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| Idling high on twin SU's https://www.ausmini.com/forums/viewtopic.php?f=5&t=59190 |
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| Author: | miniDave [ Sun Nov 29, 2009 7:29 pm ] |
| Post subject: | Idling high on twin SU's |
Finally started engine and now for the next problem. Using twin 1.1/4. Idle screws all the way out and still idles high. Thinking I should turn the jet screw up a turn????????. Also does anyone have a photo of how the throttle cable attaches to the centre swivel between the carbies. I only seem to have minimum movement on the throttle pedal (about an 1"). Also a ton of smoke coming out of exhaust. Is this usual on starting a new engine?????? Many thanks |
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| Author: | drmini in aust [ Sun Nov 29, 2009 7:59 pm ] |
| Post subject: | Re: Idling high on twin SU's |
miniDave wrote: Finally started engine and now for the next problem.
Using twin 1.1/4. Idle screws all the way out and still idles high. Thinking I should turn the jet screw up a turn????????. Also does anyone have a photo of how the throttle cable attaches to the centre swivel between the carbies. I only seem to have minimum movement on the throttle pedal (about an 1"). Also a ton of smoke coming out of exhaust. Is this usual on starting a new engine?????? Many thanks Did you remove the throttle spindles when you blinged the carb bodies up? If so you will need to centralise the butterfly in each one. This is done by loosening the 2 screws, then hold the throttle closed with the idle screws backed off, and retighten the screws. Hold up to the light with throttle closed, you should see no light at top or bottom. |
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| Author: | miniDave [ Sun Nov 29, 2009 8:10 pm ] |
| Post subject: | |
Yes - did that. Also did: Had GR look at the needles and appeared to be the right type. Screwed needle to correct position on dampner. Jets wound down 1.5 turns from flush. New red carbi springs. Fill top of dampner with correct SU oil. Fuel bowls are level - new seals All new gaskets and all nuts are tight. Might take them off again and go through the same procedure. Regarding not having much throttle - please look at these photos as I believe something might be in back to front: 
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| Author: | BALLISTIC [ Sun Nov 29, 2009 9:22 pm ] |
| Post subject: | |
Just some thoughts................. sucking air through the throttle shafts  (spray crc, wd40 etc when running and listen for engine idle difference)
were the butterfly's put in the correct way
cable to tight
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| Author: | GT mowog [ Sun Nov 29, 2009 9:27 pm ] |
| Post subject: | |
Looks like the throttle shaft is in back-to-front |
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| Author: | TheMiniMan [ Sun Nov 29, 2009 10:58 pm ] |
| Post subject: | |
yep,,, Center throttle link is wrong way round & i`d say you`re sucking air somehwere,,, maybe underneath the manifold, grab a mirror & have a look |
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| Author: | miniDave [ Fri Dec 04, 2009 6:00 pm ] |
| Post subject: | |
Well one step forward and one step back. Pulled the carbies apart and found that one of the pistons was grabbing and not falling back down correctly. Also - must have overfilled the dash pot oil and it had leaked down into carbi and was causing smoke. Replaced the throttle link with another and now have good pedal range. NOW to the latest problem . . . Engine starts OK. Even with idle screws wound fully out, still idles slightly fast. Noticeable miss at idle. Take plugs out and matt black (way to rich) Cleaned and checked gap, repeat and still matt black. So I am thinking the jet is wound down too low. I remember winding the jets up flush to the chamber and then backing off (down) 1.5 turns. Is this correct?????? Is there a starting point where the jet should start at? Will take the needle out and place it in the jet to make sure it is the correct size. |
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| Author: | drmini in aust [ Fri Dec 04, 2009 6:14 pm ] |
| Post subject: | |
8 or 12 flats is a good starting point, but don't bet they are still both the same when mixture is even, they are not a Weber... As said above, your jets may be wrong (.100" instead of .090"). |
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| Author: | slacko [ Fri Dec 04, 2009 6:45 pm ] |
| Post subject: | |
Dave have you got clearance between the idle screws and the bell cranks on the choke piviot shaft when the choke is all the way in and is the choke coming off all the way when you push it in ? . Just a thought Cheers Mark |
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| Author: | miniDave [ Fri Dec 04, 2009 7:04 pm ] |
| Post subject: | |
drmini in aust wrote: 8 or 12 flats is a good starting point, but don't bet they are still both the same when mixture is even, they are not a Weber... As said above, your jets may be wrong (.100" instead of .090"). Thanks for that - How many flats for for a complete turn (6????) Will check the needles and the jets. slacko wrote: Dave have you got clearance between the idle screws and the bell cranks on the choke piviot shaft when the choke is all the way in and is the choke coming off all the way when you push it in ? . Just a thought
Cheers Mark Will check this. Seems as if choke postion etc is OK. But then again not having the 'pleasure' of tuning SU's before I am still working things out!!! BTW brakes are still good now - however brakes lights don't come on  Rather than replace fluid switch and re-bleed brakes I bought a $9 electronic brake switch and wired that in 
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| Author: | drmini in aust [ Fri Dec 04, 2009 7:13 pm ] |
| Post subject: | |
Dave, there are 6 flats on a hex nut, so 9 is 1-1/2 turns and 12 is 2 turns. 
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| Author: | simon k [ Sun Dec 06, 2009 1:02 pm ] |
| Post subject: | |
were new bushes put in the carbs? if there is a space between the bush and the inner bore of the carb air will get past the butterfly |
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| Author: | miniDave [ Mon Dec 14, 2009 12:45 pm ] |
| Post subject: | |
Well after a house call from the good doctor, we worked towards getting the carbs to run better. The jets are in fact 0.90 - so that part is OK. The needles are AH2 (rich) and I have ordered some new 'M'needles from Burlen in the UK. Choke is not stuck on. In the meantime I take the plugs out, clean and replace and within a minute of running again there is a miss again and the plugs very black and wet. I HAVE to get the blue slip done on thursday and I need the car running reasonably. Because I don't have the correct needles I am suggesting: Wind the jets up 1 complete turn (1/2 turn from flush) which hopefully will make the mixture less rich (but just enough to run low revs) - will this work? Not a long term fix but just enough to drive to the garage and back. Currently when I drive around the block a few times, stop and try to re-start it takes a long time to re-start as the spark plugs are drowning! BTW I have just read the SU workshop manual and there is good section on setting up idle screw and jet height according to engine note etc. Regards - |
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