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05 YZF450 won't idle

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I guess I'll post this in here since I think the Yamaha guys have either forsaken the carb guys or maybe all sold out to Katooms  :banghead:

 

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.

 

Today I replaced ALL the rubber in the carb, and the connector to the engine, reassembled and same thing. This time, after it dies, as I'm kicking it over and over it will backfire without starting so loud it sounds like a .22 has been shot. 



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.

 

Bike has run for 21 hours without a single issue...until now

 

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

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Set tje floats to the factory setting and leave it alone. Once set, they nearly never go out of adjustment.

 

You need to check for obstructions in the flow from the tank to the float bowl.

With the fuel line disconnected from the carb, and stuck in a jar, open the petcock. Fuel should flow rapidly. Also confirm it is all fuel and no water.

Reattach fu8el line to the carb. Remove the 17mm cap on the bottom of the carb. Put your jar under it. Open the petcock. Fuel should readily flow, at the same rapid rate (albeit, splashy) through the bottom of the carb.

 

You should also confirm the AP is functioning corrrectly.

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AC is working

Did a draw down test on the bowl last night.....fuel doesn't move more than 1/8"

Checked the new spark plug gap: perfect

it DID run longer with 3 turns out on the pilot adjustment but then still leaned out after it got hot.

 

Should I go from a 45 to 48? 50? 

WHY would the pilot jet all of a sudden need to be increased? What am I missing here? nothing was done to the bike? Well, except it idled for long periods on the last trip it ran well on

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I would test your stator before going any farther

 

There is no reason to go larger than a 45 pilot

 

Have you cleared the passage above the pilot jet with fishing line and compressed cleaner?

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Changed fuel again. Cleaned jets and passages.

Ran for a little longer this time, about 2 minutes flawless....sprayed carb with starter fluid to test for vacuum leaks....no leaks. revved the throttle and upon the downward rev it popped and cracked like it's NEVER done before. died once it reached idle. Would NOT restart. Backfired while trying to kick
|

Again, NO CHANGES have been made in the last year before this happened

I will check the stator later today but given that it runs PERFECTLY and starts without any issue (the very first time) I'm not optimistic it's that (but thanks so much for suggesting it.....GOD I'm at the end of my rope so any NEW avenue is appreciated!)

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