2004 yz125 with vforce reed cage and keihin 38pwk fitment issues

mxracer828
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mxracer828
To you fellow riders that have this type of set up,you have clearance issues with the carb on the shock spring? Picked up this redone 125 for my son and was going through the jetting and noticed the Side of the carb was up against the spring. Also the front of the carb does not sit flush and all the way in the boot that goes to the reeds because of the angle of the carb hitting the spring. and that worries me most. Is it like this with the Mikuni also or just the keihin?
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lostboy819 3/31/2022 8:32pm
3/31/2022 8:32pm Edited Date/Time 3/31/2022 8:37pm
Not uncommon problem and two ways to get around it is before you bolt the manifold to the cylinder insert the carb fully in the manifold and then bolt on the manifold and reed cage,it will still be close to the spring but not touching. The better way is pull the sub frame and unbolt the top shock bolt and go at it that way. Some of the Vforce reed cages has a aluminum spacer which you dont need to use.
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FGR01
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FGR01 4/1/2022 11:39am
4/1/2022 11:39am
The stock Mikuni carb is 75mm length front to back. It sounds like the PWK that has been placed on this bike is one of the longer 91mm versions.

The correct way to fix this is to put a 75mm length PWK on. You can either source a used PWK from a YZ250 or buy an aftermarket PWK-AG (Air Guide) which uses the same body casting as the stock YZ250 carb, and which is what they have now started placing on the 2022 YZ125.

https://jdjetting.com/product/jdkh48-keihin-38mm-pwk-airstriker-ag-shor…

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lostboy819 4/1/2022 11:50am
4/1/2022 11:50am
FGR01 wrote:
The stock Mikuni carb is 75mm length front to back. It sounds like the PWK that has been placed on this bike is one of the...
The stock Mikuni carb is 75mm length front to back. It sounds like the PWK that has been placed on this bike is one of the longer 91mm versions.

The correct way to fix this is to put a 75mm length PWK on. You can either source a used PWK from a YZ250 or buy an aftermarket PWK-AG (Air Guide) which uses the same body casting as the stock YZ250 carb, and which is what they have now started placing on the 2022 YZ125.

https://jdjetting.com/product/jdkh48-keihin-38mm-pwk-airstriker-ag-shor…

Good catch, if its the longer PWK I doubt it will fit, wont be able to get airfilter boot on either.
Bruce372
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Bruce372 4/1/2022 11:52am
4/1/2022 11:52am
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni.

Also, as pointed out above, if its a screw cap top keihin, it's much longer than the mikuni and it will foul on the spring. Quite often, the v force might be thicker than the oem Reed block and this creates more issues pushing things backwards
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mxracer828
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mxracer828 4/1/2022 2:42pm
4/1/2022 2:42pm
Bruce372 wrote:
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni. Also, as pointed out...
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni.

Also, as pointed out above, if its a screw cap top keihin, it's much longer than the mikuni and it will foul on the spring. Quite often, the v force might be thicker than the oem Reed block and this creates more issues pushing things backwards
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot thicker then stock,I think if I put the stock cage back in it will work. I just don’t want it popping off the boot and sucking in dirt and then the motor is toast. I may just sell the carb since it is brand new with just a few heat cycles through the motor and pick up a new Mikuni.
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SmokinJoe439
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SmokinJoe439 4/1/2022 3:10pm
4/1/2022 3:10pm
Bruce372 wrote:
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni. Also, as pointed out...
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni.

Also, as pointed out above, if its a screw cap top keihin, it's much longer than the mikuni and it will foul on the spring. Quite often, the v force might be thicker than the oem Reed block and this creates more issues pushing things backwards
mxracer828 wrote:
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot...
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot thicker then stock,I think if I put the stock cage back in it will work. I just don’t want it popping off the boot and sucking in dirt and then the motor is toast. I may just sell the carb since it is brand new with just a few heat cycles through the motor and pick up a new Mikuni.
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the time.
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mxracer828
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mxracer828 4/1/2022 3:38pm
4/1/2022 3:38pm
Bruce372 wrote:
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni. Also, as pointed out...
Also, sometimes the spigot don't match between brands, so the keihin might not fit perfectly in the manifold setup for the mikuni.

Also, as pointed out above, if its a screw cap top keihin, it's much longer than the mikuni and it will foul on the spring. Quite often, the v force might be thicker than the oem Reed block and this creates more issues pushing things backwards
mxracer828 wrote:
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot...
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot thicker then stock,I think if I put the stock cage back in it will work. I just don’t want it popping off the boot and sucking in dirt and then the motor is toast. I may just sell the carb since it is brand new with just a few heat cycles through the motor and pick up a new Mikuni.
SmokinJoe439 wrote:
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the...
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the time.
I promise it’s a legit carb that was bought from jd jetting with their jet kit. I have the original reciept.
FGR01
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FGR01 4/1/2022 4:19pm
4/1/2022 4:19pm
mxracer828 wrote:
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot...
Yes it’s the screw on cap. Not sure why the previous owner went this route rather then a new mikuni. The vforce cage is a lot thicker then stock,I think if I put the stock cage back in it will work. I just don’t want it popping off the boot and sucking in dirt and then the motor is toast. I may just sell the carb since it is brand new with just a few heat cycles through the motor and pick up a new Mikuni.
SmokinJoe439 wrote:
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the...
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the time.
mxracer828 wrote:
I promise it’s a legit carb that was bought from jd jetting with their jet kit. I have the original reciept.
If that's the case, he should have told them what bike he intended to put it on and I would expect JD would have told him that was not the best version of the PWK to fit that bike. Maybe he really just wanted to save the $60 difference?

If it's legit JD and you have the receipt, I'd call JD and ask them if you can exchange it for the right PWK and pay the difference.

As far as a new Mikuni, I don't know of anywhere that sells the proper TMX-x model you need on the aftermarket and getting them as an OEM part is $500+. I'd say either finding a used OEM YZ125 carb or the correct PWK is your best bet.
mxracer828
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mxracer828 4/1/2022 4:34pm
4/1/2022 4:34pm
SmokinJoe439 wrote:
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the...
Brand new screw top pwk on a used bike sounds like one of those cheap Chinese knock off kiehin ones you see on ebay all the time.
mxracer828 wrote:
I promise it’s a legit carb that was bought from jd jetting with their jet kit. I have the original reciept.
FGR01 wrote:
If that's the case, he should have told them what bike he intended to put it on and I would expect JD would have told him...
If that's the case, he should have told them what bike he intended to put it on and I would expect JD would have told him that was not the best version of the PWK to fit that bike. Maybe he really just wanted to save the $60 difference?

If it's legit JD and you have the receipt, I'd call JD and ask them if you can exchange it for the right PWK and pay the difference.

As far as a new Mikuni, I don't know of anywhere that sells the proper TMX-x model you need on the aftermarket and getting them as an OEM part is $500+. I'd say either finding a used OEM YZ125 carb or the correct PWK is your best bet.
I’m looking into both as we speak

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