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Author Topic: 05 YZ250 jetting  (Read 11189 times)

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Offline conbread

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05 YZ250 jetting
« on: June 03, 2012, 04:10:40 AM »
hey guys im wondering what to try first.. my bike seems like it is running out of fuel sometimes, the only Power mods are procircut pipe and r302 silancer.. i just put them on and rode today, i run the bike on 100 octane and maxima 927.. The bike gets rode pretty hard and sometimes seems to get real (PEAKY) and then will come back down.. The bike was from another owner, i think the jets are stock but im going to pull it apart and look..

should i just up the main?

or up the pilot

or just drop the needle 1 clip??

i really wanted to just make 1 change... thanks for any help eric
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #1 on: June 03, 2012, 08:38:51 AM »
When I was considering doing the jetting on my 2001YZ250, cos it was just dicked, I got told by crncpala to mess around with the pilot air screw and throttle stop first.
This worked really well for me and before you go tearing down the carb I'd recommend you do the same. Turn your pilot air all the way in then out around 1, 1/2 or maybe even 2 turns. Kick the bike up and turn the throttle stop screw in and out until you make the bike idle at its slowest SMOOTH speed. Then adjust the pilot air screw in and out until you bring it back up until it idles as high as possible. Then use your throttle stop screw to lower it down to its slowest smooth speed again.

This helped me ALOT with my weird power delivery and loss of fuel/oil out the arse end of my bike.

Of course if you've already tried all this just disregard lol. Good luck to you
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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05 YZ250 jetting
« Reply #2 on: June 03, 2012, 02:41:18 PM »
I'd first do a compression test to get some kind of an idea what kind of shape the top end is in.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #3 on: June 04, 2012, 12:09:10 AM »
Sachs raises a good point (as usual). Peaky power then dropping back down may very well be a worn out piston. You said it gets ridden pretty hard so I'd look over those sort of things before messing around with your jetting.

good luck mate
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline cnrcpla

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05 YZ250 jetting
« Reply #4 on: June 04, 2012, 12:47:19 AM »
Yeah, do a compression check then check your jetting and air/fuel screw. See where your at after the compression test though, odds are if you ride it hard, depending on how many hours are on it, you may need to though some rings in it. How many hours since your last rebuild? I'm sure the guy you bought it off of said it just had a rebuild, but odds are it probably didn't.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline conbread

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05 YZ250 jetting
« Reply #5 on: June 04, 2012, 01:44:35 AM »
the bike was hardley ridden at all.. so clean and nice it was crazy.. it has tons of compression and is very crisp.. the track we was on yesterday was tight and was around 1/8 to 1/4 throttle in some spots and thats where it seemed to do it.. i have read about the 07 N3EW needle helping that out, anyone here made that switch??
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #6 on: June 04, 2012, 02:35:27 AM »
Well it is possible that you'll need to do a top end but if its bad at 1/8 and 1/4 like you said odds are its an issue with jetting. If the compression test checks out I'd take the cylinder head off and just check everything out to be sure. If that all checks out mess with the pilot air and throttle stop first. If all that fails then you're probably on the money with the jetting issues. The track you rode on the weekend when you said it was having issues, was that at a different elevation? I mean a substantially different elevation?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline conbread

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05 YZ250 jetting
« Reply #7 on: June 04, 2012, 12:13:45 PM »
it was at the same elavation just right up the road from the one we rode on saturday.. sunday was the first ride with the new pipe and sliancer.. Im going over today and ill make sure the air screw is 1 1/4 to 1 1/2 out and set the idle like you told me too..
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #8 on: June 05, 2012, 07:26:43 AM »
Yeah I'd try that first. It could very well be that the previous owner layered on the BS about the bike being "hardly ridden" and infact had 90 hours on the piston of hard riding you never know. So if that doesn't work or at bare minimum HELP then I would do a compression test. Maybe take a look at the piston just incase compression is fine but theres something else dicky. If that all seems fine, I'd move onto jetting.

The 1-1/2 turns out on the pilot air was suggested to me as a solution for my YZ250 Keihlin carb. It might be different on the RMs but it should let enough fuel and air in to give you a starting point.
Good luck I hope is an easy fix for you bro
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline conbread

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05 YZ250 jetting
« Reply #9 on: June 06, 2012, 03:25:50 AM »
so the air screw seemed to be around 2 to 2 1/4 out.. so i set it to 1 1/2....
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #10 on: June 06, 2012, 07:37:00 AM »
Like i said, its more than likely different for the RMs so don't quote me.
Quote from: Stusmoke on June 03, 2012, 03:38:51 PM
When I was considering doing the jetting on my 2001YZ250, cos it was just dicked, I got told by crncpala to mess around with the pilot air screw and throttle stop first.
This worked really well for me and before you go tearing down the carb I'd recommend you do the same. Turn your pilot air all the way in then out around 1, 1/2 or maybe even 2 turns. Kick the bike up and turn the throttle stop screw in and out until you make the bike idle at its slowest SMOOTH speed. Then adjust the pilot air screw in and out until you bring it back up until it idles as high as possible. Then use your throttle stop screw to lower it down to its slowest smooth speed again.

This helped me ALOT with my weird power delivery and loss of fuel/oil out the arse end of my bike.

Of course if you've already tried all this just disregard lol. Good luck to you

Remember to follow those steps after you've put the pilot air 1-1/2 turns out. I hope this works for you bro I can remember dreading having to screw with my jetting.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline conbread

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05 YZ250 jetting
« Reply #11 on: June 10, 2012, 01:32:42 AM »
ok so i went out to Wide open MX today, this is a fast sandy killer track.. I added the N3EW needle and the Bike loves it, she has tons of low to mid responce and wants to wheelie out of all the turns.. It never seemed to rev like it was running outta gas today.. i checked the plug a few times and it was always a pretty Tan color...

was running 100 octane and Maxima K2 high rpm mix... also while i had the carb off i seen the bike has carbon reeds in it..
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline conbread

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05 YZ250 jetting
« Reply #12 on: June 10, 2012, 01:50:53 AM »
heres a few pics with the new back grounds.




« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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05 YZ250 jetting
« Reply #13 on: June 10, 2012, 02:16:59 AM »
Pretty tan color eh? If you google: Spark plug conditions you should be able to get a good reading of where your machine and plug are at just by taking the plug out. From what you've described its worn
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Offline conbread

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05 YZ250 jetting
« Reply #14 on: June 10, 2012, 02:46:04 AM »
Quote from: Stusmoke on June 10, 2012, 09:16:59 AM
Pretty tan color eh? If you google: Spark plug conditions you should be able to get a good reading of where your machine and plug are at just by taking the plug out. From what you've described its worn

lol, thats funny.. yea it has a pretty good look to it.. way diff from my buddys Grey/black 2004 cr250... man i love this 2 stroke, dont know why i started out on a yz250f..
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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