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cybordolphin

YZ450 owners.... need some help

9 posts in this topic

I have a YZ450 and it was sitting for a few years. Cleaned carb., but bike seems to only want to run with choke open. Also bogs at differing rpms.

Figure its running rich. So removed air cleaner and it helped (not riding just idling in garage). I will remove the carburetor and work on that again.

BUT.... I noticed after running the bike for a little while, that a small amount of fluid was dripping from the front of the head. I found a rubber plug that looks like it popped out from the head?? There is a small amount of anti freeze dripping from where the plug was. My question... is what is the small black rubber plug on the right side of the head, and is there anything that goes in behind this plug that may have come out with it, that I should be looking for?

Any help is appreciated.

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Found a small thread online regarding this rubber plug. I was worried it was an indication that too much pressure was building up in the case/head. Apparently this is a common problem with this rubber plug popping out and there are aftermarket threaded plugs that can be installed in its place?

Can anyone confirm?

Thanks

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Buy a new pilot jet, do not waste the time or effort cleaning the old one. Be sure to reset the fuel screw according to the proper procedure.

The plug is the decomp block off. Common issue.

I am moving this thread to the YZ450 forum, A search there will provide you with many threads about the decomp and solutions.

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I have a YZ450 and it was sitting for a few years. Cleaned carb., but bike seems to only want to run with choke open. Also bogs at differing rpms.

Figure its running rich. So removed air cleaner and it helped (not riding just idling in garage). I will remove the carburetor and work on that again.

BUT.... I noticed after running the bike for a little while, that a small amount of fluid was dripping from the front of the head. I found a rubber plug that looks like it popped out from the head?? There is a small amount of anti freeze dripping from where the plug was. My question... is what is the small black rubber plug on the right side of the head, and is there anything that goes in behind this plug that may have come out with it, that I should be looking for?

Any help is appreciated.

Found a small thread online regarding this rubber plug. I was worried it was an indication that too much pressure was building up in the case/head. Apparently this is a common problem with this rubber plug popping out and there are aftermarket threaded plugs that can be installed in its place?

Can anyone confirm?

Thanks

It's oil, not antifreeze.

http://www.thumpertalk.com/forum/showthread.php?p=1522419#post1522419

http://www.thumpertalk.com/forum/showthread.php?t=957016

As to your carb problem, using the choke makes the engine run richer. If it will only run when made richer by the choke, why would you suspect the problem is in being too rich?

Clean the pilot jet and verify that there is a healthy O-ring on the fuel screw:

http://www.thumpertalk.com/forum/showthread.php?p=8021726#post8021726

http://www.thumperfaq.com/jetting.htm#PJ

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I am having the same issues as the below post from another forum.

Bike is a Yamaha yz450.

http://www.allthingsmoto.com/forums/f-20/yz-450-hard-starting-backfiring-47992/#post598105

I have cleaned the carb. Jetting is stock. Bike sat for 2 years. Fresh gas in tank. Removed air cleaner to see if motor was starving for air.

Runs with choke on... but as soon as the choke is off.... motor backfires and eventually stalls.

Bike ran great before sitting 2 years.

Any thoughts are appreciated. I checked the other forum..... but unfortunately the other poster..... never responded what was causing the problem.

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i'll say it again, replace pilot(idle) jet! the internal passages are too small to clean, spray all the carb cleaner you want it will still be plugged.

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I answered the question already, and gave you some links to follow. The answer hasn't changed.

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Ok.... got it. Bike is now running PERFECT! Thanks for all the help. I moved up to 8500 ft elevation and that was messing me up.

Anyway the links helped me out and did exactly as directed and obtained perfect results.

Huge smile :ride:

Again.... a BIG thanks. Your site is awsome.

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