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View Full Version : Bringing back yt125. NEED HELP!



SixFourStroker
10-16-2012, 06:12 PM
Hey guys,

I recently was given an 81 YT125. It is in fantastic shape as far as I can tell. I have a new set of tires coming in for it, and I am trying to get it running. I was able to get it to start and run on carb cleaner a few nights ago as the fuel system is completely gummed up. I cleaned the tank, carb and all the lines today. Now it wont even hit. It is blowing the fuel back through the carb. I believe the float level is set a little high but I have no specs to go on. I took the pipe off thinking that it night be plugged and it is rusted through at one point. That did nothing too. I have good spark and good compression. Oh and the plug doesn't even get wet when pulling. I am at a loss I am about ready to put it all back together and just let the dealer deal with it just to get it running. Any help is appreciated.

old-yellow
10-16-2012, 10:29 PM
Here is a link to a manual http://www.oscarmayer.net/atc/manuals/, now when you say you cleaned the carb did you soak it and blow all the jets and passages out or just spray it down with carb clean? also have you tried dumping a little premix down the spark plug hole.

SixFourStroker
10-16-2012, 10:30 PM
Ok so I tinkered with it a little more. It still won't suck through the carb. It is not blowing fuel out anymore though. It still wont so much as pop.

SixFourStroker
10-16-2012, 10:33 PM
old yellow. I have completely disassembled the carb, blown it out and soaked it in chem dip. I've tried carb cleaner and either in the plug hole and through the carb and get nothing. What kills me is I got it to fire and actually run for a few seconds on carb cleaner the other night and now I've got nothing. Thank you for your help.

old-yellow
10-16-2012, 10:38 PM
you could try to push start it or have someone pull you and see if you can get it two start that way and the plug is it coming out dry or wet

old-yellow
10-16-2012, 10:40 PM
also have you reset the float yet

SixFourStroker
10-16-2012, 11:27 PM
Yeah I reset the float. I can't try starting it until tomorrow when my tires get in. The plug comes out dry.

old-yellow
10-16-2012, 11:36 PM
well let me know what you come up with.

SixFourStroker
10-17-2012, 01:32 AM
I will be sure to Thanks for your help.

SixFourStroker
10-17-2012, 10:20 PM
Well I got to try to pull start the beast tonight. I put a little marvel oil in the bore just to make sure its lubricated. It fired and seemed to run on the marvel oil and then it died. I couldn't get it to even hint at firing after that. The plug doesn't come out wet either. I guess I need to take the carb off again.

TimSr
10-17-2012, 11:23 PM
Have you verifed gas is going into the carb? Disconnect the gasline from the carb, turn the petcock open, and see if gas comes out. If its good, put it back on the carb, and then open the screw to drain the float bowl and see if anything comes out. If nothing comes out of the float bowl, the float needle is stuck closed, or the floats are not dropping. Take the float bowl off, Hook the carb back to the gas line. Turn it on and gas should pour out. While its pouring out, raise the floats and see if it cuts gas flow off, and make a note of how high you have to raise them to do it. If you are flowing gas into the bowl, the only thing that could keep it out of the motor is a plugged main jet which is rare.

old-yellow
10-18-2012, 08:07 AM
sorry i did not get back sooner, but do like Timsr said also check that the vent on the gas cap is not plugged.

SixFourStroker
10-18-2012, 10:57 PM
The Vent on the gas cap checks out. There is good clean gas to the carb and it has good flow. There is gas flowing into the bowl and I know the main jet is clean because I just blew it out. It doesn't seem to be sucking through the carb. Thanks for all of the help. Also the chain is very loose. Is there another adjustment beside the idler sprocket or do I have to buy a new chain?

old-yellow
10-19-2012, 04:15 PM
have you put you hand over the carb to see if its sucking in, if not check the reeds also whats compression at and as for the chain the idler wheel is only way, so i would say replace the chain

SixFourStroker
10-21-2012, 03:07 PM
No it doesn't suck through the carb. As a matter of fact it blows out of it a little bit. I checked the reeds and they seemed ok. They didn't seem to hold much suction. I have a set of Boyesen Reeds coming in tomorrow. I'm hoping that does the trick. Thanks for your help I really appreciate it!

