| Author | Message | ||
     Mujahid Khan Yet to post message Username: anjumkha Post Number: 1 Registered: 12-2003 |
SRF 30074 1977 SSII One of the pressure switch is defective. This was discovered after transposing the switches. THe accumulator on side A has 700 psi. One switch will illuminate after 60 pumps while the defective illuminates after 30 on the same side when transposed. I think the spring is weak but I cant find a replacement spring. Can I shim it?? M Khan | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 195 Registered: 4-2003 |
Hi Mujahid, and welcome to the other side of the world. Don't worry about your pressure switch. Leave it alone. I don't believe that it is defective. R-R produced switches which operated at various pressures in their experimenting. The early ones switched out at about 100psi, which was instant upon starting. Later, they operated around 1200 psi, which took a little longer to reach. I believe that the change came around 1974 at chassis 22119 when the master cylinder was deleted and therefore there no longer was a conventional unassisted backup. You may have one of one rating and the other of another, but all that matters in the end is that they both work. Bill C fitted a pair of new-rating service unit pressure switches once on my father's T-Series years ago. My father demanded that the originals be put back in as, instead of going out instantly, the new ones took some minutes to extinguish. Bill was really annoyed, and he had certainly made no mistake at all. It's just that if it has behaved in one way always before, then a change may be worrying for an owner. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 161 Registered: 4-2003 |
I certainly have no memory of that Richard but I do remember that Australia had a higher switch off pressure than other countries. And of course this is what I tell myself when I go down the steep drive in Kambah with at least one brake light still glowing - its still building up!!! | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 162 Registered: 4-2003 |
Richard,while I am at it, can you find out who is the agent or manufacturer for the Colourtune kits in the UK I want one and can't believe that someone is not an agent for them here! | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 196 Registered: 4-2003 |
Bill, In the UK, Gunson's Colourtune spark plugs are available in stores such as Halfords, for somewhere in the region of £ 20. However, you are probably better off to buy one online with a credit card direct from Gunson at: www.gunson.co.uk Do a search on their site for Colourtune and you will find it easily. They even have an online price list. It is advertised as being for motorcycles, so you may even try the Canberra Bike Shop etc. It is 14mm, so with the correct spacer it will be fine in a R-R. Also http://www.gunson.co.uk/acatalog/ Regards, Richard. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 197 Registered: 4-2003 |
Gunson Ltd Crypton Technology Business Park Bristol Road Bridgwater Somerset TA6 4BX Telephone Sales +44 1278 436247 Support +44 1278 436241 Fax +44 1278 450567 Sales@Gunson.co.uk Technical@Gunson.co.uk Website www.gunson.co.uk Also see: http://www.ime.org.uk/ime/c/colourtune.html for a little entertainment. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 199 Registered: 4-2003 |
This RROC Inc article may be of interest too: this guy swears by Colourtune too. Either he can't spell in UK English, or they have renamed it for sale in the US without the "u" as Colortune. ------------------------------------------------- jwaples Active Joined: 01 Jan 1970 Posts: 18 Location: Detroit, Michigan Posted: 27 May 2004 14:33 Post subject: -------------------------------------------------------------------------------- The weakener will not cause the issue your experiencing as far as I can imagine. First, the weakener only gets vacuum at part throttle when the itty bitty venturi is on the engine side of the throttle plate and thus immersed in a partial vacuum. At idle the venturi is on the "upstream" side of the throttle plate and thus no vacuum. Similarly at full throttle, the entire manifold is at atmospheric pressure or close to it, so again, no vacuum. If there is no vacuum, it doesn't do anything. Setting theory aside, a sure way to tell is to disconnect the rubber tube that runs from the weakener body to the tall cylindrical fuel receiver adjacent to the distributor. Or... remove the acorn shaped pressure tapping nut on top of the A-carb float chamber. Both methods will neutralize the effects of the weakener and eliminate that as a cause. * * * Like the other folks intimated, the most likely cause of the problem is a profound lean hesitation. I.e., the mixture in the cylinders goes from a burnable air-fuel ratio somewhere around 14.7:1 (probably lower) to something with too much air and not enough fuel to burn. The easiest way for this to happen suddenly is if the piston dampers in the carbs aren't damping because they lack oil. A super way to slice through all of the conjecture is to buy a device called a Gunson Colortune. It is a spark plug with a clear base that allows you to SEE the actual color of combution. Normal combustion is Bunsen blue, rich is bright yellow. Too lean is violet and then black because it's misfiring. They're about $50. I got my from Little British Car Co. (on the internet) because I could pick it up. Note that A-carb feeds A1 A4 B2 and B3 and B-carb feeds everything else. For me, the easiest plugs to reach were A4 for A-carb and B1 for B-carb. Before you do anything to touch the carbs (other than ensuring that the dampers DEFINITELY have oil in them) is make sure that your ignition timing and points gap are correct. It doesn't take long and it really stinks to have to tune all of the fuel stuff twice after realizing that you has a dumb ignition problem. _________________ Jon Waples '73 Silver Shadow SRB15031 | ||
| Mujahid Khan New User Username: anjumkha Post Number: 2 Registered: 12-2003 |
Thank you, that saves me some money. I will keep the switches as they are. During my motorcycling days I considered using Colourtune. But I was told that It tunes only at idling,and not at load. Finally I got the carbs tuned,at the shop, with "DYNO". M Khan | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 200 Registered: 4-2003 |
Again, Mujahid, You are completely correct of course. A perfect idle is Nice To Have, but that is only 1% of a fine running motor on load, where the jets or injectors behave completely differently. The fine tuning on idle has a negligible effect on a motor on load. It's a good and easy place to start, though, you must agree. RT. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 163 Registered: 4-2003 |
Thank you Richard for that info. Mujahid's observation is interesting and quite true but I like to think that the two carburetters are favouring each side of the engine equally and for the mixture I can't see a better way of doing this at least in my backyard. I am a great fan of dynotuning (Braddon) particularly for diagnosis. It discovered an incorrect air filter in the Cloud three and a certain Phantom running 10 degrees out in ignition. Somewhere in some Factory manual I remember reading that with the customer's agreement it maybe desirable to tune for economy rather than a smooth idle. Well given the customer I think he would be more concerned not to feel engine shudder while sitting at the lights than to know he was saving two cents a kilometer in fuel! |
