134cc or 144cc

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May 19, 2001
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#1
i blew the topend on my bike and i called eric the other day and he talked to me about the different options i have and ive decied to to bore out the cylinder and have it replated. however i cant decide wheather i want the 134 or the 144. also i have to decide wheather i want it to be ported for mid to top or bottom to mid. as i discussed with him on the phone i live in ct and ride pits and woods. however i love the topend pull that my bike has to it. my friend has the same bike but has a fatty pipe on his instead of a bills. so his power is shifted down to the bottom instead of remaining on top. when i rode his bike i hated it. it redlined at around 3/4 throttle. but it had massive bottom end pull. so im looking for anyone with a yz 125 that has had the ama bore or the big bore kit done by eric and has had the porting done to the cylinder to reply to me with there thaughts. my only concers with the mid to bottom porting is that ill lose my top en power. any replys are much appriciated. thanks:silly:
 

chadk01

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#2
I can't comment specifically on the YZ 144 Kit, however, I did have Eric put the KX144 kit in my 2001 KX125. I asked for the MO Better Everywhere Port Job with the kit. I can say this, the 144 kit was the way to go for me. It boosted power across the entire spectrum. The bikes Mid-Range hit is nothing short of awsome. I was faced with the same choice, my plaiting on my cylinder had already came loose and I had to do something. So, I decided on the Big Bore kit. I would be very hard for me to get used to a stock 01 KX125 now that I have made these mods to my bike......I hope some of this helps:cool:
 
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#3
well ive never ridden a kx 125 but my main concern is the porting. did you feel that your power was less on the top or on the bottom than it was before the porting job was done. because eric told me that the mo better everywhere is better for the 250s and he recommends i choose one of the other two options. but i dont want to lose any top or bottom if i chose the mid to top of bottom to mid. ya know what i mean??:think
 

shaggy829

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#4
pit monkey
my 2000 yz is done to a 144 when you overbore an engine you will sacrafice
top in comparason to the stock bore . I would go eith mid top or all around
typ power you could use a fa tty pipe to get a litlle more bottom . big carbes
work great with overbores (38mil ) my pwm kiehen added more power everywhere. one more thing about the 144 i have had some trouble with right
side crankseals on several yz's including mine the seals have been installed
at an angle and can start leaking with the added primary compression .the 01
has an improved seal.:)
 

chadk01

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#5
Yeah I here ya. I forget who it was, someone here chose the bottom to mid power band and said they wish they would have went with the mid to top. Maybe they will read this and respond......
 
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#6
I also have little experience with 125's however, bigger is bigger, and often better. The big bore 125 that I rode had more power everywhere and really felt a lot better than production bikes. Some ot this was due to the wider torquer curve making it able to pull harder if the revs slip a little low.


Make sure to get the porting you need, as often times big bore kits tend to mellow out the power. This is due to many factors, one of which is the fact that the exhaust port aims down. After the bore job, the port is smaller and lower. This can also affect boost ports. It may even change the timing and size of the transfer ports.

Chris
Chris
 
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#7
ive decied on the big bore 144cc kit. i called eric today and he is sending out the engine crate on tuesday. also i chose the mo better everywhere porting. thanks for all the help. i need to ask him about the leaking seal that you guys talked about. i forgot when i was on the phone with him. also does the head get polished because my cylinder head has some major pitting in it.:silly:
 

steve125

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#8
Last year i had Eric big bore 2 bikes to a 144. The first was a 01 kx125 and the second was a 01yz125. Both bikes are still running strong and reliability has been excellent! Some riders talk trash about big bores not being able to rev high. Wrong! with proper port timing and jetting they can rev higher than stock with no problem. Both the kx and the yz had peak power at around 11k with Erics," more power everywhere porting". He's the best! period end of story.
 
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#9
i have a chance to buy a 1996 kx125 for $1500. Is it worth it if it's in good condition? I'm thinking of doing that 144cc big bore mod. How much does it cost, & does this "eric" have a website I can go to? Thanks. Btw, is 144 the largest I could bore a kx engine & is the power increase worth the price? thanks.

-dejacky
 

NO HAND

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#10
I've had the chance to spend an afternoon of riding a 00kx133 that had just been put together. It had the EG mid-top treatment. www.eric-gorr.com I really couldn't believe what I was riding. This thing made so much power that I shipped my cylinder yesterday for the 133 mid-top job. It really makes more on top- like where you don't even dream it could still make power. It's not like a subtle improvement where you have to compare stock versus modified. It's worth every penny. I've never tried the 144 though.
 
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#11
went to the site. converting kx125 to 150 will be worth the $ for me? 160lbs, about 170lbs w/ gear. I plan to keep the bike for at least 6yrs, so how often would i have to do maintenance on these 150cc engines? thanks again :).

-dejacky
 
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#12
so u think the 144 would give more power? would it be likely to also boost the low end via different pipe? thanks.

-dejacky
 

yardpro

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#13
there's no substitute for displacement. Unless you're racing ama events, go for the 144. if you're spending the money, why not get the bigger bore? On a 125, you really can't have too much power, plus you'll be spanking your friends bike. Ask eric for his opinion, tell him the riding you do and what you like and follow his recomendations. He is the man!!!!!!!!!!!!!
 
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#14
i probably wouldn't be buying the bike until april 2002, so i wouldn't want to waste his time on a scenario that could occur months from now. anything else?

-dejacky