Help with Athena big bore on YZ450

TX920
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TX920
Edited Date/Time 6/16/2014 8:57am
I have an 06 YZ450, with with a Athena 478 kit installed, everything else on the bike is stock. I cant find any jetting suggestions anywhere(including the Athena website.) She seems to be running very lean, doesn't like to start, or idle, and the head pipe glows bright red, worse then it ever did stock and more so then any 4 stroke I've owned before it... and of course it pops bad on deceleration. On the plus side when on the throttle it runs like a spotted ape! Does anyone have this setup, or have any ideas where to go with it? Oh and I run mostly pump gas, and do all my riding in North to North East Texas... so roughly at sea level in hot as hell conditions...
Thanks
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Anthony Siracuse 6/15/2014 12:06pm
6/15/2014 12:06pm
Not trying to be a smart ass but have you tried to call Athena?
TX920
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TX920 6/15/2014 12:14pm
6/15/2014 12:14pm
I emailed them. I got a reply from a real nice fella that speaks awesome Italian, but not so good English, and he told me that unfortunately there are no standard settings... and kinda wished me good luck, at least that's what I think he said at the end... lol
Paw Paw 271
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Paw Paw 271 6/15/2014 12:32pm
6/15/2014 12:32pm
Have you considered....
1. A plugged pilot jet...
2. A leaking exhaust pipe gasket where it mounts to the head.
3. Fuel screw adjustment.

All of these will create a lean condition and cause popping plus making it hard to start.

Also do a chop test to get a plug reading.

Paw Paw
TX920
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TX920 6/15/2014 1:57pm
6/15/2014 1:57pm
Thanks Paw Paw. Any suggestions on where the fuel screw should be adjusted at? Lastly I do know that the exhaust gasket is bad (didnt know it would effect it like this) does the one going from the header into the slip on make a difference as well?

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Paw Paw 271
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Paw Paw 271 6/15/2014 2:06pm
6/15/2014 2:06pm Edited Date/Time 6/15/2014 2:09pm
No, only that one gasket will cause issues. A cracked header pipe will do the same thing.
The fuel screw is located under the front of the fuel bowl on the carb. It is in a recessed hole. It should be about 2 turns out from lightly seated. Then the more you turn it out the richer it will be and the more you turn it in the leaner it will be. This effects the entire range of throttle. It needs to be adjusted daily.
It takes a very short thin bladed flat screw driver to adjust it.
You can access the pilot jet through the fuel bowl drain to remove it and clean it. There are three jets there you can get to. The pilot jet, the starter jet and the main jet.
See items # 23 for the fuel screw.
http://www.bikebandit.com/2006-yamaha-yz450f-50th-anniversary-edition-y…

Also ....Have you checked the valve clearances?

Paw Paw
Anthony Siracuse 6/15/2014 2:36pm
6/15/2014 2:36pm
That's real unfortunate man. You have any good garage mechanics or ships near you?
partialperson
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partialperson 6/15/2014 7:23pm
6/15/2014 7:23pm Edited Date/Time 6/15/2014 7:24pm
All symptoms are of a lean pilot circuit. Richen that baby up 2 sizes and try your luck, I'd bet it will start on a half kick and the decel pop and glowing pipe disappear, you wont even have to use the choke
racer369
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racer369 6/16/2014 8:57am
6/16/2014 8:57am
Had same setup. here is what I used 48 pilot,172 main, Yamaha 5TA149165206 needle. hope this helps

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