No petrol coming through??

[Colin Green]

Hi,

I just finished installing my newly re-built and cleaned carbs. Connected everything up and tried starting... no joy. Checked carb bowls and found they are empty. I can see that petrol hasn;t made it to the in line filter. Plenty of gas in the tank. I installed a new petcock and filter a couple of weeks ago (too late for the crap that blocked the jets though- hence carb re-build).

Anyone any ideas what I've stuffed up?

Cheers

 

[Colin Green]

Don't panic. I released a bowl drain and blew in the tank.. hey presto!.. petrol. But she's still running like a hairy goat unless throttle on real slow till she gets to 5000 rpm then she pulls strong and clean.

Bugger... all that work and it didn't fix the problem. I might try the old vacuum hose as the replacement hose I installed two weeks ago (a couple of days b4 she got real bad) is a much smaller inner diameter.

Fingers crossed.

 

[Freddy]

Hi there is your petcock the one with the manual prime ( lets fuel flow freely) or just on and reserve? and have you connected the vacuum hose?
I put an inline filter in also to late to stop the crap settling in the carbs. An inline filter is a choice that some here say is good and others say otherwise. I had a small inline filter on my GS1000L and it broke a long way from anywhere,they can be a hassle. I replaced it with a bigger one but as the GS's dont have a fuel pump the vac system did not fill it up quick enough. Also check for blockages in fuel line. If you disconnect the fuel line and put it in prime and no petrol flows the problem will be in the petcock. I hope some of that helps.



Did you strip and clean your carbs ?

 

[Guest]

assuming it is the carbs and not something else...
how's the starting and idle?
plug chop?
carbsync?

you may be running too rich. often the pilot mixture screws have to be out much less than what the factory suggests. use the "highest rpm" method to set the idle.

 

[Colin Green]

Hi there is your petcock the one with the manual prime ( lets fuel flow freely) or just on and reserve? and have you connected the vacuum hose?
I put an inline filter in also to late to stop the crap settling in the carbs. An inline filter is a choice that some here say is good and others say otherwise. I had a small inline filter on my GS1000L and it broke a long way from anywhere,they can be a hassle. I replaced it with a bigger one but as the GS's dont have a fuel pump the vac system did not fill it up quick enough. Also check for blockages in fuel line. If you disconnect the fuel line and put it in prime and no petrol flows the problem will be in the petcock. I hope some of that helps.

Did you strip and clean your carbs ?

Manual prime option *Check*
Tried in prime position.. no difference

Vacuum hose *Check*
Tried swap to new & back

In line filter *Check*
I now recall that I installed it (big) and new petcock "after" the problem got real bad. (crap in petrol drained from bowls 4 times suggested a filter was in order)

Line blockages *Check*
Checked and cleaned... all good

Petcock *Check*
New petcock installed

Strip and clean carbs *Check*
Fully striped cleaned (proper.. to GS Resources spec's)

Thanks Freddy.

A big thanks to all those who have contributed to the quality GS-R *How to* articles. Much appreciated.

assuming it is the carbs and not something else...
how's the starting and idle?
plug chop?
carbsync?

you may be running too rich. often the pilot mixture screws have to be out much less than what the factory suggests. use the "highest rpm" method to set the idle.

Thanks

Hey Chap... How's it going?

Seems to start fine but idle is for S**t... with or without (but most notable "with") the choke engaged she will sit at a Rpm for 5 or 15 seconds then drop to around .9 to 1.2 'ish' cough & fart till I give the throttle a blip and (readjust choke when cold) and keep the between 1.5 to 2k (repeat cycle again when using choke). When starting off she makes a sort of throaty sucky sound and behaves like it's 5 seconds to completely empty on main tank (if you leave it too late b4 switching to reserve)

What's this "plug chop" thingy?.. I checked the spark plugs and no wetness/pitting or apparent irregularities. (swapped them around just in case any change was detectable.... No issue noticed.

