2005 sewing machine then dead

2005 YZ450F


Bought new, then night of purchase owner was in car accident destroying hip. Owner kept in condition garage for 8yrs without starting. Consigned to local shop


I purchased spring of last year. Shop got it running, I took it out, then the fun began 
1st ride: blew the fork seals.
2nd ride: float Jet refused to allow fuel passage (replaced with new, carb cleaned) 
3rd ride: fork seals blew again. Replaced seals AND bushings this time, carb running rough, Installed JD jet kit

4th-20th: ride no issues (one year)

21st ride: in June multiple (running/idling) stops waiting on much slower riders. Noticed water pump seal leakage as well as rough idle. Immediately decided to head back to the truck Finally died, WOULD NOT restart. Acted like it did back on the 2nd ride where fuel wasn't getting to carb. Checked the plug....had spark upon kick, filter was fine so had to be fuel. FINALLY fired and ran like hammered ass for 5 min then bog/stop Would not kick over. Kicked till I couldn't kick no more. Buddy kicked for 5 min till started. Ran like ass. Bogged down low, could only function mid-wide open for moments before bogged and died (when it dipped into the 1/8th throttle range).

FINALLY back to the truck, replaced spark plug, no difference. Got it home and cleaned all the jets, installed new float jet with spring. Starts great (JD t-handle MUST be 3 turns out though or backfires and wont start) runs for 30-40 seconds like a sewing machine, then starts skipping, pop, DEAD. Won't restart despite near heart attack kicking. Wait a few hours then once again:  runs for 30-40 seconds like a sewing machine, then starts skipping, pop, DEAD.This has occurred multiple times.With doing the following each time:
Remove carb

Remove jets, blow out jets with compressed air

Adjust float tab gradually from one extreme to the other

Each time I disassemble, clean, and reassemble then test. Each time: runs for 30-40 seconds like a sewing machine, then starts skipping, pop, DEAD. Choke will aid for a few seconds, then behaves the same way with choke. Decompression level same results.

Bike is all stock except JD jet kit and ran fine for at LEAST 15 rides on this exact set-up without any incident or carb issues. NOW...all of a sudden it gets hot on one ride and now I can't keep it idling or running down low at all. It will run like a raped ape if I can get it past 1/8th throttle and KEEP it there, but the second I drop below 1/8th it bogs, shuts down and refuses to start back.


Guys I'm at my wits end here. Please help! 

Do you have a fuel filter on it? Old gas can leave residue in the tank that might keep making its way down to your pilot jet. I had a similar issue with a kx125. I solved it by adding an in-line filter. Also, how is your valve clearance?

Edited by atf8611

Do you have a fuel filter on it? 



Do you have a fuel filter on it? 



I do NOW. Before it started giving me grief I did NOT. 

I DO need to check the valves

I've been recently having carb issues with my bike, if you think you've got everything dialed in on the carb side I would definitely check your valves. Thats what I'm going to do.

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