The only other thing that I can think of, besides the main jetting, is the routing of the hoses.

Below 4000rpm there is no power, that is normal. Keep rpm's above 4000. I typically shift around 5500.

http://gstwins.com/forum/viewtopic.php?t=6315&highlight=shifting

You can't get it to go faster because you need the size 125 main jets. The bike is starved for fuel at that speed.

Set your pilot screws back to 2.5 turns out.

While you're waiting for the main jets to come in, move the clip on the needle down one position. Then move it back when the jets come in.

Your slides and the underside of the diaphragms getting wet are probably related to the poor fuel economy. Now, if we can figure out how those parts are getting wet...maybe the little o-ring on the float assembly? If gas is allowed past that o-ring where will the gas go?

Or, your poor fuel economy due to not filling the tank completely? Fill it to the filler neck and then add a little bit more, slowly, and a little bit more, and a little bit more, slowly...Kerry did a test to see how much more the tank would take after it was filled to the filler neck.

http://gstwins.com/forum/viewtopic.php?t=4989&highlight=filling

OK low gas mileage suggests gas leak or some other loss ...
Lack of top end is likely lean main jet, and surprisingly the weak 4K and under seems to be high float level ... I'd have bet floats too high thereby causing fuel loss and poor running at low speed, but you checked and its OK ... BTW you checked it in prime right ... and on level ground on center stand ... Any air leaks ... any other symptoms ... like smell of gas ...
OK brown stuff on the top part ... funny thing ... that part should be quite clean, and only get a very minor amount of dust and carbon blow back ... carbs that are un opened for years seem to have just enough in there to come off in your fingernails ...
Any other airbox stuff busted/missing ... hoses etc ...
Then are you likely to have 1 cyl not work right ?? at certain speeds only ...
Cool.
Srinath.

Don't the little plastic donuts go on top of the clip rather than underneath?

the little white plastic "donughts" or washers go above the needle. I made the mistake when i rebuilt my carb of putting the needle through this and it made my bike run rich, and horrible. Simply putting the plastic spacer, or washer on top resolved my problems...

Quote from: vfrocketthe little white plastic "donughts" or washers go above the needle. I made the mistake when i rebuilt my carb of putting the needle through this and it made my bike run rich, and horrible. Simply putting the plastic spacer, or washer on top resolved my problems...

I was reffering to item 9 which seems to be in the right place. Thanks

OK here is a couple ideas ...
1. Might want to buy just needles ... unless whole crabs are fairly cheap ...
2. Hose connector is bottom of airbox should be hooked up to a hose and the end of that hose should be shut, or have a little rubber plug on the thing ... that hose cannot be allowed to take in air ... its not a drain per say, its a drain only when you want it to drain, else its supposed to be air tight ... Might be the cause of your loss of power up high, and the reason low gas mileage ... if fuel got into it somehow, it will just disappear when riding ... making it hard to detect ...
Also you get 240 km per tank when you run in reserve ... right, That's like 150 miles, on 4 or so gallons ... making it closer to 37.5 ... whihc is not that far off for a bike with 40K miles+ ... I am around the mid 30's with K&N and pipe ... Its not too bad really ...
Cool.
Srinath.

Quote from: seshadri_srinath
2. Hose connector is bottom of airbox should be hooked up to a hose and the end of that hose should be shut, or have a little rubber plug on the thing ... that hose cannot be allowed to take in air ... its not a drain per say, its a drain only when you want it to drain, else its supposed to be air tight ...

I thought that it is a drain hose,but not a normal drain hose.  Mine has a rubber cap at the end but it has a small slit, so if there is fuel from blow back in the airbox, it will slowly seep out.  But since it is just a slit (I can't see the opening unless I squeeze the cap), air leak is minimal.  Maybe the slit is just torn from old age?  :dunno:

Cheers,
e.

OK splattering when hot and not when cold ... rich ... yes very rich ...
Wet slides are normal ... slightly wet ... BTW you cheanged/cleaned the air filter right ... the stock paper filter can be sloshed in gas and cleaned ... 2 -3 times I think easily ... more ... Dunno never tried ... But it might be able to take a prolonged dip in gas ... cos fuel filters are made of the same/similar paper and glue ... they take years of gas soaking ...
Cool.
Srinath.

