Very hard starting even with the choke on. Choke has been checked 3-4 times, cleaned put back in. When it gets running after trying to start it I GIVE IT GAS AND IT RUNS FOR A SHORT WHILE AND BACKFIRES THROUGH THE BOTTOM PIPE. I HAVE REPLACED THE BATTERY, STARTER, FUEL PUMP, STATER, SPARK PLUGS, CLEANED THE CARBURETOR USE NON-ETHANOL GAS AND FUEL STABILIZER ALMOST A NEW BIKE. I CAN'T GO UNDER 30 MILES AN HR. AS THE BIKE BUCKS NOT BECAUSE I'M IN HIGH GEAR AS I MUST PUT IT IN 2 OR 3 TO KEEP IT RUNNING. I HAD TO TAKE MY BIKE INTO SHOP AFTER IT DIED ON THE ROAD AFTER BUCKING. CAN YOU HELP ME WITH MY PROBLEM? BLAIR
SOURCE: 1989 tw200 yamaha won't start
G'day egdbcs . Ok.now lets see.You say good spark,so i'm presuming you are doing the old sight test.Try bending the arm on a know good sparkplug about 5-6mm,earth the plug and kick'er in the guts(crank it over)Be very carefull , high voltage danger.If there's still a good spark it's safe to say that there will also be a good spark under pressure in the combustion chamber,speaking of which you should also do a compression test,anything over 100psi should be ok. as i'm not to sure of the extent of the re-build,hopefully the valves were lapped and checked for straight and true and valve seals replaced,if you notice oil on the tip of the spark plug you could have a leaking valve seal or oil seal .Try putting a small amount of fuel directly into the combustion chamber ,tighten up the spark plug ,install the plug cap and.......Yeah ..You guessed it ..."kicker in the guts".If all the abouve are correct and true it should fire up.If it runs for 5-10 seconds then stops you've got some sort of fuel starvation problem , could be dirt in the carb,blocked idle jet ,or air passage or even the needle could have come off it's clip,believe me with an old bike like yours anything could be worn and loose inside that carby.The only other thing to consider is the timing.There may be a good spark but is it happening at the right time inside the engine???. I'll leave it all in your capable hands EGDBCS.Hope this helps to solving your worries. Chow for now......Tilleydog..
SOURCE: yamaha 125 grizzly starts and idles when choked but dies when acc
Take the carburetor apart again, remove the main and idle jets and idle mix screw, plus the float and needle valve. The main jet holds an 'emulsion tube' in--look inside where the slide valve moves, you should see a short brass tube projecting out of the bottom. Carefully push down on that tube with a plastic rod or wooden dowel, it should drop out the hole where the main jet was. Chances are that the tube is dirty and needs to be cleaned--look carefully at the series of small holes drilled into the sides of the tube. These small holes deliver air which is mixed into the fuel passed through the main jet. That air comes from a small hole just inside the intake side of the carburetor. The long needle that sticks out of the slide bottom controls low to mid-range speed fuel-mixture. Check that the 'C' clip on the top end of the needle is in the center groove and that the retainer spring is pressed down the 'C' clip. Now soak the whole carburetor with spray cleaner, then blow out all passages with compressed air. Don't soak the rubber-tipped needle valve from under the float. On reassembly, set the idle mix screw 1-1/2 to 2 turns CCW from CW stop. Adjust for best idle after you get it running and warmed up. I hope this long winded explanation helps!
SOURCE: 350 raptor only runs with full choke on ,
Hi Mike,
You will find that there is a problem with the carbie. It runs with the choke on because the choke engages the "enricher" circuit. The idle circuit is different a different circuit inside the carb. When just crack the throttle on, you use the pilot circuit, and then main jet with more twist of the grip. You will need to completely strip the carb, remove all jets, spray carbie cleaner throughout, and blow out all capillary tubes and holes inside the carb with compressed air. Pay particular attention to the fine holes inside the venturi near the butterfly valve. You may need to use a fine piece of wire, like a guitar string to open up any that are clogged.
There is not much else that will cause the symptoms you have. Check for air leaks about the inlet manifold also, spray some carbie cleaner about the manifold connections boots, the revs will change when it sucks up the cleaner through the leak.
Happy to talk to you more about it.
regards
robotek
SOURCE: Vstar 1100 idling rough and backfiring letting off the throttle
It sounds to me that your carbs might be a little gunked up - you mentioned the gas may have been old, so it's possible that the smaller (idle) jets are slightly plugged up. Fresh fuel might do the trick and/or you could try using a fuel system cleaner and water remover. This problem might 'solve itself' with a little time.
As far as the backfire - this might be either from the carb issue or it could be related to that rattle you mentioned - you could have a loose connection at or near the head - this can **** air and cause a backfire.
I hope this helped!
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