*Pilot jet*... Yikes!.... Is this the "pilot jet" under the 'plug' next to the needle jet in the float bowl!!!???... I screwed it all the way in... Oop's!.. Say I didn't f**k up.#-o
If the pilot jets you refer to are the "pointy air screws with springs, washers & O rings"... then I set those at 1.5 turns out from closed.

Carb sink not yet done as I figured that I need to solve this problem first She was going reasonably well when I got her about 5 or so weeks ago apart from occasionally behaving like this when she was getting below 33% full of fuel and after a bit of a quickie followed by a bit of coasting... when accelerating again the same symptoms were evident but she would clear fast when petcock was switched to prime. (the reason I got the new petcock):-({|=

What be this "highest RPM method"???

Cheers.

Colin

P. S I heard that an immaculate 78 GS1000 is to be made available for $3k NZ if you know of anyone... (I'd buy it if I could)

 

[Zooks]

What is this, a Kiwi only thread? Where did all of you guys come from?

 

[Colin Green]

What is this, a Kiwi only thread? Where did all of you guys come from?

New Zealand

Typical bloody aussie.... comes to a help party and brings more questions than answers.

"Where the bloody hell are" the helpful gurus who know about these things.. (Stamps feet impatiently... looks at watch):wink:

 

[climber11]

Prime?

Prime?

Sorry to hijack the thread but...

I too have a prime spot on my petcock, on, and reserve. When I switch it to on, no fuel comes out. Prime, has good flow. reserve has no flow. I took the bowl apart, and its as clean as a whistle. Could someone have put this thing together incorrectly in the past? New bike woes....

 

[MelodicMetalGod]

What's this "plug chop" thingy?.. I checked the spark plugs and no wetness/pitting or apparent irregularities. (swapped them around just in case any change was detectable.... No issue noticed.

*Pilot jet*... Yikes!.... Is this the "pilot jet" under the 'plug' next to the needle jet in the float bowl!!!???... I screwed it all the way in... Oop's!.. Say I didn't f**k up.#-o
If the pilot jets you refer to are the "pointy air screws with springs, washers & O rings"... then I set those at 1.5 turns out from closed.

Carb sink not yet done as I figured that I need to solve this problem first She was going reasonably well when I got her about 5 or so weeks ago apart from occasionally behaving like this when she was getting below 33% full of fuel and after a bit of a quickie followed by a bit of coasting... when accelerating again the same symptoms were evident but she would clear fast when petcock was switched to prime. (the reason I got the new petcock):-({|=

What be this "highest RPM method"???

Cheers.

Colin

P. S I heard that an immaculate 78 GS1000 is to be made available for $3k NZ if you know of anyone... (I'd buy it if I could)

RE: Plug Chop: Riding at a specified RPM then immediately shutting down and pulling and reading the plugs. Used to help determine if mix is rich/lean/just right. For more detail search the forum as much has been written up and there are a few variations to the method.

RE: Pilot Jets: Well, there's pilot jets which are just that and you find them INSIDE the carb as you describe and then there's pilot screws which you seem to accurately describe as ""pointy air screws with springs, washers & O rings"... then I set those at 1.5 turns out from closed." Many folks find that the bikes do much better with set over 3 turns out from closed.

RE: Highest RPM Method: It's a "by ear" method of setting the pilot screws in which you adjust them to achieve the "highest rpm". Again, do a search on the forum and you'll find the details are already written up.

RE: Carb sync: That would be last on my list as well, but it's definitely a must to get the bike up to perfect tune.

Best of luck!

 

[MelodicMetalGod]

Sorry to hijack the thread but...

I too have a prime spot on my petcock, on, and reserve. When I switch it to on, no fuel comes out. Prime, has good flow. reserve has no flow. I took the bowl apart, and its as clean as a whistle. Could someone have put this thing together incorrectly in the past? New bike woes....

