DaveNotSoSideways Posted May 24, 2015 Share Posted May 24, 2015 Min jet for emission is 55, the 50 would never work. Wait till u tune correctly the idle screws to assess higher gear running. The pump jets maybe too small. What size are they, I guess 42 or 45 would be right. 33 too small. 35 marginal. Try winding the pump rod nut up the shaft to increase the quanity of fuel it delivers. Link to comment Share on other sites More sharing options...
ChrisV Posted May 30, 2015 Author Share Posted May 30, 2015 Min jet for emission is 55, the 50 would never work. Wait till u tune correctly the idle screws to assess higher gear running. The pump jets maybe too small. What size are they, I guess 42 or 45 would be right. 33 too small. 35 marginal. Try winding the pump rod nut up the shaft to increase the quanity of fuel it delivers. First of all thank you for your answer ! The pump jets are 33.. Would it be possible to make the fuel sufficient by tightening the nut ? Or is it certain that it will never suffice with the 33 jet ? Thanks Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted June 1, 2015 Share Posted June 1, 2015 33 too small. Try 45 backfire type. There are two types, down and backfire, backfire is best. Link to comment Share on other sites More sharing options...
ChrisV Posted June 28, 2015 Author Share Posted June 28, 2015 It seems that the engine needs idle jets greater than 60. I tried a set of 58 and managed a perfect idle with good emissions (co 3.46 and hc 314) but at 7.5 turns from fully shut and a terrible progression. I changed the 58 with 60 and the progression was better but with a lean spots in low revs. I think that the idle jet is the problem because if you pick up revs and ''pedal to the metal'' it there is no lean spot so maybe the pump jets are allright (maybe)... The sign is that the 60, that also needs 7.5 turns at least to get a good idle, is also small... 65 maybe can get me to the 3.5 - 5 turns ??? which is ok. I also tried some other jetting. It doesn't work well i would say... my jetting is 145 main, 7777.8 emulsion, 210 air, 60 idle. The new jetting is 135 main, 7772.10 emulsion, 230 air and 58 idle. The jetting is from a pair of dhla 40H Link to comment Share on other sites More sharing options...
ChrisV Posted October 15, 2015 Author Share Posted October 15, 2015 I have a little update on the subject... After all this time i tried everything to make the carbs work and all this time they refused to cooperate. The thing is that the major vacuum leak from the intake manifold was cured but something else was going on for sure. After trying my luck with different jettings etc i did manage to find the problem with the help of a friend who insisted on this. The main characteristic of the situation was that the mixture screws were not responding. From time to time they were but mainly the were not. Also i connected a carbtune pro and found out that at 900 rpm idle the metal rods were not moving at all. So... the problem is a vacuum leak... its a major one and its coming from the throttle shafts... What solution do you suggest ? And my main question is when i put the new brass screws on the butterflies (if i decide to fix these carburettors) how and with what tool do i crimp them from the other side so as to ensure that they don't loosen up and fall into the engine ? I cannot find this information anywhere ! Thank you Link to comment Share on other sites More sharing options...
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