04 cr125 mods.

BILLY · Jan 30, 2004

Hello,
rather than take sides in this 4 stroke vs. 2 stroke war, i just decided to buy both. i recently picked up an 04 crf250 and an 04 cr125.
i already know that the cr125 will be slightly down from the rest in power but at least its got a great chassis and great stock suspension. i just hope someone can find some more power in this thing.
does anyone have any power mods yet for it? dyno runs? secret jetting spec? big bore?
i'll do whatever is needed to make this thing go fast because i am still not too happy about this whole 4 stroke thing. :ugg: thanks for the help...

marcusgunby · Jan 30, 2004

How slow is it compared to other 03s/04s?

BILLY · Feb 2, 2004

i have been off 125's for the past year. i rode mostly an 03 yz250f in 2003. in 02 i rode an 02 yz125 and in 01 i rode an 01 cr 125.
i have ridden a friends 02 cr125 last year at times for fun laps.
as for the 125's, the 02 yz had much more of a longer spread of power. the cr's felt the same as compared to each other. they had zero bottom and then a short abrupt mid hit without a great over rev. the yz125 had a meaty mid and kept revving compared to the cr125's. also in sand it was much easier to fall off the pipe on the cr's compared to the yz, assuming the result of the lack of torque of the cr engine compared to the yz.
however, stock for stock, the cr's had a much better chassis and suspension. i liked the overall feel, handling and suspension of the cr's way more than the yz. i decided to go red again this year. i havent ridden the crf nor the cr yet because in nj we are covered in snow and under a deep freeze for the past month. but i do know already that even after all hondas upgrades to the cr125 motor it still lacks. that's why i just want to get it faster from the start because the cr125 is my favorite except for that motor...
just look at the new dirt bike and mxa mags. they ripped on that motor real bad. :ugg:
bottom line- if only i could have a yzish feeling motor in my 04 cr. any suggestions or help from you tech guys here on DRN would greatly be appreciated. i have read a lot of these mod forums and you guys really know a lot. :worship:
there was an article in a semi-recent MXA mag. they rode michael byrne's cr125 at southwick. they loved it. sure wish i could get my hands on that motor.... :thumb:

marcusgunby · Feb 2, 2004

Billy its going to be difficult to help with the new cr for a few reasons, one is so few people have one, second its a newish engine and tuners take a few months to get to grips with a new setup, im sure it shares many parts with the 03 however.Im guessing the most gains would come from the exhaust side -a few years the std exhuast has been really good(2001) but in 02 it wasnt the best.The 03 can be improved upon as well.Im also guessing the 04 will have really big ports like the 03 and some small gains can be made here, the ignitions on a few years Crs were not optimum-the 2002 gained with a wulf ignition.Lastly the last few years the head setups were not perfect.

So theres no easy answer really, it needs someone like eric gorr to analyse the engine and look for weakness's.The other altenrative is you will have to try various aftermarket parts in the hope they work-that can get expensive.

My advice get a rm125:) all the handling and a good engine.

elf · Feb 2, 2004

Yea its to bad honda cant make a fast 125. I think those factory connection hondas were the most modified engines in the pros. You could try some ultimate 2 race gas. I guess its supposed to be good for about 1hp.Then you will have to wait and see if sombody comes up with somthing else.

crmx91 · Feb 2, 2004

Sell the CR125, and make your CRF a full race bike. I love my 03 CR125, but as soon as i get the money im going CRF.

tm-enduro · Feb 2, 2004

One of the rags did a test on a cr125 with the SRS head, pipe, piston, and reeds and really liked it.

NO HAND · Feb 3, 2004

marcusgunby said:
...the ignitions on a few years Crs were not optimum-the 2002 gained with a wulf ignition...

That's what I don't like about the new electric powervalve. It must be harder to retrofit any ignition. When I had my 00 CR125, I used the Honda ignition for CR125 1992-1995. It was one of the good mods along with the 133 kit from Eric Gorr. I wonder if some aftermarket companies have come up with ignitions that work with the electric pv.

marcusgunby · Feb 3, 2004

good question, unless it fits another bike(like the 250 which i doubt) i dont think they will make one-i think in the UK they have sold as many Cr125s this year as they have given to sponsored riders(about 10 of each)

BILLY · Feb 4, 2004

i know the writing is on the wall regarding the 125 cc 2-stroke, even i purchased another 4 stroke. i still, and will always love the feeling of railing through turns on a 125 with the bike pinned. for fun riding a 125 is my hands down favorite. on the other hand, for racing, i have to go with the 4stroke because i'll be at a significant disadvantage at the start and also have less line choice options. i'll just keep checking the boards for any hop-up ideas and or big bore kits. i know the 04 cr125 sales will most definitely be at an all time low, insuring that the aftermarkets will not spend a lot of R&D time for this bike. oh well. even though the sport is moving to the 4 stroke, i will still keep my cr for fun and for keep sake..... :whiner:
i've sent an email to SRS inquiring about their engine kits. i hope they answer. i was looking at the catalog on line but i cant read italian...

tm-enduro · Feb 4, 2004

I am seriously considering a '04 cr125 as a woods bike due to the handling, let's face it, nothing handles like a cr125. I am interested in the SRS engine kit to see if that will perk it up, note that the SRS motor runs on pump fuel. I am a 175 lb (former AA/A enduro racer, but now older and slower) and can make up for some lack of power with skill, but it must have enough torque to pull me up hills in rocky trails.

marcusgunby · Feb 4, 2004

TM the rm is the one you want, it handles just as well as any cr IMO and it has a engine no std cr was ever devlivered with.I would hate the lack of low end and 5 speed box in the woods of the cr.

marcusgunby · Feb 4, 2004

BTW i feel the SRS stuff is decent but dont expect big gains in power and a reasonable price, small gains, big money.

