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V4 1987 Looper Low Compression & Backfire In One Cylinder

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  • Fatz,

    Should I just get rid of these fitings, other carbs I have seen don't even have them
    Leave em in as richen up the midrange. At midrange spark is usually at max and carbs are not, these some set-ups run lean.
    When in doubt,Trim it out!!!
    Business Owner & Certifed Technician
    Boats I own & use
    20ft Javlin w/250 Junkrude
    17ft Bullet w/200 Merc (SOLD!!)
    13ft Allison w/150 I-6
    17ft Hydra-Sport 175GT
    15ft Allison w/75 Stinger(project)
    14 x 48 Drifter with 1100SS Merc

    Comment


    • Originally posted by Bosunsmate View Post
      haha thats some impressive control over the budget you have
      Check the firing with the timing light in that range when you hear a slight knock too. Hopefully the new control valve means temp is now right and the knock goes but while you have the light check there is no double firing on a cylinder around then. Timing lights take a bit of getting use too but theres a lot of info on you tube etc about double firing.
      And go on sell the guitar, buy some bagpipes like me
      Bos

      The throttle cable never fully retracted on its own previously, but since putting the valve in. The throttle cable wont retract more than half way without slight push with foot pedal etc. Can it be tensioned enough?, I tried with the screw adjust but stick still does it at any position.

      Comment


      • Im not sure i understand precisely what you are describing. You may have to take a video. Normally with a hand control the throttle cable moves as you manually move the lever up at the front control box in the Drivers seat.
        I take that yours has a accelerator pedal, due to being set up for racing. Is it a tired spring in the foot pedal?
        Ive never dealt with one of those, im just a guy who fixes his own or other mates motors as mechanics have ripped me off before, so i havent seen a lot of things like pedal accelerators

        Comment


        • Hi guys.

          I went to Somerset today. Went ok.

          1. Getting sneeze at low idle again. Think running too lean. See spark photo below, three all the same, port lower is a new plug but burns look different. Oil too lean? Need to replace all plugs?

          2. Goes awesome top end still. Bogs out at that low idle, especially after a sneeze/misfire. It will idle sweet for a few minutes and start snuffling.

          3. After putting water control valve and pipes in, think gear shift is clashing with it. Even though it all the moulded pipe from omc. Need to move this as it’s difficult changing gears. Photo shows how the mould goes around gear linkage, it blocks changes.

          4. New prop is awesome, no more rev out.

          5. My mate and I now think the revs gauge is out. We now doing 7k easy with new prop. No way it can be that, not even trimmed out. Do you guy know if this can be adjusted? Would explain why I can get revs down to 700.

          would appreciate any thoughts, I know it’s taking a bit me annoying you all.

          assuming the misfire could be needing more oil??? Plugs are dry brownish though. Think burning better now temp 140-160f
          Attached Files
          Last edited by Riley C; January 12th, 2019, 03:45 AM.

          Comment


          • Can a bad power pack or coils be the issue, being the sneeze is intermittent? Do you ohm test the coils?

            I feel I’m almost there, end is near. except for this idle sneeze and bog out. Maybe after we ran so rich this fouled the two other plugs which is causing it, bog out has always been there really. It never went away and is intermittent.

            Friend lending timing light light this week. Can timing cause bog out, but still perform top end? When big out occurs feel like I prime the bulb again to crank over, this may not be doing anything.

            When end I pulled down the carb the floats all maxed to same height, needles were cleaned etc.

            Looking for any advice to what parts I can eliminate from the two issues. Then dive into the suspects.

            Comment


            • Photos showing plugs. Port top seems culprit.

              Comment


              • They a looking pretty dry. What i do is i pull of lanyard line so you dont get spark. I then, with the primer firm, turn the key to activate the starter for about 5 seconds. I then remove each spark plug and check they are wet with fuel.

                Lean sneeze indicates often carbs or top or lower crankcase seal

                Comment


                • Originally posted by Bosunsmate View Post
                  They a looking pretty dry. What i do is i pull of lanyard line so you dont get spark. I then, with the primer firm, turn the key to activate the starter for about 5 seconds. I then remove each spark plug and check they are wet with fuel.

                  Lean sneeze indicates often carbs or top or lower crankcase seal
                  Hi Bos,

                  Thanks, given the lower compression numbers, and being within 5%. Could the crank seal also explain why these numbers are lower? Or just replace the carb kits and do the crank seal to eliminate any possibles?

                  Assuming it wouldn't be a timing issue then, especially if top speed non issue. High end is great!

                  Water valve clash with gear link all sorted now. It was actually crushing STB lower fuel/vacuum line when changing gear, may explain bog out?

                  I think it's a sneeze anyway, could be a misfire but tries to conk it.

                  Sorry to keep this thread going.

                  Comment


                  • ??----Crankshaft seals have nothing to do with compression in the cylinder.

                    Comment


                    • Originally posted by Riley C View Post



                      Water valve clash with gear link all sorted now. It was actually crushing STB lower fuel/vacuum line when changing gear, may explain bog out?

                      I think it's a sneeze anyway, could be a misfire but tries to conk it.

