need help quad wont run right (video)

[mpblaster287]

so i picked up another 450 i wanna set up for XC but i cant get it to run right. it will idle but as soon as i give it gas it fall on its face and wants to shut off. harness was hacked so i replaced it checked cdi and everything. checked jetting and even swapped carbs...oil is dirty but no large shavings of metal or anything. valves were set to spec...intakes were tight and exhausts were a little loose. im puzzled

http://s90.photobucket.com/albums/k276/mpsoccer287/?action=view&current=041-8.mp4

[DnB_racing]

that's a tough one!!
what year is it?

as long as your sure the replacement carb is clean, and jetted close and you have good gas, then you can rule out the carb, i see the filter is new, make sure you dont have any air leaks in the intake

have you checked starting compression?or even better a pressure leak test? this will eliminate any head gasket or top end problems,

also you could have a bad stator, I have seen them do this,they will run fine at slow rpms and fail at the higher

have you verified that the harness and all wires are run properly and insulation is not worn or shorting out

[chronicsmoke]

when this happened to me, I found that my intake boot was starting to seperate from the airbox.. I chased dirty jets for 2 days before I figured it out..

Worth a shot?

[mpblaster287]

thanks guys

the other carb was from my other quad which runs fine. i just put stock jetting in it. the whole harness was replaced with one from a running quad. i have another airbox ill throw on and check compression.



one more thing...if i have the choke on it will kick back really hard on the kick start when trying to start. its an 05 btw thanks again

[chronicsmoke]

Have you tried spraying ether around the intake boot?

Make sure it's not your top end, and work from there.

The only reason I found where the intake boot was not sealed to the airbox was because when I went to put the carb back in, i yanked on the boot, and it raised up about 3". It's a b*tch to get it back in with the airbox/fenders still attached, but it was managable..

Let us know what happens!

[mpblaster287]

could it be a bent valve? i tried spraying the intake boot with starting fluid and its not that...checked timing it seems to be right on.

it ran better all around when i got it, but still not right at all. it cut out on top and had a nasty bog on the bottom. after i set the valves it will only idle pretty much as seen in the video and its kinda hard to start. give it a shot of starting fluid in the filter and it will fire right up tho.