NO FIRE-PISTON #3

[sebby110]

Hello Fellow GSers;

I would appreciate if anyone can shed a little light on this problem of mine.
I'm also currently going thru the site's "search" resource...I'm sure someone else has had this problem. Here it goes..

When I put the full choke to start a cold bike, all 4 pipes get blazzzinnn hot. GREAT !!! ALL PIPES !!!
When I release the choke, and idle, #1,2 and 4 stay hot...#3 seems to cool down (warm) ( a nice handwarmer temperature for cold days)...but it's telling me it's not firing...or not getting any fuel ???
Plug has plenty of spark and fairly clean.
I tried tapping the external carb body if maybe something was sticking and not closing..or not opening....NO CHANGE.
Tried carb cleaner...NO CHANGE

1- How can I tell if I'm getting fuel to the cylinder ? I took the plug off to smell for fuel...couldn't tell. Is there someother way to tell for sure ??

2- What could be causing this ??

Carbs were U/sonic "professionally" cleaned last year near seasons end...bike ran very well (all pipes hot at idle). This year...Urrggg...not

3-Why would the #3 be soo hot at full choke...then cool off when idling ????

Thanks for any help.
Ride TALL....Sebby

[Anonymous]

seems like fuel is staying in the carb... the needle assy is prolly stuck..... or some crap is being trapped..... in the jet.... or the idle passage.....

i had to remove the mixture screw to clear a similar problem.... and it is still recurring.... so i believe that the needle assy needs replacement, no gas or little gas.... yes they are the original in my case

Michel
81 1100E (44,000 miles)

[Redman]

When you think of your carbs, think that each of the four carbs actaully is comprised of 3 air/fuel mixers, each carburator is actaully 3 carburators in one. There is the low speed, and there is the high speed and there is the starter (enricher or choke) system in each carburator, each one operates fairly indepandantly, and each one can have its own problem like getting blocked off with a piece of crude-rust-varnish-whatever.
So, back to your problem that you have stated with such good observations. - - Yah, makes sence that the starter/choke system is working good so it runs on choke, but the slow speed has a problem so it doesnt idle with choke off. Seems like some carb cleaning is in order. Others with more experince will need to tell you how much cleaning.
This perrty much the first start of the season?

[sebby110]

Folks;
Thanks for your responses.


It does seem like I'm having troubles with the "idle" circuit.
Now the question is...
When I open the carbs, which set of needles controls the idle circuit ?
Where do I begin to look ??

I don't think there's a problem with the float/needle cause it seems to work fine (plenty of gas) when at full choke.
I'm not Mr. Carb... Jets...needles...somewhat foreign to me.

Redman;
I have been running on and off thru the winter pretty much...except for extreme days. I've noticed this problem a couple of weeks ago.

[Redman]

- Slowspeed/idle air jet is the larger one on the left (main is the one on the right) of carb throat. Slowspeed/idel/pilot gas jet is the little one off to the side with the rubber plug (main gas jet is the bigger one in center) in carb bowl area. Slowspeed/idel circuit also includes the screw adjustment and port in top of carb throat by the throttle butterfly plates.
- I Dont have much experience with this, other than what I see in Zuki manaul, has great diagrams.
Oh, and I am refering to manaul for the CV carbs on 1980 GS850. Dont recall you specifically saying what bike you are refering to.
- The "garage" section of this web site has some (96 I think) great picks of carbs being dissassembled.
- Myself, all I have done is, pull off carbs, and taken off bowls and sprayed carb cleaner into/thru jets and ports, but havent ventured into taking out jets. Dont want to get even anywere close to having to readjust anything. So I am no expert.

[lhanscom]

Here's my take, and it only apply's if you have CV carbs, as I don't know much about the VM's. I'd say the idle jet on #3 is clogged. Here's why: In your carb there is the idle jet, that takes care of idling (strange I know), then there is the needle/needle jet that takes care of everything between the idle jet, and the main jet, the main jet is for wide open throttle. The choke circuit actually works with the needle. When you turn on the choke it opens a passage that causes the needle to rise up some, thus enrichening the mixture, and with the throttle closed, it creates the effect of a 'choke'. This cylinder is probably not running great even with the choke on, but it at least runs, when you shut it off, the needle goes back down, and the idle jet is on it's own, so the cylinder shuts down. So all that to say that you need to clean your carbs, I would probably just pop the jets out and put them in some carb cleaner to soak, then blow the crap out. It may help to open one of the carbs that is running properly first, so you can see what your jets are supposed to look like first. Hold them up to a light so you can see the size of the hole to compare to the other jets. Good luck.

[lhanscom]

Take off the float bowl, your idle jet will have a rubber plug over it, just pop it off and get a small screwdriver to unscrew it. There are no adjustments to be made with the idle jet, or the main jet, they just screw in. The idle adjustment is on top of the carb just before it goes into the engine, there may be a metal plug in the top of that, if you can't see it. Working on carbs is fun, I find it relaxing. Put on some good music, have a clean place to work, and do one carb at a time.

[sebby110]

Folks;

You all have made my day...and restored my faith in humanity.
Thanks for sooo much good feedback.
Redman, the bike I'm talking about is my '80 GS 850. I also have an '83 850 which runs like the dickens...for now..hmmmmm.

[Anonymous]

If it is built like my 82 750, the number three carb is the one that pulls vacuum on the fuel petcock. If the petcock or the attached vacuum hose has gone south, it may be sucking air into the intake manifold and starving it for fuel. Happened on mine.

[sebby110]

Just thought I'd send you all a quick update.

Glad to report that...ALL PISTONS are a GO.
I completely removed the air screw from #3 carb, sprayed a good amount of carb cleaner in the port, reset the screw (about 3 1/2 turns from bottom) and she fired right up.
Has been working fine with choke open or closed for a couple of weeks.

Thanks for all your help.

I have another question relating to sight glass on the brakes reservoir.
The round vision glass, to see the brake fluid level, is old. It has that crazed, dried-out look. I'm not too comfortable with that.
Can you just replace the sight glass or do you have to replace the entire master cylinder reservoir ???

Thanks again