carburetor spring weight

mikidymac said:
The grams are the stiffness of the spring. Increasing the preload will increase the pop-off but not the spring rate.
Keep in mind Pop-off is just a test of the spring, arm and needle/seat, it is not how the carb actually works.
When the carb is on the ski and you open the throttle butterfly there is a negative pressure inside the carb and a positive pressure with the atmosphere, this pushes the big rubber diaphragm against the lever arm, overcomes the spring pressure and opens the needle allowing more fuel into the carb. This diaphragm has a range of motion so changing the spring tension changes how much the diaphragm moves the lever arm and needle. So adding preload will change the opening pressure but not really the range of motion, this is why you change spring weights and not just adding more preload.

The stronger the spring the leaner the fueling will be since the diaphragm needs more vacuum to move and allows less fuel into the carb. A lighter spring will allow more fuel in under less vacuum and make the carb richer also a large needle and seat with a lighter spring and the engine vibration can cause the carb to dribble fuel and cause a rich bog and flooding, this is why high pop-off pressures are used.
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Love this explanation @mikidymac . Thank you. So unfortunately just getting the needle to pop at a specified pressure is not enough to guarantee that the carb/needle is going to allow the appropriate amount of fuel to enter due to spring tension, those little buggers are pretty precise then. I had thought maybe they were less crude and that maybe if it opened at the right pressure that, that would work. It would be interesting to have a tool that would compress the spring and give you a reading of force as you depress it. I’m sure that such a tool exists but.... not worth it to play around with finicky stuff such as this. Maybe when I’m old and grey, oh wait, shit I’m already partially greying and old, lol.
 
burtshaver2021 said:
Love this explanation @mikidymac . Thank you. So unfortunately just getting the needle to pop at a specified pressure is not enough to guarantee that the carb/needle is going to allow the appropriate amount of fuel to enter due to spring tension, those little buggers are pretty precise then. I had thought maybe they were less crude and that maybe if it opened at the right pressure that, that would work. It would be interesting to have a tool that would compress the spring and give you a reading of force as you depress it. I’m sure that such a tool exists but.... not worth it to play around with finicky stuff such as this. Maybe when I’m old and grey, oh wait, shit I’m already partially greying and old, lol.
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Maybe, putting holes in the hull and sinking it, might not be to far off.lol
 
I wouldn’t give up yet, I think your almost there. If it were me, I would try to get the right 130 gram spring if possible, if that’s not possible and it were me and I already had everything set up for the 130 gram spring I know myself I would have to at least try a little spacer to get to the proper pop off and see how it performs but that’s just me being curious. If that didn’t work, you can simply change up that carb with different sized jets, needle and seat, basically set it up same as another ski, you may have to eliminate the accelerator pump as well. I hope none of my suggestions have caused you any frustration, I try to let people know I haven’t actually done stuff when I haven’t but only read about it.
 
Maybe I should explain it with math. Spring rate is units of force per unit of deflection expressed as ponds per inch or newtons per millimeter or kilograms per millimeter. The load at any deflection is the free length minus the length when deflected times the spring rate. I worked in the imperial system so I will talk that way.

A spring has a rate of 2 lb/in and is 10 inches long, installed height is 9 inches and its final working compressed length will be 8 inches.
Initial force is (10"- 9") times 2 lb/in = 2 lb. Final force is (10"- 8") times 2 lb/in = 4 lb.

Now take a spring with a rate of 1 lb/in and is 10 inches long and try using it the same way as the spring above. Initial force is (10"- 9") times 1 lb/in = 1 lb. Final force is (10"- 8") times 1 lb/in = 2 lb. Now shim it 1 inch when first installed to compress it . Installed force will be the shim compression force of 1 lb plus the additional 1 lb to get the 10 inch spring and shim down to 9 inches . Cool, you now have the the same initial 2 lb force. When you compress it another inch to get to that final length of 8 inches the force will go up by 1 lb so add that to the 2 lb it started installed and you get 3 lb of force. That isn't the same 4 lb force of the stiffer spring.

Just because you shim a softer spring to get the same initial force doesn't mean it will have the same force at its working length. You can shim a soft spring to get the right pop off, but the needle will open up more when it is off its seat. How does this impact flow through the jets? I don't know. Someone with more experience with these carbs can tell you what the impacts are.
 
BrianMoore said:
Maybe I should explain it with math. Spring rate is units of force per unit of deflection expressed as ponds per inch or newtons per millimeter or kilograms per millimeter. The load at any deflection is the free length minus the length when deflected times the spring rate. I worked in the imperial system so I will talk that way.

A spring has a rate of 2 lb/in and is 10 inches long, installed height is 9 inches and its final working compressed length will be 8 inches.
Initial force is (10"- 9") times 2 lb/in = 2 lb. Final force is (10"- 8") times 2 lb/in = 4 lb.

Now take a spring with a rate of 1 lb/in and is 10 inches long and try using it the same way as the spring above. Initial force is (10"- 9") times 1 lb/in = 1 lb. Final force is (10"- 8") times 1 lb/in = 2 lb. Now shim it 1 inch when first installed to compress it . Installed force will be the shim compression force of 1 lb plus the additional 1 lb to get the 10 inch spring and shim down to 9 inches . Cool, you now have the the same initial 2 lb force. When you compress it another inch to get to that final length of 8 inches the force will go up by 1 lb so add that to the 2 lb it started installed and you get 3 lb of force. That isn't the same 4 lb force of the stiffer spring.

