mid range stumble

shu5720

New Member
Jul 1, 2008
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I had a question about how the blaster is running. It seems to have a stumble at partial throttle in the low to mid range. Goes away as rpm's come up. Plugs look okay to me but I'm no expert. this is only the second tank of gas since putting it back together. I think the first tank was probably a little rich but this one was mixed at 32:1. Any thoughts would be appreciated. Thanks guys
 
What main Jet do you have in there right now..Do you have an after market Pipe..Reason I ask is the jetting will change and cause bike to run like sh*t..From what your saying the only other thing I know is a dirty carb..Im no expert either but a few things for you to check..Give it some time and someone else will post with more knowledge about your situation..Dont get discouraged evryone here is really cool and helpful..Good Luck!! Kurt
 
well check your jetting first. get the bike to stumble, once you've found the throttle position that causes the most stumble, hold it there for a few seconds then (while HOLDING the throttle in the same position) pull in the clutch and hit the killswitch. you want to make sure that the last few combustions were within the range where you're stumbling.
then pull the plug and see what it tells you.
 
Hello Quam
I see this condition all the time on the dyno. During the beginning and middle of the power curve the engine goes lean and then comes down to ideal condition once the main jet is at full flow. Change your needle position to get the midrange fatter.
 
yea kno this is wat i heard and this is my exact problem and i searched for a needle clip position and i never found it lol. im kinda mad. i eventually went down to a 250 main jet and its better but not fixed. still stumbles at 1/4 to 1/2 throttle.
 
but fine wide open.. its a mikuni 28mm flat side but i took the middle apart and didnt find any adjustments at all. i heard theres 3 adjustmenst and i really didnt see any. is it possible i dont have one??