need some more overrev!!

[twosmoke595]

 ok so here's the deal, i've got a 2007 cr125

its got a stock engine, no aftermarket pipe, no nothing.

so..the only thing that i have done differently is change the 51 rear sprocket to a 53
i did this because it helps between shifts and the tight twisty turns that are at the tracks around here.

but the tracks also have some pretty long straights, and while shifting and shifting...and shifting i feel that i could use more top end overrev
these straights are like highways basically 4th and 5th pinned

what are some things i could do to the bike to make it have more overrev? the power is fairly mild from bottom to mid and from mid to top it flys, but like the upper top end it signs off, i have never ridden another 125 before so i dont know if this is how they all are or what. But please give me some pointers as to where i should go, i know its kind of a double edged sword with the low gearing, and i want top end, but i think thats just the way its going to be.
this being said, it has never fouled a plug, and it seems to be jetted perfectly


what are yall's thoughts?

[2T Institute]

Retard the ignition

[VintageBlueSmoke]

Yeah, add the adjustable ignition gizmos. That way you could change it for various spots of the tract.

I've never done it but all the top guys were doing it when I quit racing in the States (early 2000's).

[twosmoke595]

ive never messed with the timing except when i work on the little xr50's and their cam sprocket, how would i go about doing this, and is there any other way besides messing with the timing to get what i want?

[Super Trucker]

Take that 53 off and put the stock 52 sproket on,there you have your topend back. I,m 170-178 lbs stock gearing 52,going to a 51 sproket, 06 cr125 radvalve,icat,stock motor,pipe,pc silencer standard. The rad valve has a great low to mid increase for coming off corners, I think a 52 is over geared, going to a 51 gear in spring. So the radvalve will help ya,in the tight twisty stuff,then the 52or51 gear will spread the powerband out,the engine is strong enough to pull 52 gearing easily. Stacking 2 base gaskets will change the port timing,lowering compression,adding topend.

[twosmoke595]

hmm i think i'll try a 52 before i do anything else drastic to the engine, maybe put a 1 tooth bigger front sprocket on instead bc its cheaper?

[ford832]

Like supertrucker says,drop a tooth on the rear.You have to give here to get there.Learn to ride the clutch at slow speeds-that's how 125's are meant to be ridden.Any engine mod's you make will give minimal results.If you do enough to get more noticeable overrev,you're going to lose it on the bottom.
Compared to the YZ,s or KTM's of that era,the CR's were nothing to write home about engine wise.A good bike-just not very broad power.
Don't waste your $$ on expensive mods.Get the gearing right for your track or area and learn to ride the power you have.

Depending on your gearing,changing one tooth on the front is equivalent to roughly 3.5 on the rear.Going up one tooth on the front would put you down about 3.5 teeth on the rear.In other words,about a 49-50 in your case.

[Super Trucker]

1 tooth larger countersproket-front,would be aprox. like 2.4 tooth less on the rear.Don,t do that, it might not fit either,hitting on the cases.

[twosmoke595]

Like supertrucker says,drop a tooth on the rear.You have to give here to get there.Learn to ride the clutch at slow speeds-that's how 125's are meant to be ridden.Any engine mod's you make will give minimal results.If you do enough to get more noticeable overrev,you're going to lose it on the bottom.
Compared to the YZ,s or KTM's of that era,the CR's were nothing to write home about engine wise.A good bike-just not very broad power.
Don't waste your $$ on expensive mods.Get the gearing right for your track or area and learn to ride the power you have.

Depending on your gearing,changing one tooth on the front is equivalent to roughly 3.5 on the rear.Going up one tooth on the front would put you down about 3.5 teeth on the rear.In other words,about a 49-50 in your case.

ya i understand about the gearing thing, if i change it i'll lose bottom end and gain top, ya like i said, ive only ever ridden this 125 before. So i guess i'm just asking too much for what it is lol. And i dont remember what the front sprocket size is, but i do remember when i put it on it was already close to the case, so i guess i'll just have to deal with it unless i get a SST pipe or something

[Super Trucker]

I never heard anything good about the SST pipe, and hear the fmf fatty has fitting issues. I would throw a rad valve in it, pull the reeds and polish the internals smooth,free power. Nice low to mid gain,that,s great for coming off corners.

[twosmoke595]

really? hmmm ive never heard of any FMF having fitting issues, unless the pipe was meant for a different year bike.

[ford832]

I just put a fatty on the YZ last week.It fit perfect as far as engine/frame clearance etc went but none of the mounts lined up so I had to do some modification.No real big deal but had to bend the tabs on the pipe as well as file out/shim the mounts on the bike.

My gearing on the YZ is currently 14/50 This gives me a value of 3.57
My Sx was 13/50 that gave me a value of  3.84
If he currently has a 53 rear,to get that 2.4 ratio he would have to run a 22 front.He wouldn't then be much off the line but would just be a red streak when he got up to speed.

[twosmoke595]

ok so basically in order for me to get what i want then i'll need a rear sprocket

what would a new reed cage or just different reeds to do the power?

[ford832]

Carbon tech used to sell low,mid and upper reeds-it was all based on stiffness I tried them and they worked as stated but killed the power everywhere else.A set of Boyesen Pro series(carbon but the regular fiberglass power reeds are good too)are a good investment and will increase your power across the board.You must rejet though.I typicaly go 2 sizes leaner on both the pilot and main with the boyesen reeds.This is my baseline starting point and usually my final setting with a little airscrew fiddling.If you just throw them in and don't rejet you'll lose power.

[xandyx]

i have a 01 cr 125, the slowest 125 arround, and i've been trying to get a better bike. i don't wanna sell it for another bike because the chassi is pretty good, and as it is kinda an old bike, it's was going cheap..

i've been searching a lot, and i found an article that says that the stock reeds and boot from a yz 125 would improve top end due to a bigger air flow. honda has an intake boot that internaly measures 26mmX32mm, and yz 125 manifold measures 32mm x 37mm

you can read some info about the 02 model on this article
http://www.dirtrider.net/forums3/showthread.php?t=23066

you can also clean some cylinder casting flaws from exhaust and intake ports.

check this out
http://freedom7motox.com/cr-125-2003-mods

hope it helps!

greetings