S.U Carb jetting

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nednortonrider
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S.U Carb jetting

Post by nednortonrider » Mon Apr 30, 2018 8:54 am

I'm about to strip and clean the S.U's on my Interpol .The bike is running "OK" but as it's running through Commando "peashooter" pipes which are pretty much straight through and taking into consideration the poor quality of the fuel these days would anyone recommend any changes (main jet sizes etc) ?? . Cheers .

fogrider
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Re: S.U Carb jetting

Post by fogrider » Mon Apr 30, 2018 10:21 am

SU's aren't a carb full of jets. Just one which is almost always a 0.8". To change fuelling is a case of changing needles, a real minefield ! Stick to the stuff in there and see how it runs once the idle mixture is correctly set.
Acceleration and top revs can be affected by changes to the spring and damper oil, but if you're really keen to have it metering exactly right, book a rolling road session.
Regards, Terry.

nednortonrider
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Re: S.U Carb jetting

Post by nednortonrider » Mon Apr 30, 2018 10:43 am

Spoke to a bloke about a rolling road session .He said it could be difficult to get accurate readings due to the posifeed two stroke system on the rotary engine !!

fogrider
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Re: S.U Carb jetting

Post by fogrider » Mon Apr 30, 2018 6:51 pm

How odd !
Maybe someone who has had a rotary dyno'd will care to comment ?

I set mine with an old air/fuel meter, works fine.

johnbirchjar
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Re: S.U Carb jetting

Post by johnbirchjar » Mon Apr 30, 2018 11:37 pm

How come the "Peashooter" pipes havn't melted exclaim,and how many "Burn Marks" on your biker boots wink,J.B.

nednortonrider
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Re: S.U Carb jetting

Post by nednortonrider » Tue May 01, 2018 9:03 am

They are stainless steel and a lovely colour from straw brown tapering away to polished stainless at the reverse cone end .The colour is exactly the same both sides so I guess the rotors mixture/balance is good. Very Happy .A sort of external/visual colour tune !!!!!

johnbirchjar
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Re: S.U Carb jetting

Post by johnbirchjar » Tue May 01, 2018 11:40 pm

I'm so glad it's not just me!('cos the colour of the exhaust pipes is how I check my Carb's:Mixture& Balance Very Happy)
Someone did try to explain to me once why this method can't be used with Fuel Injection,and why (with F/Inj:) the exhausts never get that lovely pale grey almost white colour after a couple of hundred mile's motorway blast cool,J.B.

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