Manky Monkey Motors

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
(http://i423.photobucket.com/albums/pp316/fifer3w/CARB%20DETAILS/CARBSUCARBFLOATBOWLLIDWITHTHEFEEDPIPEandtheOVERFLOWjustrunsoutunderneathitSideview-1-1.jpg)

CARB ; OLD SINGLE PIPE FLOATBOWL LID ; FACE ON VIEW ; SHOWING THE VENT HOLE COVER IN PLACE
(http://i423.photobucket.com/albums/pp316/fifer3w/CARB%20DETAILS/CARBSUCARBFLOATBOWLLIDWITHTHEFEEDPIPEandtheOVERFLOWjustrunsoutunderneathit-1.jpg)

CARB ; OLD SINGLE PIPE FLOATBOWL LID ; FACE ON VIEW ; SHOWING THE VENT HOLE COVER REMOVED
(http://i423.photobucket.com/albums/pp316/fifer3w/CARB%20DETAILS/CARBSUCARBFLOATBOWLLIDWITHTHESINGLEFEEDPIPEandtheOVERFLOWjustrunsoutunderneathitFROMTHEVENTHOLE.jpg)

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
(http://i423.photobucket.com/albums/pp316/fifer3w/CARB%20DETAILS/CARBSHOWINGLATERTWOPIPEFLOATBOWLLIDpic1-1.jpg)

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

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

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

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

Yep , choice between flambéed posterior or not equals ground for me every time  ;D ;D ;D
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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

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  :).

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


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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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

I have tickled many an Amal carb amongst other things as well ;D ;D ;D
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  ;D. ;D }

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

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

Me ; Same as Merv above  ;D ;D ;D
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Well, my point has obviously been missed regarding the maintenance of an SU to prevent habitual "flooding", however, the standard 850cc motor that most seem to run, is so under stressed, and in such a low state of tune, that the SU is more than adequate for its performance capabilities as standard. Before such a motor can take advantage of superior carburation it's breathing capabilities require suitable enhancement, otherwise,sadly, like a noisy exhaust system, your just kidding yourself, Morrag

Not missed by me and agree that pre-emptive maintenance is the best thing for everything . However ,when upgraded parts are built by the manufacturer to improve the safety aspect of their products , then I will fit those at maintenance time  :).

That is spot on info and the Reliant lump can have a good few ponies released with minimal or no outlay .
The standard Reliant 850cc engine is supposed to produce around 40bhp but some folk have had them tested and some were as low as 30bhp .
So if , for example , the following modifications released a power gain of 20 percent then a 33 bhp motor will end up with around the original 40 bhp and the 40 bhp motor would be 48 bhp .
But would the 33 bhp motor have the capability to leap right up to 48 bhp ??
The inlet manifold is easily adapted with just an electric drill or a wee Dremel type tool or just a few files and emery.
The same principle can be applied to the head to take full advantage of the modified inlet manifold .
The Exhaust manifold was produced with 2 different port sizes and can be opened out , of course again matching with the ports in the head .
Goes without saying that all these items have to be matched to the gaskets .
The manifold gasket can be modified to take advantage of the inlet manifold improvement .
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Have details of any of these modifications been put up on site ?

In fact what you need is one of these!.............................

Wish I could still get one at THAT price ; It would save me a lot of time and effort as my arthritic fingers do not work as well nowadays  ;D ;D .
I would love to have seen if they took the metal between the inlet ports away by tapering the sharp face where the manifold gasket fits but unfortunately I cannot blow it up far enough and it is at slightly the wrong angle .
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I have two similar heads,Maybe a little bit more been done to mine,
Having said that at that price i think I'll have a couple more ;D

Head and manifold just starting to be modified ;

Head showing original metal between the inlet ports on the left and the starting to be modified inlet ports on the right .

(http://i423.photobucket.com/albums/pp316/fifer3w/CYLINDER%20HEAD/HEADSHOWINGORIGINALMETALBETWEENTHEINLETPORTSONTHELEFTANDTHEMODIFIEDONESONTHERIGHT.jpg)

Manifold starting to be modified to suit the head and the ports

(http://i423.photobucket.com/albums/pp316/fifer3w/CYLINDER%20HEAD/MANIFOLDGASKETMODIFIED.jpg)
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For what i can see of the pic,The inlet ports have a fair spacing,No knife edge.

We have covered the inlet manifold mod, may be of interest to some if you can post details  of them all though?

As advertised in "Motorcycle Mechanics",April,1970,priced two shillings and sixpence, or for 'younger' readers. 121/2pence!! them's were the days! Morrag

34 ich,
25mm venturi , needed the manifold bolts turning 90 deg like a 750 engine, but then went straight on, (i ported the manifold to mate it better though,)
got it off a guy who suffered poor hot starting with it, but i dont get that problem (he had it in a 3 wheeler car)
fifer, it was off wrighty on your favourite site ;D,
runs great, better power everywhere

Yep , the Reliant lump prefers the fresh air and once released from its fibreglass overcoat can pull the skins of rice puddings .
Yeah , had a few conversations over the Dog & Bone with Wrighty when he first joined .
The SU carb is a simple carb and will run under all conditions and does not ask for much BUT , as you have proved , other types of carbs can be better if you can get the size and jetting correct for your particular engine / exhaust system .
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New topic started re ; Exhaust Manifolds at

http://www.mankymonkeymotors.co.uk/forum/index.php?topic=10694.msg134949#msg134949
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