Posts
52
Joined
7/22/2019
Location
USA
Edited Date/Time
8/8/2020 3:35pm
I had worn out my stock cylinder on my 2014 yz125 and had needed to repair some detonation from the previous owner on the top corner of the cylinder. I decided to go through Max Power RPM's due to their good reputation. After talking on the phone for a few minutes they had sold me on their 139 kit.
4 weeks and a lot of great service and communication later, I received my bored and ported cylinder, machined head and power valves all assembled. They provided very detailed instructions and break in procedure along with a gasket kit and piston kit. Very professional and clean, they have 10/10 service.
After breaking in the motor and getting my lectron tuned for the cylinder it runs great! I was very worried about it having little to no overrev like 144's are known for. The 139 has more torque and hp in the low to mid range than stock, and the overrev is damn near identical to the incredible 125 overrev. It still likes to be screamed like a 125, but it can also be ridden a little more lazy if desired. The double ringed wiseco piston weighed slightly less than the stock piston, so despite the bore being bigger, very little overrev was lost. I had it ported for top end power and had the head cut for 100 octane fuel and I run klotz R50 at 30:1. I have a vortex ignition, and vforce reeds, and an fmf shorty on the bike as well that really make the bottom end punchy and responsive.
This is truly the whole package. Strong off the bottom, powerful midrange, and 125 like overrev. I fully recommend this kit, it feels like it could definitely be competitive with a 250F. I found that the power comes on the best with the stock pipe and shorty muffler. The stock pipe has a great spread and the shorty really makes it punchy out of the corners. I can't say enough good things about this kit and I definitely plan on sending more cylinders to MaxRpm's in the future!
All of my additional parts and most importantly the 139 kit created a mean 2 stroke combo that is hard to beat!
https://maxrpms.net/category/motorcycle-kits/yamaha/yz125/
4 weeks and a lot of great service and communication later, I received my bored and ported cylinder, machined head and power valves all assembled. They provided very detailed instructions and break in procedure along with a gasket kit and piston kit. Very professional and clean, they have 10/10 service.
After breaking in the motor and getting my lectron tuned for the cylinder it runs great! I was very worried about it having little to no overrev like 144's are known for. The 139 has more torque and hp in the low to mid range than stock, and the overrev is damn near identical to the incredible 125 overrev. It still likes to be screamed like a 125, but it can also be ridden a little more lazy if desired. The double ringed wiseco piston weighed slightly less than the stock piston, so despite the bore being bigger, very little overrev was lost. I had it ported for top end power and had the head cut for 100 octane fuel and I run klotz R50 at 30:1. I have a vortex ignition, and vforce reeds, and an fmf shorty on the bike as well that really make the bottom end punchy and responsive.
This is truly the whole package. Strong off the bottom, powerful midrange, and 125 like overrev. I fully recommend this kit, it feels like it could definitely be competitive with a 250F. I found that the power comes on the best with the stock pipe and shorty muffler. The stock pipe has a great spread and the shorty really makes it punchy out of the corners. I can't say enough good things about this kit and I definitely plan on sending more cylinders to MaxRpm's in the future!
All of my additional parts and most importantly the 139 kit created a mean 2 stroke combo that is hard to beat!
https://maxrpms.net/category/motorcycle-kits/yamaha/yz125/
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I'm running 13/50 gearing on the 125. If I go up to the 139, would it work better stock gearing at 13/48?
Any contact information for these guys? Site is down for me
The business was sold to a guy in NC I believe, then it disappeared.
LED in Gresham OR did my 2022 YZ125 (134) I takes several months as he is a one man shop and very busy. For my YZ125X I purchased a Athena 144 and went that route. For both the cases need to be ground for piston stroke clearance at the bottom of the stroke. I did this work myself. Removed the engine but did not split the cases. Lots of tape, putty and patience. No issues at all. Regarding the Lectron, both bikes have this carb and for me it is the hot setup! I also have the Lectron on my CR125 Shifter Kart.
Both bikes are so much fut!!!!
Looks like somebody stole all the shit out of your garage and left your bike. What is it with you organized non clutter guys lol.
My garage looks like a MX yard sale and a gun shop had a baby !
I like the mod’d YZ !
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