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  • Backfire carb off

    My friend took his 1999 roadstar to a independent mechanic to correct his exhaust leak and rejet for the freedom duals that he installed… the bike also would turn the starter over a couple of times and battery would be discharged severely… mechanic said bad starter … i informed friend to bring me starter… i disassembled and cleaned commuter, checked brushes and confirmed no crack on brush plate.. reassembled and checked good with battery… no issues with starter…
    it gets worse… mechanic kept bike for 3 months… said the carb was filthy and he cleaned… still stated bad starter and bike would not turn over.. my friend said enough time had passed for mechanic to fix and lost faith in independant mechanics’
    abilities…

    this is where i come in…. I tell my friend to buy new battery cables from davej…. Just installed the cables, charged the battery and tried to start the bike….. CV plunger popping up and down with the engine rotation to start.. i found mechanic had put the rear rocker cover vent tube on the diaphragm filter of the carb… bad idea wouldnt you say… checked the installed jets (nothing looked new although the idle jet was a little scarred up.. see photo) i suspect wrong jets for a stock airbox and freedom dual exhaust but i will defer to the carb gods…
    put it all back together and tried to start (pms 2 1/2 turns open) blew the carb off the intake with a backfire… tightened the carb clamp a bit more and repeated the start…. Bang…. Carb blown off the bike again… so now… removed carb and going to try and figure out what the mechanic F’d up…. Wish me luck boys….!!!

  • #2


    All Road Stars built before the fuel injected, 2008 models vary their ignition timing via a small sensor attached to the carburetor. This sensor is called the Throttle Position Sensor -- or TPS. Theoretically, the more you twist your right wrist, the more demand is placed on the engine, and the less the ignition timing should be advanced. In real life riding this theory has a few holes, but in my experience the TPS still out-performs other available methods for the Road Star carburetors.Hopefully he didn't try to adjust the TPS on the carb.
    ​​​​​​​

    Comment


    • #3
      Been there done that. If you roll the throttle on a roadstar it'll backfire out the carb. Unless you have the Stars aligned. So many guys here put on a aftermarket air filter like a k and n without a bracket to hold it in or in the case of a roadstar. Some of the guys here say that's okay but I'd say that's not okay for two reasons, one it's a rubber intake manifold 2 oh, your mentioned backfire problem. you don't want to go out of this world the way you came into this world, on a broken rubber

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      • #4
        After some more investigation…. I realized this particular year was prone to svs… a gentleman named brian pointed me in that direction… thanks brian….:-)
        tested the sticky valve syndrome by confirming a back puff of air through the intake manifold with carb off… pulled a rear spark plug and back puff of air still there…. Pulled a front spark plug and put the rear spark back in… retest…. The back puff of air is gone…
        sticky valve on the front jug….. isolated…. Going to try to put some seafoam in oil and turn it over to get it in the valve rocker case…. Maybe i get lucky… maybe i dont…. Beats tearing the rocker covers off first…

        Comment


        • #5
          This thread is a nice start of a mechanic fraud thread. What other horror stories do guys have regarding incompetent or dishonest mechanics? I'm sure most are decent but it only takes one to give you a bad day!

          Comment


          • #6
            It wasn't Brian me was it.?

            Comment


            • #7
              The horror stories of an unscrupulous mechanic…. Where should i begin…. This could be a novel…!!

              my friend stated that when he first bought the bike, he put the shorty pipes on it (it had a K&N filter and the shorties when i first met him a few years ago) and had the local dealer rejet the bike…. Hmmm… interesting… if you refer to the prior pic of his current jetting (165 main and a 37.5 secondary….. yes i know wrong terminology)… i believe this is the exact jetting that the 1999 roadstar 1600 came with from the factory…. I may be wrong in my research and willing to be corrected by those “in the know”…. Could this mean that my friend was taken advantage of by both the dealer and an independant mechanic…??

              i have had many personal and associated experiences with shoddy work performed by “mechanics” in the past from timing belt replacements to tire rotations…. Hence i have tackled most of my mechanical projects myself… from a 1970 6 cylinder ford maverick motor, 318 mopar motor, several 350 chevy motors, and my 454 chevy boat motors…. Lawn mowers, minibikes, and just the motorcycles that i have owned… i live by the code “once burned, twice learned”….

              my wife (before i met her) always had satisfactory mechanic work done although typically on the pricey side of the repair bill…(her recollections). Maybe i need a cuter smile …. Or maybe i have higher expectations (probably doesnt help that i inspected all work done and typically found something done poorly

              Comment


              • #8
                Where is the pilot jet (red arrow)? Doesnt even look as if there is one installed.

                The main jet looks different, nothing typical that I have seen unless another jetkit? Refer to another pic from the tech section.

                Comment


                • #9
                  The pilot jet is there… just didnt bother with a photo… there isnt any numbers on it that i can tell… a little more information from the bike owner…
                  ”the shorty pipes and K&N filter were on it when he bought it…. Ran like crap so he took it to a local shop to rejet… ran much better after that”….
                  i assume that the only the pilot jet was changed… most likely one step bigger (from the 37.5 to a 40).. the bike ran well for about 3 years until this past winter… when he dug it out of the garage, it was running badly… he brought me the carb and i opened it up and cleaned all the jet passages (several clogged with typical shellac) and inspected the float needle assembly… everything was looking good when i gave it back for him to install… at this point… my friend decided he wanted to change the pipes and air filter.. (he never bothered to test the cleaned carb before he installed the freedom true duals and traded someone for the stock airbox/filter)

                  at that point the bike was dragging the battery down and running very rich according to him… since he wanted to replace the tires as well, he took it to another local shop for new tires, exhaust leak repair, carb work and starter… 3 months later is when he picked it up and i got involved (see first post)…

                  my educated guess has several parts…
                  1. bike was running rich because he changed pipes and airbox at the same time before solving his dirty carb issue and correcting that issue first to get bike running well before he started changing things
                  2. the bike most likely had a bit of sticky valve syndrom due to the storage from last fall and not running the motor.. 1999 roadstar does tend to be prone to that… especially aggravated by the running rich from the airbox change back to stock unit for his initial testing when pipes were installed.
                  3. The dragging voltage down on the battery was because the old battery cables needing replacement (may have also contributed to sticky valve because the spark plugs were also old and neglected possibly running on reduced voltage..
                  4. My friend has the patience of a hyperactive hummingbird ….. if you catch my drift…

