Installing Aftermarket Fuel Screw (kehin fcr)

wr250f95 · 12-13-2007, 08:32 PM

An aftermarket fuel screw is one of the best modifications you can do to a high performance 4 stroke, as conditions and fuel requirements of the engine change rather quickly. An aftermarket fuel screw will allow you to change the air/fuel mixture with nothing more than your fingers, and since most high performance bikes made today use the Kehin FCR carb, most are universal.

First off, beware of the one you buy, I have heard rumors that units made of aluminum will screw up the jetting. After you make your purchase, it is time to install the unit.

1. Loosen up the clamps that hold the carb to the intake boot, and engine.*
2. Rotate the carb to face you.*
3. Towards the front of the carb there should be a impression with a screw in it, this is the factory air/fuel mixture screw.
4. Tighten the screw until it stops, do not use extreme pressure, when you do this keep track of the turns in, this will give you your factory setting.
5. Take the screw out.
6. On the end of the factory screw there should be a spring, small copper washer, small oring, transfer these over to the new air fuel mixture screw in that order.
Remember!
spring
washer
oring
7. with the parts slid on your aftermarket fuel screw in the correct order, insert the screw into the hole until it tightens up, now turn it out the number of times it took to get the orginal to tighten up!
8. rotate the carb back to its orginal postion and tighten the clamps that hold it in place.
Now your done!
* depends, some aluminum frame bikes may have you remove the fuel tank, seat and carb completly.

JThompson · 12-14-2007, 12:06 AM

Thanks for the article. My gosh I have so many ideas for howtos... We have enough going on around here to make a monthly newsletter and everything. This month we discussed yada yada yada. Sorry Im taking this off topic. Want to give us some ebay links to air screws you recommend?

wr250f95 · 12-20-2007, 04:09 PM

ok, first off I dont like zip tye, they are aluminum.
scott's has a good one, as does the first gen pro circut, Ive heard the newer ones are junk.

gscx · 12-20-2007, 05:15 PM

can you say why the pro circuits are junk

wr250f95 · 12-20-2007, 05:25 PM

the tip varies from the stock one and have heard many reports of them being easily damaged. Like I said, the old ones were pretty good but the new ones appear to be junk.

gscx · 12-20-2007, 05:36 PM

just wanted to see why they were bad

wr250f95 · 12-20-2007, 05:38 PM

yup.
I like my gytr, its made by Yamaha but like i said, almost all the high performance 4 strokes use the fcr.

gscx · 12-20-2007, 05:53 PM

i think suzuki uses mikuni

wr250f95 · 12-20-2007, 05:59 PM

really? wasnt aware of that.

gscx · 12-21-2007, 07:08 PM

im working on a friends 96 RM250 and it has mikinu, manufactuerers usally dont change this kind of stuff, just like yamah uses kayaba and honda uses showa, these things dont ever really change

12-13-2007, 08:32 PM	#1 (permalink)
wr250f95 Super Moderator Join Date: May 2007 Location: New Mexico Posts: 7,657	Installing Aftermarket Fuel Screw (kehin fcr) An aftermarket fuel screw is one of the best modifications you can do to a high performance 4 stroke, as conditions and fuel requirements of the engine change rather quickly. An aftermarket fuel screw will allow you to change the air/fuel mixture with nothing more than your fingers, and since most high performance bikes made today use the Kehin FCR carb, most are universal. First off, beware of the one you buy, I have heard rumors that units made of aluminum will screw up the jetting. After you make your purchase, it is time to install the unit. 1. Loosen up the clamps that hold the carb to the intake boot, and engine.* 2. Rotate the carb to face you.* 3. Towards the front of the carb there should be a impression with a screw in it, this is the factory air/fuel mixture screw. 4. Tighten the screw until it stops, do not use extreme pressure, when you do this keep track of the turns in, this will give you your factory setting. 5. Take the screw out. 6. On the end of the factory screw there should be a spring, small copper washer, small oring, transfer these over to the new air fuel mixture screw in that order. Remember! spring washer oring 7. with the parts slid on your aftermarket fuel screw in the correct order, insert the screw into the hole until it tightens up, now turn it out the number of times it took to get the orginal to tighten up! 8. rotate the carb back to its orginal postion and tighten the clamps that hold it in place. Now your done! * depends, some aluminum frame bikes may have you remove the fuel tank, seat and carb completly. __________________ "LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY, BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT, SHOUTING'...HOLY S*T... WHAT A RIDE!" this, is why I ride. Last edited by wr250f95; 12-13-2007 at 08:34 PM.*

