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fcr-mx-39mm

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Just finished installing a used carb. Im having some bogging issues from low-mid rpm.  If you jump on the throttle hard it just falls on its face.  if you ease in its fine.

My Setup

Sea Level

3x3 Air Box 

Fmf Power Bomb- Power Core 4 full exhaust

Main:160

need:5/7 ocem n <- My guess on the problem

Slow: 45

MAJ:200

SAJ:100

The TPS is wired in.

Before i go and mess with it i wanted some advice to make sure im on the right track.

when adjusting the fuel mixture i can turn it all the way bottomed out to the right before it starts to stumble

Edited by psilokatalist

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Did you check the squirt duration? You want around 1 sec. If your bike starts to stumble when the fuel screw is turned all the way in then you need to go down one size on the pilot jet. Go to the 4th clip position on the neeldle

Edited by mickeydee

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have not checked the duration.  it was setup used from a guy who had it on the exact same year drz 400s.  to specify on the needle his notes were fifth from the bottom.

Edited by psilokatalist

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If your bike starts to stumble when the fuel screw is turned all the way in then you need to go down one size on the pilot jet.

With correct size pilot jet, engine should stumble/ stop when the fuel screw is turned in past one turn from fully seated.

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

I know you know your sh1t mickey but maybe this time your fingers were going faster than your brain when you typed this.

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need:5/7 ocem n <- My guess on the problem..... yes too rich ,you should be on clip 3 @less than 3K ft..

If your getting a reaction to turning the fuel screw, the 45 should be fine ( even though it's almost turned fully in before you get reaction)

Tune fuel screw with procedure in Black's post..

You need to remove the pilot air jet....

Is your bogging occurring at standing free revving or when your riding it.?

It's normal for an fcr to bog without load

Edited by Craigo 485sm

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With correct size pilot jet, engine should stumble/ stop when the fuel screw is turned in past one turn from fully seated.

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

I know you know your sh1t mickey but maybe this time your fingers were going faster than your brain when you typed this.

yes, but he said once it has seated( or turned all the way in). You want the bike to stumble around one turn out from seated.on the other hand he still got a reaction so the 45 is probally going to be ok just better to try a 42.

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Also removing the pilot air jet is for the TT fcr carb or a brand new fcrmx carb. The op has said the carb is used so we don't know where it came from. If he got a reaction from the fuel screw then he dosent need to remove the pilot air.

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yes, but he said once it has seated( or turned all the way in). You want the bike to stumble around one turn out from seated.on the other hand he still got a reaction so the 45 is probally going to be ok just better to try a 42.

All good M8, I understand where you are coming from now. :thumbsup:

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Also removing the pilot air jet is for the TT fcr carb or a brand new fcrmx carb. The op has said the carb is used so we don't know where it came from. If he got a reaction from the fuel screw then he dosent need to remove the pilot air.

 

Fair enough and you are correct.. I skimmed the heading details incorrectly and thought there were TT letters in the thread tittle...

 

Perhaps the PO could provide more info as to the carb origin......

Edited by Craigo 485sm

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Keihin fcr-mx-39mm

part number 

5JG1000801

i bough it second hand but it was purchased from WWW.KEIHIN-FCR.COM

it has the short throw choke and hot start lever.

took the carb off for now.

pilot air jet was removed before i received being that it was on a drz(i checked today).

the o-ring was broken for the AP.  i bought a new one.

another oddity was that after i shut it off it would leak gas(sometimes). i am using the vacuum nipple and on position on petcock

im going to go through the carb make sure every thing is copacetic.  check the needle and jets for myself.

Seems like i had the same ideas you guys had with mixture seamed to rich.

anyway im going to check the float seat and settings since it seams like an issue if i need new parts ill order em.

im hoping i can get this all sorted seems to make more power at high rpm but almost undriveable the way it is. 

 

Thanks for the comments and support.

Edited by psilokatalist

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need:5/7 ocem n <- My guess on the problem..... yes too rich ,you should be on clip 3 @less than 3K ft..

If your getting a reaction to turning the fuel screw, the 45 should be fine ( even though it's almost turned fully in before you get reaction)

Tune fuel screw with procedure in Black's post..

You need to remove the pilot air jet....

Is your bogging occurring at standing free revving or when your riding it.?

It's normal for an fcr to bog without load

i does it in any gear low rpm moving it boggs bad then after a second or two it will pick up and go when held at wot, and of coarse free rev aswell

Edited by psilokatalist

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i does it in any gear low rpm moving it boggs bad then after a second or two it will pick up and go when held at wot, and of coarse free rev aswell

 

Adjust needle as per above....If it still bogs some...

Turn your AP timing screw in a half turn.........

 

 SIDENOTE::::Remember your starting point when adjusting the AP screw, in case you need to go back to it.......

Edited by Craigo 485sm

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UPDATE

Just went thru and checked the flat slide out.  Most of the stuff he had written down was correct.

the oring on the ap was broken and not doing its job.  im thinkin bk mod is the way im going to go.

There was a 155 main jet in it not a 160.

The needle position was correct at 3rd clip measuring from the top.

i want to buy a new float seat and needle and main jet start there. im going to order a smaller pilot just incase i need it.

where would you guys recommend getting the parts. 

 

on a related note what is the other jet next to the pilot and main.  its a 72.

Edited by psilokatalist

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on a related note what is the other jet next to the pilot and main.  its a 72.

 

Starter jet, it is what enriches the air/fuel mixture when you pull the choke.

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UPDATE

Just went thru and checked the flat slide out.  Most of the stuff he had written down was correct.

the oring on the ap was broken and not doing its job.  im thinkin bk mod is the way im going to go.

There was a 155 main jet in it not a 160.

The needle position was correct at 3rd clip measuring from the top.

i want to buy a new float seat and needle and main jet start there. im going to order a smaller pilot just incase i need it.

where would you guys recommend getting the parts. 

 

on a related note what is the other jet next to the pilot and main.  its a 72.

 

http://www.jetsrus.com/carburetor/carb_keihin_FCR-MX_carb_exploded_view_parts.html

Edited by Craigo 485sm

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