Reliant SU Carb safety advice

[fifer]

On safety grounds , If anyone has a Reliant engine with the single pipe floatbowl lid then I would recommend changing it as soon as possible for the later 2 pipe setup .
I have done a wee article as to why I think it should be changed .
Hopefully it can be understood by Members new to technical stuff and might be useful for the , what I would imagine , very competent bulk of forum members to store in the caverns of their minds ready to pass on to newbie Reliant trike owners

https://sites.google.com/site/fifersrelianthintsandtips/carb-stuff
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SU Carb FLOATBOWL LIDS .

The SU carb by design has to have the floatbowl vented to allow displaced air to be expelled from the top as the float moves upward .

The design is easier to understand if you lift your toilet cistern lid { Floatbowl lid }.

You will notice there is a float sitting on top of the water { Fuel }

Now if you flush the toilet you will see the water { Fuel } falling down the cistern { Floatbowl } as it flushes the toilet { Fuel flowing to carb body }

As it refills the float rises and shuts off the water { Fuel } flow ;

If it does not shut off , then the cistern { Floatbowl } will flood .

Look near the top of the cistern and you will see  a pipe hole near the top .

The pipe hole is the overflow and if your float system does not shut off the flow of water then the excess will flow out the cistern { Floatbowl } and out of the cistern { Floatbowl } via the pipe to the drain . This means that your toilet floor { Engine } does not get a soaking with water { Fuel }

The early SU carb does not have that overflow to take the fuel away , it only has a hole where any petrol overflow is chucked out onto the engine  ; EEK ; EEEK ; EEK

The early SU carbs fitted to the Reliants had only a single fuel feed pipe into the lid and a hole in the lid with a little cover over it to prevent blockage ; as per

CARB ; OLD SINGLE PIPE FLOATBOWL LID ; SIDE ON VIEW ; SHOWING THE VENT HOLE COVER IN PLACE

Reliant SU Carb safety advice

CARB ; OLD SINGLE PIPE FLOATBOWL LID ; FACE ON VIEW ; SHOWING THE VENT HOLE COVER IN PLACE

Reliant SU Carb safety advice

CARB ; OLD SINGLE PIPE FLOATBOWL LID ; FACE ON VIEW ; SHOWING THE VENT HOLE COVER REMOVED

Reliant SU Carb safety advice

I would advise any SU carb owner to upgrade to the later 2 pipe floatbowl lid as per ;

CARB SHOWING LATER TWO PIPE FLOATBOWL LID

Reliant SU Carb safety advice

The vent / overflow pipe can have a length of fuel hose attached and taken to a safe position away from the electrics / exhaust  to the rear of the driver / rider .

I would also advise fitting the
SU Carb FLOATBOWL KIT ; Floatbowl Kit ; Anti-Flood Kit for HS2 , HS4 & HS6   
http://www.sucarb.co.uk/ProductDetail.aspx?Id=33997

The above floatbowl kit contains an adjustable float and , on the Burlen SU carb site ,
it does not have any specific measurements relating to the minimum and maximum
height settings for that new float .
R3W forum member Dranreb contacted Burlen on 4 August 2011
and was informed that the settings for the new float were the same
as the older HS carbs with the early nylon float and steel needle .
The gap between the lever and the face of the lid should be between
0.125” { 3.17 millimetres  } and 0.187” { 4.75 millimetres }
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[terry t]

why not just tap into your existing one. then run the drain overflow  pipe away from that 

[fifer]

Could do , I suppose , but the later lids are 10 a penny and lots of folk do not have the facilities / knowledge to attempt this .
There is also the thickness of the fuel hose and hose clips to go on top of the fuel feed pipe which was probably taken into consideration when they designed the 2 pipe lid
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[BikerGran]

I remember my Moggy Minor used to do that.........

[dobber]

was wondering what the second pipe was for when i polished mine previously. so just stick fuel pipe on and vent it low?

[fifer]

Yep , over the rear of the gearbox and to behind riders right leg and dump any excess on the ground .

The Friends of the Environment folk amongst you might want to dump it into a nifty catch bottle 
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[andyrennison]

The Friends of the Environment folk amongst you might want to dump it into a nifty catch bottle 

Hmm, then i have a second tank of fuel slowly filling up? - on the ground for me it is.

[fifer]

Yep , choice between flambéed posterior or not equals ground for me every time 
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[morrag]

If an SU float chamber floods that regularly and with such volume, then an overhaul might just be the way forward!I have used the original type of carburettor top over many years with no problems,really. If there is, then that's what the baffled bleed hole is for, and its then doing what it should do,in an emergency,not as part of its general function, Morrag

[fifer]

If an SU float chamber floods that regularly and with such volume, then an overhaul might just be the way forward!

I have to agree on that point . The floats sometimes { very rarely }puncture .
The needle valve gets a groove worn in it and is prone to chatter due to the material it is made from but the viton tipped ones cure that . I used them on my British bikes with great success and at that time I was averaging 40 to 50,000 miles a year with a high of around 80,000 in 1981 when I was despatch riding  .

I have used the original type of carburettor top over many years with no problems

As have I since 1976 to about 1980 when I changed over after seeing too many results of leaking carbs.

,really. If there is, then that's what the baffled bleed hole is for, and its then doing what it should do,in an emergency,not as part of its general function, Morrag

Again I have to agree the normal general function of the hole is to vent the carb to stop a build up of pressure with the inbuilt secondary purpose to vent any excess away in an emergency.
Do you not agree that prevention of the effects caused by such an emergency should be taken into consideration .
The petrol will leak over the the exhaust so why not pre-empt the possible catastrophe by upgrading to a safer solution ?

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[morrag]

If you check out most Amal carb.setups fitted to 50's and 60's Brit. bikes, you will see neat aluminium deflectors, usually installed behind the carb.and fixed using the inlet manifold studs, to cover the fuel that would leak,by design, when the float chamber was "tickled" to enrich the mixture at start up,( there being a general lack of chokes then!).Whilst this deflected overflow fuel away from the hot exhaust pipe, it was not there to take care of poor maintenance, so, if you don't want a fire, maintain your fueling gear! Morrag

[fifer]

I have tickled many an Amal carb amongst other things as well
The art of tickling and creating a trickle is a self induced overflow and was in general on a stone cold engine PRIOR to starting . Therefore the exhaust would be stone cold as well .
The difference is the fact that on the bike you stopped pressing as soon as the petrol touched your finger and immediately the flow stopped whereas with the carb flooding whilst running it is a different scenario altogether  .
Also on the bikes the carb is situated in the middle of the bike and not directly situated above the exhaust manifold { Twin carbs excepted  . }

[digger06]

su do a punctureproof float and needle kit for around 15 quid, worth getting imo,
i run a webber on mine,
people dont often like em on standard reliant cars, poor hot starting, they run ace on open trikes though, mines a vast improvement over an su

[merv]

Hi digger06

What webber do you run and did you change any of the jets. Also does it use any more fuel than what the su would.
Would be intrested to see a picture of the webber in situ

[fifer]

Me ; Same as Merv above 
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