Just because you shim a softer spring to get the same initial force doesn't mean it will have the same force at its working length. You can shim a soft spring to get the right pop off, but the needle will open up more when it is off its seat. How does this impact flow through the jets? I don't know. Someone with more experience with these carbs can tell you what the impacts are.
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I think I get it, in basic terms springs have different tensions so if it’s shimmed up we can get the needle to open at the pop off but because of the spring tension difference it’s going to travel further/open further at a different rate.
 
I wasn't trying to beat a dead horse. Wrote my second post, got distracted with something else, and didn't hit post reply until hours later. In the meantime, mikidymac had written a very insightful explanation.
 
BrianMoore said:
I wasn't trying to beat a dead horse. Wrote my second post, got distracted with something else, and didn't hit post reply until hours later. In the meantime, mikidymac had written a very insightful explanation.
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Well, now past carb problems, on to maybe a new problems, dumped it into the lake Saturday, started ok, while still on trailer and back into the water, seems like getting some vibration when gave it some gas, but was still on trailer, would that a normal, out of water, with around 3k no vibration, I have not checked yet for loose motor mount, but looked at wear ring and prop looked fine, nothing seen sucked into that areas, is some other checks that I can do without pulling pump and shaft out, so late in season, read something about pushing engine forward, while PTO in shaft, that didn't make sense, must of not understood
 
Spoody6677 said:
Well, now past carb problems, on to maybe a new problems, dumped it into the lake Saturday, started ok, while still on trailer and back into the water, seems like getting some vibration when gave it some gas, but was still on trailer, would that a normal, out of water, with around 3k no vibration, I have not checked yet for loose motor mount, but looked at wear ring and prop looked fine, nothing seen sucked into that areas, is some other checks that I can do without pulling pump and shaft out, so late in season, read something about pushing engine forward, while PTO in shaft, that didn't make sense, must of not understood
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Maybe nothing it was still on trailer, and maybe it was trying to push forward, but was still tied down on trailer
 
On the trailer you can get cavitation as there is no ram effect forcing water into the pump without the ski moving forward.
 
Spoody6677 said:
Good, I thought maybe that might be the issue
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I am circling back, should I feel a bog on engine while on hose, after engine is running 30 second, and Rev it up, just want to know if accelerator pump is responding, I had already took it apart and cleaned and check spring diaphragm, but sure if ball is sticking in casting, did let sit in carb cleaner, and cleaned
lines, where check valve is, from carb to pump, sprayer was clear at carb throat
 
Yea, it bogs at take off in water, pulled line coming out of pump going to carb sprayer, and no fuel coming out when depressing the throttle, does engine need to be running, I can blow threw line going from carb to pump, where meter device is in line, should I blow some compressor air, say 60 pounds into the pump inlet side, where the ball meter divice should be, maybe diaphragm is wore and stretched
 
Spoody6677 said:
Yea, it bogs at take off in water, pulled line coming out of pump going to carb sprayer, and no fuel coming out when depressing the throttle, does engine need to be running, I can blow threw line going from carb to pump, where meter device is in line, should I blow some compressor air, say 60 pounds into the pump inlet side, where the ball meter divice should be, maybe diaphragm is wore and stretched
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Engine doesn’t need to be running for the accelerator pump to work
 
Spoody6677 said:
Do you know the part number, for my accelerator pump diaphragm for I can order from OSD today
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I don’t know it off by heart, I would have to look it up on the parts catalogue at seadoomanuals.net or even easier on seadoowarehouse.com here. OSD May list what machines the part applies to as well
 
burtshaver2021 said:
I don’t know it off by heart, I would have to look it up on the parts catalogue at seadoomanuals.net or even easier on seadoowarehouse.com here. OSD May list what machines the part applies to as well
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I did not see a part number, on my seadoo manual, I am not good at getting right number, so if you have a chance, can you take a look for me
 
Seadoo doesn't sell just the diaphragm and has discontinued the pump. You should be able to get them from OSD.
Typically is is the spray nozzles that are plugged, not the diaphragm.
 
mikidymac said:
Seadoo doesn't sell just the diaphragm and has discontinued the pump. You should be able to get them from OSD.
Typically is is the spray nozzles that are plugged, not the diaphragm.
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OSD has no jet or diaphragm in stock, sprayer is clear, blew threw and air came out into spray nozzle, no fuel coming out of accelerator pump, when it hand pumped,
 
Actually had a similar issue with my wife's 2003 GTI. Out of the blue it would bog and nothing I did to the OEM carb would correct it. I finally threw in the towel and for the first time ever bought a brand new carb from OSD. The ski has run perfectly ever since. I still have no clue what was up with the old carb as everything tested perfectly.
 
mikidymac said:
Actually had a similar issue with my wife's 2003 GTI. Out of the blue it would bog and nothing I did to the OEM carb would correct it. I finally threw in the towel and for the first time ever bought a brand new carb from OSD. The ski has run perfectly ever since. I still have no clue what was up with the old carb as everything tested perfectly.
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I do now realize it would of been cheaper, for me to buy new carb
 
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