No petrol coming through??

[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

[psyguy]

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

[psyguy]

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: )

[Colin Green]

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

Excellent little "how to" post thanks.

I will give it a go tonight (or this arvo if I knock early)

Good idea re carb sync. Will make enquiries when I get her settled down.

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: )

Lol.... I'll see if I can get the contact details to forward to you.... perhaps he'll rough it up for you

[Colin Green]

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: )

Just checked. My mate wants to look at it and try it out (hasn't had a bike in years and has been leaning toward cruisers but likes mine so is keen to try it out) Will let you know if he decides he would prefer a cruiser.

[psyguy]

Just checked. My mate wants to look at it and try it out (hasn't had a bike in years and has been leaning toward cruisers but likes mine so is keen to try it out) Will let you know if he decides he would prefer a cruiser.

there's one like yours on trademe at the moment
would require some work though

[Steveb64]

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.

Snip'd

Colin

:shock: The idea of 'balancing' the carbs is NOT a visual/mechanical measurement! It's to do with balancing the amount of vacuum in the inlet manifold (between the carb and the cylinder) against each of the other cylinders - so ALL are the same.

The primary reason is to do with adjusting the vacuum on each carb (by adjusting the butterflys) so that the slides (which are controlled by the vacuum applied to the diaphragm) all open the same amount in response to you twisting the throttle.

Quote from the Haynes manual: "It is of fundamental importance that air and fuel are delivered in identical quantities and proportions to each of the four cylinders. The fuel flow is governed by the jets of each carb., but it is essential that the flow of air through each is similar at all engine speeds and throttle openings."

Before doing this check - do a valve clearance check/adjustment first! Probably wouldn't hurt to do a compression test on each cylinder next - this should give you an indication as to whether any valves are burnt/leaking... ...if you've got any large discrepancies, you'll need to get them sorted first.

If you don't have a manual - go to: www.haynes.co.uk - you can order one from there - will (mine have so far) take 1 - 2 weeks to arrive!

[Colin Green]

there's one like yours on trademe at the moment
would require some work though

Yup... looks like it's all there... has a few parts that I'd happily swap out (like magneto cover)

BTW.. I checked out your pic of Bruno. You sure got the results.. it's a fine looking machine

[Colin Green]

:shock: The idea of 'balancing' the carbs is NOT a visual/mechanical measurement! It's to do with balancing the amount of vacuum in the inlet manifold (between the carb and the cylinder) against each of the other cylinders - so ALL are the same.

The primary reason is to do with adjusting the vacuum on each carb (by adjusting the butterflys) so that the slides (which are controlled by the vacuum applied to the diaphragm) all open the same amount in response to you twisting the throttle.

Quote from the Haynes manual: "It is of fundamental importance that air and fuel are delivered in identical quantities and proportions to each of the four cylinders. The fuel flow is governed by the jets of each carb., but it is essential that the flow of air through each is similar at all engine speeds and throttle openings."

Before doing this check - do a valve clearance check/adjustment first! Probably wouldn't hurt to do a compression test on each cylinder next - this should give you an indication as to whether any valves are burnt/leaking... ...if you've got any large discrepancies, you'll need to get them sorted first.

If you don't have a manual - go to: www.haynes.co.uk - you can order one from there - will (mine have so far) take 1 - 2 weeks to arrive!

Thanks for the tips... I needed to attend to other things tonight so didin't get around to doing any more than wind out the air/fuel mix screws another 1 turn (=2.5) out.. Didn't make any difference.

I did note that the biggish fuel filter that I installed was only partly full. It lays almost flat on it's side and the filter was all but empty (though started fine) but even when running, the petrol level stayed at the minimum height required to reach the outlet height. I thought that it would be full (shrugs)

Will look at it tomorrow night.

Thanks all

[Steve]

I did note that the biggish fuel filter that I installed was only partly full. It lays almost flat on it's side and the filter was all but empty (though started fine) but even when running, the petrol level stayed at the minimum height required to reach the outlet height. I thought that it would be full (shrugs)

As mentioned early on in this thread, in-line filters can sometimes be more aggravation than they are worth. The idea of a filter is sound. However, some filters are a bit restrictive, as they are meant for an automobile with a fuel pump that will push the fuel through the filter. Your best bet for a filter is finding one meant for a lawn mower. Most of them also have gravity-fed fuel systems, so are less restrictive. You may also find that a half-full filter is more restrictive, too. The surface tension of the petrol coats the filter screen and won't let anything through. It might help to re-orient the filter temporarily to let the air bubble out and fill it with fuel so it flows better.

.

[Colin Green]

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.

I followed the above steps and managed to find the best (and least wound out position) for each screw. More by best sound than revs (as revs didn't seem to vary bugger all (between 1.5 and 3 turns out)).

The end result was .. no discernible difference.

As mentioned early on in this thread, in-line filters can sometimes be more aggravation than they are worth. The idea of a filter is sound. However, some filters are a bit restrictive, as they are meant for an automobile with a fuel pump that will push the fuel through the filter. Your best bet for a filter is finding one meant for a lawn mower. Most of them also have gravity-fed fuel systems, so are less restrictive. You may also find that a half-full filter is more restrictive, too. The surface tension of the petrol coats the filter screen and won't let anything through. It might help to re-orient the filter temporarily to let the air bubble out and fill it with fuel so it flows better.

.

Thanks... I am starting to think that the lack of gas in the filter is a bad thing and will attempt to find a smaller filter to try as you suggested.

have a couple of links to video clips of the problem areas with the sound of the bike missing regularly when idling below 1000 rpm. Please check them out, just in case you see or hear something that means something that you can slap me around with.

http://s251.photobucket.com/albums/gg305/flyingcrocodile46/?action=view&current=MVI_0002.flv

http://s251.photobucket.com/albums/gg305/flyingcrocodile46/?action=view&current=MVI_0003.flv

Cheers

Colin

[twistedwankel]

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 the way it's supposed to work. The vacuum of the engine makes the other two work. The "prime" fills the bowls when the bike has sit a couple weeks. That is all.

[psyguy]

it sounds like you did well at tuning the carbs, so i'd leave the mixture screws as they are
i'd ditch that filter (if only temporarily) as it doesnt look too convincing - your new petcock should be enough of a filter at least for a while

next, i think i'd check for a definite spark on all cylinders
you may want to use new spark plugs (sometimes they can be faulty from new... so it pays trying a different set on even if you changed them recently)

do a compression reading at some stage, but i dont think thats your main concern as the problem occurs only at low and mid-range rpm