12-14-2007, 12:06 AM	#2 (permalink)
JThompson Administrator Join Date: Aug 2006 Location: Bellingham WA Posts: 4,819	Thanks for the article. My gosh I have so many ideas for howtos... We have enough going on around here to make a monthly newsletter and everything. This month we discussed yada yada yada. Sorry Im taking this off topic. Want to give us some ebay links to air screws you recommend? __________________ Tired of ads? Become a member for an almost ad free site! Also we give away monthly prizes just for posting! Register today! Looking for places to ride! Want to review a riding area? Check them out! PRE-ORDER MOTOTIPS Stickers now. Help keep mototips running! Get your order in today! Buy NOW! Special Discounts for members only! Check out our new discount forum for retailers offering to help you save money! Mototips Discounts

12-20-2007, 04:09 PM	#3 (permalink)
wr250f95 Super Moderator Join Date: May 2007 Location: New Mexico Posts: 7,657	ok, first off I dont like zip tye, they are aluminum. scott's has a good one, as does the first gen pro circut, Ive heard the newer ones are junk. __________________ "LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY, BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT, SHOUTING'...HOLY S**T... WHAT A RIDE!" this, is why I ride.

12-20-2007, 05:15 PM	#4 (permalink)
gscx Pro Mototips Member Join Date: Aug 2007 Location: bridgeville DE Posts: 2,199	can you say why the pro circuits are junk __________________ Sold

12-20-2007, 05:25 PM	#5 (permalink)
wr250f95 Super Moderator Join Date: May 2007 Location: New Mexico Posts: 7,657	the tip varies from the stock one and have heard many reports of them being easily damaged. Like I said, the old ones were pretty good but the new ones appear to be junk. __________________ "LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY, BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT, SHOUTING'...HOLY S**T... WHAT A RIDE!" this, is why I ride.

12-20-2007, 05:36 PM	#6 (permalink)
gscx Pro Mototips Member Join Date: Aug 2007 Location: bridgeville DE Posts: 2,199	just wanted to see why they were bad __________________ Sold

12-20-2007, 05:38 PM	#7 (permalink)
wr250f95 Super Moderator Join Date: May 2007 Location: New Mexico Posts: 7,657	yup. I like my gytr, its made by Yamaha but like i said, almost all the high performance 4 strokes use the fcr. __________________ "LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY, BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT, SHOUTING'...HOLY S**T... WHAT A RIDE!" this, is why I ride.

12-20-2007, 05:53 PM	#8 (permalink)
gscx Pro Mototips Member Join Date: Aug 2007 Location: bridgeville DE Posts: 2,199	i think suzuki uses mikuni __________________ Sold

12-20-2007, 05:59 PM	#9 (permalink)
wr250f95 Super Moderator Join Date: May 2007 Location: New Mexico Posts: 7,657	really? wasnt aware of that. __________________ "LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY, BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT, SHOUTING'...HOLY S**T... WHAT A RIDE!" this, is why I ride.

12-21-2007, 07:08 PM	#10 (permalink)
gscx Pro Mototips Member Join Date: Aug 2007 Location: bridgeville DE Posts: 2,199	im working on a friends 96 RM250 and it has mikinu, manufactuerers usally dont change this kind of stuff, just like yamah uses kayaba and honda uses showa, these things dont ever really change __________________ Sold

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