carb needle jet

[ROD]

Just been looking at needle jet choices.
 Heres some more of Rods ramblings,I hope this helps somebody and Im not teaching anyone to suck eggs.......... Putting a Reliant engine in a trike means having the carb hanging out one side in the air that is blasting past it,whereas in the reliant body it is protected and all nice and snug. Whatever choice of filter is used ,but more than likely a pancake for looks,or maybe even a aly stack,it is going to significantly change the fuel /air ratio with air being more or less forced down the carb.Im also wondering if chopping off the inlet  heated jacket is a good idea (for looks,yes) but for workability? Whatever is used ,the carb is probably going to be unable to cope even at the most extreme settings,so for a start a needle change is required.

[digger06]

 not seen many trikes with  jet changes, however i will say my needle was adjusted to cope,
seemed to run fine, although i never dyno,d it,  dunno if the carb was standard though, never stripped it,

i run a webber now, not cos its better, (it is slightly)
cos it was smaller in size an fitted better,
the best mod i did inlet wise was smooth/gasflow the inlet manifold etc, (and fit a larger bore exhaust, )
that seemed to smooth things out quite well

i dont think there is a definite standard to reliant carbs on trikes, owing to the build variations, age and the fact that every reliant engine seems to need different timing,
swap a good carb onto another engine and it often needs adjustment,
 heated manifold, ? some have it, some dont, mine didnt need it,
i recon it depends on set up/airflow  of the trike ,,theres a lot of variables there..
my 1st choice would be get rid of the manifold, see if it needs it, gets rid of complication
but before that make sure everything else is ok,  ignition and engine are spot on , otherwise its a waste of time,
rough setting might be necessary to get it running.
but  fine carb settings are the LAST thing you do imo.
if ,after that its not right, but everything else is, would i change needles etc

[Olds]

Without a rolling road and exhaust gas analyser in a wind tunnel getting the right needle is going to be trial and error.(like most things we do   )
The heated section of the manifold adaptor is there to prevent the fuel condensing on the 'outside wall' of the bend. The change from a downdraught carb to the SU via an adaptor was a bodge by Reliant.
 From what I've seen with my own engine pots two and three tend to run a bit richer than one and four. There is a 'performance mod' for the manifold that involves cutting the webs and mating faces between 1 & 2   3 & 4. I would expect this to even out the fuel air mixture flow to some degree.
I doubt that the standard needle will be far from wrong.

[ROD]

Ive still got to sort a better needle for mine,but I disagree that the orig needle cant be far from wrong.Far from wrong ,can mean maybe the 'next' type of needle ,but its still a needle change.  There must be a difference in mixture VS type of filter/stack etc,and the way the carb sits in full air flow.Im going to change my pancake filter for a more conventional type with intake away from the main airflow.The manifold is probably more prone to condensing and icing sat in the airflow than it is under a bonnet.

[scannerzer]

any of the mini tuning companies can advise on needles for an hs2.with a decent exhaust manifold on a mini
you can see 20% performance increase with a needle change.

a good book for tuning su's is David Visard's tuning bl's a series engine

it is trial and error but there is a huge range of needles and the option of filing/sandpapering the one you have but you also run the risk of destroying it!

this advice come's from years of rallying a 1399 cc metro,a well set up su is pretty close to the 45 weber i tried and easier to set up

[digger06]

a rolling road is the best way to go if you wanna get it spot on,

20% increase with a needle change,
must have been standard to start with, on a tuned motor?

[scannerzer]

yeh tuned motor 286 cam,1.5 roller rockers branch and 2"system

[scannerzer]

this may help

http://www.minisport.com/alt9501-su-carburettor-needle-chart-book.html

[ROD]

I had a 1098 a series engine with different cam etc that was in my A35 van a few yrs ago. It went up the road like a scalded cat after a session on a rolling road somewhere out Cmbridge way,respected mini tuner..unbelievable difference!(bit worried about riding the trike on a RR though,even though it is chained down.) They revved the 1098 to near destruction,flat out just over 90mph..jesus..but great fun!
 I looked at the Vizard book a few years ago,a bit heavy to read,but good stuff.