                  I will give the bike a few days of the seafoam oil treatment (spinning motor to put oil up in the rockers)… i will also be spraying some seafoam in the intake manifold as i try to unstick the valve… i will most likely end up removing the rocker cover and cleaning the valve stems from the top end … but i am kinda hoping the “oil/seafoam/intake spray” will loosen the valve enough to start the bike and then “run the piss out of it down the interstate a couple of exits…)

                  Comment


                  • #10
                    Update….
                    removed rocker cover… inspected the valve train and discovered the push rod for the exhaust valve was not pushing the rocker shaft… push down the rocker shaft and heard the oil squirt out of the lifter… while holding pushrod down with rocker shaft… turned motor over to confirm the camshaft still had a lobe… (didnt measure anything… waiting for breakdown to access lifter and visually inspect camshaft for excess wear)

                    conclusion….. collapsed lifter…. Anyone have another opinion??

                    Comment


                    • #11
                      Have you verified that you have oil pressure? The lifters are the first place the shows an issue when the oil pump drive gear breaks and a 99 is one of the years that had the old style gear.

                      A collapsed lifter should have been clattering real bad and you should have had an indication long ago from the noise. A broken oil drive gear happens all of the sudden..

                      Comment


                      • #12
                        A very good point davej…. I will put a gauge on it and spin the motor… not so sure how much i will see with just starter spinning motor… i am not the owner of this bike…. It might be a better idea to pull the cover off the clutch basket and pull the gear to ensure that the newer oil pump gear is installed… i will discuss this with the owner… ( i am just a friend with a wrench on this one )

                        owner never mentioned a problem or clatter last year when it was running…. Problem showed when it was first started this year… (the thread discusses that aspect including a paid bike mechanic shop time frame..)

                        Comment


                        • #13
                          Take apart the "Y" line on the left side of the engine. You should see volume of oil and may not be able to check actual pressure. If no volume when cranking the engine then it is likely broken.

                          Comment


                          • #14
                            After talking with my friend (bike owner)….. it has been decided to check the drive gear for the oul pump….. he doesnt recall hearing valve clatter last year but has no idea if the drive gear has been changed… the serial number has been checked for recalls and none are outstanding…. I do not recall the oil pump drive gear as being any “recall” item but i may be mistaken….
                            I shall bow to davej for his knowledge of the roadstar and his contributions to this forum… his insight has helped many overcome anxiety in the maintenance and repair of these awesome mechanical marvels of V-twin engineering…. Thank you davej for pointing out some of the things that i should check… sometimes a little prodding will sent this old curmudgon down a path in which i missed…

                            still recovering from my water skiing “hold my beer” moment… another quick update…. My first day back to work yesterday resulted in me shocking myself with a little jolt of 120 vac… short story… electrical jolts tighten all the body muscles instantly… resulted in my butt cheek muscle stressing out and knocked me right back to “unable to walk”….. went from a cane back to crutches…. I am now trying to graduate to a cane again….

                            (I am pretty sure i popped a hamstring and tendon on the initial injury…. I refuse to go to doctor and pay him to tell me to stay off of it for a few weeks… i am not one for pills and physical therapy on this type of injury is basically stretches… and i am one cheap ‘son-of-a-b..tch)

                            Comment


                            • #15
                              The oil pump drive gear isn't part of the trans recall. They will install one during the recall if you ask, but if you don't ask then purchase one they will never even bring up the subject of the weak pump gear.

                              Comment


                              • #16
                                Update….
                                removed left side cover/ clutch/ clutch basket… removed and examined the oil pump drive gear…. Confirmed as old style….
                                repairs will consist of new oil pump drive gear, one new lifter, fresh gaskets… parts will be ordered by bike owner…

                                it appears that the exhaust lifter of the front jug has failed…. Lifter does not pump up and you can hear the oil discharge when you press the pushrod down… intake lifter works fine… oil pump works fine…

                                rehash of symptoms so members can be aware:

                                bike would discharge battery rapidly during engine turnover at start.. when bike started, engine running rough and sputtering..… evidence of rich condition of mixture… owner had just replaced the pipes and air cleaner before bike was prepared for the season.. ( installed freedom true duels and stock airbox to replace k&n filter and shorty pipes ).. owner wanted new tires so he dropped off at an independant motorcycle shop… told mechanic to rejet carb and fix the starter issue… sat at shop for 90 plus days… new tires installed, carb removed and installed incorrectly, mechanic states it needs a new starter… owner picks up non-running bike and gets me involved…

                                this thread discusses the events that have transpired since i became involved… i am headed to the nhra promod races in dallas so it will be a couple weeks before i re-assemble bike and fire it up… wish the imperial racing crew and prs racing best of luck in the pro mod race events with me…. That will be the crew i will be hanging with all week…!!!

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