Iain T Posted May 2 Report Share Posted May 2 I've noticed both jet assemblies are proud of the carb body bridge. The rear is only 0.2mm but the front is 0.7mm . As I set both needles the same height on the air piston I've compensated for the 0.5mm higher front assembly by lowering the jet the same amount thereby making the jet the same height in relation to the carb body. This will also make the needle penetration the same front to rear when in operation and the air pistons are moving. Question is are there differing aluminium washer thicknesses available? I know I'm being picky but it's bugging me! Iain Link to comment Share on other sites More sharing options...
johny Posted May 2 Report Share Posted May 2 Does that mean the pistons dont smack down on the bridges Iain? Link to comment Share on other sites More sharing options...
Iain T Posted May 2 Author Report Share Posted May 2 (edited) Not on the bridge as both jet holders are proud the pistons hit the jet holder. The pistons do move freely and clonk down. I think it's the Ali washers that may be too thick. I can live with the rear being 0.2mm proud but the front is 0.7mm which I think is too much. In my working life I've measured everything from simple brackets to full car bodies and can't get it out of my system! I think the most important feature is the needle taper to jet penetration is equal over both carbs. I might take out the front jet assembly and see what the problem is. Iain Edited May 2 by Iain T Link to comment Share on other sites More sharing options...
johny Posted May 2 Report Share Posted May 2 So theres an air gap under the piston but I suppose not enough to affect anything? Link to comment Share on other sites More sharing options...
Iain T Posted May 3 Author Report Share Posted May 3 9 hours ago, johny said: So theres an air gap under the piston but I suppose not enough to affect anything? To adjust the jet to obtain the correct relationship between the needle, jet and carb body I had the turn down the bottom jet adjuster by half a turn. As I have a afr meter I can see that made a significant difference to the fuel ratio at tick over. However at tick over virtually all the needle is in the jet so the ratio of the extra 'exposed' area will be higher than when the needle is higher and there is a larger gap between the needle and jet. Very interesting for me as I love to twiddle and research. The tick over is stable but I can't do a test run as it's raining. Iain Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 3 Report Share Posted May 3 15 hours ago, Iain T said: Question is are there differing aluminium washer thicknesses available? i guess thats down to who supplies /gets em from the base spec all should be the same its not known to be "shimable" its only the holder dimensions the counter bore and the washer that control the holder height so youre into some juggling !!!! Pete Link to comment Share on other sites More sharing options...
micklewis Posted May 3 Report Share Posted May 3 on one of my other forums this has been discussed before , have you bought aftermarket jets as diameter can be wrong and the nut doesnt control it well ? check thickness of washers between carbs . suppliers supply a 1mm washer as standard some cases it too thin . any hydraulic or fuel injection agent can supply thicker washers mick 1 Link to comment Share on other sites More sharing options...
Iain T Posted May 3 Author Report Share Posted May 3 36 minutes ago, Pete Lewis said: guess thats down to who supplies /gets em from the base spec all should be the same its not known to be "shimable" its only the holder dimensions the counter bore and the washer that control the holder height so youre into some juggling !!!! Dave at Carburetter Exchange refurbished them so I'll give him a call. This is all in the search for the perfick carb setting. My idea of fun! I did take one jet body apart but can't remember the detail through the brain fuzz. Iain Link to comment Share on other sites More sharing options...
Iain T Posted May 5 Author Report Share Posted May 5 On 03/05/2024 at 11:02, micklewis said: on one of my other forums this has been discussed before , have you bought aftermarket jets as diameter can be wrong and the nut doesnt control it well ? check thickness of washers between carbs . suppliers supply a 1mm washer as standard some cases it too thin . Mick, What other forum is it? It's the Ali body around the jet that is proud of the carb bridge body and I'm not sure if that's part of the jet holder assembly. Cheers Iain Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 5 Report Share Posted May 5 can you photo just what you mean as surely its the alloy cast body forms the bridge ???? Pete Link to comment Share on other sites More sharing options...
Iain T Posted May 5 Author Report Share Posted May 5 (edited) Pete, it's the ring sandwiched between the brass jet and the carb bridge. It's 0.7mm above the bridge on the front carb and 0.2mm on the rear. When I unscrew the jet assembly (5/8 nut) the brass jet and the 'ring' move to facilitate needle centering. The air piston hits these 'rings' and not the carb bridge. All I want to do is make it flush so the jet depths can be measured from the bridge. Edited May 5 by Iain T Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 5 Report Share Posted May 5 i still feel any snags here is down to the thickness of the sealing washer you can unscrew the jet holder without upsetting the needle position check the washers and refit with the same mixture setting unchanged unless you change the washer thickness as then the jet will need some small adjustment . Pete Link to comment Share on other sites More sharing options...
