ryant67 Posted August 2, 2014 Share Posted August 2, 2014 Was working on tuning my Mikuni 44's, changed the pilot jets, and the one for cylinder two didn't screw in smoothly. I backed off and after a few goes back and forth it went all the way in. Now cylinder 2 isn't firing... I've tried changing back to the pilot that was in and work before, no change. I checked to ensure that it is cylinder 2 that is missing, and when I yank the plug wire, the engine tone doesn't change. I am pretty much at the point of taking the carb off the intake manifold and opening it up, but before I do, does anyone have any suggestions? I think I might have loosened some 'gunk' when changing pilot and it has blocked something? Carbs are synced, everything else runs well. The plugs are new. The wires have been tested and work fine. It was running great up until this point, albeit a little rich. Quote Link to comment Share on other sites More sharing options...
z240 Posted August 2, 2014 Share Posted August 2, 2014 oh oh.... You likely have a shaving of jet thread or a piece-o-poop in the pilot passage that has blocked it. Take the carb off, remove the pilot jet, and blow compressed air though each of holes in the bore, starting with the idle screw hole, then each of the other three slight upstream of that. Plug the other holes you're not blowing through so the air goes out the pilot jet well. About your only shot at this... Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 2, 2014 Author Share Posted August 2, 2014 Cheers for the reply! Figured that was going to be what I had to do, good to have specific directions though. Time to pull the carb and learn a little more about how these things work. Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 3, 2014 Author Share Posted August 3, 2014 Took the carb off, opened it up and went over everything - compressed air and copper wire - couldn't find any debris or clogs. Put the carb back on, and the problem persists, cylinder #2 isn't firing. Going to swap the 1-2 carb with the 3-4 carb and see if the problem shifts to another cylinder or not. If it does, the carb is the issue. If it doesn't, guess it could be the valves? PS: How much FUN is it getting to the carb bolts on these suckers? Ugh... Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 4, 2014 Share Posted August 4, 2014 Have you done a compression check on #2 cylinder yet? Swapping carbs would help the process of elimination. Carbs are easy peasy to take off. 12mm on an extension gets to all the nuts. Make sure you don't pinch an O ring when putting them back on Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 4, 2014 Share Posted August 4, 2014 Saying the obvious here- but when you pulled the 2 wire was it sparking for sure? Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 4, 2014 Author Share Posted August 4, 2014 Yup, lots of spark, electrocuted myself pretty good too. Tested the errors with the multimeter, all is great. Swapped the carbs, now cylinder 4 isn't firing, but 2 is running fine. I'll take this as good news. Can't be arsed pissing around much more, so I'll call Todd and see if I can buy another carb from him.. . Can rebuild this carb at my leisure then. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 4, 2014 Share Posted August 4, 2014 I am kind of having the same issues, but elimination process was not quite as definitive . If I were you it would take a second look- a looonnnngggg look, you might have missed something. Sure seems you have a blockage, so it should be apparent when looking Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 4, 2014 Author Share Posted August 4, 2014 * tested the wires, not the errors. Autocorrect... Had some issues with the o-rings actually, they seemed a little too large, is that normal? Cheers for the tips! Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 4, 2014 Share Posted August 4, 2014 Yes- it's normal for them to swell and get too big. Eventually you might have refridge them to try and shrink them or replace or try cutting, glueing resizing Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 4, 2014 Author Share Posted August 4, 2014 I am kind of having the same issues, but elimination process was not quite as definitive . If I were you it would take a second look- a looonnnngggg look, you might have missed something. Sure seems you have a blockage, so it should be apparent when looking Yeah, I agree completely. I read your issue thread, some good info in there - hopefully you figure things out. For the expense of buying another carb, I think what I can learn with a spare one to tinker with is well worth it. Toss the new one on, and hopefully the issue is resolved - then try and rebuild my problem carb at my own convenience, rather than losing precious drive time. Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 8, 2014 Author Share Posted August 8, 2014 Pulled the carb, and blasted all the passages out with an air compressor I borrowed from a friend - much more powerful than a can of air. No blockage is apparent, air seemed to be moving quite freely throughout the pilot system. One butterfly was found to be slightly open when the other was fully closed. I corrected this, no change to my problem. The cylinder is still not firing. The issue moved with the carb when I swapped them, so it really shouldn't be on the engine side. I'm at a real loss here, and not sure what else I can do.Fuel supply is good. Fuel pressure is steady at 4psi. I have a very good fuel filter between my regulator and the carbs, and it's clean. The floats are properly set. There doesn't appear to be any blockages. I switched from the 57.5 pilot I was using to a fresh, never before used, 60 pilot jet, so it's not the pilot jet that was the issue. The butterfly is properly adjusted. Not sure if this helps with a diagnosis, but when I put my hand over the air horn for the problem cylinder, there is noticeably less suction present than the others, and my hand quickly gets saturated in fuel - a puddle of fuel builds up on the bottom of the carb by the venturi. With all other cylinders, the engine RPMs drop quickly when I cover the air horn. Very lost, and getting tired/frustrated with this. Any suggestions or helpful ideas are extremely welcome! Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 8, 2014 Share Posted August 8, 2014 Boy this is getting interesting. This sounds so much like my issue with 40's Quote Link to comment Share on other sites More sharing options...
Leon Posted August 8, 2014 Share Posted August 8, 2014 (edited) Sounds like a vacuum leak, likely from the throttle shaft seal on that barrel. There are a few methods to use to try and seal it up. First thing I'd do is just put your fingers around the shaft seal and try to hear or feel a difference in how the engine runs. Maybe apply some grease to the seal to temporarily seal it. Edited August 8, 2014 by Leon Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 11, 2014 Author Share Posted August 11, 2014 Still no luck. Cheers for the suggestion though! I've thrown in the towel, and have dropped the car off at my Z mechanic. He knows these cars well, so maybe he will see something I missed. If not, well... I've ordered new o-rings and a rebuilt kit for the carb, and can strip it right down and start fresh. Quote Link to comment Share on other sites More sharing options...
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