1985 YT125 tuning help

[guitarist93]

First off this is my first project with something that has a motor, so I don't have a vast expanse of mechanical knowledge. I have a 85 YT125. I finally got it to consistently start and run for a while, but only when the idle screw is all the way screwed in and the choke is pulled out the entire time. As soon as I start to let off the choke it begins to die. Some times it even will rev high then die when letting off the choke. Can somebody please try and help me out with what i need to do to get it to idle without having to hold the choke the whole time.

Thanks!

[3wheelrider]

Honestly, I am not familiar with that motor. But since no one familiar with it has posted yet I'll say that -I can tell you its not getting enough fuel. Not sure if it has a fuel pump or not? if its carb only, then the pilot jet/carb sounds clogged. check fuel flow too. If it has a fuel pump-then all the lines must be inspected(vacuum & fuel) for tiny cracks.- if those check out OK then the pump may be bad. With out mech. abilities you might be in over your head tring to fix it yourself tho. Its a little more complicated when it has a pump. Oil line also must be checked to ensure the motor gets oil too.
-good luck.

[3wheelrider]

So I now see you started a thread about this 1 1/2 years ago.- So Im not of much help then. -
I assumed it was new to you & now see youve had it a while and it used to run I assume.
I seen what all you had & far you got changing the hoses/lines. & you said its carbed & has no pump- there was some mixed replies about whether they did or did not come with a fuel pump? Anyway, you never mentioned if youve cleaned the carb. The carb works with vacuum?wtf- anyway clean the pilot if you cant see thru all the openings. (Or better get a new one same number-take the old one with you if you get it locally)-thats where Id start since you already changed the hoses.

Im sure youll get it resolved -this time around.
& youll get some more help here with it here soon by someone else familiar with it again.
Anyway,-sorry Im not much help then. good luck with it.

[old-yellow]

do what 3wheelrider said also the yt125's never came with a fuel pump only the yt175's did [if your cylinder head has 4 bolts its a yt125 if it has six then its a yt175], i would try checking your fuel petcock is flowing gas from the tank, make sure the carburetor is clean, check the vent on the gas cap is not clogged. Also do a compression test to see where its at.

[Vealmonkey]

A good suggestion would be to get a shop manual. Also, your initial posting was very vague. You should be running the trike with an air filter. The 2 stroke engine is way more tempermental than a 4 stroke. No idea if you are premixing your fuel or using the factory oil injection. No idea about all the basics of the engine. Clean carb, properly lubed and set throttle cable, engine compression, sparkplug cleanliness, airfilter cleanliness, etc. You need to provide alot more info to able to get a better idea of what you have going on. Not trying to be mean, just saying.

[old-yellow]

here's a link to a manual.http://www.oscarmayer.net/atc/manuals/ let us know

[guitarist93]

Thanks for the replies.
Veal, i'm using the stock oil injection, properly adjusted, and have a brand new Uni air filter on it. The carb is clean, but will check once more for any clogs.
I have no way of checking compression, but will go check the carb and get back to yall.

[Vealmonkey]

If you have a harbor freight local to you, they have cheap compression testers that will give you a better idea how tired your top end may be. Just make sure you get one that works with metric spark plug threads. Along with your idle screw, you should have a fuel/air ratio screw. With the shop manual, it will give you a better idea of what your settings should be. When you say uni air filter, it worries me though. Do you mean one of those cup shaped uni air filters? If so, that is more than likely your problem. A stock air filter box flows less air than one of those little uni air filter and the carb is jetted from the factory to use the stock air box. More air flow, less fuel to air. You need to up your jet size my friend or go back to the stock air box. And don't even start with what jets you need! LOL You'll have to figure that one out on your own. You will need bigger jets though.

[guitarist93]

I'll look into the compression tester. And the the Uni filter is just a replacement foam filter that inside the stock air box

[guitarist93]

I'm making progress!! Thanks guys!
I got it idling pretty good with the idle mix screw at the stock setting, and rode it around the pasture for about 20 mins. the throttle stuck open a little sometimes, so I'll have to look into that. Its did die a couple of times though while riding around, but got it started back up and rode back to the house, killed it then restarted it maybe 30 secs later. it idled nicely for 25-30 secs then it got kinda rough for another 10 secs or so, then sputtered out like it was out of gas, but still had half a tank. Any ideas? should i tighten/loosen the idle speed screw? tighten/loosen the idle mix screw?

[Vealmonkey]

Firstly, you need to lube that throttle cable and make sure it's not kinked or bound up against anything. If the throttle sticks open, it could be bad. Glad to hear you are using the stock airbox, it makes things simpler. You should have a fuel/air mixture screw. You may have to open this up. Also, under the top of the carb where the cable goes in, once you unscrew the carb top, you can pull your carb slide and needled out of the carb. Your needle should have a couple notches and an e-clip. If you try adjusting your air fuel mixture, and it doesn't help, you may want to change what notch the e-clip is in. But try adjusting the air/fuel mixture first. If that doesn't help, you may have to put the e-clip on a lower notch on the needle. This will actually raise the needle in the carb allowing more fuel through. But you want to only adust a single notch at the time because this can help to foul out the plug with too much fuel. Ideally the e-clip should be in the center notch, but that's why there are several notches for adjustability. But changing the e-clip not position should only be done after trying to adjust the fuel air ratio. This is a good example of why people should use a shop manual and give tons of info when asking for help. Glad to hear you are making steps forward though.

[guitarist93]

well i have no clue what happened but it feels like i've taken 10 steps backwards. when i happen to get it to idle now as soon as i barely get on the throttle it bogs down and dies. I tried adjusting the mix screw both ways, nothing...tried the e-clip in every position...nothing..now its back on the notch it was on when i actually rode it around for a while, and i'm still at square one. I might have just bitten off more than i could handle for a first project of this kind.

[old-yellow]

it sounds like your still dealing with a fuel issue, have you checked your fuel petcock for free flow also have you installed a fuel filter (check and clean carb if no). make sure that you did not bend the needle when you went to change the e clip position have you done a compression test yet. we need more info.

[guitarist93]

yes i have free flow from the petcock and do have a fuel filter. I still haven't done a compression check, i'm i broke college kid so even buying a cheap comp tester isn't something i can really do right now, so this will likely be a long project for me, but i will see if my neighbor has a comp tester since he used to do some motorcycle work. i did however put a new spark plug in tonight for the heck of it. after a few pull it idle nicely so i took it around our driveway and it did fine until the very slight uphill rise, then it just lost power and kinda bogged and died, couldn't get it to restart so i pushed it back to the shop took out the plug and it was covered in wet oil. so i'm thinking maybe i need new rings. or maybe change the oil injection setting, even though its set at where the service manual says it should be. would this excess oil cause symptoms to what i have been having such as the bogging?
I really really do appreciate yall replying to me, i'm sure i can be frustrating since i really don't know what i'm doing or talking about, but i am loving the learning process.

[old-yellow]

yes if the mixture is wrong then it will bog like crazy so check to make sure you have the oil injection set right also its a two stroke so there no oil in the lower crankcase like a four stroke so it cant be the rings the only oil that there is in the transmission side of the motor so if its burning that off that would mean that you need a crankshaft seal on the transmission side check this thread out this well help you understand more about this http://www.3wheelerworld.com/showthr...Duck-Questions