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Extended Air Fuel Screw

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Did a search and found info on the Extended Idle Screw but nothing for a Extended Air Fuel Screw. I see ones on Fleabay for CRF's but not XR's. I will be jetting for the first time hopefully this weekend and thought this would be a good idea since I will be more than likely adjusting it constantly as I learn. Is this even necessary and if so is there an Extended Air Fuel Screw you use and recommend?

 

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51 minutes ago, William1 said:

It is a fuel screw on nearly all 4S bikes. It is used for fine adjustment of the idle mix only, above idle, you change needles and near/art full throttle, the main jet.

Maybe I asked the wrong way. I'm looking for this instead of trying to get my claw burned using a tiny screwdriver.

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1 minute ago, cmbthumper said:

Maybe I asked the wrong way. I'm looking for this instead of trying to get my claw burned using a tiny screwdriver.

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Neither one of those will fit your carb, those are for the FCR-MX. What model and year XR?

I understand not wanting to get burned or fight the PITA the stock screw location is. All my FCR-MX equipped bikes run an extended screw.

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42 minutes ago, William1 said:

Neither one of those will fit your carb, those are for the FCR-MX. What model and year XR?

I understand not wanting to get burned or fight the PITA the stock screw location is. All my FCR-MX equipped bikes run an extended screw.

Gotcha learning something everyday.

My bike is a 00 XR400 Commie model. As far as I can tell right now stock everything carb wise but will be opening it up this weekend.

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TT store may have them. I did a little looking and it looks like they have/can get them. All my other sources (old links) are not showing them. I'd email the store and ask. Or you can try James Dean Jetting.

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6 minutes ago, William1 said:

TT store may have them. I did a little looking and it looks like they have/can get them. All my other sources (old links) are not showing them. I'd email the store and ask. Or you can try James Dean Jetting.

Thanks for the quick reply and look.

I learned two more things

1. New here so will have to see what the site store is. Rather support the site than ??

2. Always saw JD Jetting but now I know what it stands for.

Thanks again

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1 minute ago, cmbthumper said:

Thanks for the quick reply and look.

I learned two more things

1. New here so will have to see what the site store is. Rather support the site than ??

2. Always saw JD Jetting but now I know what it stands for.

Thanks again

Sure thing! 

I'd definitely speak to a person though as I did not see a definitive list for your bike and that part, though I am pretty sure it is available.

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My experience with extended mixture screws have not been goo, but interesting. Keihin carbs on Hondas seem to have two different thread pitches for the mixture screws, which is one reason FCR mixture screws will not work on PD carbs. And I believe there are two thread pitches among the PD series. I bought a Kouba mixture screw for an early XR carb, and wrong threads.  I finally splice a knob from a $10 extended fuel screw to my PD fuel screw.

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4 hours ago, cmbthumper said:

Did a search and found info on the Extended Idle Screw but nothing for a Extended Air Fuel Screw. I see ones on Fleabay for CRF's but not XR's. I will be jetting for the first time hopefully this weekend and thought this would be a good idea since I will be more than likely adjusting it constantly as I learn. Is this even necessary and if so is there an Extended Air Fuel Screw you use and recommend?

There is no need.  The fuel screw on an XR4 is very accessible with a normal screwdriver.  The only reason aftermarket CRF screws are popular is because you can't reach the stock one without a normal screwdriver.  Mine is a '98, and If memory serves (it's been a LONG time) I think I ended up with a 58 pilot, 158 main, one clip lower on the stock needle, and probably 2 1/2 turns out on the screw at ~500ft.  Tune the pilot jet/screw for instantaneous throttle response right off idle.

Edited by jayc250x

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I agree, it's easy enough to modify/extend the stock screw with a little imagination and ingenuity.

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^^^^

Appreciate all the info sharing. I did a little experiment with a tiny screwdriver and with my E-Start motor and my andre the giant mits it was doable on a cold motor but wouldn't want to go near it after it warms up. I was thinking of brazing a small knurled extension onto the screw and then fuel line to a more accessible area. Still thinking though.

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Could braze a rod onto it and bend a L in the rod.  If you do find a screw avoid ones with alum tip, better ones should use brass.  Also the number of turns you were using can change if the tip is made different.

fwiw I used a 50/ 52 pilot  summer/winter,  you got e start so may not be a big deal but the trick was always to get them where they cold started AND hot started well .  Pilot and mix screw seemed critical.

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53 minutes ago, cmbthumper said:

^^^^

Appreciate all the info sharing. I did a little experiment with a tiny screwdriver and with my E-Start motor and my andre the giant mits it was doable on a cold motor but wouldn't want to go near it after it warms up. I was thinking of brazing a small knurled extension onto the screw and then fuel line to a more accessible area. Still thinking though.

I used a sleeve and solder to join the two screw parts. And I did the work on a lathe to insure a good fit. But I could have done it without a lathe. I wish I could post a pic but I don't have access to the bike.

I used a screw with 4 numbers on it asit.makes it easy to see where the screw is set, if you always do it from the same side of the bike. :facepalm:

 

 

Edited by Chuck.
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^^^^ I appreciate all the info and Fab tips. Was going to take a spare as suggested and extend it myself. Called my dad for some advice and he gave me his spare. He's been retired as a GM and Elevator mechanic for some time but you know you can't touch Dad's tools so never crossed my mind to ask him. Will cut it down to a manageable size for the tool kit.1460063699_AirFuelScrewdriver.jpg.8b26e343fe4a81a0620da4005a2d5e35.jpg

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10 hours ago, cmbthumper said:

Will cut it down to a manageable size for the tool kit.1460063699_AirFuelScrewdriver.jpg.8b26e343fe4a81a0620da4005a2d5e35.jpg

I'm probably around the age of your Dad and it may just be me but, Seems like a sin to me to cut down and ruin a classic tool like that. Personally, I'd stick with fabbing up one of the other options you were considering before you found out you could use Dads tools.

Then later, you can make him proud of your ingenuity and opting of not to hack up his classic tool.

Edited by Trailryder42

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24 minutes ago, Trailryder42 said:

I'm probably around the age of your Dad and it may just be me but, Seems like a sin to me to cut down and ruin a classic tool like that. Personally, I'd stick with fabbing up one of the other options you were considering before you found out you could use Dads tools.

Then later, you can make him proud of your ingenuity and opting of not to hack up his classic tool.

He is 73. Even though he "Gave" it to me I'm still scared and agree with not cutting it. So I will more than likely just fab a small extension.

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Thanks again for all the tips

Did a little Fleabay shopping and got these. Works perfect with knob a few inches past the frame and small enough for the tool bag.

 

Flexable Drill Extension with bits $4

Aluminum Sound System Knob $3

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