That's how it's designed when the engine is off. Engine vacuum is required to pull fuel in the "On" and "Res" positions so that you don't leak fuel when the engine is off. Prime is a simple "open pipe" for use only when you think the bowls are low are empty and you need to ensure that you have enough fuel in the bowls to start. The idea is leave the thing in the "On" position under normal circumstances.

 

[mortation]

There are so many possibilities.

so let me see what they have not already covered...

1) Gas cap, vents not clogged?

2) If you hold the gas line in one hand and suck on the vacuum line do you get gas in your hand?

3) Do you have gas in all 4 bowls?

4) Did you sync the carbs? Bench sync? Mannometer?

5) Do you have good spark from each wire?

6) If you have access to a color tune, are your Fuel/Air Screws set correctly?

7) Any vacuum leaks?

8) Do Plug chops. Take pics and post



Thats all I got off my head.

 

[Colin Green]

RE: Plug Chop: Riding at a specified RPM then immediately shutting down and pulling and reading the plugs. Used to help determine if mix is rich/lean/just right. For more detail search the forum as much has been written up and there are a few variations to the method.

RE: Pilot Jets: Well, there's pilot jets which are just that and you find them INSIDE the carb as you describe and then there's pilot screws which you seem to accurately describe as ""pointy air screws with springs, washers & O rings"... then I set those at 1.5 turns out from closed." Many folks find that the bikes do much better with set over 3 turns out from closed.

RE: Highest RPM Method: It's a "by ear" method of setting the pilot screws in which you adjust them to achieve the "highest rpm". Again, do a search on the forum and you'll find the details are already written up.

RE: Carb sync: That would be last on my list as well, but it's definitely a must to get the bike up to perfect tune.

Best of luck!

Thanks for that.

I'll try winding the air pilot screws out another 1.5 turns when I get home from work.

I take it (from your lack of comment) that the pilot jets (inside the carb) are ok screwed in all the way?

Thanks for your time

Colin

 

[mortation]

Thanks for that.

I'll try winding the air pilot screws out another 1.5 turns when I get home from work.

I take it (from your lack of comment) that the pilot jets (inside the carb) are ok screwed in all the way?

Thanks for your time

Colin

The pilot jet should be all the way in. The only adjustment on CV carbs is the Fuel Mixture screw.

2 - 2.5 turns out is usually a good place to start tuning.

 

[Colin Green]

There are so many possibilities.

so let me see what they have not already covered...

1) Gas cap, vents not clogged?

2) If you hold the gas line in one hand and suck on the vacuum line do you get gas in your hand?

3) Do you have gas in all 4 bowls?

4) Did you sync the carbs? Bench sync? Mannometer?

5) Do you have good spark from each wire?

6) If you have access to a color tune, are your Fuel/Air Screws set correctly?

7) Any vacuum leaks?

8) Do Plug chops. Take pics and post


Thats all I got off my head.

That's a terrific effort thanks.

1) Gas cap, vents checked ok

2) Bloody good test idea... will try when I get home from work

3) Gas in all 4 bowls checked ok

4) Carb Bench sync???? WTF?? I guess the anser is 'No' What? How? Please expand... Thanks.

5) good spark from each wire.. will check when I get home from work

6) Colour tune??? don't know what it is. Air screws set at 1.5 turns out, recent advice suggests that 3 turns would be better. Intend to try screw adjustment when I get home from work.

7) Any vacuum leaks? I honestly don't know, but don't think so. new petcock installed tried new vacuum line, visual inspection of carb diaphragms while lightly stretching revealed not holes/tears or thin bits. What else is there to check?

Thanks for your post of very helpful comments.

Regards

Colin

 

[Colin Green]

The pilot jet should be all the way in. The only adjustment on CV carbs is the Fuel Mixture screw.

2 - 2.5 turns out is usually a good place to start tuning.

Cheers

Will change to 2.25 turns out when I get home from work.

Thanks

Colin

 

[mortation]

That's a terrific effort thanks.

