Cleaned carb, now bike wont start

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3/12/2018 9:53 PM
Edited Date/Time: 3/12/2018 10:35 PM

Hey guys, new to the site.

I've ridden dirtbikes my entire life but never really worked on them. Got a 1998 yz 125 (bored out to 145) for my girlfriend to learn on.. (i know, powerful learner bike, lol).. and I decided to go for a project bike to save some $$..

It would start with choke on but would idle extremely high (even if i played with pilot), and when choke is off it died. Since I got it i've been cleaning top to bottom. Changed tranny fluid, radiator fluid, spark plug, air filter.. drained gas and put new 94 octane 32:1 premix.. it was kicking over in 1-2 kicks but kept dying when choke wasn't engaged.. I figured the carb was the issue otherwise it needs more than a tune-up.. (maybe top end).. so i got some carb cleaner and compressed air in a can and cleaned out all those jets real nice with a guitar string.. put it back together and now it wont start at all!!

I made one mistake.. I think i unscrewed the fuel mixture screw without counting the turns.. so when i put it back in, the carb isn't getting what it wants anymore. Literally tried going all the way in and then 1 turn out at a time.. (while the idle (air) screw was set to 2 turns & 1/4) ... no dice. Got it to fire up once with choke, was still idling super high, turned choke off and tried to play with the screws and it died. Spent a solid hour (making sure i didn't flood it).. nothin..

(i put a tablespoon of 10w30 in the spark hole because i heard it helps lubricate the cylinder walls.. kicking over bike while holding kill switch.. anyways, i took it out and dried it off just to make sure the wetness wasn't the issue)..

Really hoping i can get some solid guidance on what to try before looking into a top-end kit..

Also, IF I need a new top end, will i use the standard bore 53.94mm or because it's bored out to 145 the size changes?

Thinking it might be the top end just the way i watched the prev. owner cold start and ride off without warming up.. heard that the expansion can ruin the piston or something.

Edit:
Oh, also the fuel line keeps popping off now since the carb clean... and unrelated sidenote: when i replaced radiator fluid it seemed to have all leaked out of the overflow? .. but i opened the cap and it was sitting at the top?

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3/12/2018 10:17 PM

Holy shit... my bike won't run... maybe I should change the juice in the radiator... wtf???

Best thing you can do is give it to someone that has a clue. Cuz you don't.

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Even a broken clock is right twice a day.

3/12/2018 10:28 PM

I changed the radiator fluid because the bike was clearly not well-maintained.. it came out filthy.. and i read that you're supposed to change it every 2 years.. since i got the bike, I've been cleaning it top to bottom.. the reason i took off the carb was because it wasn't running good. Radiator fluid was just a part of my overall maintenance of the bike.

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3/12/2018 10:34 PM

Did you put the float back together upside down?

Is your spark plug connected ?

Are you getting spark?

Did you turn the gas off, lean bike over on its side and allow the fuel to dump out (in an eco friendly catch pan.... of course) ?

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GP740
Since 1987

3/12/2018 10:39 PM

GeorgiePorgie wrote:

Did you put the float back together upside down?

Is your spark plug connected ?

Are you getting spark?

Did you turn the gas off, lean bike over on its side and allow the fuel to dump out (in an eco friendly catch pan.... of course) ?

I'm not sure if it's in upside down.. I flipped it around a few times trying to figure that exact question out.. didn't seem to fit properly the one way so i put it the other. Could definitely be upside down! I read that someone else with similar issues put his float upside down, lol. Seems like a rookie mistake I would make.

Plug is connected.

Getting spark.

Turned off the gas and leaned the bike on it's side to dump fuel (unfortunately not in an eco-friendly way).. but i have a pan, next time I will be conscientious of that.

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3/12/2018 10:41 PM

Does anyone know the factory settings for fuel & air screws? ..

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3/12/2018 10:46 PM

Hell, every two stroke rider in the world only empties said carb in an eco friendly catch pan......OF COURSE.

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GP740
Since 1987

3/12/2018 11:15 PM

This manual is for an '01 which I think is close enough.

Photo

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3/12/2018 11:45 PM

Bman_145 wrote:

This manual is for an '01 which I think is close enough.

Photo

Thanks a lot man!! Been lookin' for a manual since i got the bike!! Everyone's tryin to charge $20+ even for a .pdf

I believe the bikes are the same from '98-'03

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3/12/2018 11:48 PM

Ryno23 wrote:

Holy shit... my bike won't run... maybe I should change the juice in the radiator... wtf???

Best thing you can do is give it to someone that has a clue. Cuz you don't.

W. O. W....

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3/12/2018 11:55 PM

Even though you cleaned the pilot jet, make sure the carb fluid sprays all the way through the pilot jet passage. The jet and the passage way need to be cleaned.

Idling extremely high, might be an air leak. Maybe a crack in the rubber intake between the carb and the cylinder, or the crank seal behind the flywheel.

Good luck!

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3/13/2018 12:43 AM

if your going to put new rider on bike , after messin with carb , not knowing what ur doing, better let someone that has knowledge check out or u could get new rider hurt if u put together wrong... could cause wfo throttle and really get injured ,nothing to fuck with if u don't know .....

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3/13/2018 1:27 AM

This post gave me cancer

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3/13/2018 2:29 AM

Did you try adding more spark powder?

How about topping off the injector cream?

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3/13/2018 3:48 AM

Ryno23 wrote:

Holy shit... my bike won't run... maybe I should change the juice in the radiator... wtf???

Best thing you can do is give it to someone that has a clue. Cuz you don't.

