User Tag List

+ Reply to Thread
Results 1 to 18 of 18

Thread: Twin webers air leak

  1. #1
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Twin webers air leak

    Ok so iv got a new built pinto with new weber 45s trying to set carbs up but getting pops and bangs and the odd flame i am assuming air leak on manifold to carb area? I have used new misab plates was careful not to over tighten on the rubber bobbins/cups etc as per instructions.i cant do the usual spray carb cleaner round joints as cant get to idle properly.its not to bad if i hold revs at 2k plus which i have been doing to bed new cam in anyway but if i ease off it just spits n pufs.im sure timing is not to far off but again cant check that with light as it wont run long enough!! Any ideas?i was thinking about taking the mishab plates off and just put a gasket on (only tempory) just to see if air leak? Cheers guys

  2. #2
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: Twin webers air leak

    I think you may have more of a problem than a carb air leak. What type of ignition system are you using? It maybe timing or a problem with the ignition side. I had the very same problem and it was the Accuspark type ignition module Dicking about. There's something said for basic points in your distributor.

  3. #3
    Spanner Monkey

    Join Date
    Apr 2020
    Location
    Essex
    Age
    52
    Posts
    210
    Thanks
    34
    Thanked 9 Times in 9 Posts

    Re: Twin webers air leak

    I’d have a play with the dizzy, loosen the nut so you can just twist the dizzy and have a play and see what you come up with for a starters, as you state you’ve run the cam in so no worries there

  4. #4
    Bodger

    Join Date
    Jan 2011
    Location
    norway,west
    Posts
    160
    Thanks
    34
    Thanked 21 Times in 18 Posts

    Re: Twin webers air leak

    Can you get someone to fire it up when you handle the trottle on the carbs? Then spray and see.
    I believe you can check timing with light, just remember it advances on revs. Should give a pointer. I found that spit back in carb is lean or timingissue, but I have a 32/36.

  5. #5
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by Forest_rallying View Post
    I think you may have more of a problem than a carb air leak. What type of ignition system are you using? It maybe timing or a problem with the ignition side. I had the very same problem and it was the Accuspark type ignition module Dicking about. There's something said for basic points in your distributor.
    Thanks. Im running bestek electronic ignition not had probs with it before.there is bit of play in cap
    In the fact that it can move fractionly.i have magnicor leads with good spark at plugs tho

  6. #6
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by notenoughtime View Post
    I’d have a play with the dizzy, loosen the nut so you can just twist the dizzy and have a play and see what you come up with for a starters, as you state you’ve run the cam in so no worries there
    Thanks.done that with a m8 when it does start its not sharp tho and will pop when you move it.i still think its dizzy related as i was very carefull mounting carbs i just cant see how theres air leak

  7. #7
    Racer Decade Plus User

    Join Date
    May 2012
    Location
    Camberley, Surrey
    Posts
    3,237
    Thanks
    5
    Thanked 353 Times in 339 Posts

    Re: Twin webers air leak

    You could be running lean at idle / off idle - what jetting is installed? Some better informed adults may advise changes if they know what you have fitted!

  8. #8
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by katana View Post
    You could be running lean at idle / off idle - what jetting is installed? Some better informed adults may advise changes if they know what you have fitted!
    Twin 45 152 carbs 36 chokes.f16 emulsion tubes 145 mains 180 airs.iv tried 55f8.55f6 and 60 f6 idles so far ??
    Cheers

  9. #9
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: Twin webers air leak

    I doubt it's carb related, I would be looking at the ignition side, especially timing. Is your rotor arm sittting fully home and locked in the slot correctly on the disributor shaft and is there any abnormal free play there ?

  10. #10
    World Champion Decade Plus User alladdin's Avatar

    My 1st Project
    My 2nd Project
    Join Date
    May 2005
    Location
    s.wales
    Age
    60
    Posts
    9,200
    Thanks
    167
    Thanked 446 Times in 432 Posts

    Re: Twin webers air leak

    you have not mentioned (i dont think ) if you have balanced correctly and set idle mixtures ?

