450EXC jetting

[MrLuckey]

Originally posted by geremacheks
So far, no need for quick access to the fuel screw. I'll try to keep mine stock, without any additions. Shouldn't be falling out then. :thumb:

I believe E-Ticket stated that the '03s used a different carb than the '02s and that the hole in the carb is large enough that the fuel screw can fall out if backed out far enough. The stock fuel screw on the '02 400SX could not. I have doubts that the addition of the fuel screw extension could have played much of a role in it vibrating/dropping out.

 

[E-Ticket]

Yup. But I think that this is a bike-to-bike problem... and is more related to far the fuel screw is backed out. If you ever have the fuel screw out, you'll notice that there is just not much a range on the threads - stock or otherwise

The next time I'm working on my bike, I'm going to add a second o-ring aroubd the fuel screw body and try to position it about the outer edge of the fuel bowl. Hopefully this will help hold/brace the fuel screw so that vibration can get it to back out/fall out.

Will try to report back when done. Cheers! - E-Ticket

 

[MCassle]

Well, since the bike was under warranty I took it back to the dealership where I had bought it. The dealer (supposedly -- not sure if I completely trust the slicks behind the counter) contacted KTM about this issue, and was told to replace the missing parts and reinstall. I had recovered the fuel screw, but the spring/washer/oring were missing.

Took a week to obtain the parts, dealer reinstalled and I picked up the bike. Figured instead of going through the trouble of planning on a day of riding (gearing up, driving, etc. lots of effort as the nearest riding area is about an hour & a half away) that I would terrorize my neighbors and run the bike up & down my street.

Not even 100 feet of riding and the fuel screw (from 1.5 turns out) fell out again. Load the bike up and take her back to the dealership. This time around my mode is pretty foul, and I'm not so mr. nice guy.

Dealer insists that they will replace the carb.

Turns out not so. Instead they reorder parts and use a different spring, this one is 1/16" longer for more tension on the fuel screw.

Another week goes by & I pick the bike up. This time I test ride the bike at the shop, and proceed to terrorize the locals in the dealer’s vicinity. Dealer had marked the fuel screw with a paint pen to see if it vibrates out at all. Turns out it didn't, and the hour meter showed that the dealer put .4 hours into testing the bike. Good enough for me, and I take my (new) bike home with only 2.7 hours on it.

The real test will come on my next real trail ride. Next week or two is the plan, I'll report back with the results & verdict. I still think they should have replaced the carb due to a reoccurring problem. I spent $8k on this bike, and I'll be real unhappy if I get stranded miles away from my vehicle.

Matt

 

[E-Ticket]

Best of luck, Matt... keep us informed!

By the way, did a 4-hour team race over rough ground -- and that didn't shake out or back out my Kouba extended fuel screw. So that was a pretty good test!

I'll reply as well on when I add the "supplemental o-ring."

Cheers! - RandyB

 

[MrLuckey]

Randy, just wondering if you added the second O-ring to your fuel screw yet. I rode for about 4 hours this past Friday and another 6 or so on Saturday. My fuel screw dropped out just before we got back to camp. It was about 1.5 turns out and I hadn't got around to putting safety wire or a zip tie on the extension yet. I plan on getting 2 complete fuel screws including the O-ring and spring and carrying a spare along with doing the zip tie or something similar. Trying to come up with a good idea that'd not only hang on to it but also keep it up inside to avoid losing spring and O-ring but dont have a good solution yet.

 

[geremacheks]

TTRGuy---So did it have the extension on it when it fell out? Or were you running it stock?

I don't have the extension, and I'm running it 2 1/2 to 2 3/4's out. What? Me worry? :eek:

 

[MrLuckey]

Neither really. It wasn't the stock fuel screw nor was it the press on extension, it was a longer (complete) fuel screw with the t-handle from koubalink. I am still trying to come up with something that'll hold it in place even if it tries to back itself out. Wide rubber band up over the carb? ;)

I guess the good news was that aside from not idling, popping on decel and a bit of 'crackling' when I got on it, she still ran fair. I don't know that I would have tried to do 2 more laps in a HS but it wasn't going to leave me stranded either.

FYI This is on my 02 400SX

 

[E-Ticket]

Hey TTRGuy,

Nope, not yet. But I am doing the China Hat ISDE this weekend - and if I don't get the "secondary-holding" o-ring in place.... I think I might try your rubberband trick!

Will reply back with what I do... and what happens. Cheers! - RandyB

 

[MrLuckey]

I am actually thinking about a longer spring and/or 1 or 2 wraps of plumbing tape on the threads. I'd carefully trim the tape so its only on the threads but that seems (at least in my head) like it'd really help to keep the thing from vibrating out while still leaving it adjustable. What do you guys think?

 

[geremacheks]

Sounds like a good plan. The more you adjust, the more you may want to replace the tape. Should work.

 

[MrLuckey]

I was thinking the same thing about replacing the tape. So far I haven't been turning it much more than a 1/4-1/2 turn and once the temps get more stable I don't think I'll be adjusting much. Elevation changes around here are about non-existent too.

Anybody know if gas will hurt thread tape? I may throw a piece in a jar of gas if nobody knows for sure.

 

[MCassle]

Well, the verdict is in on my first real trail ride. Let me just say that the power of this bike is astonishing, as I was blasting through all sorts of trail trash with no problems. With the exception of an impossible hill climb, I didn't dump the bike all day (that's a major accomplishment for me ;) ) Just power out of bad situations it seemed like, and the thing just motored through whatever was giving me grief.

Fuel screw stayed put! :) I'm using a different needle and adjusted the fuel screw another 1/4 to 1/2 out from where the shop had it, so it should be around 2 turns out. Never moved, and I was hammering that bike with the biggest $hit faced grin I've had in a long long while ...

Other than the front fender brace nut & bolt vibrating out during the 55 miles I put on the bike last Saturday @ Clear Creek, nothing went wrong. Great day to ride, great bike to be riding on :)

I ordered a spare fuel screw kit anyway, just in case ... that'll be in the ol' fanny pack (along with the Space Blanket, ehem, John ;) )

Matt