[TR] setting the float level on a SU H6 Long

[Graham Stretch]

Hi Guys
I am taking a guess here that the question has arisen due to flooding?
I had a run in with a Spit a few weeks ago, petrol pouring out of the rear 
carb car new to owner.
Fit a pair of new needles and floats, the floats were not a pair and as they 
are reasonably cheap here we decided to remove the risk of a sinking float. 
Still fuel poured out, so having had a problem before with the seal around 
the thread that secures the float valve, I taped these with ptfe tape, yep 
fuel still leaked out! Time to get technical, got a low pressure gauge and 
measured the fuel pressure, 5 to 6 PSI. Looked for literature and found that 
SU's like 2 PSI so suggest to owner shell out for pressure regulator, he 
looked at the price and asked if I could think of any other way. As it 
happened I could, shorten the spring in the pump. (The pump works by the 
lever pulling the diaphragm down and filling the pump with fuel and then 
releasing the tension as the cam turns and the spring pushes the diaphragm 
up therefore the spring is what provides the pressure, when the flow is shut 
off and the pressure rises the spring is overpowered and the diaphragm is 
held down until the float level falls and allows fuel to flow again.) So we 
set about cutting the spring, this is a very crude way of reducing the 
spring rate by reducing its free length, we took a quarter at a time and 
eventually got to 2.5 PSI which as I have not had a return visit from the 
owner I guess was low enough. I have checked out several other cars with 
"NEW" fuel pumps and found that they all run in the 5 to 6 PSI range but 
some carbs seem to hold it back whilst others don't even when the float 
level is correct, though on 2 of the cars I have looked at there were signs 
of staining on the float chamber lids so these are probably running on the 
limit.
I too have found that exact fuel levels are not too critical it just means 
that the mixture jet will not be at the same height on both carbs.

Hope this helps

Graham.


----- Original Message ----- 
From: "Randall" <tr3driver at ca.rr.com>
To: "'Paul Dorsey'" <dorpaul at negia.net>; "'list Triumph'" 
<triumphs at autox.team.net>
Sent: Friday, November 30, 2007 9:20 PM
Subject: Re: [TR] setting the float level on a SU H6


>> When setting the float level on the SU H6 carb, the manual
>> says to pass a
>> 7/16" rod between the float level aluminum forked lever and
>> the inverted lid.
>> However, when this is done does this mean the needle
>> completely shuts off
>> (with the mimicing of fuel by one's breath).  Or does it
>> mean, 'that at
>> 7/16"ths the fuel level just  begins to stop' or other?
>
> Paul, I don't actually think it's all that critical.  Small errors in 
> float
> level don't seem to cause a problem.
>
> But I take it to mean that the valve should be closed (unable to blow
> through it), with the fork dragging on the rod (on both sides).
>
> Randall