Possible throttle cable problem ?

[sweetip2000]

After I feather the throttle the idle climbs a little and hangs on then the rpms go down after about 20 seconds.
Could it be a problem with the throttle cable ? Its a new cable and routed properly,,,,, otherwise besides that it runs great.

[ps2fixer]

I have a 85 250es doing the same thing, revs up between shifting gears, and takes a while to idle down, but runs perfect at idle. Pretty sure it is a carb issue. Possible air leak or I was told the 250es carb bodies develop a crack sometimes which sucks air.

Keep us posted if you find anything!

You could remove the cable as a possible part at fault by taking the side of the carb apart and try to get it to mess up while you can see the cable at the carb end (assuming it is a carb like a 250es big red). I was also thinking it might be the slide sticking partly open.

[250rRoostmaster]

Check your pilot jet.

[BOB MARLIN]

lean condition ?

[RIDE-RED 250r]

Agree with Roostmaster and Bob.. Assuming you do not have an air leak, check idle mixture screw. You didn't say what engine/carb you are having the issue with... But if it's a 2-stroke it likely has the idle mixture screw that regulates air at idle. And air regulating idle mixture screw will be found on the carb body, above the fuel bowl gasket, between the slide housing and airbox end of the carb. If this is what you have, to enrich idle mixture, turn this screw in... (clockwise).

Most 4-strokes use a fuel regulating idle mixture screw. It will be either on the side of the carb body above the fuel bowl gasket, or it may be facing downward on the front of the carb body (closest to engine). Either case, a fuel regulating idle mixture screw will be found between the slide and engine. (opposite that of an air regulating screw) To enrich idle mixture with this setup, open the screw (counter clockwise).

If you can't achieve a stable idle, and reasonably quick return to idle after stabbing the throttle with the idle mixture screw set between 1 and 2 turns out, that usually indicates that you need to make a pilot jet change.

[sweetip2000]

yeah sorry if I didnt mention its a 4 stroke 250sx, no air leaks, I checked the snorkels too. The guy who had the bike before me had the choke cable routed the wrong way which reeked havoc on the carb. He said he replaced all the cables with new cables, I dont understand why the original owner would want to replace oem cables when the bike was never used. I will check the idle air again.

[RIDE-RED 250r]

If I remember correctly (been awhile since I put a wrench to an SX) that will have a fuel regulating idle mixture screw, and will be at the front of the carb body (toward the engine) and facing straight down. Can be a pain to get a screwdriver on... I use a screwdriver bit to adjust the one on the wife's 350x.

[ps2fixer]

Attached a photo from the service manual for the 250sx. in 85-86 the pilot screw should be 2 turns out, after 86 is 1 1/4 turns out. Factory slow jet is #38.

Just for reference while I'm looking in the manuals, the 250es specs are 2 turns out and "primary jet" is #45. Looks like all other specs are the same. I'm pretty sure my big red is at 1 1/4 turns out, so that would be a dead give away that I'm too lean.

Interesting the big red has such a larger jet unless the terms do not match up. I know the big red carbs have a start jet circuit too, I thought the sx and es were the same carb or extremely similar? I would think if anything the reverse would be true, larger jet in the sx.

[Flyingw]

I rebuilt the carb for Andy. The air screw is set to factory and the jets were replaced. The book does say to turn the air screw in until the motor stops then back it off 1 full turn. I did test the carb and it idled just fine on my end. The ES and SX carbs are jetted exactly the same. I also inspected his intake boot and found no discrepancies with it. We thought the misrouted choke cable fixed the high idle problem but apparently Andy still has a problem.

[ps2fixer]

Oops forgot to attach the photo, edited the post above.

Flyingw the master of the 250sx and 250es carbs, you are of course right. I dug further into the 250es manual (mine don't have the nice quick links to jump around) and the slow jet is the same #38.

[Flyingw]

Mines the same way. I wish somebody would rescan the ES manual with the indexes on the left. Having to scroll through the entire book looking for something kinda sucks.

[ps2fixer]

I haven't done much with pdf's, but the version of the 250ES manual I have I can copy the images directly out of it, so creating a new pdf with the bookmarks (shortcut links) should be do-able.

EDIT:

Stupid pdf won't let me select the whole thing to copy, copying 284 pages and pasting them in word to recreate the file would be a pain :(. If I was to go that far with it, I'd use an OCR to convert the images to text and recreate it so you can search the document, or even make a web version out of it.