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Dialing in jetting w/ a 250x, new 7 clip needle causing sputter...

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Jetting-

I started w/ a 152 main, stock needle, moose fuel screw (2 turns) and 42 then a 45 pilot. The bike ripped w/ these jets except there was still a bog w/ the pilot. I put a 48 pilot in and the bog was gone, perfect all the way thru!! Then I got an NCVS 7 clip adjustable needle (on the 4th position) 2 days ago and the bike seems to have a bit of a gargel now @ 1/8-1/4 throttle. I've tried adjusting the fuel screw 1-1/2 turns out to 2-1/2 turns out (and everything in between) and I can't seem to get it to run 100% or near to what it was. The bike does rip alot better off the bottom, mid and top, but theres that little in between 1/8-1/4 that seems to have a bit of a sputter or gargle.. Doesn't seem like a bog, not sure what it is as I'm learning 4 stroke jetting....Do I need to adjust the clip position or am I just off on the fuel screw? I can't seem to get that smooth idle that I had. When I was adjusting the fuel screw today the bike would stall when it was adjusted in (lean)..

Mods-

airbox mod

pink wire mod

removed baffle

removed screen w/ new twin air

Moose fuel screw 2 turns out

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1. the 48 pilot masked the real issue: accelerator pump is not right

2. go back to the 45

3. change your leak jet to a 55, and adjust your pump linkage so the spray misses the slide, just barely

4. NCVS on 3rd or 4th position

5. Fuel screw adjust for MAX IDLE,, then drop idle with idle screw and repeat, until you have it running a smooth a possible. There will be a sweet spot of 1/8-1/4 turn of fine tuning that you will notice it idles with more rhythm and clarity. If that position of the fuel screw is less than 1.5 turns, you need a bigger pilot. More than 2 turns, you need a smaller one.

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It ran awesome w/ the 48p and stock needle. (bike is an 07) I know you told me before to adjust the linkage, I will do that. I thought these bikes come stock w/ a 55? Because alot of guys are always moving up to a 50.. My main is still to small according to JD and my recent mods. I'm moving up to a 160, will that have any influence on this? It may be more on the 1/4 -1/2 throttle where the gargle is now that I really think about it.. Its a light gargling sound, something I haven't yet through out the jetting process..

So you think its all about the linkage now?? Even if the bike ran great w/ the 48p and stock needle?

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It ran awesome w/ the 48p and stock needle. (bike is an 07) I know you told me before to adjust the linkage, I will do that. I thought these bikes come stock w/ a 55? Because alot of guys are always moving up to a 50.. My main is still to small according to JD and my recent mods. I'm moving up to a 160, will that have any influence on this? It may be more on the 1/4 -1/2 throttle where the gargle is now that I really think about it.. Its a light gargling sound, something I haven't yet through out the jetting process..

So you think its all about the linkage now?? Even if the bike ran great w/ the 48p and stock needle?

The stock needle is very lean. You added a pilot that is very rich. It evens out, but not in transition.

If you want more spedific advice, you should try the 250X forum.

Stock pilot is a 42.

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I have, 1 guy suggested I lean the needle out. Which way is lean and which is rich? up or down...

As the clip rises up the needle, It gets leaner.

...but don't guess! Copy someones tuning that works.

The stock needle is no good. Go to a JD Red or a NCVS needle.

45 pilot

160 main

adjust fuel screw: if it's less that 1 turn out for high idle, pilot jet is too big Over 2.0, it's too small.

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As the clip rises up the needle, It gets leaner.

...but don't guess! Copy someones tuning that works.

The stock needle is no good. Go to a JD Red or a NCVS needle.

45 pilot

160 main

adjust fuel screw: if it's less that 1 turn out for high idle, pilot jet is too big Over 2.0, it's too small.

Krannie,

I just put in a NCVS adjustable needle in my carb 3 days ago right after I moved up from the 45p to the 48p and this is why I'm having a bit of jetting issues... Its on the 4th out of 7 position It came out of a YZ250 :smirk: . I think I have it (1-3/4, 2, 2-1/4, 2-1/2) turns out, cant remember. Actually when I was riding yesterday, it was overcast and it had just stopped raining. Bike still had the slight gargle @ 1/4 throttle or so. When the sun broke and it warmed up to 68+ degrees, I had to lean out the fuel screw out to (1-3/4) and the gargle actually went away for the most part. Do I need to adjust it say when it warms up in spring, cools down in fall, or the dead cold of winter?

