i have a problem, need help

K

killer454

Member
Jan 3, 2011
47
0
i have a 04 honda cr 125r with pro cuircut header the rest is stock. i just rebuilt the top end. i had a steel sleeve put in it. the stock piston i took out was oem and it was a flat top piston and i replaced it with pro-x piston and it has more dome shape.

it idles perfect but when i crack into the throttle all the way it bogs down (if its at idle and i snap the throttle to all open it boggs). if i ease threw the throttle, no bogging and it hits powerband and runs perfect.in neutral it revs from idle perfect,but when under a load in gear it will bogg off idle but if i hold it their it will bog and then rev fine once in the powerband.

i adjusted air/fuel srew a hundred times and the carb is clean. still boggs off idle.

the plug is tan.

keep in mine im running stock jets and its 40 degrees outside right now in missouri.

i think i need to rejet because of the header but have no idea which way to go.
could anyone please help me?
 
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whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Do you have a manual? Do you know how to adjust your air screw, for best results? For jetting, adjust it to its highest rpm. Count how many turns from closed?
 
K

killer454

Member
Jan 3, 2011
47
0
yes i have a manual,i have been trying to get rid of this off idle bog all day.
i have tryed the airscreew at 1turnout,2turns out 2.5 turns out and 3 turns out.

from researching on here i am thinking maybe i need to go to a 40 pilot jet.

this bike idles fine,if you are in first gear and moveing and floor the throttle it will bog for 3 seconds and then rev to top end with no problems.once you get to the powerband it will screem.idle to 1/3 throttle 3-4 second bog.

manual says under 1 turn on air screw change pilot
says over 3 turns out go bigger pilot am i right.

what do you think on this problem
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
It does seem to be what the engine needs. You can have a lean or rich bog off bottom. The air screw says bigger, try it with the choke half way on?
 
M

Matt90GT

Member
May 3, 2002
1,517
1
I would bet it is rich since the air is more dense in the winter. More than likely you will need to drop the pilot and main 1 size. Then play with the needle. but do a WOT plug chop.

Also inspect the power valve operation. 04 is the ONLY year of the 125 with the servo operated RC valve
 
K

killer454

Member
Jan 3, 2011
47
0
wow guys i just removed the pilot jet on this bike and it says 32.5!
the manual says factory pilot is a 40!
this bike has a pro-circuit header and stock cylincer,and a new sleaved cylinder with a pro-x piston with a higher dome than stock.
now im thinking the bog off idle may need a bigger pilot jet.

what do you guys think now?
 
B

baxterj787

Member
Oct 4, 2001
36
0
I had a 2003 CR125 with a FMF Factory Fatty pipe, otherwise stock. The motors are BASICALLY the same, except for the electronic PV control on the 04. PC and FMF pipes had basically the same profiles, so jetting between the two was pretty similar.

I had best results with a 40 pilot and a 410 main. Not sure what needle, but I think it was stock. Had a really weird, long alphanumeric code on it. In really hot /humid conditions, I would drop in a 37.5 pilot. Airscrew was sensitive to (+/-) 1/4 of a turn adjustments.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
It does not matter how much bolt on magic your bike has. Only the air screw adjustment matters. You have no idea where or what temperature it was outside, when the engine was last jetted. Wow? No, not a big deal at all. If the air screw is ineffective, it is more than 1 jet off. You did not try the choke?
 
K

killer454

Member
Jan 3, 2011
47
0
ok guys, heres the new update. i got some jets and tryied every one i had and its still bogging off idle. i tryied riding with the choke like u all said and it did run better. what does this mean? i noticed the reeds were fraying but they were closed. im going to get some new reeds and see if that helps it. would reeds play a factor in all this bogging?

we have the cover off the servo motor to see if its working properly and its moving a little but doesnt seem like its moving the full action. we have adjusted the cables just like the manual says a million times and still no difference.

im going to try the reeds and see what that does but would like ur guys advice.
 
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K

killer454

Member
Jan 3, 2011
47
0
i have tryed the following jet combos
in the bike from beggining was 32.5 pilot-420 main

i have tryed
40 pilot-430 main
37.5 pilot-410 main
45 pilot-420 main

jets i have here at the house
pilots-32.5,35,37.5,40,45
mains-380,390,400,410,420,430

it seems after useing the jets that the airfuel screw is not working with any combo on jets.what would cause the air/fuel screw not to work?
 
M

mike-evans

Member
Sep 16, 2009
142
0
Really need to get the reeds done first. Im having a off the throttle bog which I beleive is rich. I inspected my reeds and they looked good, but I still replaced them as you need to get these things right first....when I was reading/searching for problems caused by worn/old reeds, I read alot of times that it can do all sorts to the jetting....

