34 Pict wont idle??? any ideas? anf timing settings??

Discussion in 'Mech Tech' started by Rixy, Oct 21, 2011.

  1. hi people, i've just finished fitting my engine to my bus, and cant seem to get the carb to idle? Its a stock 34 pict 3, on a stock manifold. The carb has had a rebuild kit on it from coolair, and i fitted the brass spindle bushes as the old nylon ones were worn out.

    The carb starts on the button, and revs really well, and really cleanly, but wont idle very well. we also dont seem to be able to make a huge amount of differenct to the tuning no matter how much we fiddle with the screws, they just dont seem to do anything??

    We have however got it to idle finally, but the larger air bypass screw is wound out a hell of a long way, almost out of the carb body, and its still really rough idle?

    I've checked for vacuum leaks all over, and there arent any, also if there was a leak, i'd imagine the screw would need to be wound it wouldnt it, not out?

    What else could be wrong?

    Also, what should my timing be set to with a light, as im runnign stock vac advance dizzy, points and condensor etc.

    The engine is a 1641 with engle 100, rebuilt with 165psi compression in every cylinder give or take a few psi.

    HELP ME, I NEED THE BUS MOT'D, asnd i dont wanna drive it until it runs properly for fear of breaking summit??
     
  2. I know you have said thet you have checked for leaks but. so had I. Still sounds like it might have an air leak. check the following areas with WD40 when running.

    Manifold garsket to C/heads
    Manifold boots
    carb base gasket,
    the blanking plugs in the carb

    if you get an increase in engine speed when you spray the WD40 one area at a time then you have an air leak. Same symptoms as i had on mine before the twin carb swap.

    Other than that check that the throttle screw is set up properly.
     
  3. First step I'd say is to forget the carb - there's nothing much you adjust on them - and make sure your tappets and timing are spot on. You can set timing statically with a light bulb without the engine running. 7.5* BTDC will do nicely. Set the carb screws to the recommended starting positions - no reason why the engine shouldn't run. Make sure the choke comes off.

    You've prob done already, but check again.

    As you prob know, carb-fiddling is the very last step. Assume you've cleaned all jets, yes?
     
  4. yes matey, all jets were soaked and blown thru with 120psi compressed air :)

    As for choke, its operating perfectly :)

    Urm....how do i set timing at 7.5 btdc with a bulb, is this set engine to tdc, put test light on points terminal and earth, then turn distributer till light just comes on, and lock it off, then do i measure round the pulley and go backwards so far?? if so how far etc??

    As for air leaks, i'll check again tomorrow, but im pretty sure there arent any??
     
  5. I recently had this issue. turned out to be the pilot or idle jet. I blew through it several times and thought it clear. Zed advised me to use a gas lighter canister. Worked a treat. Now he idles fine. Try this. I blew through mine countless times and the lighter jobbie worked a treat.
     
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  7. I had the same problem with my old van and the idle jet was blocked (well not just the jet but bits in the carb too) the carb had somehow sucked in some strands of fabric duct tape.

    Anyway a blast of carb cleaner through all the orifices and it was ok. Took a few attenpts though.

    Cheers
    Ben
     
  8. ok, i'll try it on evening this week if i get chance. :) thanks peeps
     
  9. right then, a bit of an update.....

    changed carb for another one (that works perfectly on another bus) and it still doesnt wanna play ball?

    it wont adjust, neither of the adjusting screws make any difference to the idle speed, or make the engine sound any different? timing is spot on, no air leaks i can find, and all seems to be ok, just cant get it to run properly. Ran it up for an mot the other day finally, and couldnt get above 27mph all the way there?? fecking thing, any ideas peeps?

    Im thinkin of trying another carb, or re fitting the weber progressive, what should i do??
     
  10. Zed

    Zed Gradually getting grumpier

    Look again for air leaks - I think you've missed one. A big one.
     
  11. Honky

    Honky Administrator

    When you say you checked for air leaks all over, where have you checked exactly?
     
  12. base of carb
    manifold centre section to manifold ends
    manifold ends to heads
    servo end of servo pipe
    all other joints on the servo pipe

    where else is there to check?
     
  13. i had this with mine after some one messed with it wouldnt go over thirty
    had a look and spotted what the prob was,vac pipe was off put it back on and went fine

    is yours on or is the can on the dizy shot
     
  14. i dont know, i suppose the can in the dizzy could be the problem? will give this a try again tomorrow, or chuck yet another carb on it and see what happens.

    i might just go and change tha manifold and shove the weber on it again, what ya think?? at least if it runs the same with the weber, it rules out carb issue and says there's summit deeper going on?? its just a royal PITA changin it all over again.....
     
  15. tried everything, and got annoyed......so i;'ve now removed the fan housing, the inlet manifold centre and both ends, and im gonna replace the gaskets again, with new ones, again.

    Now i dunno whether to fit the weber or the solex back on, what ya think peeps?
     
  16. Rixy do you have any issues with your 1641cc with eagle cam? Running to lean on the standard carb ? An does yours hv the standard jets? ? As I'm running the same set up just with 009 dizzy =]
     
  17. It sounds like your pulling air in from somewhere


    Get a butane or propane blow torch like plumbers use and without lighting it put the nozzle in the area where air leaks could be likely on the inlet

    If the revs pick up then you have found your problem area

    If you have servo assisted brakes it could be somewhere in the vacum line to the servo
     
  18. i havent got mine set up properly yet, only just re fitted the engine saturday and got it running finally. its running on its base settings for the carb, and is still on static timing marks. My carbs are set up using the larger mains, airs, emulsions and idles that seem to be the ideal ones that everyone uses on 34ict's as apparently the stock ones are far too small. I have also drilled and run a balance pipe between the 2 manifolds, and drilled and tapped the front boss on the left carb manifold to take the servo vacuum pipe :)
     

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