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o3 xr80 wont idle

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just traded go kart for 03 xr80 cleaned carb+jets+air cleaner+rplcd old gas starts when choked but wont idle even when warmed up has dmc pipe and k+n air cleaner I dont know this bike so I dont even know where air/fuel mixture screw is, saw 2 screws on pipe side of carb and tried adj all over the place but no changes bike wont idle with or without choke engaged when started(with choke on) idles fast for a second then dies will run good if get revs up,tried running up+down street fast to see if would clear up but when pulled in clutch and off gas just died any help untill I get manual would be great :banana:

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Just off hand I'd say pilot jet still needs help.Also check the intake manifold for leaks,they are rubber between 2 aluminim pieces and can crack and not easy to see.

Bob

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+1 on the pilot circuit being gunked. If either (or both) boots leak, that tends to make the A/F mixture lean and the bike have a hanging idle.

If I'm not mistaken, the XR 80 has a PWK carb.

Airscrew on a PWK carb (CW = richer). toward the airbox side of the carb on the left.

The Idle Screw is in the middle where the slide is. CW = faster.

Here's a link to a PWK carb diagram and parts.

http://www.psep.biz/store/keihin_pwk_carb_parts.htm

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just got back from cleaning carb agin and did find some gunk I had missed but still wont idle but dosent have hanging idle anymore,the link to csrb pic isnt same carb mine has round slide not sure which is piolet jet,the jet i found that still had gunk came out in 3 pieces(used flathead screwdriver to take 2 pieces off then like 7/8 mm wrench for 3rd piece the other jet was smaller as far as holes in it go is it supposed to have a hole from top to bottom and not just sides? if so that is clogged tried bread wrapper tie wire and would only go in apx 1/4 inch from either top where side holes are or bottom where screwdriver slot is

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sometimes easier to replace the jets when they get so gooed up with caked / baked in crud. See the dealer and get some new jets - cheap, easy sure fix, IF you know it is a bad jet. Worst case scenario would be a leaking head gasket making it extremely lean and unable to idle.

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just got back from cleaning carb agin and did find some gunk I had missed but still wont idle but dosent have hanging idle anymore,the link to csrb pic isnt same carb mine has round slide not sure which is piolet jet,the jet i found that still had gunk came out in 3 pieces(used flathead screwdriver to take 2 pieces off then like 7/8 mm wrench for 3rd piece the other jet was smaller as far as holes in it go is it supposed to have a hole from top to bottom and not just sides? if so that is clogged tried bread wrapper tie wire and would only go in apx 1/4 inch from either top where side holes are or bottom where screwdriver slot is

Best not to poke wires into a carb or jet. Scratching things can change flow characteristics and can also damage the casting. Carb cleaner and compressed air are ideal, as is replacing jets instead of cleaning them (especially small pilot jets). Plenty of threads on this.

The pilot jet is generally the long one with the tiny hole. The main jet fits into the emulsion tube that the needle slides into and has a larger orifice.

If the mixture adjustment screw is on the engine-side of the carb, then it's a fuelscrew (CW = lean). Does the carb look like this (Mikuni VM)?

vm.gif

Post a pic if you can.

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so now I know which is pilot and main thats a good thing,no clue how to post a pic,my carb looks a little like that but is a keinen (sure spelling is wrong but its close) anyway does the pilot have a hole lengthwise?

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Probably something like this then (Keihin PC18 or PC20).

The Pilot Jet (or "slow jet") has a small hole lengthwise plus some extra holes at the end that goes into the carb body.

010-4-05-018_lg.jpg

Edited by davidl9999

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Thanks for the info I went to honda shop to get new jet they sold me the wrong one,so I went back with the carb in hand and they didnt have any in stock but they did clean the old one so got my money back $5.08 and put bike back together and now it idles. BUT now I see what people were saying about a little bog from idle to not quite wfo so still need to mess with carb some to see if can eliminate that. not sure how many turns to set air/fuel mix screw has aftermarket pipe and k/n air filter(clean) air srew any suggestions as to where (how many turns out)to start or is to many variables pipe /air filter altitude here?

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The pilot circuit pretty much gets adjusted whenever the weather changes. Try to set the airscrew (I think the PC 18/20 has an airscrew and not a fuelscrew; maybe someone else knows) between 1 turn and 2 1/2 turns out from the seated position. I'd start at 1 1/2T open and see how it goes.

At a high idle (set it high with the idle speed screw), find the peak rpm by turning the airscrew one way or the other until the RPMs peak and then turn the airscrew slightly to the rich side of the peak (CW). Fwiw, if the PC carb does use a fuelscrew, then just turn it CW for leaner and CCW for richer. I hope that makes sense... :banana:

If the airscrew is less than 1T open, the pilot jet is too large, get one a size smaller.

If the airscrew is more than 2 1/2T open, the pilot jet is too small, get on a size larger.

(reverse this for carbs with fuelscrews).

I'm not a big fan of K&N filters for dirtbikes; just seems to let too much crap through. There are some threads on this. I use Twinair and UNIs - depends on what's available when I need to replace the element. GL!

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thanks for the info got the pilot cleaned(dealer didnt stock) and got bike idleing,rode it around back yard and got tires muddy then WAS going to ride it up the street to clean tires off, but it sputtered and died and wouldn't start so pulled plug and no spark went over to z 50 pulled plug to see if could swap it was a 6 wile 80 was a 7 other letters matched and length of plug was same put 80's plug into 50+started rite up so plug is still good so somewhere I lost jucie to plug, This year has cdi so I'm kinda stumped what to do next? dont think anything came unpluggd as I was going real slow when it died anyone got any clue's?

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Disconnect the kill switch and see if the bike starts (very common). If it does, replace the kill switch.

If not, check that any electrical connectors are tight and dry. If that's all good, check the stator ground (bolts are tight, ~0 ohms), pickup, and coil resistances. No idea what the values are. The only thing left after that is the CDI or a bad wire. GL!

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Had the same problem on my 2003 xr 80 clean the carb multiple times no difference still high idle pointed to words a air leak. Slide in order all the way seated could not find the problem. Started to spray break clean all round carb boots still now luck but idle increased when I sprayed by the head re sealed the full top end and re set idle and air screw runs great now something to keep in mind

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