YZ 125 project bike

b8res
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Lodi, CA US
b8res 5/4/2016 4:29pm
5/4/2016 4:29pm
I raced cross country, enduro and moto on my 2005 YZ125 for several years. For cross country and enduro I felt the best power combo was the OEM pipe w/ Leo Vince Stainless Steel / Carbon fiber silencer. The Leo Vince was just about the same length if not the same as the OEM silencer but it was USFS approved spark arrestor with a removable screen.




I had RB Designs perform his carb divider plate and circuit mod which helped on the bottom end, it just felt like it more grunt. I was able to compare a RB carb and my OEM both jetted the same and RB carb was much better all a round.



For moto I went with a FMF Factory Fatty and Shorty, with the RB carb mod and V Force 3 it had no problem pulling my fat ass around the track





cwtoyota
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cwtoyota 5/4/2016 4:35pm
5/4/2016 4:35pm
That VF3 reed cage makes a notable difference in the mid range on the 05 and later engine.
It's a better mod than any of the pipes in my opinion.

Of course the best mod for any 125 is a fresh piston.
usafwx
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Trussville, AL US
usafwx 5/4/2016 4:39pm
5/4/2016 4:39pm
cwtoyota wrote:
That VF3 reed cage makes a notable difference in the mid range on the 05 and later engine. It's a better mod than any of the...
That VF3 reed cage makes a notable difference in the mid range on the 05 and later engine.
It's a better mod than any of the pipes in my opinion.

Of course the best mod for any 125 is a fresh piston.
So I should get the VF3 first? require rejet? I love the bike right now in stock form, minus coming out of corners right before a jump, sometimes just not enough torque and bottom end to shift quick enough to get over the jump, i.e. need 3rd to clear it but have to be in 2nd through the corner.
cwtoyota
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cwtoyota 5/4/2016 4:51pm
5/4/2016 4:51pm
usafwx wrote:
So I should get the VF3 first? require rejet? I love the bike right now in stock form, minus coming out of corners right before a...
So I should get the VF3 first? require rejet? I love the bike right now in stock form, minus coming out of corners right before a jump, sometimes just not enough torque and bottom end to shift quick enough to get over the jump, i.e. need 3rd to clear it but have to be in 2nd through the corner.
Use that clutch and consider a 13:50 sprocket setup. One tooth extra on the rear sprocket makes these little bikes easier to ride.

The VF3 adds power in the mid and helps you stay on the pipe with less clutch. I raced a lot of motos last year at Washougal with a VF3, a stock pipe and the standard PC 304. I would choose the reed over a pipe if I had to choose because it helps the specific area you mentioned.

Stock jetting is really good on these bikes. Depending on your climate and fuel, you won't have to do much to get it dialed in.

The Shop

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b8res
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b8res 5/4/2016 4:54pm
5/4/2016 4:54pm
cwtoyota wrote:
That VF3 reed cage makes a notable difference in the mid range on the 05 and later engine. It's a better mod than any of the...
That VF3 reed cage makes a notable difference in the mid range on the 05 and later engine.
It's a better mod than any of the pipes in my opinion.

Of course the best mod for any 125 is a fresh piston.
usafwx wrote:
So I should get the VF3 first? require rejet? I love the bike right now in stock form, minus coming out of corners right before a...
So I should get the VF3 first? require rejet? I love the bike right now in stock form, minus coming out of corners right before a jump, sometimes just not enough torque and bottom end to shift quick enough to get over the jump, i.e. need 3rd to clear it but have to be in 2nd through the corner.
I did not rejet with the VF3,If you go with the VF3, make sure you use some Yamabond on the sealing surface, the VF needs a little extra sealing. I went up 1 tooth in the rear, but then again, I had 48, 49, 50 &51 tooth sprockets to play with.
cwtoyota
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cwtoyota 5/4/2016 5:05pm
5/4/2016 5:05pm
b8res wrote:
I did not rejet with the VF3,If you go with the VF3, make sure you use some Yamabond on the sealing surface, the VF needs a...
I did not rejet with the VF3,If you go with the VF3, make sure you use some Yamabond on the sealing surface, the VF needs a little extra sealing. I went up 1 tooth in the rear, but then again, I had 48, 49, 50 &51 tooth sprockets to play with.
Yeah, that's a really good point! I heard the same about the VF3 leaking before I got mine, so I use a little of the gray Permatex Silicon (exactly like Yamabond) on the sealing surface.

There are a lot of sharp edges on the plastic VF3 that clean up nicely with a razor blade and a delicate hand. I was less concerned with flow and more concerned with reed longevity, but I'm sure it helps flow. The reeds last about as long as a new OEM crankshaft for me.

The gearing changed when they dropped the dedicated USA model after 2010. I think it was 49 tooth stock for the USA and Europe/World got a 48. So I think 48 is stock now. Myself and 2 other friends all have been running 50 tooth. 51 would be great for tighter tracks, 49 for faster tracks and/or to smooth out the hit.
YZ125H1
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Elizabethtown, PA US
YZ125H1 5/4/2016 6:27pm
5/4/2016 6:27pm
Use clutch first and foremost one of the most critical things on a small bore 2 stroke. Gearing is cheap alternative too go with steel sprockets till you find what you like. Last choice is vforce 3 or a shorty pipe. I put an fmf shorty on my yz really gave her more snap which helped for tighter tracks. Seemed to lose a little overrev, but was barely noticeable.

After riding a 250f for awhile I switched back to my 125. Didn't realize how lazy I was on the 4 stroke.
Coach529
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ID US
Coach529 5/5/2016 6:12am
5/5/2016 6:12am
Thanks for all the info guys.......been keeping an eye on the local classifieds and craigslist. Just waiting for the right one to come up for sale.

Pit Row

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