
Is this about right?

Dave.

[scifi]

Yea Barnsey, but by ticking you are putting 3 or 4 CCs of fuel beyond the main jet straight into the venturi.

In the case of my Ossa Mar it needs about 10cc to flow into the crankcase to make it start first thing in the morning.

[idie]

Have you tried changing the shut off needle and seat.

[Barnsey]

Shut off needle in the carburettor?