bclapham · Feb 4, 2004

Billy: if you are looking for power, there is no replacement for displacement. send that cylinder to Eric Gorr and have him do the 56mm piston/134cc big bore- that should help and he can have a good go at the ports etc as well. other than that, it sounds like you need to find a dyno and start testing pipes, reeds, etc etc and maybe an ignition if you can find one. also, if you can find the VP ultimate 2 race fuel, that will add power also and liven up the bike. also, wasnt the hot ticket on the cr125 a 8 plug????? what about running a spacer plate under the cylinder and using a longer rod?

i dont think the writing is on the wall just yet for the 125, but it might be for the cr125- they havent sold many since they came out months after the other bikes, and it sounds like the cr engine has been a bag of nails for quite a few years. at least kawasaki and suzuki wised up and copied the best engines in the class.

BILLY · Feb 5, 2004

hey TM, Marcus is correct. i had an 00 ktm exc125 for some random hare scrambles. for a 125 motor, it was awesome everywhere, hills, trails etc. i decided to use my 01 cr125 one time. i couldnt believe how much more difficult it was. the cr125 really showed its ugliness by not having any low end whatsoever. it wasnt an impossible task, it was just more work mentally. i dont think the cr125 would ever be my first choice for scrambles and especially enduros. it would be too much work. pick a good 125 with a known great low end and good overall power delivery. in my opinion i would probably grab a ktm 125sx and valve it for woods. motor will never be an issue with that bike and handling of all 125's in general are not that bad, even the worst one is still good compared to big cc bikes. and yes i know how good a cr125 handling is.
on an mx track however, i rarely feel the lack of low end on the cr because i always have the motor between the mid and over rev part of the powerband. only when i get tired and sometimes get lazy do i ever feel it.
so i am just looking for more mid and over rev from it. hopefully another 5-6 hp would be nice. a big bore is not out of the question. how is eric's work? i hear good things.
would a 134 and ported for race gas eric gorr kit be more powerful overall compared to a highly modified 125 with all the add ons?
thank you very much marcus for your input regarding SRS. i will keep that in mind. :thumb:

marcusgunby · Feb 5, 2004

Some 04 cr125 info ,std one made 31hp compared to at least 32-34 for the other 04s.It has better bottom than the older crs(back to 99) but it doesnt have a good top end power.In 2000 this engine would be good.After a fair amount of work it had 33hp and it wasnt easy to see where any more would come from.

well thats the summery not great news im afraid but the with cr engines when is it LOL.

tm-enduro · Feb 5, 2004

Marcus and Billy, thanks for the advise re: the CR125. Maybe I'll just have to get another TM, or make my own exc out of a sx125. I have ridden the cr and yz and both felt very weak compared to the TM, I was hoping that a few $$ in parts would perk one up. The TM is ~7K US$, ouch!!!

fastwes · Feb 6, 2004

We had the 04cr125 on the dyno a couple of weeks ago for about 10 days with Eyvind massaging it. Stock it has ports high enough, wide enough, a tight squish with fair compression, and a nicely working power valve system(but poor shape match) but doesn't make enough power. The width of powerband is great with peak torque around 9000 and peak power at 12000, but just not enough of it! With some transfer changes and internal exhaust port modifications it is way more powerful, about 4 more hp, with the same powerband. Then with more compression it has more middle. Now it will be fast and still easy to ride. Watch out for Jacqueline Ross!
Wes Gilbert
Boyesen Precision Porting

Rich Rohrich · Feb 6, 2004

Thanks for the update Wes. Will we be seeing you guys at the Indy show with any cool new products?

bclapham · Feb 6, 2004

Good to hear from Wes, its been a while!

Just out of interest, have you had any of the other 125's on the dyno yet and are they good for another 2-3HP with mods?

tm-enduro · Feb 6, 2004

Fastwes, tell me more! Do you have a website? I'm curious about making an enduro/hs/gncc bike, ie lots of midrange power and torque are nice. What are costs? Should I call you?

fastwes said:
We had the 04cr125 on the dyno a couple of weeks ago for about 10 days with Eyvind massaging it. Stock it has ports high enough, wide enough, a tight squish with fair compression, and a nicely working power valve system(but poor shape match) but doesn't make enough power. The width of powerband is great with peak torque around 9000 and peak power at 12000, but just not enough of it! With some transfer changes and internal exhaust port modifications it is way more powerful, about 4 more hp, with the same powerband. Then with more compression it has more middle. Now it will be fast and still easy to ride. Watch out for Jacqueline Ross!
Wes Gilbert
Boyesen Precision Porting

elf · Feb 6, 2004

Wes does the 04 show more potential than the 02-03 motors?

marcusgunby · Feb 9, 2004

Heres a treat for you all the std 04Cr125 vs std 04Rm125-i think you can guess which colour is which

next is the same bikes both fitted with a pipe
:thumb:

marcusgunby · Feb 9, 2004

And last of all a dyno to show std vs a aftermarket pipe-as you can see it gives a nice gain at the top but nothing massive.

BILLY · Feb 10, 2004

marcus,
i cant seem to open up your dyno attachments, or any dyno attachments for that matter. i dont know whats wrong. could you possibly send them to my email address?
wostlin@inteplast.com.
thanks a lot. i sure appreciate it. i am guessing by your post that the cr is really down on power and a pipe just adds a tiny bit. thanks for depressing me so early in the morning. :)
i guess i will just have to wait it out a bit until most hop up shops have some R&D time with this slug. i'll spend what i need to. i just want a REAL fast cr125. in the mean time i reluctantly will use the crf250 for now. oh well.
i am riding a 4 stroke now, but i dont have to like it..... :whiner:

04 cr125 mods.

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