1980 yz125 help?

Yamaha YZ125 1980

10 replies to this topic
  • 1980Yz125

Posted March 17, 2013 - 04:55 PM


im new to the forum and if im posting in the wrong section, them in sorry, but i need help. i bought a 1980 yz125 about a 3 ago. it is dumping gas out the carb and will not start at all it pops every 5 or 7 kicks but just wont go. The reeds are good and i got a rebuild kit and i re adjusted the float, but it still dumps gas out the overflow like crazy. should i just buy a new carb or keep driving myself insane trying to get the float right. Also i did a compression test on the bike and its at around 120psi. How much more time do you guys think i have left on the top end, if any? Any help would be greatly appreciated, because I've been stumped for 3 weeks and i really want to ride the bike.

  • arnego2

Posted March 17, 2013 - 10:09 PM


with 120 psi you have no time left on the top end IMO. In regards to the carb just adjust the float.

  • ickfinger

Posted March 18, 2013 - 07:59 AM


Have you tried bump starting it?

  • souliog

Posted March 18, 2013 - 08:19 AM


Float height could be fine. Probablly needs a new float needle and seat. Parts 35. 24X-14107-33-00 and 36. 239-14195-00-00

Attached Thumbnails

  • 1980_yz125_1.JPG

  • Jeekinz

Posted March 18, 2013 - 08:22 AM


Sometimes you can get a little extra life out of the float needles by turning the point in some fine 400+ grit sandpaper. Just enough to clean it up a bit.

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  • 1980Yz125

Posted March 18, 2013 - 12:24 PM


i already got a carb rebuild kit for it, but the kit didn't come with the float. i tried adjusting it and i test it and it works fine, then when i put it on the bike it dumps fuel like crazy. and im still deciding whether or not to actually do topend on the bike. this is my first 2 stroke bike so im not sure. so should i just keep playing with the float until it works? like i said the bike will pop and if i dont turn the gas on all the way it wont dump. and my friend did bump start it, but it only stayed running, only half throttle for 10 seconds and just died

  • Jeekinz

Posted March 18, 2013 - 01:30 PM


If the float level is set properly but fuel still leaks out, the needle is bad. Look real close at the tip of it, you might see a tiny ring from wear. Magnifying glass helps. That's what you (carefully) need to polish out with the fine sandpaper. If you can't get it to stop you need to order a new set.


A bike that old you need to fix all that little stuff.

Edited by Jeekinz, March 18, 2013 - 01:31 PM.

  • 1980Yz125

Posted March 18, 2013 - 02:31 PM


thanks man ill see if that works. and do you think 120psi is low for that bike? i cant find specs anywhere and like i said im debating on doing a rebuild because that could possibly be half my issue. right?

  • Jeekinz

Posted March 19, 2013 - 04:57 AM


I just found this in 2 seconds using Google: http://projectyz.jfn...vice-Manual.pdf

Here's the site it's from, the guy restored one of those: http://projectyz.jfn3.com/manuals/

You'll get more help with that bike on the Old School forums at VitalMX. Was that the one for sale on Craigslist back in January or so?

Edited by Jeekinz, March 19, 2013 - 04:58 AM.

  • nicko-31

Posted March 19, 2013 - 09:48 AM


I liked the 1980 model more than both the 1981 and 1982 model.Super clean and light.

  • 1980Yz125

Posted March 19, 2013 - 12:43 PM


yes it was the one with the black paint and stuff about a month ago. it really isnt as bad as it looked in those pictures. the plastics are actually decent and he had the whole headlight assembly for the bike so it was a kind of good deal. at first i was going to part it out but its a really cool, rare mx bike and its probably worth saving Also thanks again for showing me the manuals :thumbsup:

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