Need diagnostic help please! - Yamaha ATV Forum
 
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post #1 of 3 Old 04-28-2019, 03:42 PM Thread Starter
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Need diagnostic help please!

Hi guys. Can you help me diagnose this issue? I have a 2012YFZ450 carb model. It is a hard start, idles fine, can rev cleanly in neutral, but it is very rough and choppy under power and lacks power. I believe it is electrical. Has anyone had a similar problem and any ideas?
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post #2 of 3 Old 04-29-2019, 09:34 AM
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Garage
the first thing to check is the valve clearance.
electrical is not out of the question but normally electrical either works or does not. however there are some things to check.
if you still have the parking brake unplug the wires that go to it, as that switch fails it can cause similar symptoms. if that fixes the issue just leave it unplugged you dont need it. it is a rev limiter to keep you from driving with the brake on
check the 2 small wires going to the coil pack (possibly orange and blue but not positive) i had one break right at the plug and cause intermittent spark with similar symptoms. it took me 2 years to find and a lot of money
you can test everything electrical but the cdi with an ohm meter and a manual. (i see in you next post you are asking about cdis, probably not your issue and definitely dont order one until you have made a proper diagnosis )
my guess is you need a carb rebuild. tell me how the symptoms started from the last time the machine ran correctly. the carb model yfz is my specialty so i will be able to get you fixed up. if you dont have a manual order the clymer paper manual you are going to need it to properly diagnosis your machine. trust me it will pay for its self.
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post #3 of 3 Old 05-02-2019, 01:31 AM
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Join Date: Dec 2016
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Clean the carburetor first....

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Originally Posted by perplxxd View Post
Hi guys. Can you help me diagnose this issue? I have a 2012YFZ450 carb model. It is a hard start, idles fine, can rev cleanly in neutral, but it is very rough and choppy under power and lacks power. I believe it is electrical. Has anyone had a similar problem and any ideas?

Carburetor cleaning. Quick and fairly easy. You will need carb cleaner, compressed air is also very helpful and a tiny strand of wire to poke the and clean the tiny holes.


Part I



Part II



Part III



It is a good idea to clean the carb if the motorcycle has been sitting unused for awhile and clogging caused the motor to run lean which is hot and hot is bad.
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