I have a Honda CB700S that doesn't want to stay running after sitting last winter. My guess would be carbs. My only question would be how hard is it to remove and clean the carbs.

 

Not difficult at all, check out this website for help on pulling/cleaning the carbs.

http://en.wikibooks.org/wiki/Honda_N...retor_Cleaning

Good Luck.

 

not very hard at all mine sat all winter and i just put half a can of seafoam and a gallon of gas and then opened the float bowls and let it run out till it was clear. she started up and stayed on. mine is a cb650sc btw but they are fairly close

 

hello,

usually, when motors that are carbureted are allowed to sit around for awhile and they don't start, it could be because of several reasons. in this case, since your motor is a 4 stroke motor that doesn't require a 2 stroke oil mixture, i will list the most common causes.

a symptom that you may have gummed up carbs is that the tank has fuel and the motor starts, but does not idle. many times it will idle if you pull the choke, but it dies when you turn off the choke. this is different than an electrical problem with rough idle, but at times the symptoms cam mimic each other, ie: rough running, not all cylinders firing/running. if you suspect this, when the engine is nice and cold, start the motor for a second or two at the most and feel the exhaust pipes coming out of the head carefully. lightly tap them with your fingers so that you don't get burned if they are too hot. remember, run them just a second or two. you can feel if a particular cylinder is combusting or not, or erratically. smell the fuel to make sure it doesn't smell like varnish. do not stick your nose into the tank's fill up hole, but rather, like in science class, 'fan' the area near the fill up hole up towards your nose.

make sure that the fuel petcock valve is in the on position and that there is enough gas for the valve's position. if it's on run but has only a little gas, you may need to turn it to reserve if the petcock has that setting.

get a flashlight (not match or other open flame sources of light) and look into the tank. is the tank metal shiny metal or is it rusty? look at the bottom of each side of the tank, also the front to rear for drops/pools of water on the bottom of the gasoline. if the tank is really rusty or has a lot of debris in the gas, you'll have to pull the tank and drain the fuel in it. then you'll have to remove the petcock valve and clean it, and the filter in it that protrudes into the gas tank. some models don't have this, but rely on an external filter. some have both. the mesh if very fine so it can clog easily.

gasoline has additives (cleansers, octane, etc.) and as the gasoline evaporated over time, the things that can't evaporate, or evaporate at a much slower level are left behind in the carburetor bowls, where they get thicker and thicker. it will reach a point where gas also changes its composition into a kind of a varnish. it is thick, sticky, and won't run in an engine. in fact, it may plug up many of the brass parts that have small holes like the pilot jet, the air holes in the emulsion tube (it's where the gas pulled up through the main jet gets broken up into smaller droplets by 'jets of air'
that is pulled through the main air jet at the mouth of the carb, so that when these smaller droplets hit the venturi, they're more easily broken down to even smaller droplets like mist), and other smaller parts. if really bad, the varnish can stick a float valve open or closed.

nowadays, with the gasoline containing ethanol, there is also water contamination. ethanol is an alcohol, like methanol that is used for racing. they both are water soluble and have the ability to absorb moisture (humidity) right out of the air and over time, these tiny molecules of water bond to each other to form larger and larger droplets of water. since water is heavier than gasoline, it will settle to the bottom of your carburetor and roll around unless your carburetor bowl has a lowered section in which the main jet sits in. this is precisely why the pilot jet, which controls the amount of fuel in the air/fuel mixture from idle to 1/8th throttle (on some carbs i've found it can affect up to 1/4-1/3 throttle position). think of your gas tank as a lung of sorts. if your tank is almost empty, during the day it heats up a bit and at night it cools. since air expands with heat, the air in the tank expands and vents out of the tank. when it cools, the air condenses and in doing so, pulls in air outside of the tank, which has a certain % of humidity which will be absorbed by the ethanol in the gas. if your tank is 1/2 full, it will breathe in and out half as much air/humidity as the empty tank. if it's almost full, it will breath in and out hardly anything at all. so, if you're going to let your bike sit for a long time, either fill it up all the way and add a fuel stabilizer, or drain it as much as you can and start and run the carbs until the motor dies from lack of fuel. if you want to take it a step further, as you hear the motor start to sputter when it's running out of fuel, pull the choke as it will drain your carbs even more as the pilot jet sits higher in the bowl than the main jet. or, you can just let it run until it dies, then open the screws at the bottom of the bowl to drain what gas is left in there (some are phillips head, some are hex head screws).

if you want to try an easier fix besides yanking the carbs off. try this, i've done it before. first, take out the screws at the bottom of the bowl to drain any gas, varnish type gas. if nothing comes out, look at the end of the screw. is it clean or does it have a dried yellowish powder/shiny yellowish varnish on it? if it does, then there is most likely a buildup of varnish in your carbs. raise the tank (if needed) and remove the main fuel line(s) that go from the tank to the carburetor fuel fitting. most 4 cylinder motors have one line that splits into 2 that go to the carbs. buy a couple cans of carb cleaner with the red straw attachment, or you can use a small funnel to insert into the fuel line going to the carbs. spray as much carb cleaner as you can until the line is full of carb cleaner and let it sit for a couple of days, or a little more if you think the varnish is really bad. open the drain screws on all carbs and drain the carb cleaner that's been sitting in there. the dirtier it looks, the more it will have done its job. drain all of the carbs, then do this step individually. fill and drain each carb several times until the gas is coming out clean with no debris or unusual color. when all of the carbs are done, plug the bottoms up, attach the fuel hose back to the gas tank petcock valve, make sure there's enough good gas in the tank, and start it up. hopefully, this will have cleaned the carbs enough to run well for you.

if you decide to pull the carbs and need help, you can find online instructions, or you can post and i'll try and write you a simplified instructions. i'm thinking that there are many great simplified ones out there though.

good luck,

david

 

Wow thats a long post when the answer is it needs a carb clean.

 

this is why i don't go on forums and came here in hopes of finding mature members. at least my post offered help. besides your cynicism, what did you offer? only a 8 year old's answer and no help. also, learn punctuation before trying to look smarter than the person you're trying to cut down.