3 Wheel Drive
10-21-2012, 03:25 PM
I had a similar problem with my Suzuki, cleaned everything just like your doing. I replaced the head and manifold gaskets, and carb, it started right up after that. It could be low compression check your gaskets and torque down everything.

Just my 2 cents, good luck.

SixFourStroker
10-22-2012, 05:48 PM
Ok so the reeds came in today. They are Boyesen #603 which indicates they should be correct for an 1981, problem is they wont come close to fitting. I called Yamaha and verified that it is indeed a 1981. Do I have a different reed cage?

captainweezy
10-22-2012, 07:33 PM
If you ever get over my way(4 hours to your east) i have a 1984 yt 125 and a ton of parts i am trying to get to a good home. Good luck on your 125, sounds like it will be very soon and you will have it whipped.

old-yellow
10-23-2012, 01:32 PM
you could have a different reed cage from another year, is it four reed pedals or just two large ones.

SixFourStroker
10-25-2012, 02:26 AM
Thanks for the offer weezy! I might have to take you up on it someday.

Old Yellow- It is the 2 large petals, but the cage has 4 holes in it. What baffles me is the reeds appear to be working as when I suck on them there is a pretty good resistance. It has 0 suction at the throat of the carb though. I am pretty confused with it. Thanks for all of your help!

old-yellow
10-25-2012, 09:25 AM
okay you have a 1980-81 reed cage so whats wrong with the set of Boyesen reeds you bought can you get pics? as far as no suction that makes me think low compression, have you checked it with a gauge to see what its at and if so what is it at? also look down the intake at the piston for any damage on the piston skirt?

SixFourStroker
10-25-2012, 06:06 PM
I'll grab some pictures later. They are way too big and the screw holes don't even come close to lining up. I put my gauge on it but it will not hold a reading so I am not totally sure. It read about 75lbs with one pull as best as I could tell. I am kind of thinking it needs to be re ringed. I really appreciate your help!

old-yellow
10-26-2012, 11:16 AM
well let me know if you need more help

SixFourStroker
10-29-2012, 11:54 PM
Well guys... She runs and runs pretty good all things considered. I have a few more questions. It seems to idle too low and dies, but I can fix that. It seems to grind a but when down shifting. Is there some trick to downshifting on a semi auto? Also this thing smokes like there is no tomorrow. I think the oil injection has gone wack. It smokes like a white grey color, with a little blue. Like honestly it smokes like a diesel on a really cold morning. What a fun machine though. It will pull one heck of a wheelie.

old-yellow
10-30-2012, 12:35 AM
i am glad to here it runs but you got my worried about how much its smoking that could mean you need a crankshaft seal on the transmission side causing it to burn off transmission oil and smoke, try resetting the oil injection according to the manual http://www.oscarmayer.net/atc/manuals/ to see if it will stop smoking so bad. also is it fresh oil in the oil injection tank? and it should not grind when down shifting

SixFourStroker
11-05-2012, 10:10 PM
Ok so the smoking has ceased aside from the normal 2 stroke smoke. It also quit grinding when downshifting, which turned out to be the chain jumping the cog. I replaced all of that and it is god to go now. I need to source an air cleaner and the carb needs adjusting. It seems to want to idle too low and die. Its little things at this point but I am looking forward to finally getting out and riding it! Here are a few crappy cell phone pictures of it. http://i602.photobucket.com/albums/tt109/jeephemi/3hheeler.jpg
http://i602.photobucket.com/albums/tt109/jeephemi/3wheeler2.jpghttp://i602.photobucket.com/albums/tt109/jeephemi/3wheeler1.jpg

jb2wheels
11-05-2012, 10:18 PM
Nice - worth all the effort!

jedster
11-05-2012, 10:57 PM
mined if i ask where you got em tires at? i might get a pair:wondering

SixFourStroker
11-05-2012, 11:08 PM
I got them at the local tire shop. They are identical to the originals. I think they were $60 a piece.

jedster
11-06-2012, 12:15 AM
sweet i like the look of yours it seems to be in great shape:w00t:

old-yellow
11-06-2012, 12:28 PM
looks good, i am glad to hear that its running good. here's a link to a manual for tuning the carb.http://www.oscarmayer.net/atc/manuals/

guitarist93
12-15-2012, 01:39 AM
So after you got the new reeds you were able to get it started? I'm having similar problems to what you had.