Josherichy
Member
- Sep 23, 2006
- 125
- 0
I have a 2005 yz125 and im thinking about a 144 or a 134 bore, but i dont know how reliable the 144 is. I want somthing that will give me the edge but i dont want to change rings and pistons to often
i need help with the yz144
- Thread starter Josherichy
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robwbright
Member
- Apr 8, 2005
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Depends on how you ride it. According to Eric Gorr, a Pro can sometimes grenade the engine in an hour.
He recommends 5 hours actual ride time for rings, 10 hours for piston. This is to be safe.
He had one RM144 that went 100 hours on one piston.
I had mine done over winter 2005/2006. I rode maybe 15 hours practice/play riding and 10 race motos.
Pulled the cylinder and checked it out - nothing needed replaced, but I changed the ring anyway since I had the jug off. It didn't appear to me to be any different as far as wear than the bike was stock. Eric's 144 piston is only a half ounce heavier than the stock 125 piston.
Then again, I'm not that fast, so it probably takes me awhile to wear one out.
The 134 and 144 have about equal peak HP. The 134 will tend to rev out further and the 144 will have a little broader power spread.
He recommends 5 hours actual ride time for rings, 10 hours for piston. This is to be safe.
He had one RM144 that went 100 hours on one piston.
I had mine done over winter 2005/2006. I rode maybe 15 hours practice/play riding and 10 race motos.
Pulled the cylinder and checked it out - nothing needed replaced, but I changed the ring anyway since I had the jug off. It didn't appear to me to be any different as far as wear than the bike was stock. Eric's 144 piston is only a half ounce heavier than the stock 125 piston.
Then again, I'm not that fast, so it probably takes me awhile to wear one out.
The 134 and 144 have about equal peak HP. The 134 will tend to rev out further and the 144 will have a little broader power spread.
Josherichy
Member
- Sep 23, 2006
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- Thread starter
- #3
ok cool...
well I race and ride pretty hard, but will the 134 or is there a 139 that will last longer than recomended 10 hours.
Thanx
well I race and ride pretty hard, but will the 134 or is there a 139 that will last longer than recomended 10 hours.
Thanx
robwbright
Member
- Apr 8, 2005
- 2,283
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Well I ride and race pretty hard too, but there's a big difference between over-reving the bike for an hour straight and riding "hard."
Because the 134 tends to have the power a bit higher in the range, I would think it will likely wear a little faster - if you're good enough to keep it at 10,000+rpm all the time.
What class rider are you?
Because the 134 tends to have the power a bit higher in the range, I would think it will likely wear a little faster - if you're good enough to keep it at 10,000+rpm all the time.
What class rider are you?
Josherichy
Member
- Sep 23, 2006
- 125
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- Thread starter
- #5
I just started racing during the summer so I am only in novice class but I am geting faster each race, and I am 195 pounds
We only have 20 min motos, but practice days are longer
We only have 20 min motos, but practice days are longer
KTM125 with Eric's 144cc kit - I ran it forever - I kept taking the cylinder off checking the piston and it never wore out. I put fresh rings on it and the darn thing lasted for over a year on the first piston. I finally just changed it to a new one because I was tired of pulling the jug off every couple months to check it out - actually on the 2nd piston, I started pulling the exhaust pipe and peeking up into the exhaust port to see if there was any blow by on the rings... never was. I sold it before it ever needed a 2nd piston, and I rode it for a year on/off that time as well.
So I dunno - Eric might just be being safe saying to change them so often, but they lasted longer than any 125cc bike I ever owned!
Mike
So I dunno - Eric might just be being safe saying to change them so often, but they lasted longer than any 125cc bike I ever owned!
Mike
chrislaw1968
Member
- Oct 6, 2006
- 12
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hi mikeMikeeeP said:
how was the bike after you installed the 144 kit and how did it affect the jetting, i am waiting for my sx 144 top end to turn up.
chris
I am putting loads and loads of money in to my YZ144 (Which I am currently waiting to get back from Eric), but the 144 over bore was the least expensive thing yet. I figure, if you have a 250f, you could spend $850 on an exhaust or pay half that on a 144 over bore on a light, nimble yz125. It cost me $475 I think. Check out his new web site.
Eric Gorr
Engine Builder
- Jun 29, 1999
- 384
- 12
Some technical information on reliability:
The width of the exhaust port and the shape as well as the width and radius of the bridge corners, are all critical to piston and ring life. The YZ125 since 1993 has used very narrow exhaust bridges. The wider the bridge the longer pistons and rings last but the more low end the powerband becomes. As an option I offer TIG welding and stress relieving to widen the stock exhaust bridge.That might be a better powerband to get too. In Hawaii you have loamy dirt and big elevation changes in hills so you need the torque. This can be done to a cylinder in the 124,134,139 without grinding the cases and the 144 and 155 with case mods.
For the 139 I use the new Wiseco Honda CR139 piston part number 841MO5700. The Honda and Yamaha use the same relative dimensions. This piston is dome shaped on the 841, so it has better life in general.
The 134 and 144 Wisecos 846MO5600 and 5800 have stock dome shapes and the 5600 doesn't require head mods, both require powervalve clearancing.
The width of the exhaust port and the shape as well as the width and radius of the bridge corners, are all critical to piston and ring life. The YZ125 since 1993 has used very narrow exhaust bridges. The wider the bridge the longer pistons and rings last but the more low end the powerband becomes. As an option I offer TIG welding and stress relieving to widen the stock exhaust bridge.That might be a better powerband to get too. In Hawaii you have loamy dirt and big elevation changes in hills so you need the torque. This can be done to a cylinder in the 124,134,139 without grinding the cases and the 144 and 155 with case mods.
For the 139 I use the new Wiseco Honda CR139 piston part number 841MO5700. The Honda and Yamaha use the same relative dimensions. This piston is dome shaped on the 841, so it has better life in general.
The 134 and 144 Wisecos 846MO5600 and 5800 have stock dome shapes and the 5600 doesn't require head mods, both require powervalve clearancing.
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