wonkey eyed barmaid Posted April 25, 2005 Share Posted April 25, 2005 just briefly - what do the PUMP JETS do..? and how does thier size effect the running of the car... is the size on the jet a direct indication of its flow rate/capacity or whatever... so for nstance is a 35 actually "smaller" or more restrictive than a 50..? trying to understand carbs ta. Link to comment Share on other sites More sharing options...
oilyhands Posted April 25, 2005 Share Posted April 25, 2005 They meter the fuel to the accelerator pump circuits, these provide instantaneous enrichment when the accelerator is suddenly opened, this extra fuel covers the weak spot which occurs when the air in the induction system accelerates into the engine faster than the fuel through the main jet, without the acclerator pumps the engine would stumble and die. There is also a bleed back system which prevents too much fuel being modulated. Too large a pump jet will flood the engine when the throttle is opened and will cause a slight misfire coupled with much black smoke. Oily Link to comment Share on other sites More sharing options...
Firemang Posted April 27, 2005 Share Posted April 27, 2005 Interesting...am rejetting my carbs after a Blydenstein conversion on my 1600vx. Current jets are Mains 115 Emulsion F7 Airs 195 Idle 60F6 Chokes 30 Pump 45 On advice i am changing only Idles 45 F9 Pumps 35 It is running rich with black smoke being blown out on quick pulses of the throttle.Its floods when hot.And tick over surges. are these symptoms cause by the pump jets? Am i going to lose performance by going to 35? Or Is it the Idles which control this? Thanks Ian Link to comment Share on other sites More sharing options...
wonkey eyed barmaid Posted April 27, 2005 Author Share Posted April 27, 2005 firemang, i think my idle jets are 50's - and I am also planning to change down to 45. just waiting to fit the jets next time im at home. my pump jets are 50, and I have been advised by redline to change them down to a 35. my main jets are 115. oilyhands. thanks for the informed response. it may explain when my car stutters and farts a bit when I open the throttle quickly. I always assumed it was overfuelly, but thought it was down to general setup etc. I now suspect that the pump jets are overly large. will let you know the results of the change. Link to comment Share on other sites More sharing options...
oilyhands Posted April 27, 2005 Share Posted April 27, 2005 Firemang, 60F6 idles are the act of desperate man.. 45F9 or 50f9 should be fine. A 35 or 40 pump jet is probably about right. The rest of the calibration looks reasonable, the mains may be marginally lean and the airs a little on the large side. oily Link to comment Share on other sites More sharing options...
Firemang Posted April 28, 2005 Share Posted April 28, 2005 oilyhands@granteuk, Thanksfor the advice. I have the jets now from Southern Carburetters. Going to pop them in and tune up today! Cheers Ian Link to comment Share on other sites More sharing options...
wonkey eyed barmaid Posted April 28, 2005 Author Share Posted April 28, 2005 firemang, what jets have you bought, and what was the basic cost + vat...? contact details for southern carbs? pump jets are £4.63 from Redline Link to comment Share on other sites More sharing options...
wonkey eyed barmaid Posted April 30, 2005 Author Share Posted April 30, 2005 how did the carb tweak go Firemang.../ Link to comment Share on other sites More sharing options...
wonkey eyed barmaid Posted May 3, 2005 Author Share Posted May 3, 2005 Link to comment Share on other sites More sharing options...
Chas Guirey Posted May 3, 2005 Share Posted May 3, 2005 Firemang - how did you get on at Southern carbs? How much did they charge to set up your carbs regards Chas Link to comment Share on other sites More sharing options...
Firemang Posted May 3, 2005 Share Posted May 3, 2005 Hi Chas, I bought 8 jets and a couple of gaskets from Southern Carbs for about £25 and did the set up myself using a carb vacuum guage and a color tune plug. They are worth owning to keep your carbs in a good state of tune. It is easier than you think to tune them aslong as you have the correct jet sizes. After the Blydenstein conversion and rejetting the car tick over is much better,smoother,loads more power and torque. Its is like having a bigger engine. Better fuel economy also even though i tend to stick my foot down more than ever! A standard engine will benefit from rejetting though as i think the standard jetting is way off. Ian Link to comment Share on other sites More sharing options...
Firemang Posted May 3, 2005 Share Posted May 3, 2005 Granteuk, Have you had a go at rejetting? Chas. How is you conversion now? How many miles have you put on it? Ian Link to comment Share on other sites More sharing options...
Chas Guirey Posted May 4, 2005 Share Posted May 4, 2005 I have put on about 2000 miles since the conversion - goes very well but wont tick over and I will need to get it tuned to get it through the mot. I was wondering if anyone knows what Southern Carbs would charge to set it up for me and if they are experts. I have had poor experiences in the past with some of the so called tuning companies so would welcome any recommendations in the west london area thanks Chas Link to comment Share on other sites More sharing options...
oilyhands Posted May 4, 2005 Share Posted May 4, 2005 There is a section on setting the idle for Webers at here it may help you to sort your idle out. Oily Link to comment Share on other sites More sharing options...
wonkey eyed barmaid Posted May 4, 2005 Author Share Posted May 4, 2005 I'VE GOT ALL MY JETS, EXCEPT THE PUMP JETS. IM IN WALES JUST NOW, AND CAR IN SCOTLAND - SO NOT FITTED THEM YET. HOME NEXT WEEK THOUGH, SO WILL BE EXPERIMENTING THEN. Link to comment Share on other sites More sharing options...
Firemang Posted May 4, 2005 Share Posted May 4, 2005 Where are you Chas? If you close enough i can give you a hand tuning it up if you want. Ian Link to comment Share on other sites More sharing options...
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