Bogging down, anyone help please?

[ironwood]

here is my situation:
i got a 1997 YZ 80 for my girlfriend, the bike came mostly stock except for a Pro Circuit silencer. now the pipe that came on the bike was actually some home made chop and weld job that was all dented up, but the bike ran just fine...

then i got a really good deal on a almost brand new FMF REV pipe so i put it on. (im not a fan of mix/matching products but it happened) since then i've also added a v-force reed cage, but my problem is this.

since i put that pipe on, the bike boggs like crazy from a stopped position, like 0-1/4 throttle. i have adjusted the air screw numerours times (both lean & rich to be sure) without any impovement. i've taken the carb out, checked the float level, cleaned out the entire carb, checked the hoses for cloggs, etc.. still no good. once the bike gets past 1/4 throttle it goes good, but you can rev it to the moon and dump the clutch and it still just boggs way down.

Anyone with any idea? im willing to try anything at this point. thanks

 

[njkx]

did you try a different pilot/slow jet? a smaller jet should lean it out.

 

[elf]

A rev. pipe is going to take away some low end power and add it on top. Its best suited for expert riders who keep there left foot moving and keep the revs up. You could try a richer pilot jet. A bog usally means its to lean. But dont expect much low end power with that pipe.

 

[ironwood]

yeah, someone told me the same thing about losing power on the lower end. i think this is more-so a jetting thing than a loss of power. like i mentioned i was playing around with the air-screw leaning it out, with no improvment so i kind of figured it might be something more than switching to a leaner pilot jet. (plus i dont ride the bike so it's not like i have to deal with it, got a bit lazy)

anyways, brain fart i guess. should have just spend the 5$ for the jet and tried it a while ago.

thanks for the posts guys.

 

[reelrazor]

a) what does the plug look like?

Your comment "....can rev it to the moon, dump the clutch and it still bogs down.." tells me it may be lean everywhere.

b) Does the air screw have ANY effect?

If not, the pilot air circuit is plugged or the pilot is waaaaay too lean- I know, I know, you said you cleaned the carb, but...........

c) How's the compression?

poor compression engines will usually rev but not make any torque

d) possibly the timing slipped(least likely)

 

[ironwood]

alright, i went on FMF's page and got the jetting specs, changed my pilot jet to the recommended #30 instead of 32.5. i removed all the jets and totaly cleaned the whole carb out. the bike has olny improved about 15%.

i mean it runs great through the gears, lots of mid/top end power in all gears and the bottom end is fine from 2nd gear up. the compession seems good, just recently put a new wiseco top end in, usually starts first kick.

the only way i can describe the problem would be if you were sitting at the starting gate of a race in 1st gear, you rev the bike up, drop the clutch to take off but the bike bogs(sometimes stalls) for about 10-15 ft. then clears up and takes off.


any suggestions??

 

[Bodge]

Its too lean. Richen the pilot and go from there. Why do you think its too rich?

 

[reelrazor]

What Bodge(and I will point out) I said.

 

[ironwood]

i just assumed it was, in the yamaha book it mentioned if you have poor engine response from 0-1/4 throttle to reduce the calibration # on the pilot. that would also match what FMF's jetting specs recommended, and finally the bike seems to run worse when i richen the air screw (although makes no improvment when leaned) . for someone who isn't a mechanic, three things pointing in one direction seemed right.

i'll go richer and see what happens i guess. thanks

 

[J-ROCK]

My KX 80 is having the same problem.. keep this thread updated as you go.. thanks :laugh:

 

[Cutlass72]

spark plugs i have a 1974 mt125 that was having somewhat of the same problem i played with the carb alittle cleaned it mostly and threw in some new plugs and it ran great after not starting and bogging.... just throw in some new plugs and it should run better then when u got it.