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Car Forum / MINI / October 2004carb worn out help
One, maybe both carbs on my '67 S need to be rebuilt. I'm wondering if there is a better way to go? A single carb, larger carbs, or? What are the best options? > One, maybe both carbs on my '67 S need to be rebuilt. At the risk of sounding cynical, "worn out" is a fairly normal state of affairs for an SU carby. Certainly don't just repair one! > I'm wondering if > there is a better way to go? A single carb, larger carbs, or? > What are the best options? Modern thinking seems to be that you're better off with a single 1-3/4" carb than a pair of 1-1/4". The cross sectional area is much the same. And Elvis was sitting next to Graham W in the spaceship, which I thought was kinda weird, but then they turned to me and said: > > One, maybe both carbs on my '67 S need to be rebuilt. > > At the risk of sounding cynical, "worn out" is a fairly normal state of > affairs for an SU carby. Certainly don't just repair one! Very true. The throttle spindle bearings in older H and HS types seem to be made out of some form of cheese... I must have fixed up dozens of those things. Drill out the carb body and fit nylon bushes sized to fit a new spindle. Better than new. > > I'm wondering if > > there is a better way to go? A single carb, larger carbs, or? > > What are the best options? > > Modern thinking seems to be that you're better off with a single 1-3/4" > carb than a pair of 1-1/4". The cross sectional area is much the same. If you can source the later type HIF carb in 1-3/4" size it's a damn fine instrument. Much improved over the older models (it has decent bushes for the throttle spindle for a start...) Flows a little better than the older carbs of the same size too - it's generally said to be perfectly good for engines up to the 110-115HP mark. > And Elvis was sitting next to Graham W in the spaceship, which I thought > was kinda weird, but then they turned to me and said: [quoted text clipped - 22 lines] > than the older carbs of the same size too - it's generally said to be > perfectly good for engines up to the 110-115HP mark. And with a single carbie, you don't have to balance! -Rock http://www.rocky-frisco.com -- JJ Cale Live CD and video: http://www.rocky-frisco.com/calelive.htm The Wednesday Night Science Project: http://www.wednitesciproj.us Rocky Frisco's LIBERTY website: http://www.liberty-in-our-time.com/ >I must have fixed up dozens of those things. Drill out the carb body and >fit nylon bushes sized to fit a new spindle. Better than new. Where do you get these kits, and what are the tell-tale signs of a worn carb? For the single SU in a MK1... > -AD- wrote: >>I must have fixed up dozens of those things. Drill out the carb body and >>fit nylon bushes sized to fit a new spindle. Better than new. > Where do you get these kits, and what are the tell-tale signs of a > worn carb? > > For the single SU in a MK1... When the throttle spindle bush is worn air leaks in past there, more at higher manifold vacuums, less at higher throttle opnings. SO your part of full throttle mixture is unaffected, but at idle the mixture is far to rich. To get the car to idle you wind the jet down making the idle mix richer. Because the amount of air leaking is erratic, you can't get the mixture to make sense, but it ends up very rich. Because this adjuts the mixture across the entire operating range, it now operates rich when the throttle is open, resulting in horrendous fuel consumption. > When the throttle spindle bush is worn air leaks in past there, more at > higher manifold vacuums, less at higher throttle opnings. SO your part [quoted text clipped - 6 lines] > across the entire operating range, it now operates rich when the > throttle is open, resulting in horrendous fuel consumption. If this gets bad enough (rich mix) it can wash the oil off the bores, resulting in rapid ring wear and possibly even broken rings. -Rock http://www.rocky-frisco.com -- JJ Cale Live CD and video: http://www.rocky-frisco.com/calelive.htm The Wednesday Night Science Project: http://www.wednitesciproj.us Rocky Frisco's LIBERTY website: http://www.liberty-in-our-time.com/ >When the throttle spindle bush is worn air leaks in past there, more at >higher manifold vacuums, less at higher throttle opnings. SO your part [quoted text clipped - 6 lines] >across the entire operating range, it now operates rich when the >throttle is open, resulting in horrendous fuel consumption. Thanks for the advice, but one problem... the engine in question was stripped down for a rebuild (that never happened) in 1991! I'm hoping with just 20,000 miles on the clock, the carb should be ok. If it was worn, would the throttle spindle be loose? I've only ever dealt with Solex carbs before! >>I must have fixed up dozens of those things. Drill out the carb body and >>fit nylon bushes sized to fit a new spindle. Better than new. [quoted text clipped - 3 lines] > > For the single SU in a MK1... You can order all SU parts new from www.burlen.co.uk, including service kits and rebuild