1) Gas cap, vents checked ok

2) Bloody good test idea... will try when I get home from work

3) Gas in all 4 bowls checked ok

4) Carb Bench sync???? WTF?? I guess the anser is 'No' What? How? Please expand... Thanks.

5) good spark from each wire.. will check when I get home from work

6) Colour tune??? don't know what it is. Air screws set at 1.5 turns out, recent advice suggests that 3 turns would be better. Intend to try screw adjustment when I get home from work.

7) Any vacuum leaks? I honestly don't know, but don't think so. new petcock installed tried new vacuum line, visual inspection of carb diaphragms while lightly stretching revealed not holes/tears or thin bits. What else is there to check?

Thanks for your post of very helpful comments.

Regards

Colin

4) A carb bench sync is done when you reassemble the carbs to make sure the butterflys open at the same time (Or as best you can till you tune with a manometer). Since yours are already on you may just want to use a a manometer (carb tuner).

6) Color tune is the best way to tune your mixture screw. I dicked with mine for a week or more till borrowing one of these from a guy here. zero'd right in with it. It is a clear spark plug you install and look into and as its running you turn your mixture screw till you get the right color. Easy as cake and very accurate.

You can grab them from eBay or Morgan (UK).

7)Try spraying around all your rubber with water or WD40 and watch for idle drops. This will help track down leaks as the wat/WD40 will get sucked in.

Hope that helps!

 

[mortation]

oh, and going 3 turns out on your mixture screw is heading pretty rich. Its fine to get the bike running but you will need to tune it down from there using highest rpm method or the color tune. Or you are going gunk up every set of plugs you put in

 

[Colin Green]

4) A carb bench sync is done when you reassemble the carbs to make sure the butterflys open at the same time (Or as best you can till you tune with a manometer). Since yours are already on you may just want to use a a manometer (carb tuner).

6) Color tune is the best way to tune your mixture screw. I dicked with mine for a week or more till borrowing one of these from a guy here. zero'd right in with it. It is a clear spark plug you install and look into and as its running you turn your mixture screw till you get the right color. Easy as cake and very accurate.

You can grab them from eBay or Morgan (UK).

7)Try spraying around all your rubber with water or WD40 and watch for idle drops. This will help track down leaks as the wat/WD40 will get sucked in.

Hope that helps!

Cheers

4) I actually played with the butterflys a bit and noted how they all snapped shut at the same point & time.. so am happy with that issue.

6) I'm partially colourblind but will consider accessing one (and a pair of good eyeballs to assist)

7) Thanks... will give WD40 a try when I get home after work.


Re air fuel mix screws... I will try 2.25 turns out to see if it makes any difference.

Thanks for your help.

Colin

 

[Guest]

rarely you'll find that the pilot mixure screws are out equally on all 4 carbs
thats why you use the highest rpm method

take of the tank
set the above screws at 2 turns out
warm up the engine and let it run
adjust the idle at aprox 800-900rpm
SLOWLY turn the screw at carb #1 in - at some point the rpms are going to start dropping and the engine wont run as smoothly
start turning the screw back out while you get the highest rpm read and a smoother sound from the engine
at some point further turning out the screw wont make any difference (and even further out may again take away the smoothness and the rpms)
you want your screw as much IN as possible without affecting the rpms/smoothness
re-adjust the idle to 800-900rpm
stop the engine to let it cool down a bit or place a big fan in front of the engine and do this while the outside air is cooler (morning/winter)

proceed with carb #2
etc.


before doing the above as well as carb sync you cant really expect any decent results (or take the carbs out of the equation as the culprit of your problems)

maybe someone at KB can lend you a carb sync, i dont have one myself but would be happy to assist you using it

 

[Guest]

P. S I heard that an immaculate 78 GS1000 is to be made available for $3k NZ if you know of anyone... (I'd buy it if I could)

i'm definitely interested
would like to see it, although i think i'd prefer the route of restoring one myself (BEWARE: you can get addicted to resto's :shock: )