I have a 2003 yamaha yz 85 . I have doin everything i can think of to try to get it to quit bogging ,I have put a new top end rebuilt carb put a new silencer change the fuel mix to 32.1 36.1 & 40.1 change the spark plu to a ngk iridum bg9eix and a b10eg and gapped it from .28 to .32 and i still cant seem to find out why it keeps bogging out. any suggestions??

SOURCE: 1999 Yamaha YZ 125 will not start

If it starts and idles, but will not rev up, it is your carb. Recheck your rebuild and make sure float height and all is correct.

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: RM85 w/ 105 kit bogs down with rapid throttle onset rate

hi buddy set the needle clip to its normal condition and also on the carb is the mixture screw you need to turn this all the way in and out 1 turns and try this you will always get a bog if you rev fully too quick i had this problem with my kx85 and it was just this hope this helped mate i will send the pic in a mo

Testimonial: "Appreciate the help. I've been all over w/ the air mixture screw. Still smokey and bogging down."

SOURCE: 1981 suzuki gs550l wont start, rebuilt carbs, new plugs, new bat

did you adjust the iddle screws? Those black plugs need to be installed. Those carbs pull all gas threw the main jets. If you remove the black plug and look closely you will see a small tunnel going from that tube to the main jet tub. The fuel gets pulled threw that tiny hole from the main tube. (This also puzzled me the first time I saw one, don't worry, that was the first thing I thought of doing also, but since then, I have found tons of bikes and boats like this) I found mine runs best on 2-1/2 turns on the idle screws. Also try sincronizing you carbs, the cheep way to do this is by blocking them open slightly and checking the butterflies with a feeler gauge to see if they all open the same amount. I also found that sometimes it could be as simple as the choke slide not returning completely back to the proper position, this will cause the diaphrams to not operate properly. Good luck and hope I helped a little.

SOURCE: My 04 blaster smokes and idles poorly,dies pushing throttle

stock pump sucks. i run 32:1 in my bike and runs great. take it to a dealer and have them check it out