I have tried other guys jetting, but you know just as well as I do that everybodies bikes are different, the weather they ride in, terrain, temp, mods on the bike, gas, altiude, humidity, ect, (you get the hint) is all different!!! So to copy someone elses jetting is just a waist of time IMO and my tuner as well.. Sure its a good guideline to go by!!

Edited by GoonSquadRMZ450

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Yeah, everybody's bike isn't all that different. Altitude and relative humidity are.

48 pilot is TOO BIG.

Fuel screw at 2.5 turns out can't be right for that pilot. Follow the turning procedures.

You should NOT be putting in a used needle! They don't last forever, and a new one is only $12.00.

Have you read the 250X forum jetting sticky?

There will be dozens of bikes exactly like yours in similar surroundings to copy from.

http://www.thumpertalk.com/topic/146241-jetting-settings/

Edited by Krannie

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Kranne,

Another quick jetting question about the X's. Whats up w/ people "closing off' theri leak jets? Whats up w/ that. what does it do, have you done it to your X, and can and should I do it to my 250x??

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Yea of course. I live in the 250x fourm, literaly. Those guys don't seem to know really what to do except lean it out on the needle.....

Edited by GoonSquadRMZ450

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Kranne,

Another quick jetting question about the X's. Whats up w/ people "closing off' theri leak jets? Whats up w/ that. what does it do, have you done it to your X, and can and should I do it to my 250x??

The leak jet is not a 'jet', it's a bypass to the acclerator pump circuit. A bigger leak jet 'leaks more fuel' out of the apump. Hence, a smaller leak jet gives you more gas for the pump to squirt.

Leak jet size determines length (duration) of squirt.

Linkage determines timing (early, late) of squirt.

Diaphragm type determines volume of squirt (distance).

You are trying to get .8-1.2sec of squirt that goes all the way into the intake valve portion of the head, missing the slide every time just barely, and with no 'dribble' out of the squirt nozzle.

You achieve this (250x) with a 55leak, a properly timed linkage, and a stock diaphragm, using the merge racing linkage return spring, and the merge or R&D diaphragm tension spring (which comes with the R&D floatbowl).

If you can't get a long enough (time and distance) squirt, you go with a 2005 CRF450R diaphragm (shorter rivet, more pump throw).

Putting in a smaller leak jet (or closing it off) does nothing past a certain point, because the pump diaphram is limited to a specific pump throw; adding more gas to the pump won't make it pump any more fuel to the nozzle. It can be effective, BUT, it is usually too much squirt, and it dribbles upon slow thorttle roll on, which gives you hanging idle, partial throttle gurggle, and other issues.

You should go to the JD jetting site and poke around. He has tryed EVERYTHING there is to the FCR MX-CR carbs, including mounting the carbs on a stand and measuring apump squirt distance and volume....!

http://www.jdjetting.com/html/faq.htm

Edited by Krannie
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The leak jet is not a 'jet', it's a bypass to the acclerator pump circuit. A bigger leak jet 'leaks more fuel' out of the apump. Hence, a smaller leak jet gives you more gas for the pump to squirt.

Leak jet size determines length (duration) of squirt.

Linkage determines timing (early, late) of squirt.

Diaphragm type determines volume of squirt (distance).

You are trying to get .8-1.2sec of squirt that goes all the way into the intake valve portion of the head, missing the slide every time just barely, and with no 'dribble' out of the squirt nozzle.

You achieve this (250x) with a 55leak, a properly timed linkage, and a stock diaphragm, using the merge racing linkage return spring, and the merge or R&D diaphragm tension spring (which comes with the R&D floatbowl).

If you can't get a long enough (time and distance) squirt, you go with a 2005 CRF450R diaphragm (shorter rivet, more pump throw).

Putting in a smaller leak jet (or closing it off) does nothing past a certain point, because the pump diaphram is limited to a specific pump throw; adding more gas to the pump won't make it pump any more fuel to the nozzle. It can be effective, BUT, it is usually too much squirt, and it dribbles upon slow thorttle roll on, which gives you hanging idle, partial throttle gurggle, and other issues.

You should go to the JD jetting site and poke around. He has tryed EVERYTHING there is to the FCR MX-CR carbs, including mounting the carbs on a stand and measuring apump squirt distance and volume....!

http://www.jdjetting.com/html/faq.htm

So is the leak worth messsing with? Changing the size, blocking off, etc? How do you block it off anyway? Thanks for all the help!

Edited by GoonSquadRMZ450

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So is the leak worth messsing with? Changing the size, blocking off, etc? How do you block it off anyway? Thanks for all the help!

Yes, you HAVE to change the leak jet!

You are not reading what I post; don't block it off, it will cause other issues.

I'm done here.

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