Who is the ultimate at YZ 125 porting/head work?

blaze 57
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blaze 57
Edited Date/Time 4/20/2021 4:32pm
Just bought a new 21' YZ 125 and just want a good port job and the head cut to still run on pump gas. With a few more horses on mid-top this thing would be perfect I have zero idea who is the best out there? Thanks
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Bruce372
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Bruce372 3/31/2021 11:39am
3/31/2021 11:39am
Heavy duty racing on the east coast.
Falcon
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Falcon 3/31/2021 1:33pm
3/31/2021 1:33pm
Terry Varner.
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Falcon
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Falcon 3/31/2021 1:35pm
3/31/2021 1:35pm Edited Date/Time 3/31/2021 4:05pm
Laughing Laughing Laughing Woohoo

Actually, I had a ported/milled Varner cylinder on my '01 YZ125. It was, hands-down, the fastest 125 I have ever ridden. I pulled good starts at Glen Helen on that bike against 250s and 450s. (Well, 426es.)
Judging by all the issues that guy has had recently though, I wouldn't send my stuff to him.
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JBoneMotorworks 3/31/2021 2:21pm
3/31/2021 2:21pm
I would do a Bill's Pipe set, VForce reeds, and take the squish clearance down to .95mm..run a mix of VPc12 and 93 oct at 40/1 and it will be a ripper and reliable. About 100 octane is perfect, Maxima Formula K2 is good for the oil.

Good luck-
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navalseabee
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navalseabee 3/31/2021 2:51pm
3/31/2021 2:51pm
Bruce372 wrote:
Heavy duty racing on the east coast.
Pete did my 150, it was a ripper.
Bruce372
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Bruce372 3/31/2021 4:28pm
3/31/2021 4:28pm
Bruce372 wrote:
Heavy duty racing on the east coast.
navalseabee wrote:
Pete did my 150, it was a ripper.
Pete has spent a lot of dyno time on the yz125.
soggy
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soggy 3/31/2021 4:46pm
3/31/2021 4:46pm
Tom Morgan has done lots of yz, or pc.
drivrswntd
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drivrswntd 3/31/2021 5:38pm
3/31/2021 5:38pm
Falcon wrote:
Terry Varner.
What year you plan on riding it?
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opyguy
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opyguy 3/31/2021 6:02pm
3/31/2021 6:02pm
JBoneMotorworks wrote:
I would do a Bill's Pipe set, VForce reeds, and take the squish clearance down to .95mm..run a mix of VPc12 and 93 oct at 40/1...
I would do a Bill's Pipe set, VForce reeds, and take the squish clearance down to .95mm..run a mix of VPc12 and 93 oct at 40/1 and it will be a ripper and reliable. About 100 octane is perfect, Maxima Formula K2 is good for the oil.

Good luck-
any 21 KTM 250sx ideas j-bone?
love the bike, need a bit more top end pull...
i hear your the go to guy (that retired)
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MotoChris
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MotoChris 3/31/2021 6:40pm
3/31/2021 6:40pm
Tom Morgan. We got a new YZ125 a few months ago and I sent the cylinder and head to him as soon as I got it home. The bike is very strong. We have another YZ125 built by someone else with more work done and my son says that the Tom Morgan motor is a lot stronger. We had the competition at our local state championship race asking me about it and they are on different color bikes.
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jaredkeller96
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jaredkeller96 4/1/2021 9:09am
4/1/2021 9:09am
Dean baker ex JGR,Kawi, and legendary Yamaha of Troy knows a thing or two about yz125s…check him out on Instagram..@baker_speed
eric513anderson 4/1/2021 9:12am
4/1/2021 9:12am
I’d get a Apex head for it while you have it apart
blaze 57
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blaze 57 4/1/2021 9:35am
4/1/2021 9:35am
Thanks for the feed back everyone. Sounds like some good source here so far to prevent my cylinder from becoming a paper weight.
Falcon
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Falcon 4/1/2021 1:17pm
4/1/2021 1:17pm
Falcon wrote:
Terry Varner.
drivrswntd wrote:
What year you plan on riding it?
2026. Cool
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Moto520
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Moto520 4/1/2021 2:37pm
4/1/2021 2:37pm
Add the Apex head if you have the means....nice improvement.
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MXJIM10
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MXJIM10 4/1/2021 4:20pm
4/1/2021 4:20pm
Had Tom Morgan do my engine and it was terrible. No better than stock,plus powervalve bolts fell out. Not tightened enough. Great Guy and good service,but did a half ass job on my engine. Not trying to be an ass,but he can do better than that.
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Moto520
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Moto520 4/2/2021 8:05am
4/2/2021 8:05am
TZR Motorsports in Illinois. Tom is really good and meticulous. Never heard anything bad about them. They have done a ton of my 4 strokes and they have all been great. No affiliation....don't care.
JBoneMotorworks 4/2/2021 5:51pm
4/2/2021 5:51pm
opyguy wrote:
any 21 KTM 250sx ideas j-bone?
love the bike, need a bit more top end pull...
i hear your the go to guy (that retired)
Hey opyguy. I did get out of the engine biz a while ago but a head cut to get your squish down to about 1.1mm would be a good start, some hi rpm reeds, a pipe set to match the tune, there is a lot that can be done in the pv flapper area but can't really explain it without a tutorial lol.
You could also add a base gasket of like .25mm or so and then cut the head back to get the squish down, this would accelerate the port timing and have more hi rpm.
Bills pipe sets work great. Best- J
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Motofinne
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Motofinne 4/2/2021 10:51pm
4/2/2021 10:51pm
The guy doing the Fantic EMX bikes has to be up there with the best
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Bearuno
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Bearuno 4/3/2021 1:26am
4/3/2021 1:26am
Motofinne wrote:
The guy doing the Fantic EMX bikes has to be up there with the best
Well, if Dr Jan Witteveen is behind the mods done to the YZ engines, or even someone, or 'someones' that are working under him, you're not wrong.

He's far more than just a 'tuner', which the vast majority of industry types are.

I'd love to see him let loose to create new, modern 2t engine designs. What phenomenal powerplants they could be! His previous engine designs won multiple World Championships, for those who have no idea who he is.
sebastianer 4/4/2021 3:38am
4/4/2021 3:38am
Motofinne wrote:
The guy doing the Fantic EMX bikes has to be up there with the best
yes probalby Jan Witteveen but i dont think you can get him to do your cylinder, but i would send the cylinder to two stroke preformance in au, he does a lot of cylinders for many fast 125 racer around the world.
Bruce372
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Bruce372 4/20/2021 4:32pm
4/20/2021 4:32pm

captmoto
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captmoto 4/22/2021 9:22am
4/22/2021 9:22am
Why would you go with a modded motor and then use pump gas? Even something like T2 will give you more consistent performance.
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