Iain T Posted May 5 Author Report Share Posted May 5 (edited) 15 minutes ago, Pete Lewis said: still feel any snags here is down to the thickness of the sealing washer you can unscrew the jet holder without upsetting the needle position check the washers and refi I agree I think it must be varying washer thicknesses. Can I you say unscrew the jet adjuster and take out the jet without taking the whole assembly out and emptying the float chamber? Can I then push out the jet from underneath. On checking the ali washers I assume I could use some fine wet and dry to thin them and make the jet holder flush with the bridge. I'm itching to tackle this as I want to know exactly how it works. Or if proud do I need a thicker washer? Iain Edited May 5 by Iain T Link to comment Share on other sites More sharing options...
johny Posted May 5 Report Share Posted May 5 Are you using the workshop manual Iain as it shows exactly what controls the jet bush height and what you can remove to change it.... Link to comment Share on other sites More sharing options...
Iain T Posted May 5 Author Report Share Posted May 5 3 minutes ago, johny said: Are you using the workshop manual Iain as it shows exactly what controls the jet bush height and what you can remove to change it.. I have a Haynes which is less than ideal. I did download the wsm from vitessesteve? website and stored it somewhere extremely safe on my laptop....... Thanks I'll download another and put it on my desktop! Iain Link to comment Share on other sites More sharing options...
Iain T Posted May 5 Author Report Share Posted May 5 (edited) 56 minutes ago, johny said: Are you using the workshop manual Found it! The item that is proud is item 56 bushing the adjustment to make the top flush with the bridge is item 57 washer. I assume I'll need a thicker washer achieve this. What a plonker I forgot about downloading the wsm..... Cheers 😀 Iain Edited May 5 by Iain T Link to comment Share on other sites More sharing options...
johny Posted May 5 Report Share Posted May 5 Thatll do it👍 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 6 Report Share Posted May 6 unscrewing the whole jet bushing holder will dump the fuel out of the float chamber the whole assy will just unscrew with jet spring jet sealing etc dont drop it in the grass and yes thicker washers to drop the bushing Pete Link to comment Share on other sites More sharing options...
Iain T Posted May 6 Author Report Share Posted May 6 1 hour ago, Pete Lewis said: unscrewing the whole jet bushing holder will dump the fuel out of the float chamber the whole assy will just unscrew with jet spring jet sealing etc dont drop it in the grass and yes thicker washers to drop the bushing I knew those Charlie Bighams ceramic bowls would come in handy. I'll take both out and measure and phone Carb Exchange for new washers. A bodge would be to sand down the top of each bushing so they are flush with the bridge. Then all I have to do is start a new chapter on Vitesse Needles..the Story for modified engines! Getting a decent tick over afr is easy it's the rest that is head scratching and I have to run the gauntlet of 20mph limits and Newham Way race track/traffic jam before the 70mph A13. Mind you it's very mixed driving. Thanks again for yours and Johnys help. I searched for ages online for sectional diagrams but forgot about the wsm...... Iain Link to comment Share on other sites More sharing options...
johny Posted May 6 Report Share Posted May 6 Finding the correct size washer might be difficult as dont think theyre listed by thickness. You might be able to measure yours and then get a supplier to do the same for theirs, oooerr! Doesnt matter if it sits slightly low... Link to comment Share on other sites More sharing options...
Iain T Posted May 6 Author Report Share Posted May 6 I hope Carb Exchange have a box of washers or it might be bodge time! I do have a fastening supplier my old company uses who are very good and my wife is fortunately going into the factory to do the monthly management accounts so if I ask nicely she could pick up a couple if they have thicker washers. Or I could ask if my old company could punch out a few for me as they keep ali sheet in various thicknesses. Iain Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 6 Report Share Posted May 6 in general terms having the bush a bit lower than the jet does help with atomising the fuel from the jet so being lower is better Pete Link to comment Share on other sites More sharing options...
Iain T Posted May 6 Author Report Share Posted May 6 36 minutes ago, Pete Lewis said: so being lower is bette At 5'2" wife says that! Link to comment Share on other sites More sharing options...
Iain T Posted May 6 Author Report Share Posted May 6 The whole jet and holders out. Charlie Bighams pie did was too big so I used a cut down milk bottle end to catch most of the petrol. The washers on top of the bushing are 0.2 and 0.7mm thick and appear to be brass not aluminium. New washers need to be at least 1.0mm thick for the bush head to be flush with the bridge so 1.2mm even better. I've checked my washer supply and nothing close to the 11/16" od x 3/8" hole size I need. However I do have some copper washers that are 1.2mm thick with a 10.2mm hole as opposed to the 9.52mm to give a tight fit on the bush. The od is 19.2mm but I can reduce that with careful sanding. The question is copper too hard for the washer as it should be aluminium (although mine are brass so hard anyway). Is it worth a go? Iain Link to comment Share on other sites More sharing options...
johny Posted May 6 Report Share Posted May 6 Yes deffo aluminium and think someone has been bodging it before. You can see in the manual theyre much chunkier than that... Link to comment Share on other sites More sharing options...
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