kits. And Elvis was sitting next to Howard Rose in the spaceship, which I thought was kinda weird, but then they turned to me and said: > >I must have fixed up dozens of those things. Drill out the carb body and > >fit nylon bushes sized to fit a new spindle. Better than new. > > Where do you get these kits, and what are the tell-tale signs of a > worn carb? It's not a kit. I cut a length of nylon rod stock and drill the carb body to be a tight fit, then gently press in a slug of the nylon in each side with a drop of epoxy. After it's cured, I trim it flush and drill it as acccurately as I can (slightly undersize) then use a small adjustable hand reamer to make a nice fit for a new spindle. > One, maybe both carbs on my '67 S need to be rebuilt. I'm wondering if > there is a better way to go? A single carb, larger carbs, or? > What are the best options? If you don't mind using a setup that's not original, I can highly recommend a single HIF44 or HIF6 on the aftermarket intake manifold. My Mini, The Luggage, is a 67 S, 1293 cc. APT 286 scatter cam, 2" freeflow exhaust with LCB manifold. I use the HIF6 and it works a charm. http://www.rocky-frisco.com/WeeLuggage.jpg -Rock http://www.rocky-frisco.com -- JJ Cale Live CD and video: http://www.rocky-frisco.com/calelive.htm The Wednesday Night Science Project: http://www.wednitesciproj.us Rocky Frisco's LIBERTY website: http://www.liberty-in-our-time.com/ If its a genuine S, and not a home built "replica" then keep it original. Spend the dollars and get the carbs either rebuilt or purchase a set of new carbs which are still avaliable. Try Mini Mania in the States or Min Spares, or one of several reputable Mini specialist in the UK...a genuine S is worth big money these days, but only if genuine, as soon as bits start to disapear their value drops. As to issues surrounding tuneing/balancing etc, once set up and in good repair then you dont need to touch them. Its only when you start "playing" around with them in the belief that they need to be balanced that you run into problems. I have a genuine 66 Cooper which I rebuilt the carbs on 10 years ago, and other than basic tunes IE filters etc I've never had to touch them. Yes it cost a lot of dosh to get them rebuilt and set up by a proffesional, but 10 years later they are still perfect. The proof as they say is in the pudding. > One, maybe both carbs on my '67 S need to be rebuilt. I'm wondering if > there is a better way to go? A single carb, larger carbs, or? > What are the best options? > If its a genuine S, and not a home built "replica" then keep it original. > Spend the dollars and get the carbs either rebuilt or purchase a set of new > carbs which are still avaliable. Try Mini Mania in the States or Min Spares, > or one of several reputable Mini specialist in the UK...a genuine S is worth > big money these days, but only if genuine, as soon as bits start to disapear > their value drops. My advice would be to pull the original setup and mount the HIF6 and aftermarket intake with a K&N Cone filter. Save the original setup to remount if you sell it (unless you're planning to enter concourses where originality is important). > As to issues surrounding tuneing/balancing etc, once set up and in good > repair then you dont need to touch them. Its only when you start "playing" [quoted text clipped - 4 lines] > proffesional, but 10 years later they are still perfect. The proof as they > say is in the pudding. I tend to agree with the old adage that 80% of carb problems are really something else. The carbs should never be touched unless the timing and valve lash have been set perfectly. The exception to this would be something obviously wrong with the carb(s), like a leaking float chamber or sticking dashpot piston. -Rock http://www.rocky-frisco.com -- JJ Cale Live CD and video: http://www.rocky-frisco.com/calelive.htm The Wednesday Night Science Project: http://www.wednitesciproj.us Rocky Frisco's LIBERTY website: http://www.liberty-in-our-time.com/ The problem is that one of the carbs has a sticking piston. I've cleaned it etc, but it must just be worn out. I'm not sure if they can be rebuilt if the slide or piston is worn out? It's an orginal S, bought new by a friend. I have it 25 years. > If its a genuine S, and not a home built "replica" then keep it original. > Spend the dollars and get the carbs either rebuilt or purchase a set of new [quoted text clipped - 15 lines] >>there is a better way to go? A single carb, larger carbs, or? >>What are the best options? It sounds like you have a jet alignment problem rather than it having worn out. Speaking from memory, the jet is held inplace by a large nut at the bottom, and if the needle has gone off line at all, it could now be catching the jet. I remember removing the dashpot section on my twins to clean them and try different oil one weekend, and causing this problem many years ago. I would love to have a pair of 1 1/4 SU,s with standard cooper air filters on show under the bonnet of a cooper or an S. Singles even big ones or Webbers never quite did it for me. > The