Question: lets say his air filter is old, nasty rusty and just generally piece of shiite.  Do you think that could cause his bike to run rich like that?

The air filter was my 1st suspect and I have replaced it with a new one as well as the oil filter, oil, and the sparkplugs.

I'm getting my new needles on Saterday so then I'll strip the carbs and replace the o-rings as well. According to my dealer he thinks the new needles only have 1 notch at the top so no way of getting that setting wrong lol

I was checking carb prices and a 2ndhand set will cost me about $250 (not willing to pay that much). I can't find anybody here to source me those 125 mains so I'll have to stick with the 120s

If the problem is that you are running rich, then the change in needles may help (since you broke the needle, you are running with the circlip set further down, so richer).

Another thing to check is the choke.  With the tank off the bike, you can see the choke slide on the top right of the carbs.  Try pulling the choke  lever (on the handlebars) towards you to enrichen the mixture; then push the choke lever away from you to lean the mixture out again.  Did the choke slide on top of the carbs move all the way to the right?  Reach down and see if you can push it further to the right with your hand (it's probably OK if you can push it another 1mm... my bike does that).

Also, looking at the top of the carbs, turn the handlebars left and right stop-to-stop and see if that may be pulling on the choke cable, causing the choke to richen-up again.


The way I set the pilot screws, is to go for a ride until the bike is fully warmed-up (say, 15 minutes or more).  Then put it in neutral, turn the idle up to 2k RPM or so, and adjust the idle mixture screws on each side.  As you enrichen the idle mixture, the RPMs will go up, up, up... then plateau, then come down slowly (too rich).  

You want each carb set so that the RPMs are somewhere on that RPM plateau.  If performance is your goal, you want the setting to be towards the richer side (but not so rich that RPMs start to come down).  If economy is your goal, then set it towards the lean end of the plateau (which is how the stock bike is adjusted in the US).

The choke assy has a plunger with an O ring on it, a spring and its held inside the carb body with sorta a U shaped clip ... you just look and the clip part is black ... just use like a pick or a screwdriver and press the clip ends together ... and the mechanism should slide out ... spray wd40 on it prior to doing it ...
I have seen the springs missing making the bike run like crap ... Though doubt its causing the high end probelms.
Cool.
Srinath.

Quote from: gerharddvsI have noticed that if I pull the choke all the way the engine wants to die so I usually only set it about half-way

Do you mean that you set it half-way when starting/warming the bike, or all the time?  You should only need the choke on while the bike is warming-up.  

The most-common choke problems I've read here are: broken choke cable, sticking cable, missing cable, etc.  I don't recall reading about anyone "setting" it.  

Where the cable connects to the right carb look a bit like this:



The red dot at the right is on the ferrule, at the end of the cable.  
The spring needs to be compressed between the red dot and the green dot.
The rigid end of the cable sheath (yellow dot) inserts into the cable stop (blue dot).
One mistake I have made is that the spring can slide left while disconnected, onto the rigid end of the cable sheath, so that when you put it back together, the spring is to the left of the cable stop (rather than to the right, where it belongs).  That leaves you with no spring tension on the choke at all.

Have you checked to see how well the spark plugs were firing? Just today my bike absolutely wouldn't start at all. Yesterday it would only backfire like a cannon. After replacing the plugs she fired right up. I don't know much about engines but the ones I've worked on sometimes had ignition trouble that seemed to be a carburetor problem.

Derek

You say it gets better when the bike warms up - that tends to indicate either a lean condition or valves needing adjustment.

From your description I would guess a bit of both.  Check that all the carb passages are clear & clean (blow them out with compressed air) and that the jet sizes are the same in both carbs.  You should be able to visually sync them while they are off the bike to do those checks.  The fact that the mixture screw does not change anything makes me believe that something is blocked and/or leaking there - take the screws out and make sure that they are in good shape and all springs/o-rings etc are there and in good shape.