  11. #11
    Bodger
    My Race Car
    My 1st Project
    Join Date
    Sep 2020
    Location
    south wales valleys
    Age
    62
    Posts
    183
    Thanks
    0
    Thanked 34 Times in 30 Posts

    Re: Twin webers air leak

    Quote Originally Posted by alladdin View Post
    you have not mentioned (i dont think ) if you have balanced correctly and set idle mixtures ?
    that would be my suggestion as well. or better still get it on a rolling road some where and get it set up expertly,

  12. #12
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by alladdin View Post
    you have not mentioned (i dont think ) if you have balanced correctly and set idle mixtures ?
    Hi cant set mixtures as cant get to tick over below 2k same as balance really.i do have airflow meter.but hard to do when you got flames lol.

  13. #13
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by modifyitmike View Post
    that would be my suggestion as well. or better still get it on a rolling road some where and get it set up expertly,
    Yes needs to get on rolling rd but cant drive till i can get it running basicly

  14. #14
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by Forest_rallying View Post
    I doubt it's carb related, I would be looking at the ignition side, especially timing. Is your rotor arm sittting fully home and locked in the slot correctly on the disributor shaft and is there any abnormal free play there ?
    New bosch dizzy cap from burtons.rotor fits nice tight.magnicor leads all fitting correct on cap and plugs.new plugs.take plugs out theres fuel on them prob due to trying to start.when you switch off after running big puff smoke out carb

  15. #15
    World Champion Decade Plus User alladdin's Avatar

    My 1st Project
    My 2nd Project
    Join Date
    May 2005
    Location
    s.wales
    Age
    60
    Posts
    9,200
    Thanks
    167
    Thanked 446 Times in 432 Posts

    Re: Twin webers air leak

    Quote Originally Posted by Theyellowmex View Post
    Hi cant set mixtures as cant get to tick over below 2k same as balance really.i do have airflow meter.but hard to do when you got flames lol.
    you dont need to.
    back off the idle screw on the lead carb to get it as shut as possible, remove a progression hole cover on that carb and adjust the idle screw to move edge of butterfly under one of the holes. a torch into carb may help..
    now remove a p.h. cover on the other carb adjust that butterfly via the balance link to get it under the same equivilent hole. they should now be roughly balanced.
    lightly close all 4 mixture screws and wind all back out an even amount - say 3 full turns. ( it differs with carb age /type) -
    adjust idle screw out to fast idle position and you can now start it up ( put covers back lol) and drop idle to lowest you can to allow mixture setting.
    thats a starting point anyway.

  16. The Following User Says Thank You to alladdin For This Useful Post:


  17. #16
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: Twin webers air leak

    if you have flames the timing is probably a mile out, usually retarded, what happens is the mixture burns so late its still burning the next time the inlet valve opens
    Last edited by Graham; 08-01-2021 at 08:48.

  18. #17
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by Graham View Post
    if you have flames the timing is probably a mile out, usually retarded, what happens is the mixture burns so late its still burning the next time the inlet valve opens
    Graham i got tdc on piston 1 with timing marks lined up and dizzy at number 1 via rotor.iv checked its on firing stroke ie not firing on 4.iv then turned dizzy anti clockwise to where it will fire up and then only turned anti clockwise to see if improves but not really still get backfire which i know is symptom of retarded ignition.iv took the carbs off now bought some new mishabs and will put them together and start again.cheers

  19. #18
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Twin webers air leak

    Quote Originally Posted by alladdin View Post
    you dont need to.
    back off the idle screw on the lead carb to get it as shut as possible, remove a progression hole cover on that carb and adjust the idle screw to move edge of butterfly under one of the holes. a torch into carb may help..
    now remove a p.h. cover on the other carb adjust that butterfly via the balance link to get it under the same equivilent hole. they should now be roughly balanced.
    lightly close all 4 mixture screws and wind all back out an even amount - say 3 full turns. ( it differs with carb age /type) -
    adjust idle screw out to fast idle position and you can now start it up ( put covers back lol) and drop idle to lowest you can to allow mixture setting.
    thats a starting point anyway.
    Cheers i initialy did that when i fitted carbs to manifold although i only turned mixtures out 2 turns.il start from scratch try again

+ Reply to Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts