2 stroke jetting for VPR?

Alex814
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Alex814
So it seems to me that VPR fuel runs WAY richer (more rich?) than 93 octane pump gas. I just picked up a '22 YZ125 and started it once before swapping out the fuel from 93 to VPR. It smokes a lot more and feels rich on the VPR at 32:1. A CR250 I just finished rebuilding also runs similarly with a lot of smoke..

So where should I expect to start with jetting adjustments to compensate? Will smaller jets be needed or just some turning of the air screw in most cases? I'm pretty new to this and want to avoid going the wrong direction on a brand new bike. I also understand jetting cannot be perfected on a stand or purely with advice over the internet. Thanks

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alien
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alien 5/27/2022 6:45am
5/27/2022 6:45am Edited Date/Time 5/27/2022 6:46am
I use VPR mixed 50/50 with 93 pump gas at 32:1 using the same jetting I did on straight pump gas. With 100% T2 I leaned the clip one notch. My bike runs just as good at 50/50 as it does on straight VPR so I mix it to save money.
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Alex814
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Alex814 5/27/2022 7:06am
5/27/2022 7:06am
alien wrote:
I use VPR mixed 50/50 with 93 pump gas at 32:1 using the same jetting I did on straight pump gas. With 100% T2 I leaned...
I use VPR mixed 50/50 with 93 pump gas at 32:1 using the same jetting I did on straight pump gas. With 100% T2 I leaned the clip one notch. My bike runs just as good at 50/50 as it does on straight VPR so I mix it to save money.
Thanks for suggestion on the leaner clip position, I'll give that a try on the YZ before changing any jets.
As for fuel cost yeah, I'm just not wanting ethanol in my bikes right now. Plus the premium pump here is now over $6/gallon.
FGR01
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FGR01 5/27/2022 11:45am
5/27/2022 11:45am
The 2022 YZ125 is way rich to begin with. Adding the VPR is going to make it even richer. The settings most folks seem to be trending towards is way leaner on the pilot.. like dropping from the stock 70 to a 50 or 52. Then running clip-3 and maybe a bigger main, as they are lean on top.
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Alex814
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Alex814 5/27/2022 1:01pm
5/27/2022 1:01pm
FGR01 wrote:
The 2022 YZ125 is way rich to begin with. Adding the VPR is going to make it even richer. The settings most folks seem to be...
The 2022 YZ125 is way rich to begin with. Adding the VPR is going to make it even richer. The settings most folks seem to be trending towards is way leaner on the pilot.. like dropping from the stock 70 to a 50 or 52. Then running clip-3 and maybe a bigger main, as they are lean on top.
That's a big change, wow. My manual says a 75 pilot is stock, and I received a 72 with the bike so I'll check that out and go with the leaner of the two for my first ride.

I just ordered the JD jetting kit to try and get a better baseline setting.

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Alex814
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Alex814 5/27/2022 6:00pm
5/27/2022 6:00pm
FGR01 wrote:
I was helping a few guys with these bikes and talked to Jay Clark at Dirt Bike TV IG channel. He used the JD kit and...
I was helping a few guys with these bikes and talked to Jay Clark at Dirt Bike TV IG channel. He used the JD kit and settled on this:

JD Red needle, clip4
Main 170-172
Pilot 50
Air Screw - 2.5

That's extremely helpful, thanks!
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digger
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digger 5/28/2022 2:56am
5/28/2022 2:56am Edited Date/Time 5/28/2022 2:57am
Just from looking at the specs in those 22' YZ 125 carbs, I can tell it's a cost saving type deal, similar to the current Mikuni's on the small bore KTM/Husky/GasGas 125's. Yamaha is trying to share the same carb on the 125 and 250 YZ's. While I think the Keihin is a better carb for 95% of the 125 riders/racers, what Yamaha has in the 22' 125's carb, is a compromise at best, and what appears to not be a very good one. I haven't had the opportunity to work on a 22' yz 125 yet, but look forward to it. I do have an idea as to where I would start with it though. Sorry, I guess I wasn't very helpful.
Alex814
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Alex814 5/31/2022 1:09pm
5/31/2022 1:09pm
digger wrote:
Just from looking at the specs in those 22' YZ 125 carbs, I can tell it's a cost saving type deal, similar to the current Mikuni's...
Just from looking at the specs in those 22' YZ 125 carbs, I can tell it's a cost saving type deal, similar to the current Mikuni's on the small bore KTM/Husky/GasGas 125's. Yamaha is trying to share the same carb on the 125 and 250 YZ's. While I think the Keihin is a better carb for 95% of the 125 riders/racers, what Yamaha has in the 22' 125's carb, is a compromise at best, and what appears to not be a very good one. I haven't had the opportunity to work on a 22' yz 125 yet, but look forward to it. I do have an idea as to where I would start with it though. Sorry, I guess I wasn't very helpful.
Any and all input is helpful. I received the JD jetting kit today and it suggests the same specs that FGR01 posted above, so I'm going to try those out. I rode the bike last weekend with the 72 pilot in hot temperatures and it was rich off idle for sure.
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