what's wrong with my YZ450F??


17 replies to this topic
  • nightwhler

Posted January 03, 2006 - 01:55 PM

#1

I have a YZ450. My buddy and I decided to check the valving and carb since our season is basically over for the next few month here in Utah. The intake valve was to close so we put in 180's instead of the 185's it had in it. Then we went through the carb and found nothing. Cleaned it up and re-installed it. The main jet was a 42 and on the 4th clip. Now I'm getting a ton of popping and the exhaust pipe is getting extremely hot when running in idle. Before we messed with it, it didn't seem to run very well and would never start in gear.

Would adjusting the intake valve really have that much to do with the carb performance? My buddy is gonna try changing the jet and move the clip to see if that helps.

HELP!! We wanna head south soon to get some riding in if we can get this thing running properly.

Thanks in advance!

  • jimmyg

Posted January 03, 2006 - 02:09 PM

#2

if you took the carb apart check the engine side of the throttle slide there is a little plate on that side that is easy to put on upsidedown if its on right it will follow the contour of the bottom of the slide if its wrong you will see a point.ive seen alot of people make this mistake. :applause:

  • bikinnotdykin

Posted January 03, 2006 - 11:19 PM

#3

thanks we will check that out but I am pretty sure it's on the right way. we only adjusted the intake one shim incriment and it checked good with the feeler gauge so then we went through the carb and cleaned it out, no big deal. well we put it back together with a new plug and this thing is super lean. it had a 40 pilot well that is now at 48 and a 162 main which is now at 180 and the clip is on the 3rd from the bottom. finally the plug is getting a better color and the bike is running much better but it still seams a little lean by the popping and the plug color. I have never seen such a drastic channge in jetting needed at the same altitude after a valve adjust. anyone have an idea??? the seal on the header to muffler is good. could air be leaking in through the hot start plunger?? thanks guys
the bike is currently still a little lean but the settings are this:
pilot 48
main 180
fuel screw 1.5
needle clip 3 from bottom

  • bikinnotdykin

Posted January 03, 2006 - 11:23 PM

#4

here's a longer explanation from an earlier post http://www.thumperta...30&parentpage=4

  • bikinnotdykin

Posted January 04, 2006 - 12:03 AM

#5

ok I'll check tomorrow then kick myself when I find it wrong (I hope) thanks.

  • MotoGoalie

Posted January 04, 2006 - 08:13 AM

#6

thanks we will check that out but I am pretty sure it's on the right way. we only adjusted the intake one shim incriment and it checked good with the feeler gauge so then we went through the carb and cleaned it out, no big deal. well we put it back together with a new plug and this thing is super lean. it had a 40 pilot well that is now at 48 and a 162 main which is now at 180 and the clip is on the 3rd from the bottom. finally the plug is getting a better color and the bike is running much better but it still seams a little lean by the popping and the plug color. I have never seen such a drastic channge in jetting needed at the same altitude after a valve adjust. anyone have an idea??? the seal on the header to muffler is good. could air be leaking in through the hot start plunger?? thanks guys
the bike is currently still a little lean but the settings are this:
pilot 48
main 180
fuel screw 1.5
needle clip 3 from bottom


FOR 4000 FEET?

Your jetting is WAY too rich now bro. :applause: Only make one change at a time.

I live at 5700 feet. and I'm running 155, 38, #3, fs2 out.

I think you should try a 40 or 42pj, 162 or 165mj, #3 and make sure the exhaust doesn't have any air leaks in it.
and a new plug.

Right now the jetting you describe is way RICHER than anyone at sea level is running. :bonk:

  • bikinnotdykin

Posted January 04, 2006 - 01:46 PM

#7

yep the slide cover was on upsidedown. that thing is running great now, after of course I rejetted it. thanks TT you guys rock!!!

  • MotoGoalie

Posted January 04, 2006 - 01:56 PM

#8

yep the slide cover was on upsidedown. that thing is running great now, after of course I rejetted it. thanks TT you guys rock!!!


We have all done it. :applause:

say post your jetting specs in the sticky so you can help a fellow dude out.

  • grayracer513

Posted January 04, 2006 - 03:07 PM

#9

Not all of us. I learned from YOUR mistakes on this one. :applause:

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • MotoGoalie

Posted January 04, 2006 - 03:10 PM

#10

Not all of us. I learned from YOUR mistakes on this one. :applause:



Arent' you busy building wheels and handing people thier debating asses? :bonk:

  • Punisher660

Posted January 04, 2006 - 03:26 PM

#11

And what do you mean the season is over? Thats what the dunes are for, and I'm pretty sure bunker hill raceway is still open. Sandy terrain, with the wet cold it is perfect!

  • bikinnotdykin

Posted January 04, 2006 - 04:33 PM

#12

45 pilot 1.5 on fuel screw 165 main seems to run really good except when you give it a quick gas off idle when it isn't warm yet sometimes it'll die. maybe a little rich on the pilot but it's running good and when we go down south we may have to rejet anyway so I think I'll leave it for now. thanks again guys!!!

  • bikinnotdykin

Posted January 04, 2006 - 04:34 PM

#13

oh and the clip is on the 4th

  • falshh

Posted January 04, 2006 - 05:39 PM

#14

I'll admit that I did that on my 03 YZF250. I felt like a complete idiot, but I learned my lesson. 100 to 1, that's the cause. BTW, mine would only stay idling with the choke on. It took me about 5 tear downs and re-jets and cleanings before I talked to my buddy at the local Yamaha shop about it. He said that he's done it, but it only took him once to never make that mistake again. I'll agree with him, I know I'll never do that again. Lesson learned! It seams back wards, but the hole in the plate goes down. Here's a parts schematic if you need a visual reassurance.
OEM+%28Stock%29+Parts~dept_type_id~2~model_dept_year~2003~model_dept_mfr~Yamaha~model_dept_id~845675~model_dept_name~YZ450FR.asp#stay' class='bbc_url' title='External link' rel='nofollow external'>http://houseofmotorc...Z450FR.asp#stay

Hope this helps.


Great infor thanks for the input Ill have to remember this next time im in the carb.

Just curious I believe these carbs dont need internal maintenance?Is this correct It almost seem like the slide would need something (Lube it maybe?)

  • SureBlue

Posted January 04, 2006 - 05:52 PM

#15

Great infor thanks for the input Ill have to remember this next time im in the carb.

Just curious I believe these carbs dont need internal maintenance?Is this correct It almost seem like the slide would need something (Lube it maybe?)

The slide needs lubing just as much as the seat does.

  • bikinnotdykin

Posted January 04, 2006 - 06:13 PM

#16

sometimes I lube my seat, it causes less friction on the air moving over it = faster!!!!

  • SureBlue

Posted January 04, 2006 - 06:42 PM

#17

sometimes I lube my seat, it causes less friction on the air moving over it = faster!!!!

:applause:
I'm glad you got the carb issue fixed.

  • grayracer513

Posted January 04, 2006 - 10:12 PM

#18

The main reason to pull your slide would be to change needle or clip position on the needle. But a little squirt of WD40 on the slide wheels probably wouldn't hurt anything.

Note that it's unnecessary to remove the slide on an FCR to change the needle position, only the top cover and the needle retainer screw. As far as lubing the slide, that is mostly accomplished by gasoline anyway, and the FCR slide runs up and down on a set of 4 rollers to take the friction loading off of the slide. The only time you need "internal maintenance" is when the float level's wrong (needle/seat wear) or it gets dirty.

Arent' you busy building wheels...?

No takers on the wheel deal yet. :applause:





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