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| SU carby, bent needle? https://www.ausmini.com/forums/viewtopic.php?f=2&t=34735 |
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| Author: | buztoy [ Sun Aug 12, 2007 2:53 pm ] |
| Post subject: | SU carby, bent needle? |
hey guys i have got a 1&1/2" SU with what i think is a bent needle, could never get it to idle properly but when using the choke, the small rod pushes a tube on the bottom of the carb down, fuel line is connected to that, what im trying to say is the part inside of the carb that is vacume opperated and goes up and down that holds the needle does not go up and down, when i removed the needle it seems straight but the part that holds it always sits at an angle, can this stop it from returning to its normal position, the long spring is in there and at times it cant be returned even when jiggled and physically forced. i'll post a pic in half hour. cheers |
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| Author: | simon k [ Sun Aug 12, 2007 3:22 pm ] |
| Post subject: | |
doubt it's a bent needle - there are 2 types of piston though, one with a spring loaded needle holder that pushes the needle against the side of the jet, and one that holds it solid - the solid ones are best... sounds like you have the spring loaded one, but it shouldn't be causing the piston to bind - unless I've misread your problem it is sometimes hard to get the piston to move smoothly in the dashpot, when you screw it down, if it's not perfectly aligned the force of the screws seem to distort the dashpot, or make it come down crooked. What I usually do is put my finger under the piston, through the air intake hole and jiggle the piston up and down shile doing up the screws, if it binds, I reposition the dashpot slightly and keep doing up the screws. On a bad day, it can take me 10 minutes to get it right.... I also make sure the piston slides freely in the dashpot before I put it on the carb - if it binds anywhere, I make a thick paste with Ajax and a little water and use it to hone the dashpot, working the piston in and out and around.... |
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| Author: | buztoy [ Sun Aug 12, 2007 5:28 pm ] |
| Post subject: | |
Quote: Ajax and a little water
substitute for auto tranny fluid, i remember seeing this on bush mechanics when his car deid so he drove it in reverse and then reverse died. anyways i will give the dash pot alignment trick a go, there aren't any o ring or anything around the bottom of the dashpot or around the piston, could that have caused it to not hold a vacume, |
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| Author: | Blokeinamoke [ Sun Aug 12, 2007 6:51 pm ] |
| Post subject: | |
try turning it around, it may have worn unevenly and you have put it opposite to original . I have had the same thing before. |
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| Author: | Matt68 [ Mon Aug 13, 2007 9:19 am ] |
| Post subject: | |
Try aligning the jet bearing, this will make it do as you have described. Do as simon said and check the piston moves in the dashpot, with them off the carbie. This is the contact surface that may need a good clean, between the piston and the inside of the dashpot. NOT where the damper goes, and do not put ajax in the damper chamber in the top. Clean well with carbie cleaner before reassembly. Cheers matt |
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