is this fuel screw stripped or broke off!

Ok, so I have had this 06 kx450f for about a month and it suffers from the normal hanging idle and off idle bog. I was planning to do the o-ring mod and adjust the fuel screw.

As I was taking the carb off to do the o-ring mod, I noticed the air/fuel screw was missing. Then I shined a light into the hole and found this.

SAM_1120.jpg

Apparently the guy i bought it from had either stripped the hole or broke the screw off. can you tell me if thats the screw or if its just stripped out and give me a possible way to fix this?

The piece with the arrow pointing to it goes up and when i push it like a spring. that is why i think the screw is broke off.

SAM_2.jpg

Ok, so I have had this 06 kx450f for about a month and it suffers from the normal hanging idle and off idle bog. I was planning to do the o-ring mod and adjust the fuel screw.

As I was taking the carb off to do the o-ring mod, I noticed the air/fuel screw was missing. Then I shined a light into the hole and found this.

SAM_1120.jpg

Apparently the guy i bought it from had either stripped the hole or broke the screw off. can you tell me if thats the screw or if its just stripped out and give me a possible way to fix this?

The piece with the arrow pointing to it goes up and when i push it like a spring. that is why i think the screw is broke off.

SAM_2.jpg

Is that view with the float bowl cover already off?

Should look like this with it still on:

float-drain-bolt-2.jpg

IMAG0198.jpg

it was with the bowl off. i figured it out though, it was the screw broke off. i managed to get it out but slightly damaged the top threads. im going to try and tap it then put in a new screw. i think the tap size is M6 x .50?

Amazes me how some people find ways to butcher things like that screw. I mean the previous owner. What I'd be more worried about was how good he was with air filter and oil changes and oil filters too. These motors are so tough with just some basic care. But without that care the situation is grim.

The hanging idle could be fixed as easily as installing a new 42 pilot jet. But for sure the fuel screw and hotstart circuits need to be working properly.

The bogging issue is not fixed in this carb by an AP o-ring mod. If the AP works properly, the pump timing is immediate and perfect duration. Properly working means put a new AP diaphragm in there and ensure the AP rod is clean and lubed. Also ensure you have a 55 leak jet, and then adjust the AP screw as described here http://www.thumpertalk.com/forum/showthread.php?t=956041

numroe, well I already took the carb apart cleaned it and oil it. Then cleaned the hotstart plunger which was pretty dirty and adjusted it because it was set to tight. The hanging idle seems to be gone but I didn't get to ride it much yet so we will see. I did do the o-ring mod (it already had a 55 leak jet) because I couldn't find a thread about setting the apump timing and it did help the bog. But now that you gave me the thread I will remove the o-ring and adjust the timing.

The previous did give me the paperwork showing me it had a new cam chain, top end. the air filter was clean and the oil was pretty new. although the fact that they failed to do simple chain maintenance makes me nervous. Apparently they broke the chain and it put a small hole in the ignition cover and broke one of the chain guard mounts. I found this out while I was installing new chain and sprockets.

That's what you get when you buy used bikes, other peoples mess. Thanks so much for your help. Would you happen to know the thread pitch of the fuel screw?

No, I dont know the thread pitch of the fuel screw. You'll have to buy one and measure it up. Try TT, RMATV or Motosport.com

That's a worry if someone can ride on a powerful dirt bike until the chain snaps. Maybe he only did low speed stuff, but if the guy cared so little about his physical safety, then I guess the bike care came in a distant second. But you might be fine. The motor is tough. Beware the stock piston is a risk in your bike.

I've done 295 hrs on my 06, at medium pace and I try to use the middle revs. Original bottom end. 3rd piston, and 2nd set of OEM valves and timing chain. 2nd clutch basket. No signs of any bearing damage yet. Big end runout gap is fine. I use Shell or Delo 400 diesel oil with a K&P SS oil filter. Twin air filters and NoToil filter fluid. I like the KX450 motor. If I did 300 hrs on a 2 stroke with the equivalent output demands on the engine I'm sure I'd be spending more $ on a 2 stroke. The engine on these bikes is the easy part, IF the basic maintenance is done.

If you want your 06 to handle much better than stock then consider:

  • Suspension revalve (both ends were terrible stock on the 06).
  • 08 rear linkage (the whole thing).
  • 08 front end mount (do it yourself for a few bucks).
  • Thin down your cylinder hanger mounts (09 style). For even more flex.
  • 22mm triple clamps. Let you lay it over much more easily.
  • Tires to match your dirt. When the front is vague it really suxs.
  • Basic setup: springs, fork height, sag and clickers. Makes a massive difference. The KX450 (any year) is for some reason overly sensitive to the sag adjustment.

I usually don't keep something very long but i think i may keep this bike. I just sold my 98 cr250 yesterday so this bike is a huge improvement on the handling. lol. I am a little short on cash being a college student and i haven't had much time to spend setting the bike up for me because i live an hour away from it. I will however be moving back home for the summer and will have some extra cash to put into it. I have been reading many threads and am planning to do all the adjustments and mods you mentioned. I don't need springs however because the stock ones are for a 185 lb rider and that's exactly what I am, so at least that's a little money saved. I would love for it to not push me through the corners, that is also partially due to the hanging idle problem. Went into a briar patch once because of it.

Here it is by the way. i don't really like the black, more into the green. but cosmetics is low on my list of parts.

2006 KX450f

IMAG0089.jpg

and the 98 cr250 i just sold. Looks a lot better than when I bought it. It was my first bike. I have always been a quad guy, but now I would rather be on a bike.

IMAG0096.jpg

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