jetting bog

[yarrowkevin]

just jetting my bike and have a flat spot between 1/4 and 3/4 throttle , it screams at full throttle :yeehaw: but has a boooahh bog when I snap the throttle open from slow idle, is this sound from too much or too little gas or do I have to do another plug chop. the reading seems to be fine on the plug and doesnt really help me , any thoughts would be appreciated, is this a clip position problem and if so should I just try moving it up or down, its in the midclip position , 155 main , 45 pilot around 2000 feet

 

[moridin]

I am no jetting jedi - but your throttle snap is a complicated combo of your airscrew pilot and needle position.

Your jetting sounds pretty good - so warm the bike up and set your airscrew correctly - if you need help there - check out Can Dave's site as he gives good instructions.

Get it set and see if you improve. If there is no change - try dropping or raising your needle (I think you may want to drop the needle one (raise clip).

Only change one item at a time and chck out the results. At 2000' you may be due for a 42 pilot - hard to say.

sn

 

[Colorado Mike]

I'd got to a 42 pilot and see what it runs like. I think you'll also want to lean the needle (raise the clip), but I don't like doing two things at once since the different items overlap in the throttle range they effect. Ditto on adjusting the air screw. I can adjust mine for fastest idle, and the thing will barely run under a load. You have to play with it and make small adjustments. That's where a thumb screw would really be nice. Oh, if you adjust the needle, don't tighten the retainer nut much at all. See my thread about the fun you'll have when it seizes.
Good luck,
Mike.

 

[Rhodester]

yarrowkevin, Sounds lean to me in that "wicking it" zone. Start by turning your air screw in to about 1 out and try it again to see how it reacts. Another trick is to pull the choke out and try it again. My guess is that you're lean on the needle. I can't begin to get rid of my bikes hesitation with the stock needle, but it improves as I continue to raise it (lower clip).

What modifications are you running? A 42 pilot works well for me at 2500' and over (haven't ran it at below 2500' yet).

 

[Nice Guy Eddie]

that sounds like my friends YZ125 when it was running WAY lean (as a result of the clip on the needle being missing so the needle wouldn't allow the main to feed well)..... now he's getting a bore over done... :bang: I would raise the needle and tighten the airscrew a bit and see how that does.... (you raise the needle by moving the clip down a notch)...

did you change anything since it ran good? jetting, air filter, pipe, air screw, stuff like that (what did you change? change it back and see if that remedies it... then go from that) let it sit a long time? (it could be gunk in a jet)... was the plug you checked a new one?(if it was used it may still read darker as a result)...

try adjusting it richer first... then if you are wrong (it gets worse) you haven't damaged anything but a plug... too lean can mean some substantial cash for parts... :| .. to rich just means goo out the exhaust and perhaps some internal cleaning (but not if you catch it quickly)