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| Fueling Advice https://www.ausmini.com/forums/viewtopic.php?f=5&t=62866 |
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| Author: | Stuart2004 [ Mon May 03, 2010 9:59 pm ] |
| Post subject: | Fueling Advice |
Can anyone help. I have a 1310 that i have been building for a while and the first and only time i have driven it was with a 1 1/2 inch su on an old manifold. when i built the head for the engine i decided to get the twin carbie manifold ported to match the head. I have a twin 1 1/2inch package on the car now but am having trouble tuning it. I really want to get the car back on the road so I have two options. - tow the car to my mechanic and get him to tune the car as is. go with the twins. or - sell the SU twins and buy a keihin set of carbies like these. http://www.ausmini.com/forums/viewtopic ... highlight= i am in a pickle. please help |
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| Author: | simon k [ Mon May 03, 2010 10:57 pm ] |
| Post subject: | |
option 1. stick with the twins, I'm running a 1310 with 2x1.5" SUs and it's great... the bike carbs will need to be tuned as well, so you're not going to gain anything, except more expense because your mechanic won't know what to do with them |
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| Author: | awdmoke [ Mon May 03, 2010 11:19 pm ] |
| Post subject: | |
Only stick with the twin 1.5" SUs if they are in good condition. Are you having trouble tuning them because they are worn and doing stupid things like sucking air in around the shafts? |
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| Author: | miniobsessed [ Mon May 03, 2010 11:35 pm ] |
| Post subject: | |
What state are your twins in? If they're old and worn out it will be pointless attempting to tune them... If they're all nice and fresh and tuned well they will give very good performance. A few things you might be interested in checking before you take your car to your mechanic... - Make sure the carbies both have the same needle in them. - Make sure you have the same (correct) dampening fluid in both carbies. - Check the 'drop time' of both pistons (how to do this should be in the workshop manual). - Check the idle mixture (this is the only point at which you can 'set' the mixture - the profile on the needle will dictate the fuelling throughout the rev range) for both carbies and make sure it's correct. Once all that is done you need to make sure the carbies are balanced (so they both have the same amount of air going into them) and then make sure both of the butterflies are 'taking up' at the same time. Balancing can be done 'by ear' if you've got a good ear, close enough to get you around until you can get your hands on a balancing tool (basically just an air flow meter)... If not get your hands on a balancing tool before you start. It's really not too difficult (and I don't believe beyond the capability of most mini owners) to tune twin carb's. Just get a good guide and follow it. If you go through all the motions you should at least be able to get the car to idle. If your needles are wrong the car will not perform very well through the rev range... But at least then you'll know it's just (most likely) the needles that need sorting out. |
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| Author: | Stuart2004 [ Tue May 04, 2010 4:25 pm ] |
| Post subject: | |
Thanks for all your help. I think I will stick with the su I may look at getting them looked at again. I had them rebuilt about a year ago but I know the pistons fall at different speeds. I have been fiddling with them for a while and tried everything you have suggested, I think it is the carbies. |
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| Author: | Hanra [ Sun May 09, 2010 9:38 pm ] |
| Post subject: | |
miniobsessed wrote: What state are your twins in? If they're old and worn out it will be pointless attempting to tune them...
If they're all nice and fresh and tuned well they will give very good performance. A few things you might be interested in checking before you take your car to your mechanic... - Make sure the carbies both have the same needle in them. - Make sure you have the same (correct) dampening fluid in both carbies. - Check the 'drop time' of both pistons (how to do this should be in the workshop manual). - Check the idle mixture (this is the only point at which you can 'set' the mixture - the profile on the needle will dictate the fuelling throughout the rev range) for both carbies and make sure it's correct. Once all that is done you need to make sure the carbies are balanced (so they both have the same amount of air going into them) and then make sure both of the butterflies are 'taking up' at the same time. Balancing can be done 'by ear' if you've got a good ear, close enough to get you around until you can get your hands on a balancing tool (basically just an air flow meter)... If not get your hands on a balancing tool before you start. It's really not too difficult (and I don't believe beyond the capability of most mini owners) to tune twin carb's. Just get a good guide and follow it. If you go through all the motions you should at least be able to get the car to idle. If your needles are wrong the car will not perform very well through the rev range... But at least then you'll know it's just (most likely) the needles that need sorting out. All very good points there, one other is to ensure the float bowl level is correct also! |
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