Read again smart ass

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3/13/2018 4:02 AM

Did you remove the jets when cleaning? Sure you got all the passages passing?

Good chance it's an air leak as mentioned above - which will toast your engine if run that way. And likely also would call for someone who knows their stuff on it. A leak down test should tell.

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HAF

3/13/2018 4:08 AM

Ryno23 wrote:

Holy shit... my bike won't run... maybe I should change the juice in the radiator... wtf???

Best thing you can do is give it to someone that has a clue. Cuz you don't.

Cripes, how do you learn to work on shit if you’re always taking it to someone else. I applaud the guy for wanting to learn and ave some money.

To the OP, how’s cylinder compression? Start with the basics and rule out the obvious. When I clean my carbs, I really only need some high pressure air to plow out the jets and ports in the carb, then hold the jets up to some light and visually check that the passages are clear.

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3/13/2018 6:56 AM
Edited Date/Time: 3/13/2018 6:58 AM

I would suggest doing a compression test ( you will need at least 120psi) and a leak ( it should hold 6psi for about 1 minute) test before going any further.
Check float and float height setting ( see chart).
Check the filter screen in the fuel tank for dirt or dried fuel deposits.
Remove the carb and do a soak cleaning.
While you are there, check and or replace the reeds.

Paw Paw

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3/13/2018 7:08 AM

Have you checked the air in your tires?

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3/13/2018 7:19 AM

In all seriousness, check the basicis: compression, fire, fuel, and air. first make sure you have compression. Then check for fire in the spark plug. Then check for fuel - take the carb apart after you put it back together and see if there is fuel in the bowl. If not, you aren't getting any fuel. It's very easy to accidentally mess up the float or float spring. This happens often when cleaning up an old bike. Then make sure all your jets are clean. Lastly make sure you have air. Once you check these, you should be able to get some kind of feedback on what the source of the problem is. Depending on the severity, you may just want to get a carb rebuild kit along with some additional jets.

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3/13/2018 8:07 AM
Edited Date/Time: 3/13/2018 11:28 AM

I like working on my bike almost as much as riding it, but when it comes to anything beyond moving the needle, cleaning a jet or jiggling the float bowl to get it unstuck....I load up the bike and carb and take it to a real mechanic (former shop mechanic now on his own) who solves that baby like a Rubik’s cube. And the throttle response is right there.

It is a 200 mile round trip but it is worth it to me. My Wife and daughter jump in and off to the mall for them.

The best thing to do is find “that guy”, only hopefully closer to keep costs down for you.

I have done a few unstick the bowl operations. Bike will only run full choke when bowl is stuck.

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In my 60’s and still loving dirt scoots up here in the frozen north.

2021 Husky 501s

3/13/2018 8:07 AM

Only runs with the choke engaged, pilot is clogged clean it again

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If you like uncle tony's meatballs, you'll love his sausage

Now that's Italian

3/13/2018 11:34 AM

downard254 wrote:

Cripes, how do you learn to work on shit if you’re always taking it to someone else. I applaud the guy for wanting to learn and ave some money.

To the OP, how’s cylinder compression? Start with the basics and rule out the obvious. When I clean my carbs, I really only need some high pressure air to plow out the jets and ports in the carb, then hold the jets up to some light and visually check that the passages are clear.

How??? Buy a service manual. Or even google some info on it. Or heck, there is a TECH section to this forum! Heaven forbid the kid actually TRIES to find some answers on his own. That's part of the problem with society today. They are too lazy to put in the effort and find their own answers. "Meh, I don't know, I'll just ask Vital." Brilliant idea!!

Peely should have told him to check the sprocket bolts. I find this shit hilarious and sad all at the same time. I'm just falling in line with the hundreds of other vitards in throwing advice. Yet, mine is right.

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Even a broken clock is right twice a day.

3/13/2018 12:37 PM

Uncle Tony wrote:

Only runs with the choke engaged, pilot is clogged clean it again

Another cause for this symptom is it could be sucking air anywhere after the carburetor. Anything from a cracked reed block or boot to any compromised seals/gaskets after the carburetor like the head gasket. To summarize, if it only runs when more fuel is applied to the air fuel mixture via actuating the choke, it must be getting the air from somewhere else or it isn't getting enough fuel to begin with.

Oh, and don't listen to these guys giving you crap. Your initial post made sense if you have a sliver of internal combustion engine knowledge, which they apparently don't have.

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Before responding to any post, consider these three things...
1. Context!
2. Context!
3. Context!

3/13/2018 12:47 PM

It’s a mental hurdle to jump, but, do yourself a favor and order a carb rebuild kit, new pilot jet, and a float needle. Buy new fuel and possibly vent lines. Rebuild the carb right and you’ll be rewarded.

I’ve found over the years you’ll save time and frustration if you do things the right way.

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3/13/2018 1:51 PM

Let us know how it turns out and what you learned OP!

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GP740
Since 1987

3/13/2018 1:54 PM

Trade the bike in for a pair of these

Photo

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3/13/2018 1:59 PM

You need to perform a compression and leakdown test. If the pressure is below 120 it is time for a rebuild. Your engine should be able to hold 5 psi for 5 minutes during the leakdown test. If it doesn't, you have a leaky seal or gasket that needs to be fixed. Once the compression and leakdown yield good results, then you can start working on the jetting.

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Bret Bonham

3/13/2018 2:22 PM

Put the dirt you cleaned out of the carb back. Dirt bikes like dirt.

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3/13/2018 2:28 PM

Check for a rag in the airbox. Check the gas tank. I'm serious.

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