                      Sorry to keep this thread going.
                      It may cause a bog out, you will have to try it now and see.
                      No, crankcase compression relates to that area between the reeds and the combustion chamber.
                      Post a video of the sneeze as its often very clear which it is to those who have seen it before.
                      No worries, its a very good thread, the number of individual views gives you the clue to that!

                      Comment


                      • Originally posted by racerone View Post
                        ??----Crankshaft seals have nothing to do with compression in the cylinder.
                        Sorry Race,

                        I meant crankcase compression.It's obvious I'm still learning some ropes lol.

                        Comment


                        • Originally posted by Bosunsmate View Post

                          It may cause a bog out, you will have to try it now and see.
                          No, crankcase compression relates to that area between the reeds and the combustion chamber.
                          Post a video of the sneeze as its often very clear which it is to those who have seen it before.
                          No worries, its a very good thread, the number of individual views gives you the clue to that!
                          Hi Bos,

                          From the pics of plugs do you think to lean, enough to sneeze? Could it be dry due to higher temps now?

                          I will get a video out. I should have taken it the other day. I will try your fuel check method, just don't have a lanyard.

                          Appreciate your advice on the thread mate.

                          I'm trying to work through this in a real methodical way now. I have logged everything for whats become an issue and when, if memory if serving me correct the following may be happening. Please anyone, correct me if I'm wrong.

                          1. Purchased boat it sneezed a lot then, blow back through port lower carb throat. NO bog out as far as I know. Then again I only ran it once before it all came about.

                          2. The first lync I did may or not have brought the issue of the bog out into play, as when I read about the three main aspects of lync process. The three parts must be in sync - spark adjustment (timing base), the advance idle screw and the cam roller must be fully inline. I suspect spark adjust is not aligned with the other two - idle screw and roller? As it's the only screw I have never adjusted and have been to scared to do so.

                          When the throttle cable is pulled the bog seems to occur depending on revs. If not enough revs but put the foot down, the bog would happen. If the throttle is eased into revs in gear slightly the bog wont always occur. If you put your foot down at 1000rpm it will bog.

                          Could the spark advance cause this issue of bog or sneeze, as when I go high revs there is no problem.

                          Air idle jet blocked perhaps ?

                          3. The second lync I performed when the thermos and full carbs pull down occurred at x-mas. The idle advance screw was somewhat higher. This is when I found the brass fitting in the reeds. Sneeze stopped.

                          4. Third lync where we are now completed pull down of carbs again thoroughly soaked and sprayed on new years. Ran perfect on the Thursday 3/01/19 with the kids, no sneeze, but one or two bog outs.

                          Saturday 5/01 It ran through rich and suspect fouled plugs (25:1). Sprayed carbs & jets down, replaced two suspect plugs but misfire or sneeze comes back, doesn't happen at higher revs.

                          5. Port lower has always been the suspect, it is the one with the different looking plug (more oil unburnt). And was found to be the one blowing back through carb throat. So could this be a carby issue, with idle jet?

                          However, FATZ did say the carb is not inline with the cylinder it serves but is actually in a cross formation. Meaning port lower carb serves the Starboard top piston?

                          Have completed sync procedure all the way up to the timing light requirement (As I don't have a timing light currently), with cable off.

                          6. Throttle cable doesn't retract all the way on it's own, may need new cable... I have tried grease the throttle pin but to no avail. The water control valve has made the retraction worse. Throttle doesn't snapped back more than half throttle now on its own. I have tuned the throttle screw eighth direction and doesn't do a lot.

                          Can this affect the sync?

                          I must say I have to eighth degree aligned the throat valves up perfectly. The idle mark on the throttle cam is exactly centre of the roller, do you guys have it centred like this also? I want to ensure the advance screw and carbs valves are inline with the throttle....

                          7. Next phase will be replace all plugs, blow down the passages jets again of the carbs, add some more oil (Bos you think it's a little to dry?), get it in the water and warm up. Adjust the idle advance a little if needed. That's the only items I can see being my issue to adjust.

                          Now the thermos and water valve is installed, at least the temp is correct now. I can scratch the plugs from oiling up not enough burn temps.

                          Is there a way determine if it's coils or power pack? The coils look original, power pack seems now CDI type. Or as it can start and go 90ks, can scratch electrical also?

                          I definitely believe the Faria RPM gauge is out, new prop shows 7k easy (It's not screaming). Could this be an electrical issue at the rectifier sending false reading? May explain way I say it's idle at 1k but could be lower?

                          Would appreciate any advice if I should go further into other areas.
                          Last edited by Riley C; January 13th, 2019, 06:20 PM.

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                          • A lower carburetor DOES NOT service the top pistons !----What setting is the tachometer on ?

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                            • Originally posted by racerone View Post
                              A lower carburetor DOES NOT service the top pistons !----What setting is the tachometer on ?
                              Thanks Race,

                              I was only reading what FAZT had said earlier in the thread.

                              I don't know what you mean by setting? But the idle is at 1k in neutral on the water, 1100 on the muffs. 900 in gear and it doesn't like it. That's why I don't think gauge is correct to then almost go past 7k at WOT and not even half trim.

                              Can a fuel/separator filter cause a lean issue?

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                                Think of also doing a air leak test spray soapy water outside around carbs inlet manifold, to see if any bubble inflate....

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