worn needles and tubes, symptoms
 

I was wondering if anyone has replaced needles and emulshon tubes in their carburators because of wear? If you have could you explain the symptoms the bike had before you replaced them.
thank you, winston

I had worn needles on an old CB550/4 years ago. Symptoms were high fuel consumption & a lack of throttle response as there was always too much fuel being sucked in to the engine - felt a little like the choke was permanently open. Symptoms started to disappear as you got to full throttle when the main jet took over.

I got around the problem by dropping the needles one notch. Vast improvement in fuel economy - went from 75 miles before hitting reserve to 130 miles. If you try this, keep an eye on plug colour etc.

had this problem several times on a trx850 (design fault...) - i agree with the above - feels like a sticky choke - and very "fluffy" around town and on part throttle.

the replacement tubes on teh trx were only a tenner each from a main dealers, they had them in stock, took 5 minutes to fit and made it feel like "new" again...

if yo uwant to check, take out teh emulsion tube and look down it into a (reasonably) bright light - it should be PERFECTLY round, any ovaling or wear marks and it is f88ked. (they get worn by the needle rubbing / chattering on the tube. as the needles are generally hard metal and teh tubes soft, the needle (generally) doesn't get damaged.

putting the carbs together very carefully, (so the the needle falls in the hole without touching the sides) is time worth spending....

dan

Some good info here http://www.factorypro.com/tech/needle_jet_Mikuni.html

EDIT (another link): http://www.factorypro.com/tech/needle_jet_wear.html

As mentioned by dan, the OEM tubes used on the Mikuni carbs for the trx/tdm are dreadful.

A magnifying glass is also a huge help to check for oval tubes.

Cheers
dapleb

[This message has been edited by dapleb (edited 07 October 2005).]