sportbikenut2

Member
Jun 7, 2005
7
0
I have a 2001 CR 125 and i have problems with it wanting to run at low rpm's. Once i get going the mid and high rpm range is very strong however it wants to bog and sputter down low. I just got it last week. It run fine then, however this week it runs to bad down low to even think of idling.. I did notice that i got a gas oil leak seeping around one of the head bolts. I suspect a possible bad head gasket but not sure. Havent tore into it yet.. However i thought that if i lose compression somewhere like the gasket that it would affect the powerband.. Is this my problem or do i have a jetting problem also perhaps? It has an aftermarket exhaust but stock air filter.. Got absolutely no clue if there been any other mods done to this machine.. Thanks for any info..
 

viking20

Sponsoring Member
Aug 11, 2002
428
0
If the bike ran fine , when you got it , I would clean out the carb , and check the reeds while the carb is off.
The head gasket would then be next , unless you have any signs that its leaking.That is , loss of coolant , or pressure building up in the radiators.
The cr´s head gasket is an old fashioned steel gasket , it doesnt cost much , and its an easy job. Be sure to tighten the head to the correct torque , if you need to remove it. Maybe its a good idea to change the piston as well , if you are not sure how many hours since the last top-end ?
 

sportbikenut2

Member
Jun 7, 2005
7
0
Yeah i have no clue as to when or if it has been rebuilt.. As long as i could keep the rpm's up some over idle i could keep it running alright. However if not it would die.. Also if i didnt run it hard now and then it would kinda i guess load up and then the powerband would sputter rather then hit hard.. Plug looked good though..
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
2,958
0
are you running the same fuel as was in it before?
 

JTurn36178

~SPONSOR~
May 17, 2002
131
0
How about the pilot jet? Is it clean? Too small? Too large? What about the air screw?

These things beside the slide affect the engine at idle. I'm not familiar with the model of carb on that bike. It would be a good idea to do some research on that carb. Most Mfg. have web sites with a wealth of technical data that will give you answers to the components that effect these problems.

Just some ideas. Good luck,
Jim
 

viking20

Sponsoring Member
Aug 11, 2002
428
0
If the bike is in stock shape , sea level , and summer temps it should run ok with a 40 pilot jet (stock 45 ) , std needle in the 2 or 3 clip groove and a 360 -380 main ( stock is 380 )
If it dies completely at low revs/idle I would think an air leak is causing it , or the slow jet is clogged up.
 

usgpru27

Member
Jan 15, 2005
105
0
I had the same issue with my 01 CR125 when I got it this year. I run 50/50 race gas to premium pump 40/1. I am running a 30 pilot with the air screw at 2 3/4. The range in the book for the screw is up to 3 turns out till you go to the next size. I have the stock needle as well as the one leaner 69 needle. I have the 69 on the second clip and a 350 main. This is at about 1000ft. with 75 deg. temp and medium humidity. Not sure if this helps but after you go through it (head gasket and top end) lean out you low circuits a bit.
 

Dakota922

Member
Jun 22, 2005
6
0
Speaking of,...

if you have the Reed valve in your hand should the reeds sit flat on the body,(meaning is their relaxed state closed)?

and I have seen a couple posts about the importance of Torque on the topend, what effect does incorrect torque have?
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
2,958
0
Dakota922 said:
and I have seen a couple posts about the importance of Torque on the topend, what effect does incorrect torque have?

torque wrenching the bolts down to proper specs.
keeps the head from warping, bolts from stretching or snapping, prevents leaks etc etc...........
 

Ryone

Member
Jun 18, 2004
391
0
I have the same bike, but have meticulously taken care of it.
If I were you, I'd do the top-end, buy the VForce3 reeds, repack the silencer, fresh plug, fresh tranny oil, then see how she does. If you cover all the bases, you should be alright. It's a great bike.

Good luck

Ryan
 

Welcome to DRN

No trolls, no cliques, no spam & newb friendly. Do it.

Top Bottom