need help, air screw?

I need some help I took my bike out on the road today and it won't rev high enough to hit the powerband, it doesn't die it just makes allot of popping and doesn't pull any more. I think I need to adjust the airscrew but I don't know if it is running rich or lean any help is appreciated thanks.

sounds rich, is there alot of smoke?

yeah but no matter which way I turn it it smokes the same

Air screw works in conjunction with the pilot jet. Sounds like you need to experiment with your main jet.

if it smokes that bad try turning the air screw 2 1/2 turns out from fully in. Then when warming it up try the upper gears like 3rd, 4th and 5th to clean it out. If it is rich it's not going to clean out in first gear, once in 3rd open it up if it starts to load up shift to 4th and try again, if it loads up in 4th go to 5th and if it does it in 5th start back over in third and go through the process again. it should be warmed up and cleaned out after 1 or 2 trys. once it cleans out then first gear will be great.

The amount of smoke has nothing to do with the air screw. Revving out on the top end is the main jet anyway.

Have you recently changed a setting? The symptoms sound like a worn out top end. If you didn't change the pilot or air screw, then this condition isn't related to those settings.

If your main jet was too rich, and it ran ok during cold weather, but won't run during warmer weather, then you need a leaner jet.

I suggest a compression test to verify that you have a workable top end before you go chasing other cures.

Screw in the airscrew until it's lightly seated, and then back it out 1.5 turns. That is close enough to get it to run if you haven't changed the pilot.

okay I went out to ride again yesterday when it cooled off some and it was doing the same thing,at 3/4 throttle it starts popping and won't pull any more so I try and give it full throttle and it tries to throw me off the back. it loses power starts popping and than hits the powerband between 3/4 and full throttle. is all this normal on a 2 stroke? the jetting is stock and the top end has less than 3 hours on it and starts first kick.I have the air screw set at about 3 turns out any less than that you have to keep the rpms up or it'll also won't idle on its own unless I have the throttle stop all the way in but than it revs way up when I start it than about 15 seconds later it comes back down and idles fine,also the smoke seem to clear up between middle and top end.

anyways thanks for all your help

Now you need to adjust your needle and clip position. Pilot Jet/Air Screw affects low RPM's, needle and clip pos. affects mid range RPM's, Main Jet affects high RPM's

do I need to raise or lower the needle? never done it before

Raise the clip(lower the needle) to lean it out, lower the clip(raise the needle) to richen it up. Do you have a manual? This will help you with just about any question you could have.

Also, 3 turns out on the air screw is too many. You may need to go up one size on your pilot jet.

What exactly what do you mean when you say poping? Is it loading up and missing or is it making a loud popping noise? As the post before said you may need to lean the needle out if it is loading up at 3/4 throttle. move the clip up witch will let the needle hang down more into the carb. will make it leaner.

making a loud popping noise kinda like back firing out the exhaust

I took apart the carb and the made sure jetting is stock #125 main #52 slow the only thing that's not stock is the clip position on the needle, stock is 2nd groove from the top it's on the 3rd groove from the top also the float level is correct.I went ridding today and it smokes on the low end and stops pulling at 3/4 to full throttle tell I run it through all the gears a couple of times giving it lots of gas than it stops smoking and than I can hit the powerband and rides fine, does it sound to rich?maybe raising the clip back to the stock position will help? I don't want to risk seizing it so I want to make sure before making all kinds of adjustments. again thanks for any help.

have you tried to ride it with the choke on vs off and see witch one does best. that may tell you what way you need to go on jetting. What bike do you have.

1990 cr80r and no I haven't tried using the choke it would be kinda scary bending over holding the choke wile trying to hit the powerband:smirk:

first off: did you have any mods on the bike? bolt ons, permanents?

second: adjust your float hieght and change your float valve needle.

third: change your gasoline and run NEW spark plug. the correct heat range. some gas stations rarely dumps fills new gas in their stations and that "new" gasoline that youve bought actually was 6 months old.

fourth: after all steps, assuming youve drained your carb from gas, open your petcock and lean the bike til it drips gas out of the tubes. you then turn that petcock off and start the bike. warm up the bike for 5 minutes but always do a bit of blips to clear the motor out. when i say blips i meant small ones, not 1/2 throttle and dont even hold it for 2 seconds.

hope this helps.

iv been here just recentley and this is what iv came up with.

there are no mods except silencer, float hight is correct float valve is good it has a new spark plug the one my manual recommends br10eg, new gas 93 octane it's fresh also my bike won't run for 5 minutes on one float bowl of gas that's why I buy gas so often that's why I'm guessing I'm to rich so I might try to lower the needle back to stock position and see if that helps

okay I lowered my needle back to stock position to lean it out and it helped some but not a lot, it still pops like it's missing when I hit the powerband what would cause it to miss in the powerband?. I'm still looking for suggestions thanks for your help

.. ignition timing or incorrect plug will make it pop or ping ..

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now