problem is that one of the carbs has a sticking piston. I've cleaned > it etc, but it must just be worn out. I'm not sure if they can be [quoted text clipped - 20 lines] > >>there is a better way to go? A single carb, larger carbs, or? > >>What are the best options? It appears that the piston is sticking in the chamber. It touches the side at the top. > It sounds like you have a jet alignment problem rather than it having worn > out. [quoted text clipped - 61 lines] >>>>there is a better way to go? A single carb, larger carbs, or? >>>>What are the best options? It seems strange after all these years that this would happen. Grasping at straws now ... Does it still catch if you unscrew it and bolt it back down after turning it 180 degrees? Does it drop down if you pull the choke on. This would indicate the jet or needle has moved. > It appears that the piston is sticking in the chamber. It touches the > side at the top. [quoted text clipped - 64 lines] > >>>>there is a better way to go? A single carb, larger carbs, or? > >>>>What are the best options? > The problem is that one of the carbs has a sticking piston. I've cleaned > it etc, but it must just be worn out. I'm not sure if they can be > rebuilt if the slide or piston is worn out? > It's an orginal S, bought new by a friend. I have it 25 years. If these are the original HS type SUs, it may be that the jet has become uncentered. This allows the needle to drag on one side of the jet, effectively sticking the piston/needle mechanism. Here's how to test for that: 1. Remove the dashpot and lift out the piston and needle. 2. Remove the dashpot oil filler top. 3. Make sure the piston rides smoothly up and down the dashpot, with no rough spots or sticking. 4. Inspect the needle to see if it's worn on one side, which would indicate an uncentered jet. 5. Another indication of an uncentered jet would be an oval hole in the top of the jet (from wear). If you find the needle or jet to be worn or otherwise damaged, they must be replaced. 6. It's a seriously fiddly job to recenter the jet in the carb body. It usually takes lots of adjustment and re-adjustment to get it right. When it's right, if you lift the piston and release it, it makes an audible "click" when it falls all the way to the bottom of its travel. This is another reason I recommend the HIF series carb(s): they do not require jet centering, since it's built-in. -Rock http://www.rocky-frisco.com -- JJ Cale Live CD and video: http://www.rocky-frisco.com/calelive.htm The Wednesday Night Science Project: http://www.wednitesciproj.us Rocky Frisco's LIBERTY website: http://www.liberty-in-our-time.com/ Those damn SUs. For some reason no one can get more than 25 or 35 years use out of them... If this is an original 'S' I would suggest you get the twin SUs rebuilt. Joe Curto is the name that usually comes up for this sort of thing in the U.S. http://www.geocities.com/jcurtoinc/ Obtaining an HIF44 in good shape and a proper manifold in the U.S. will probably cost as much as getting the original carbs rebuilt. I have helped a number of people locally who got a used HIF44 and manifold from the UK and then couldn't get it to work any better than their old carbs. A worn out HIF44 is no better than a pair of worn out HS2s. In my experience, balanceing a pair of HS2s isn't too difficult and they tend to stay tuned once you get it right. As long as they are in good shape. Most people are trying to set and balance a pair of 30 or 40 year old carbs. Cheers, Kelley >One, maybe both carbs on my '67 S need to be rebuilt. I'm wondering if >there is a better way to go? A single carb, larger carbs, or? >What are the best options? the twin su's on my 69 S were worn, so i when i rebuilt the engine, i put them in a box, and fitted a 45DCOE weber on a redline 3.5" manifold (no firewall/bulkhead cutting). probably doesn't perform any better than a big su, but its certainly responsive, and i'm now addicted to that wonderful sound a weber makes :) > One, maybe both carbs on my '67 S need to be rebuilt. I'm wondering if > there is a better way to go? A single carb, larger carbs, or? > What are the best options? It turns out that the jet was not centered. Now I'm in the tedious process recentering the jet. Thanks to all. > the twin su's on my 69 S were worn, so i when i rebuilt the engine, i put > them in a box, and fitted a 45DCOE weber on a redline 3.5" manifold (no [quoted text clipped - 5 lines] >>there is a better way to go? A single carb, larger carbs, or? >>What are the best options? > It turns out that the jet was not centered. Now I'm in the tedious > process recentering the jet. > Thanks to all. Would suggest that you replace the jets as well as the needles cause both will be worn if they haven't been centred. r >> the twin su's on my 69 S were worn, so i when i rebuilt the engine, i >> put them in a box, and fitted a 45DCOE weber on a redline 3.5" [quoted text clipped - 5 lines] >>> if there is a better way to go? A single carb, larger carbs, or? >>> What are the best options? |
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