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Pilot Jet - To many contradictions xr4

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Hi All

 

Only my second post but I need some help/direction

 

2003 XR4 + Gordons mods (header welds removed , Uni , Free flowing but std exhaughst) std Carb , I ride between 600 and up to 3800ft (rare occasion)

 

When I Honed out the Header welds I test rode the bike and it created massive bog on acceleration and it took some time for the bike to catch up. I did the std air/fuel screw and there was no change in RPM unless it was screwed to 1/4 out from seating at which point it started to die burble etc  I new was the Jetting given TT advice forum so I checked the plug and it was sooty and black indicating it was running rich . The Jets in the bike at teh time were 55 and 162 set as Std for Australian models . I ordered a heap of jets from Rocky mountain and installed 60 pilot +160 main. also  needle 3rd clip as std . The bike is running a lot better however I want to fine tune the air/fuel screw .

 

My Question is that I found conflicting net based advice  - I started with 2.5 turns out and turned the screw in at 1/4 turn intervals to tune .. the idle flattens and becomes great with a very noticable improvement at 3/4 out  and there is no change when its screwed all the way in.

 

The online information I see states that 1/14 to 2 1/4 out is the ideal range.  But I have read that under 1 turn out the setting is to rich -- however ---- I also read that under 1 turn out the setting is to Lean ... my conumdrum !!! ,  is it rich or is it lean when the screw is under one turn out ?

 

I have a 58 and 62 pilot here and was thinking the 58 is worth a try first - Advice or opinions please ?

 

 

With thanks

 

AL

Edited by almcb

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 I would say drop down to the 58 or even the stock 55 (still richer then stock USA bike BTW), If you have the stock air filter and cage still it might not like the richer pilot. Make sure current air filter is fairly clean and oiled.

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Sorry for the spelling and word omissions - I should also add that the valve cam adjustments are spot on new plug , oil change and I am running the UNi brand new and oiled with UNi cage  (not the stock cage) the snorkel is removed as well and I run unleaded 98 through a spotless carburetor I think the 58 is the way to go as well --- but wasn't sure

Edited by almcb

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On my 250L, if I run a #40 I have the screw open three turns.  If I run a #42 I have it at one turn out.  

 

I put a #58 in my buddy's 400 and it works very well.  

 

Keep in mind that stuff gets in the carb and clogs the tiny holes in the pilot very easily.  This makes starting difficult.

 

 

http://www.thumpertalk.com/topic/271735-how-to-confirm-your-pilot-circuit-setting/

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Forgot to add It starts like a dream , always has really 2 x Kicks cold with decompression or 1 kick hot ...  #58 is looking good ... I might film the diference as i bet a lot of XR4 users go through the motions with this ..

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Hi All

 

My Question is that I found conflicting net based advice  - I started with 2.5 turns out and turned the screw in at 1/4 turn intervals to tune .. the idle flattens and becomes great with a very noticable improvement at 3/4 out  and there is no change when its screwed all the way in.

 

The online information I see states that 1/14 to 2 1/4 out is the ideal range.  But I have read that under 1 turn out the setting is to rich -- however ---- I also read that under 1 turn out the setting is to Lean ... my conumdrum !!! ,  is it rich or is it lean when the screw is under one turn out ?

 

I have a 58 and 62 pilot here and was thinking the 58 is worth a try first - Advice or opinions please ?

 

 

With thanks

 

AL

Just remember that your carb has a fuel screw, it meters fuel. When you open it (counter clockwise) you provide more fuel to the circuit (richer). Closing it (clockwise) provides less (leaner).

So using your example, if your setting for best idle and throttle response off idle was less than 1 turn out, your pilot jet is too rich (too big), making you have to close down the amount it's delivering with fuel screw too much.

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The pilot jet does the major tuning of the pilot circuit.

The fuel screw fine tunes the pilot circuit.

The range of the fuel screw is 1/2 to 3 turns out from fully closed.

If there is no effect in this range, the pilot jet is too large or too small.

Test too small by adding choke. If more choke makes it run better, pilot is too lean, go larger.

55 pilot testing

Need less than 1/2 turn out, go to 52 pilot jet.

1/2 to 3 turns of the pilot, right pilot jet.

Need more than 3 turns... Go to 58 pilot jet

Adapt this method for any size jet.

See the FAQ for DREADED BOG.

Edited by Kev_XR

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Done ! I just ran these combinations as the bog (mid range ) was still there . I ran 160/60 bog mid throttle but screw was 1/4 out , then 160/58 still bog but pilot was quite good ahh onto something 158/58 a lot better but still a touch of bog mid throttle pilot was great at 1 1/4 . I finally ran the 155/55 no bog and very very snappy screw 2.5 turns out , unhappy neighbors now happy as I have stopped tearing up and down the street . The morel of this story for me is that every xr4 is different in its own way ..... But I am confused how I came back to a 55 pilot and it wasn't until I put in a new 55 that the mixture screw changed how it ran ... Thanks for all the help !!

Al

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On pilot jets 55-58-60-62.Where at sea level ride up to 10,000 ft.(all our bikes 62) it dependes on header,muffler,air cleaner,air box mods.Pumper carb we use 25 p jet.Its good to run the xr4 a little rich,keeps it from over heating.To make the xr run hard,Big time air box mod,Big tube header,hi flow muffler.Just the normal mods,You should be fine with 55-58 p jet.BTR

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