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  • 1986 honda 350X Starts when it wants to

    Fuel tank flushed new fuel line new fuel valve gas cap breaths no rust in tank. New in line fuel filter. Swappeed CDI swapped ignition coil new plug fresh gas just swapped out kill switch on handle bars. Adjusted decomp cable. Carb cleaned and dialed in. Gets a spark. Ordered new O ring gasket for carb insulator boot. Today kicked over and it backfired really loud. Intermittant random starts turns over and runs like a mad dog when running. After motor is warmed up same starting issues. Flying W informed me pilot assembly was incorrect and gave me the fix so carb is ok. The odd thing is it always seems to start when it wants to and when it does its always with the choke off.
    I put a liquid high heat silicone seal on both surfaces for carb insulator boot. Someone told me that can cause problems. problem remains the same. So I am thinkin there is a vacuum leak. Inspected everything from air box to everything up front. No rips holes ect as far as I can see. Removed carb insulator boot and there is no dry rot anywhere. I will be getting the new gasket from the honda stealer this week. Hopefully its just a bad O ring ?
    Randomly starts if motor is hot or cold. Backfires a bit at low rpm feathering throttle when running and cant idle on its own without stalling. Any feedback will be appreciated. Thanks

  • #2
    I too have seen this, it was very confusing! Check the top cover, it has 3 short screws that hold a thin metal cover. Under that cover is a gasket, almost like a O-ring. If it is not installed perfectly (i've seen them pinched) it will rev for no reason.

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    • #3
      are you talking about the carb ?

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      • #4
        I believe he is. Hey X. I completely rebuilt that carb with everything new including the top cover seal. In fact, I pack the seal groove with petrolatum then set the seal in it and wipe up the excess. The petrolatum is specially made to lubricate and condition rubber plus it aids in the seal of the cover to the carb body. I also do this for the carb bowl seal. I'm 100% sure the carb is tight. Every hole blew through to where it is supposed to.

        The motor acts allot like a possible timing problem. The backfiring is whats concerning me. That usually comes with a lean condition but slight changes in timing can also cause this especially in the retarded direction. This may come with a badly stretched timing chain. A stretched timing chain on a 350X is not as common as one would think but it does happen in extreme cases. The carb was completely rebuilt and the problem remains the same. If the problem changed because of the carb then that gives you a direction to go but not in this case. Timing or an intermittant electrical connection is the direction I would go.

        Hey Sweet, was it you that told me you had to do a repair on a wire going to the CDI?

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        • #5
          Well I put a new o ring on the carb insulator thinking it might be a vaccum problem.
          Today it didnt even turn over at all. I am thinking along the lines of what W is saying.
          Question: Could it be the valves that need to be adjsuted ? And about the timing is a stretched timing chain mean the motor needs to be totally overhauled ? I noticed twice today it doesnt turn over sounds like it wants to turn over then ocasionally just backfires.
          Yesteday it fired up and I ran the motor for a short period of time, the problem seems to be intermittant. I would like someone who is proficient to work on this motor but what I am trying to avoid is someone ripping me off on labor and or holding my trike hostage for money. This has happened to me once before. If you guys can recommend someone in southern NY or southern CT let me know. I am willing to pay someone who knows about this motor. Otherwise if the labor is gonna be too much I will just keep the bike as a complete roller and look for a new crate motor on ebay worst case scenario.

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          • #6
            BTW yeah I soldered a positive wire on the harness before the plug that goes into CDI. It was doing this odd strarting before I soldered the wire too. Here is what I was thinkin but I am so damn low on money I shouldnt be doin this. Completely swap out wire harness. If problem persists swap stator and pulse generator.

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            • #7
              I have never had a 350x apart so it is a stranger to me.
              I have had similar issues on some bikes. Most were easy cheap fixes.
              You already covered a few so I will skip those.
              When yours runs do you hear a slapping metal sound like chain on a fence pole. If not then the chain is probably ok but still could be.

              1. Not sure if the 350 has this. Another Honda pulse rotor advance mechanism was sticking in advance time.
              It would pop backfire, rip boots, ect then just fire up normal. Also the idle would stay high and sometimes drop to nothing and stall. All from the timing being advanced when it shouldn't be. Just sticky. Good cleaning fixed it right up.
              2. Another honda, the advance springs were all shot. Same symptoms and just stick in full advance. Was all loose, replaced it. 5$ part.
              3. China bikes do this often!! just magnetic junk on the flywheel trip magnet for the trigger coil. Also junk stuck to the trigger itself. Good cleaning and on the way.
              4. Yamaha Virago. Melted trigger coil. Cold would not start backfire ect. Warm ran fine. Common problem, expensive part to find.
              5. honda 110 trail bike. Wire to stator broken and all insulation on it and the lighting coil were bear. Same issues. Just soldered it up and rtv sealed it.
              6. Trigger coil wires, trigger coil wires trigger coil wires.

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              • #8
                No, the 350X is all solid state. No mechanical timing advance. All that is handled in the CDI.

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                • #9
                  Well that shoots 1 and 2.

                  Does the 350 have a trigger coil or just a stator like the later 2 strokes?

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                  • #10
                    It has a stator and pulse generator. I have swapped everything except for stator,
                    pulse generator, and wire harness. I took the plug out of the cylinder and kept it connected to the ignition wire. Put spark plug up to a metal bolt and I see a blue spark but it does not spark on every kick. I am wondering if this is because I am not making good contact all the time as I hold up the spark plug to frame.

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                    • #11
                      Sounds like timing, vacuum leak or dirty pilot jet.
                      Check the timing, if not that then get it running and perform a vacuum leak test by spraying carb cleaner or starting fluid around the intake to engine carb to intake, base gasket, head gasket, etc. If it revs when you spray in a certain area then you have a leak. If not that, then take a teaspoon of gas and pour it into the cylinder. Does it fire and run? If so then you likely have a carb problem. My money is on a dirty pilot if non of the other items are the culprit.

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                      • #12
                        I rebuilt his carb and the problem remains the same. Timing would be consistant. This problem is intermittant so I'm thinking electrical.

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                        • #13
                          could still be a vacuum leak. Glad to know the carb isn't the issue.

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                          • #14
                            I replaced the O ring in the carb insulator ( that intake boot off the cylinder). Thick rubber very tough no dry rot or cracks I can see. Thinking that was the issue cause the original o ring I removed was pretty old and worn. Same problem. If anything it wouldnt kick over at all after that. Its almost as if this bike is possessed or something, If it is electrical the only things left I can think of to swap out are the wiring harness stator pulse generator and regulator. BTW I ordered that multimeter off ebay 18 bucks. Its auto range as w mentioned to get. Otherwise when it does decide to fire up and run its got crazy power and no clunking or clackety noise inside motor.

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                            • #15
                              The regulator is part of the lighting system and does not effect ignition.

                              Ignition System:
                              Exciter coil
                              Pulse coil
                              CDI
                              Ignition coil
                              Run/stop switch
                              Spark plug
                              Wiring
                              Ground

                              when your meter shows up, these are the items you will be checking with the exception of the CDI. If you have the Honda manual, review the electrical section. This needs to be approached systematically. One can throw a bunch of parts at it but that gets a little spendy.

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