carb diaphrams will not open - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 5 (permalink) Old 05-24-2010, 11:07 PM Thread Starter
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Question carb diaphrams will not open

well i finally got the bike back together. got the fatboy seat mounted decided to take it on its first test ride since the engine reinstall. first i balanced the carbs and then took off she felt like a beast in the parking lot then at more than half throttle it fell on its face. upon more careful examination i found that when you crack the throttle the diaphram does not pull the piston up which does not move the needle off the main jet. starving it for fuel i removed the carbs checked the hole in the pistons the last time i put them together i put the spring holder over the hole and it wouldnt open i checked this again not the case. so i am lost any suggestions.


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post #2 of 5 (permalink) Old 05-24-2010, 11:14 PM
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Sounds like the piston diaphram is not seated properly causing a leak, how old are the carbs?


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post #3 of 5 (permalink) Old 05-25-2010, 08:22 AM Thread Starter
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they are original. i thought that too but it ran fine last season (I know winter is a long time to sit i will take them apart today and try again)


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Keep the shiny side up
coastered
de-goat and baffles removed
jetted 42-150 2 shims
Earshaved with unifilters
inside of tank coated
spline lube
long Beach Blue Pearl Paint 4/07
Shindengen FH012AA r/r
TPE stator
Exide sc30lfa Battery 28ah 445cca
Saddlemen saddlebags
2001 HD fatboy solo seat
Custom taillight & rear turn signals
Fergy's coil relay mod
Fiamm El-Grande high/low tone horns
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post #4 of 5 (permalink) Old 05-25-2010, 08:37 PM
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Ditto what Lance said. If the diaphragms aren't seated right, you'll have exactly the problem you describe (basically, think about trying to use a straw that has a hole in it - all that suction, but a lot of it is wasted on pulling air through). An easy way to check is to push the piston up with your finger and listen for a nice "whoosh" sound - there should be slight resistance if you've got a good seal.

Lance'll kill me for saying this, but on older diaphragms, I have used a tiny bit of sealant (INSIDE the groove where the diaphragm is seated) to ensure that the seal stays tight. The risk, of course, is that you put too much sealant and pull it into your carb, but I've not experienced that to date. Just a wee bit of sealant...enough to make sure the diaphragm sits where it's supposed to until you get the cover on.

C
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post #5 of 5 (permalink) Old 05-25-2010, 09:20 PM Thread Starter
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Lance was right i bricked on both of them i was in a hurry when i put them back together. but now due to todays disassembly I am in need of new needle shims (long story)either way i put it back together without them and bingo there she was. thanks lance and cindy


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Keep the shiny side up
coastered
de-goat and baffles removed
jetted 42-150 2 shims
Earshaved with unifilters
inside of tank coated
spline lube
long Beach Blue Pearl Paint 4/07
Shindengen FH012AA r/r
TPE stator
Exide sc30lfa Battery 28ah 445cca
Saddlemen saddlebags
2001 HD fatboy solo seat
Custom taillight & rear turn signals
Fergy's coil relay mod
Fiamm El-Grande high/low tone horns
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