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Old 10-16-2012, 08:49 AM   #1
Padriug OP
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Joined: Mar 2010
Location: AZO, MI
Oddometer: 345
1980 Yamaha yz80

Picked up a 1980 Yamaha yz80 for cheap, PO mentioned bike was dumped then would not start/run and was put away for approx. 2yrs. I cleaned out the mice nest from the airbox, carb was somewhat rebuilt and tank was cleaned. It was dropped on the left side, so the shift lever is slightly bent and the clutch cable perch (I think) was a little bent. I put a new plug in it and tried to bump start it with no success. What's odd is when trying to kick start in neutral, the bike will go into gear. Any ideas on where to start to get it started/running? Thanks.
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Old 03-28-2014, 08:58 AM   #2
Padriug OP
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Joined: Mar 2010
Location: AZO, MI
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Okay, so I replaced the ignition system and now have spark. However, bike will still not start. I'm going to try bump starting this weekend. Any other areas I should be looking at? What's typical for compression specs on a yz80? Thanks any and all!
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Old 03-28-2014, 11:55 AM   #3
chaddhamilton
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Location: Charleston, SC
Oddometer: 200
Quote:
Originally Posted by Padriug View Post
Okay, so I replaced the ignition system and now have spark. However, bike will still not start. I'm going to try bump starting this weekend. Any other areas I should be looking at? What's typical for compression specs on a yz80? Thanks any and all!
You should have about 170 psi. I'm not a master 2 stroke mechanic, but I have owned a few and been in the same situation. I'd take the carb off and clean it first thing. Then make sure I am getting gas to it. Open the bowl drain screw and see if gas flows out. After you have verified a clean carb with fuel to the bowl, and no luck starting, try a quick shot of carb cleaner to the carb intake and see if she fires off that. Don't keep spraying if she lights up. If she does start here, then I'm guessong old gas? That's a fun bike.
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Old 03-28-2014, 12:07 PM   #4
Padriug OP
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Joined: Mar 2010
Location: AZO, MI
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Chad,

Thanks for the info. I did clean the carb awhile back, looks like I should try again. I know it gets gas to the carb, and I've read the spark will not appear as bright as a car spark plug. If compression is low, new rings or rebuild upper end? Thanks again!

Padriug
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Old 03-29-2014, 10:48 AM   #5
welder
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Joined: Feb 2008
Location: paradise
Oddometer: 1,520
Subscribed! 1980 yz 80 was my first bike! I have a very soft spot in my heart for that bike. A real jump in performance from the previous years. I used to waste my buddy on his 77 yz80 on a regular basis. Then he bought an 81 yz80 and could edge me in a drag race by a bike length. Anyway, on any old 2 smoke a leak down test is required to determine the condition of the crank seals. This is imperative to the bike running well. without good crank seals the bike will run lean by sucking in air through the seals and seize. next you want to make sure you have good compression , may need a fresh top end, don't forget to check the rod for up and down play while you have the top end off! Best case scenario is the seals are in good shape and the compression is good. Then you should have to just clean the carb. Make sure when cleaning the carb to get into all the small passages with compressed air using a air chuck with a rubber tip(very important). check the timing , use fresh gas, change out the crankcase oil with a good synthetic 2 stroke tranny oil. should be good to go after that. http://www.youtube.com/watch?v=Ii5K0vbOoSEThose little 2 stroke 80's are a blast to ride. A very quick little bike for sure. pls. post some pics!!!Good luck. cheers, Fergie.
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welder screwed with this post 03-29-2014 at 11:04 AM
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Old 04-01-2014, 10:41 AM   #6
Padriug OP
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Thanks all! I'll report back when I have some more information.
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