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engine cutting out

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I just did a top end on my 07 450 and rode for the first time after break in yesterday. I was trail riding yesterday and everytime i went through a real rocky section or whooped out section my bike would start to bog and then shut off, if i pulled in the clutch and revved it wouldn't shut off sometimes. Im thinking its a problem with jetting but im not sure any help would be appreciated. thanks

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Push down the spark plug cap harder.

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the spark plug cap is all the way on i even put a new plug in it half way through the day on saturday which didnt help. I think im gona buy the merge adjustable leak jet and hope that helps.

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Did you go from OEM to a high comp. piston? Not sure if I'm right , but maybe that would require some jetting changes?

Otherwise like MXJOSH stated a new piston should not make the bike run bad if it was running fine before. If my jetting theory is off then I guess you probably did not put it all back together correctly.

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yes the timing is correct and its stock compression. Its fine everywhere except when im going fast through a real rocky section.

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Did you check float height?Also you should check all electrical connections?(make sure they are not coming undone slightly when ride rough)

Hope this helps

Ernie

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i was thinking it had to do with float hieght or the pilot jet. I'm gona work on it on friday when i get back home.

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So it only plays up on real bumpy sections?

How about on/off throttle or does it still cut out holding the throttle steady?

You must ask yourself what could have changed. If you did not change the jets then the only way the air fuel mix will be wrong is some result due to improper carb storage or re-installation.

eg. air leak, some crud went down the fuel line into the carb, hot starter plunger freeplay (held open), throttle posn sensor plug, fuel line routing.

Did you disconnect any of the electrical wires or coil pack when you had the cylinder off?

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Numroe is on the right track. Air leak

Check your carb connections to your air boots. Either you didn't tighten them securely or they are not seated right.

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alright that makes sense. If im on and off the throttle or if the throttle is held constant, i figured it was my fault at first and started hitting the rocky sections with a little more throttle but it continued. I didnt have anything elctrical disconnected during rebuild.

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no i dont and i have my tank insulated so i dont think thats the problem

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My bike was doing that everytime I would land from a jump. I noticed the fuel was boiling inside my gas tank. Do you hear hissing coming from the gas cap hose?
High altitude things are so different and interesting to me, but I don't see how he changes his piston and that suddenly makes his fuel boil.

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High altitude things are so different and interesting to me, but I don't see how he changes his piston and that suddenly makes his fuel boil.

At high altitude everything boils faster. But if it didn´t do it before it´s not because of that.

At the top of Everest water boils at like 88 degrees C, versus sea level where it boils at 100 degrees. So boiled eggs is not for breakfast at the peak...:)

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High altitude things are so different and interesting to me, but I don't see how he changes his piston and that suddenly makes his fuel boil.

Breaking in a new top-end can make a motor run hotter.

A hot motor would make the fuel boil.

Boiling fuel could cause vapor lock.

Wish I could help you out better buddie.

Might try spraying some starting fluid around the carb (not into) while the bike is running, and listen for a high rev caused from a air leak.

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Well i had the bike apart this weekend could see any bad connections or air leaks. Cleaned out the carb and that didn't help. I had to go back to school so i dropped it off at my friends house who is a motorcycle mechanic teacher so im hoping he can figure it out while im gone. Ill let everyone know whats wrong with it when i hear from him. maybe i shouldn't have done the top end it was still running good not smoking at all before this but i figured 160 hours wa getting up there. haha

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Hey man don't be hard on yourself, it was a good decision to do that top end.

It'll all work out; just may take a minute! Peace out man keep us informed...cool?

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