runs like crap after anything more than 1/4 throttle...popping and black smoke galore

[ryanh250ex]

ok, here we go

went to NJORVP saturday. quad idles rough, but smoothes over after i rev it a little. i begin to take off and wind it out through the gears a bit.

15 minutes later, i'm riding the track, and all of the sudden, it just dies on me. i go to re-start it, and all it does is pop, it wont idle. i have to push it off the track. i get pissed.

after trying several different things, i try to see how it runs with the airbox lid off. amazingly, it will idle now, and runs fine up to 1/4 throttle. i ride 1/4 throttle back to the truck and try to mess with the carb a bit.

after 1/4 throttle it pops, puffs a ****load a black smoke, and just refuses to pull. the rpms will not raise at all.

i check the plug, and everything is black. that, along with a stranger hearing the noise coming from the pipe, leads us to believe i'm running a rich main.

this is my current setup right now: i am stock besides a modded airbox (now running lidless on a stock filter) , full T-4 pipe and silencer, 100 main jet, needle 4th groove down (1 below stock).i should note that i have a little bit too much oil on the filter.

since this is not my 1st time trying it at all with this set-up (before sat. i was running with my lid on, and i had done one WOT run down my street and it ran good), could it be possible that one of my vent tubes had gotten clogged and so anything past 1/4 throttle is starving it of air?

by accident, i had run it briefly with the breather tube that goes from the motor to the airbox not attached to the airbox. after i noticed it i immediately put it back on. this didn't cause any damage, right?

can anybody help me out here?

[ex kid]

what jetting are you using? when was the carb last apart.?sounds like you are way to rich. i am running a big gun full system with a uni filter and the air box lid on and the only jetting changes i made was 104 main jet with the air/feul screw turned out 2 and 1/2. i used the recomended 108 main from big gun with a piolet change(40) and needle change and the bike ran horrible. try jetting down on the main to a 104 or 106. leave the lid on. if you changed the neddle change it back to stock! and make sure the carb has no dirt in it. at a race last week i DNF'd because of a dirty carb.

[Doibugu2]

U sure u weren't running with the choke on? That's kind of what it sounds like.

Put a new plug on there and see how it is after than.

[4wheelboy]

Originally posted by Doibugu2
U sure u weren't running with the choke on? That's kind of what it sounds like.

Put a new plug on there and see how it is after than.


did that once an it let out a loud back fire after reapeted tries to start it:confused:

[ryanh250ex]

the choke was not on. i am positive of that.

[Out_Sider]

100 main jet, WTF???

[skemp]

Sounds like the main jet could have fallen out into the float bowl. Check that out. Very likely cause.

[Ryan]

I have heard of a problem where the oil backs up into the engine somewhere. That could explain the extra oil in your air box.

Anyone know more about this?

[JOEX]

Originally posted by skemp
Sounds like the main jet could have fallen out into the float bowl. Check that out. Very likely cause.
I agree with that.

Joe

[swamprider7]

Originally posted by skemp
Sounds like the main jet could have fallen out into the float bowl. Check that out. Very likely cause.

^^^What he said^^^

[Chanman420q]

i had the main jet fall out before. The day i got my slip on i jetted it and rode down the strait, ran 100%. Next day, anything past like 1/4 throttle was crap. i backfired a little, popped a little, it would go but it ran like ***.

[ryanh250ex]

i think i found the problem.

this afternoon i tore apart the carb and when i took off the float bowl, both the needle jet and the main jet fell out into the bowl. i dont know how it came off in the first place, but i just screwed them in as far as i could (some threads were still sticking out) and put the carb back together. since it's dark out , i didn't bother to try it out, but before i put the airbox back on i just wanted to hear what you guys had to sayon one or two things:

do you think my jetting is good for with a lid, or if not, is it good for no lid? i have a 102 around in case i need to raise it for whatever reason.

also, is there any way to keep a jet on without it falling off? a buddy of mine suggested loc-tite but i wasn't crazy about that idea.

[chad502ex]

Originally posted by Ryan
I have heard of a problem where the oil backs up into the engine somewhere. That could explain the extra oil in your air box.

Anyone know more about this?

Funny you should say this Ryan,...... Many garage mechanics think that they can change the clutch easy enough without any issues, but the truth is many garage mechanics forget to realize that the "figure 8-looking" oil ring/seal behind the clutch cover is not istalled where it should be when the mechanic re-installs the clutch cover. In other words, be sure that the oil seal behind the clutch cover is installed on the oil pump, if its not- the oil pump will pump the oil into the crankcase and spill out the breather tube into the airbox. I'd imagine the oil pump would pump most of its oil in the bottom end of the motor and make it difficult for the piston to complete the down stroke because of the backpressure.

Just something to consider, but I don't think this explains his 1/4 throttle problem unless he changed the clutch recently..,.... ;)

Chad502EX.com

[ryanh250ex]

Originally posted by chad502ex
Funny you should say this Ryan,...... Many garage mechanics think that they can change the clutch easy enough without any issues, but the truth is many garage mechanics forget to realize that the "figure 8-looking" oil ring/seal behind the clutch cover is not istalled where it should be when the mechanic re-installs the clutch cover. In other words, be sure that the oil seal behind the clutch cover is installed on the oil pump, if its not- the oil pump will pump the oil into the crankcase and spill out the breather tube into the airbox. I'd imagine the oil pump would pump most of its oil in the bottom end of the motor and make it difficult for the piston to complete the down stroke because of the backpressure.

Just something to consider, but I don't think this explains his 1/4 throttle problem unless he changed the clutch recently..,.... ;)

Chad502EX.com


my clutch may or may not be nearing the end of it's life......but i have not replaced it.

[Bad Habit]

Originally posted by ryanh250ex
i think i found the problem.

this afternoon i tore apart the carb and when i took off the float bowl, both the needle jet and the main jet fell out into the bowl. i dont know how it came off in the first place, but i just screwed them in as far as i could (some threads were still sticking out) and put the carb back together. since it's dark out , i didn't bother to try it out, but before i put the airbox back on i just wanted to hear what you guys had to sayon one or two things:

do you think my jetting is good for with a lid, or if not, is it good for no lid? i have a 102 around in case i need to raise it for whatever reason.

also, is there any way to keep a jet on without it falling off? a buddy of mine suggested loc-tite but i wasn't crazy about that idea.

In my wife's 250, I've got a 110 main with no lid and a Yoshi pipe. 100-102 should be right in the ball park with the lid on. These things are picky about the jetting, one size up or down can make a huge difference.

BTW, I had my main fall out one time in my 400. The only thing that you can say is WTF:confused2 I just put it back in without any loctite (I wouldn't recommend it in there) and it never came out again. Just a case of sh!] happens I guess.

[chad502ex]

Originally posted by ryanh250ex
my clutch may or may not be nearing the end of it's life......but i have not replaced it.

yea i figured as much. I was on a tangent for others cause I've seen ppl have oil in airbox.

Chad502EX.com