YZ125 Replacement Carb

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6/13/2018 5:42 PM
Edited Date/Time: 6/13/2018 5:45 PM

In the final stages of restoring my 97 YZ125. The slide in the carb is pretty worn to the point the majority of the chrome is flaked off the sides. The part is NLA from Yamaha, dosen’t cross reference with any other brands and Carb Parts Warehouse and Sudco said I’m SOL, so it looks like it’s time for a replacement. (For reference it’s a Mikuni TMXx 36)

From what I’ve gather the Keihin PWK Air Stryker is the way to go, I’m at a cross roads though as not sure if I should stick with a 36mm or upgrade to a 38. Bike will be ridden/raced vintage moto 3-5 times per year. The majority of the 38mm I’m finding come with a #7 slide which will be way to lean for the little 125. Replacement slides can be had but for around 60-70 bucks. My other option is a 39mm from a mid 00’s KTM which is also a PWK Carb (Non a/s) 5.5 slide, and plenty to be found for around 100 bones. Also have a bunch of extra Keihin jets in the garage so that would make it much easier.

I’m all ears for suggestions or thoughts.

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6/13/2018 6:16 PM

A 2002-2004 250 Honda slide should fit, think it is a #4, the stock YZ is a 4.5 I believe? Get it recut if needed. I would just keep it a 36 but that is me. A 38 would work well too however. Lots of low hour or new take off late model Miks out there. But they have the rep of being a PITA, I think they are misunderstood.

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vomiting equals disqualification.

6/13/2018 6:30 PM

BR8ES wrote:

A 2002-2004 250 Honda slide should fit, think it is a #4, the stock YZ is a 4.5 I believe? Get it recut if needed. I would just keep it a 36 but that is me. A 38 would work well too however. Lots of low hour or new take off late model Miks out there. But they have the rep of being a PITA, I think they are misunderstood.

You know I asked the guy at Sudco the same thing today and he said while they are the same carb, the slide is dimensions are different he believed. Every picture I found looked pretty damn close and having it cut is no big deal. I would prefer to keep it with the stock carb as well as it seems to run great with it!

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6/13/2018 7:20 PM
Edited Date/Time: 6/13/2018 7:20 PM

Not saying I know more, but I would be shocked that Honda would have a dimensionally different Mikuni, slide, etc. Just like the late model Mik, getting the Honda slide is way cheaper than the other mfgs.

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vomiting equals disqualification.

6/14/2018 5:26 AM
Edited Date/Time: 6/14/2018 5:28 AM

Have you tried calling Bobby Barr, Fred Vertuchi, Eric Gorr or any of the old tuners from back then?

I have bored 125 carbs before to give more mid-top end but it gets peakie

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6/14/2018 6:26 AM

lumpy790 wrote:

Have you tried calling Bobby Barr, Fred Vertuchi, Eric Gorr or any of the old tuners from back then?

I have bored 125 carbs before to give more mid-top end but it gets peakie

Lumpy, I haven’t. I’ll try calling Gorr this morning. It looks like the Honda part is NLA as well, honestly, I’m surprised no one reproduces the TMX slides aftermarket as they came on quite a few bikes.

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6/14/2018 7:54 AM

BR8ES wrote:

A 2002-2004 250 Honda slide should fit, think it is a #4, the stock YZ is a 4.5 I believe? Get it recut if needed. I would just keep it a 36 but that is me. A 38 would work well too however. Lots of low hour or new take off late model Miks out there. But they have the rep of being a PITA, I think they are misunderstood.

Premix wrote:

You know I asked the guy at Sudco the same thing today and he said while they are the same carb, the slide is dimensions are different he believed. Every picture I found looked pretty damn close and having it cut is no big deal. I would prefer to keep it with the stock carb as well as it seems to run great with it!

The 01'-03' Mikuni TMX carbs that Honda spec'ed used a slide that had slightly different dimensions than the other OEM Mikuni TMX carbs.

Premix, I believe the carb on your 97' yz125 is an older style std TMX and not the updated TMX-x.

TMX--https://www.partzilla.com/catalog/yamaha/motorcycle/1997/yz125-yz125j1/carburetor

TMX-x--https://www.partzilla.com/catalog/yamaha/motorcycle/2011/yz125-yz125a1/carburetor

I believe this is the slide you are looking for,https://www.frankmxparts.com/epages/62910900.sf/en_US/?ObjectPath=/Shops/62910900/Products/1548 but call first to verify, as the slide for the Honda only TMX is still being sold.

