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i cant fart
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10,917 Posts
Discussion Starter · #1 ·
just got running this morning, rode it for a few mins after work. not really all that hard, i hear a loud pop out the exhaust and it stopped. and wont start. what did i mess up? or did i blow it up completely? im super mad at myself, shoulda taken it easy on it.

any help appreciated
 

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i cant fart
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10,917 Posts
Discussion Starter · #5 ·
Turns over when i kick it but no fire. No engine noise, just out the exhaust. No leaking fuel

Sent from Motorcycle.com Free App
 

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ShamanFighter
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22,340 Posts
check valves. pull plug see if piston moves up n down. check cam chain. those things are super easy to work on. so if its a rebuild its cake
 

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ShamanFighter
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22,340 Posts
also check the cdi box with theold to see if the old gets spark. maybe the chain skipped a tooth and jumped timing
 

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sickboy
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3,544 Posts
with a big pop like that my guess is the valves are out of spec, was it hard to start when u got it running? you could try n push start it. When valves get tight it is very hard to kick start but should fire up when you push start it.
 

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i cant fart
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10,917 Posts
Discussion Starter · #12 ·
with a big pop like that my guess is the valves are out of spec, was it hard to start when u got it running? you could try n push start it. When valves get tight it is very hard to kick start but should fire up when you push start it.
wasnt hard to start at all, carb needed a cleaning so i had to choke it but one kick and it would start.

how would i push start this thing? :confused: no clutch
 

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UnicycleMode
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7,584 Posts
I would surely pull the plug and check if you still have an intake valve in there. Might be bent if the spring started to collapse a bit, but that would be a hell of a unique failure on one.

I've heard of cam chain tensioners breaking in them too, much more common to come out of spec and the pop you hear is the intake valve not closing all the way before TDC allowing the fuel in the intake tract to detonate with a pretty good amount of noise.




You can literally bend those little XR valves by hand once they get tweaked a little, so once they are done, they are done. Might want to pull the valve cover and then the head, the two gaskets for the job are less than $20 together. A whole gasket kit for the engine can be had for pretty cheap too. I've gotta rebuild my XR75 some time, no clue why I keep putting it off, it's really easy.
 

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Registered
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4,653 Posts
Why fix it when you can buy a new one lol. I used to have a ttr125 when I was kid I thought I was the coolest fucking kid in town.....until my buddy got a cr85 big wheel
 
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