wont start

[tomo]

Hi Matchless, no offence taken, I quite agree that there must be something amiss. I guess I`m a bit old school in that provided the bike runs well I leave things alone. I`ve just got so used to having to blow into the tubes its become part of the starting procedure !. Only required if the bikes been stood a few days though. But to answer your question, one of my GS750`s, the chop, has an in line filter but the other bike is stock. The CX is stock too, no in line filter either.

[rustybronco]

My opinion.

A likely scenario...
You would be pressurizing the fuel in the bowls when blowing air in the vent tubes,
force feeding fuel into the intake system.

with the choke circuit not properly working, ether by plugged passages in the fuel bowls or, in the transfer tube in the main body, you would get no "extra" fuel for cold enrichment.
with the added presurization of blowing into the vent tubes, extra fuel would go to up the main jet past the needle in the needle jet and also some additional fuel through the "pilot" circuit: allowing the engine to start.

when the engine has started, you have the negative pressure of the engine vacuum drawing up fuel as normal: keeping the engine running.

not enough information to properly diagnose at this time.

whatever the reason for blowing into the vent tubes, a problem still remains with the carbs.

[tomo]

Hi Rustybronco. I agree blowing into the tubes forces a bit of fuel through, but when I had the carbs stripped a few years back I know all the passageways were clear, used carb cleaner, guitar string & compressed air. Still needed to blow into tubes to start it after the bike had been off road a few days. I agree something is not right, but its not what I`d call a problem, the bike starts and runs well and at the end of the day thats all I want. I have wondered whether it may be connected with something else. All my bikes are high mileage, don`t know about the others the trick has worked for. Wonder if compression is a bit down, whether air is`nt sucked through the carbs enough when the engine is cold to "pull" the fuel into the stream. I guess once its fired the air is getting pulled in a lot quicker. Can`t remember what the readings were last compression check, I remember they were less than spec but not by too much. Think I`ll check all the bikes compression this week-end out of interest. Could be barking up the wrong tree, but I guess it sounds like a possible reason they need "blowing" after a few days off the road. What do you reckon ?.

[Matchless]

My opinion.

A likely scenario...
You would be pressurizing the fuel in the bowls when blowing air in the vent tubes,
force feeding fuel into the intake system.

with the choke circuit not properly working, ether by plugged passages in the fuel bowls or, in the transfer tube in the main body, you would get no "extra" fuel for cold enrichment.
with the added presurization of blowing into the vent tubes, extra fuel would go to up the main jet past the needle in the needle jet and also some additional fuel through the "pilot" circuit: allowing the engine to start.

when the engine has started, you have the negative pressure of the engine vacuum drawing up fuel as normal: keeping the engine running.

not enough information to properly diagnose at this time.

whatever the reason for blowing into the vent tubes, a problem still remains with the carbs.

rustybronco,
You are making a lot of sense here. The symptom is then like trying to start the bike without the choke (OK, this is a starting enrichment device and does not reduce the air, but provides a very rich fuel/air mix for starting via its own passage) Thus if the starter jet is not passing fuel into the starter circuit, it could be due to blockage, starter circuit not opening or not reaching the fuel level in the float bowl, then the choke would not work.

tomo,
Do you think your choke is working properly? Maybe its not opening fully or blocked. On my bike if you goose the throttle with the choke out it becomes hard to start, the throttle must be left closed when the choke is out. When cold it definitely will not start without the choke and with full choke with throttle closed it takes on the first or second swing of the starter, then climbs to 3000 rpm and I then gradually push the choke back and the rpm's settle at 1100 after about 30 to 60 seconds. When warm even after a few hours it still does not need choke.

My apologies for asking this as this solution actually intrigues me quite a bit.

[rustybronco]

My apologies for asking this as this solution actually intrigues me quite a bit.

The only way to know the answer would be to take apart the carbs on a bike with the problem.
plugged/partially plugged passage(s) in the choke circuit would be my guess.

It is my opinion that the carb bowls are more often, not cleaned well enough and tested for proper flow through the very small passage in it.

which would make the proper cleaning of the rest of the choke circuit, about useless.

[raider]

Can someone explain how the choke works. I am having a hard time understanding what it does and how it works.

