O'MALLEY_808

Member
Dec 28, 2003
10
0
I am considering making my 06 CR125 a 144. I've been doing some research and have read that if you are a high revver than get the 134? Is this true? Also where can I find some information on how to do it/who to send it to? How reliable is a 144? I rev the hell out of my bike and it is currently ported and polished, high comp head, with the timing advanced and race fuel and it revs at least an additional 1000rpm over stock noticed on the dyno. Anyways any info is greatly appreciated. I was debating just getting a 06/07 cr250 but I was told they are really bad for rattling?

Thanks

John
 

robwbright

Member
Apr 8, 2005
2,283
0
Call Eric Gorr for answers to all your questions. I don't have time to post answers right now . . . If you don't have answers later, I'll try to post.

Eric Gorr
Forward Motion
P.O. Box 69
Streamwood, IL, 60107
Tel.1-630-825-5645
ericgorr@hotmail.com
 

robwbright

Member
Apr 8, 2005
2,283
0
O'MALLEY_808 said:
I am considering making my 06 CR125 a 144. I've been doing some research and have read that if you are a high revver than get the 134? Is this true? Also where can I find some information on how to do it/who to send it to? How reliable is a 144? I rev the hell out of my bike and it is currently ported and polished, high comp head, with the timing advanced and race fuel and it revs at least an additional 1000rpm over stock noticed on the dyno. Anyways any info is greatly appreciated. I was debating just getting a 06/07 cr250 but I was told they are really bad for rattling?

Thanks

John

My 144 revs better than the bike did stock by the "seat of the pants" test. I've never had it dyno'd. I had Eric do the "mo betta everywhere" porting with high compression for race gas.

After having the motor done, I pulled the jug after 5 races and about 15 hours of play/practice riding. I changed the ring at that time, but it wasn't really necessary yet and the piston was fine.

Eric recommends 5 hours for rings and 10 hours for pistons. However, he says that an expert rider can blow one up in an hour of hard riding. However, again, he has had a 144 go 100 hours on the same piston.

Eric's designed the 144 pistons for Wiseco - his piston weighs only on half ounce more than the stock 124cc piston, so I would think there would be relatively little increased wear on the bottom end - other than from the extra 6-8 peak HP.
 

robwbright

Member
Apr 8, 2005
2,283
0
Josherichy said:
Check out the new dirt rider mag there is a review on it.

Not really. The CR144 in the Dirt Rider was bored and stroked to get to 144 - which is actually illegal for the 125 class - at least as I understand it - because of the stroking.

Plus, the 144 Eric did for me essentially retained the same spread of power as stock, it just added to it everywhere.

The Dirt Rider bike has a VERY "thin" powerband with lots of boggy spots. The initial review of that bike several months ago talks about the work in more detail.

Oh yeah - my 144 kit was less than $500. Theirs was about $1200+, if I recall.
 

Eric Gorr

Engine Builder
Jun 29, 1999
384
12
Wiseco makes a 139cc 57mm kit for the CR that is really light and works the best out of the overbore kits. I've installed 5 so far over the summer and they're holding up well. The porting on the CR125 is really close to a YZ now and it doesn't require case mods.
 

robwbright

Member
Apr 8, 2005
2,283
0
Josherichy said:
Do they make a 139cc for the yamaha that does not require case mods?

I can't answer that question, but may I ask, what's the big deal about the case mods. You're going to have to take or send part of your motor to someone to be bored/plated/port/head work anyway - unless you do it yourself, which most of us can't or won't.

I sent my whole motor UPS to Eric Gorr for about $20-25 and he did it all, including the case mods and he put it all back together. All I had to do was reinstall the motor in the frame and start it up.

Some guys do their own case mods. It's apparently not a big deal and Eric can tell you exactly how to do it.
 

Eric Gorr

Engine Builder
Jun 29, 1999
384
12
Actually the Honda 57mm piston fit the YZ125s but of course the head and valves need to be modified. The case mod is relatively simple and doesn't require case splitting, just carefull masking and chip removal.
This week I am doing a 144 kit on a 07CR125. The 2005-07 have a fairly thick cylinder wall since it is a good copy of a YZ125
 

yamahuh

Member
Oct 23, 2005
5
0
Eric,

I was researching the CR144 last year for an 05 CR125 and I was told that the cylinder walls were too thin to make it a 144. Is that not the case anymore? Can an 05 CR125 be bored to a 144 or would it still need to be stroked? Also, I was told that the 139 was an all-around better bike than the 144. Is that correct?

Thanks,

Brent
 

lwsmithjr

~SPONSOR~
Sep 18, 2002
194
0
What about the '03's. I have a friend who has the pleasure of owning a 2003 CR125 and it really needs the help. He was impressed by the power of our new EG YZ144 (me too!), but I told him I wasn't sure it would have the same overall increase.
 
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