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6/14/2018 8:05 AM

digger wrote:

The 01'-03' Mikuni TMX carbs that Honda spec'ed used a slide that had slightly different dimensions than the other OEM Mikuni TMX carbs.

Premix, I believe the carb on your 97' yz125 is an older style std TMX and not the updated TMX-x.

TMX--https://www.partzilla.com/catalog/yamaha/motorcycle/1997/yz125-yz125j1/carburetor

TMX-x--https://www.partzilla.com/catalog/yamaha/motorcycle/2011/yz125-yz125a1/carburetor

I believe this is the slide you are looking for,https://www.frankmxparts.com/epages/62910900.sf/en_US/?ObjectPath=/Shops/62910900/Products/1548 but call first to verify, as the slide for the Honda only TMX is still being sold.

Digger, you are correct it is the older style, my mistake. I called Eric Gorr and he recommended the 05 and up newer Tmx-x that's on the YZ125. Looking through ebay most are 200 used, new can be had for just over 300 on rocky mountain, local dealer will match. Also considering a 38 Keihen PWK Airstryker from Carb Parts warehouse. 249 out the door set up with whatever slide and jets I want.

Opinions on those two options? Bike is a stock rebuild motor running on C-12. Moto only.

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6/14/2018 8:25 AM
Edited Date/Time: 6/14/2018 8:26 AM

It depends how you are going to ride the bike. The newer 38mm TMX-x's spec out closer to 40mm and will produce more over rev and higher peak hp #'s at the expensive of lowend. The screw on top PWK that you would be using will have much better lowend response, but will not have the same over rev. The 38mm PWK screw top carbs are usually right around 37.60mm to 37.80mm.

Something else to think about is the fact that the TMX-x carb is somewhere around 15mm shorter than your current TMX carb. I think the TMX-x is 76mm while the TMX is 90mm in length.

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6/14/2018 8:34 AM

digger wrote:

It depends how you are going to ride the bike. The newer 38mm TMX-x's spec out closer to 40mm and will produce more over rev and higher peak hp #'s at the expensive of lowend. The screw on top PWK that you would be using will have much better lowend response, but will not have the same over rev. The 38mm PWK screw top carbs are usually right around 37.60mm to 37.80mm.

Something else to think about is the fact that the TMX-x carb is somewhere around 15mm shorter than your current TMX carb. I think the TMX-x is 76mm while the TMX is 90mm in length.

Good info, I was just noticing that. Seems like the PWK May be the best bet.

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6/14/2018 2:48 PM

i have a 36MM mikuni off a yz125 for sale.

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6/14/2018 7:00 PM

Bruce372 wrote:

i have a 36MM mikuni off a yz125 for sale.

Thanks for the offer Bruce, I ended up ordering a new Keihin PWK Airstryker from Carb Warehouse.

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11/5/2018 3:42 PM

Premix... I find myself in the same dilemma that you may have just solved. I just purchased a 97 yz125 for my son. Bad tmx carb... can you share what you did, what extra parts were needed to accomplish this and how it runs now? Any other modifications to make what you did work? Thanks Chris

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11/5/2018 3:55 PM

YZChris wrote:

Premix... I find myself in the same dilemma that you may have just solved. I just purchased a 97 yz125 for my son. Bad tmx carb... can you share what you did, what extra parts were needed to accomplish this and how it runs now? Any other modifications to make what you did work? Thanks Chris

I've got a yz125 carb for sale

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11/5/2018 4:00 PM

Price??

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11/5/2018 4:03 PM

YZChris wrote:

Price??

$100 shipped

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11/5/2018 4:07 PM

It’s all there? Working condition?

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11/5/2018 5:20 PM

I think you should by a round slide Amal.

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11/5/2018 6:07 PM

YZChris wrote:

Premix... I find myself in the same dilemma that you may have just solved. I just purchased a 97 yz125 for my son. Bad tmx carb... can you share what you did, what extra parts were needed to accomplish this and how it runs now? Any other modifications to make what you did work? Thanks Chris

Chris, I ended up with a Keihen PWK 38mm Airstryker. It was a tight fit into the intake side but works awesome. Bike is an animal with it on. I believe I was right around 250 bucks in the carb plus a few jets.

Here’s the jetting I’m running. It could be richened up even more. I may try a richer needle but for the 80 degree plus days this worked well. Running 32:1 with VP110

P-50
M- 180
Slide-7
AS-2.5
Needle. DDJ 2nd clip.

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11/5/2018 8:26 PM

YZChris wrote:

It’s all there? Working condition?

Text me 858 775 two two 31

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