1985 big red 250es running lean....how do i fix this?

[dylanisaacs]

my 1985 big red 250 is running lean because i pulled the plug today and the bottom-inside of the plug was white. how do i fix this? and can this cause overheating?

[dougspcs]

Can definitely cause engine damage..

Remove your carb and look for dirt or restriction in you main jet, if none then move the main up to the next size number jet to richen the mixture.

But double check you are running the correct plug..too hot a plug will also give the appearance of running lean..

Either us bad..the stock NGK # DR8ESL

[TxPowderCoater]

like said, check for crap in carb, take the time to unscrew the low speed jet and the main jet and get them clean with #bits and air pressure. also check emulsion tube to make sure the holes are open and happy as well.

[dougspcs]

like said, check for crap in carb, take the time to unscrew the low speed jet and the main jet and get them clean with #bits and air pressure. also check emulsion tube to make sure the holes are open and happy as well.

What's the emulsion tube? Your BR got parts on it mine doesn't?

[tri again]

emulsion tube?
as I recall there some tube under on of the carb jets full of holes and usually muck.
may have been called an emulsion tube. and yes, mr Tx, I missed that sucker 3x.
Good call.

Reminds me, I never replaced the external venting tubes on
my 87 es after a 2 week carb fiasco that ended with it on the kitchen stove and some marriage counselling. Those are the only other tubes that come to mind that may make a difference.

do you have:
factory exhaust?
un messed airbox?
stock air filter?
as doug said, the correct plug?

When my 100 runs lean the exhaust gets cherryred and see through.
Can't be good.

[dougspcs]

Emulsion tube..googled it. Hey yeah I got one of those. Starting to feel jealous cuz everyone had one but me!

Handled it like a hundred times..no idea it had a name.

Always good to learn new stuff!!

[barnett468]

Hello Dougspcs

check emulsion tube to make sure the holes are open

What's the emulsion tube? Your BR got parts on it mine doesn't?

This is an item that people who are not thoroughly familiar with how some features of a particular carburetor work either don’t know their carburetor has and/or don’t know how it works.

There are many good books on carburetors that explain what effects different parts/circuits etc, have.

The “emulsion” tubes in question are actually misnamed, because they quite simply do not emulsify anything. They are simply tubes with holes called “aerator” or “aeration” holes [in this application].

Their primary function in this application is to partially “regulate” or “control” the amount of fuel that can flow through them up the maximum amount the main jet can flow at different atmospheric pressure levels inside the tube when used in a “siphon” [not forced like fuel injection] type system.

The amount of atmospheric pressure inside the tube is relative to the atmospheric pressure immediately above the open end of the tube which is relative to the velocity of the air passing immediately past the open end of the tube.


See links below for photos of “emulsion” tubes.


NEEDLE JET/EMULSION TUBE COMBO

http://www.ebay.com/itm/Emulsion-Tub...-/290294228981


NEEDLE JET/CHOKE WITHOUT AERATION HOLES (NON EMULSION TUBE TYPE)

http://www.ebay.com/itm/Mikuni-Needl...-/150847544454


PILOT JET/EMULSION TUBE COMBO

http://www.ebay.com/bhp/honda-pilot-jet

[dougspcs]

Hello Dougspcs

This is an item that people who are not thoroughly familiar with how some features of a particular carburetor work either don’t know their carburetor has and/or don’t know how it works.

There are many good books on carburetors that explain what effects different parts/circuits etc, have.

The “emulsion” tubes in question are actually misnamed, because they quite simply do not emulsify anything. They are simply tubes with holes called “aerator” or “aeration” holes [in this application].

Their primary function in this application is to partially “regulate” or “control” the amount of fuel that can flow through them up the maximum amount the main jet can flow at different atmospheric pressure levels inside the tube when used in a “siphon” [not forced like fuel injection] type system.

The amount of atmospheric pressure inside the tube is relative to the atmospheric pressure immediately above the open end of the tube which is relative to the velocity of the air passing immediately past the open end of the tube.

Barnett, you're doing it again!!

I just hadn't heard that term before and was having fun with it. I've always called it the primary nozzle!

Please don't megapost me! I didn't ask to be schooled..

But thank you for putting the big words in quotes for me to look up.

Quit being so "patronizing" and "condescending", it's not winning you any friends!

[TxPowderCoater]

What's the emulsion tube? Your BR got parts on it mine doesn't?

dunno what BR is, but my 200 has a keihn carb with an emulsion tube on the end of the mainjet, its what the needle drops into.
I guess the 250 has a different carb and if so, still clean it no matter what type it is, sounds plugged.

[dougspcs]

dunno what BR is, but my 200 has a keihn carb with an emulsion tube on the end of the mainjet, its what the needle drops into.
I guess the 250 has a different carb and if so, still clean it no matter what type it is, sounds plugged.

BR = BigRed

[dylanisaacs]

do you know how many turns to adjust it when i put it back in?

[TxPowderCoater]

do you know how many turns to adjust it when i put it back in?

there is no adjustment on the emulsion tube, snug it down and then snug down the jet into it. The air fuel screw is adjustable and it is usually 1.5-1.75 turns out is a good starting point and then fine tune from there but only when the engine is up to operating temp.


wooot 10!

[dylanisaacs]

ok but where is the air screw? i caint seem to find it in the online manual or on the carb

[TxPowderCoater]

some are actually blocked off with a small disc, If so, I usually drill through with an 1/8 bit and then use an ease out to grab the disc and pop it out. but I havent a clue w/o seeing what ya have. Some are out in the open easy to get to on the neck area that mates to the engine intake, some are on the side of the carb and some are under the very bottom of the carb by the edge of the bowl. I dunno what ya got but usually there is 2 screws that are adjustable, one is idle and its usually on the slide neck and the other is usually the air/ fuel screw.
send me a link to your online manual and I'l see what ya have and possibly help you better.
Sorry I couldnt help more.

[dougspcs]

Some carbs have air mixture screws, some have fuel mixture screws..you're has the later.

The fuel mixture screw is behind the float bowl under the carb..it isn't plugged.