[tomo]

Hi Matchless & Rustybronco. I`m sure the choke works ok, like I said I only need to use the trick when the bikes been stood a few days. If I`ve been riding say the day before, in cold weather I have to use choke to get the bike started next day and it starts ok. I know that a lot of people don`t clean carbs properly, but believe me I`m pretty thorough. I`m certain that all the passageways were cleared when the carbs were stripped. Also, all three of my older bikes need blow starting if they`ve been stood, can`t see them all having the same blockage. I am intrigued as to why the trick works too, but at the end of the day it does. When I see a post about a bike not starting, or if I`m out and about and see someone having a problem getting one started, its the first thing I suggest. Nine times out of ten it works. At the end of the day, getting the bike started is all that counts and provided it runs well, where is the problem ?. And to be fair, my chopped GS was built in 95, had to blow start it to get it running then and been doing so ever since, still runs like a dream.

[Matchless]

Hi Matchless & Rustybronco. I`m sure the choke works ok, like I said I only need to use the trick when the bikes been stood a few days. If I`ve been riding say the day before, in cold weather I have to use choke to get the bike started next day and it starts ok. I know that a lot of people don`t clean carbs properly, but believe me I`m pretty thorough. I`m certain that all the passageways were cleared when the carbs were stripped. Also, all three of my older bikes need blow starting if they`ve been stood, can`t see them all having the same blockage. I am intrigued as to why the trick works too, but at the end of the day it does. When I see a post about a bike not starting, or if I`m out and about and see someone having a problem getting one started, its the first thing I suggest. Nine times out of ten it works. At the end of the day, getting the bike started is all that counts and provided it runs well, where is the problem ?. And to be fair, my chopped GS was built in 95, had to blow start it to get it running then and been doing so ever since, still runs like a dream.

Thats very interesting. I have never looked at how the choke is affected if the floatbowl is low. If you have evaporation of fuel rom the floatbowl and a vacuum petcock, usually such a problem is sorted by putting on prime to start. I am just shooting in the dark here, but as you say it works for you and you do not mind doing it so thats OK.
Makes me think of those alcohol test things that were on the market and your car would not start unless you blowed in it and was under the limit! Some called it "Quickstart" ands said they were just giving it a high octane boost!
Thanks for all the replies and if you ever localise the issue let us know please.
Keep well.

[rustybronco]

I know that a lot of people don`t clean carbs properly, but believe me I`m pretty thorough. I`m certain that all the passageways were cleared when the carbs were stripped.

My comments were of a general statement, not directed at you. my apologies if they came off that way.

Also, all three of my older bikes need blow starting if they 've been stood, can`t see them all having the same blockage. I am intrigued as to why the trick works... too

localized fuel volatility issue? fuel evaporating after a few days?
I wonder how many factors may be involved...

[skidMarkNZ]

so hang on, fuel in carb bowls but dry plugs, ummmmm have you got an idle set at all on it? if the slides are fully closed it aint gunna do ****.

[skidMarkNZ]

Can someone explain how the choke works. I am having a hard time understanding what it does and how it works.

www.howthingswork.com

www.wikipedia.com

[tomo]

Hi rustybronco. Sorry, I did`nt mean to come across sounding offended or defensive, I know you were`nt having a dig or anything. You are right though in that there must be a reason for it. Thats the trouble when we write, can sometimes come across the wrong way. Much easier if we could sit down with a beer or two to chat about these things.

[rustybronco]

Much easier if we could sit down with a beer or two to chat about these things.

You buying? I'll bring the wrenches!

[tomo]

Ok with me !. Could be a long walk and quite a bit of swimming to get to the pub though !.

[rlong74]

Hi Raider. Before doing any work on the carbs, try first turning the petcock to prime for about 30 seconds then turn back to the normal position, then put on full choke and try to start her up. If that fails, try blowing into each of the two carb breather pipes a couple of times. Pull on the choke again and try the starter. Some of the other guys are probably thinking "oh! not again" as I`ve posted this tip a few times, but its helped get a lot of bikes going too !. My GS 750`s won`t start without a "blow job" if they`ve been stood a while. Worth a try !.

Thanks for the tip.
I had gone through just about everything electrical to no avail. I saw your tip and it worked. It only works however with the fuel cock on prime. But it works. Thanks!