My air screw was inaffective with factory jets in there, so I dropped the pilot one size and it made a bit of a difference on the air screw effectiveness....I just need to run it now and see..weather aint good at the minute tho here :-(
 
U

Uchytil

LIFETIME SPONSOR
Jun 29, 2003
814
9
Boyssen power reeds. They are dual stage fiberglaqss and will improve the low end (and off idle snap) but lose some on top. That's if you are looking for a reed replacement over the stock, stiff, carbon reeds.

Course that's after you try jetting, good luck with that chief - the CR125R is a PITA when it comes to trying to get it to run correctly stock. But then again your's has a few mods (sleeve) :yikes:
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
All the parts are good, seemingly, still rich, the choke makes it bog worse off idle, REPLACE the needle valve and seat, oem parts preferred.
 
K

killer454

Member
Jan 3, 2011
47
0
i have ordered the boysen power reeds from rocky mountain will be here tuesday.
i will let you guys know tuesday if they helped the lowend bog off idle.
 
K

killer454

Member
Jan 3, 2011
47
0
played with the jetting a littlebit yesterday and it did run better off idle with the 40,45 larger jets in it.but the off idle bog was still their just come out of the bog sooner with the 40 and 45 in it.
anything lower than 40 seems to get worst so im going to try the new reeds like you said and then go back to jetting.

with the 40,45 pilot and the 410 main the plug has a cardboard color to it looks prety good.im hoping your right on the reeds,they are on the way.
 
U

Uchytil

LIFETIME SPONSOR
Jun 29, 2003
814
9
Hopefully you'll see a difference with the Boyesen power reeds. I have the PC header also and did not notice a difference when I installed it. At the time I was running the dual stage fiberglass BPRs. I have a stock bore though so I don't know how that affects your set-up of a steel liner with a domed piston. You should start with the stock jetting and air screw setting. Then follow one of the many jetting guides you can find on this site.
 
K

killer454

Member
Jan 3, 2011
47
0
need help on cr125r i just cant figure this thing out

ok guys here gos im going to get you detailed info on this bike and tell me what to do please. im almost ready to sell this darn thing and buy another bike,i just cant figure this thing out.

2004 cr125r it has that electronic rc valve on it which i hate with a passion.

here is what has been done to this bike-
*NEW STEEL SLEEVE IN CYLINDER WITH A PRO-X NEW PISTON
*NEW BOYSEN REEDS
*CARB HAS BEEN CLEANED SPOTLESS BY ME
*I HAVE TRYED PUTTING THE THROTTLE POSITION SENSOR IN EVERY PLACE I CAN.NO CHANGE.
*I HAVE TRYED EVERY JET COMBINATION FROM MAINS-380,390,400,410,420,430 PILOTS FROM-32.5,35,37.5,40,45 NO CHANGE WITH ANY COMBINATION.
*I HAVE TRYED ADJUSTING THAT ELECTRONIC RC VALE EVERY WAY THAT IS POSSABLE.NO CHANGE.
*I HAVE TRYED THE NEEDLE ON 3RD,2NDFROM TOP,AND NOW 4TH FROM TOP.NO CHANGE.
*I HAVE TRYED FUAL/AIR SCREW WITH EVERY COMINATION ON THE JETS NO CHANGE

HERE IS WHAT IT IS DOING-
*IT RUNS REAL GOOD EXCEPT FOR A SLIGHT BOG WHEN TAKING OFF IN FIRST GEAR.YOU CAN REV IT WHILE IN NEUTRAL NO BOG.WHEN RIDEING IN FIRST IF YOU NAIL THE THROTTLE AT A LOW SPEED BOG FOR 2-3 SECONDS THEN RUN GREAT.
*ITS THROWING BLACK OIL OUT THE TAIL PIPE,AND SMOKING BLUE SMOKE WHEN REVING.
*I PUT A 380 MAIN AND 32.5 PILOT IN IT AND DID A PLUG CHOP PLUG IS BETTER ON COLOR BUT STILL SEEMS A TAD RICH,BUT NOT MUCH.
*I HAVE CHECKED FLOAT LEVEL IT IS GOOD

WOULD A BAD CRANK SEAL CAUSE THIS LOW OFF IDLE BOG?
I DONT KNOW WHAT TO BUY TO FIX IT,CAN ANYBODY GIVE ME ADVICE PLEASE?
THANKS FOR THE HELP GUYS IM ABOUT READY TO EITHER BUY MY NEPHEW A DIFFERENT BIKE OR BUY A NEW CYLINDER 357.00 OEM WITHOUT THE STEEL SLEAVE.
 
E

EncyclopediaRonnie

Member
Nov 8, 2010
142
0
check out the crank seals it could be just leaking enough oil down low to drown it out can you do a leakdown test? hows spark too? low rpm could be a weak spark till revs jump up
 
K

killer454

Member
Jan 3, 2011
47
0
i have ordered new seals complete seal kit and the flywheel puller their on the way right now.

this bike is burning richer than heck with a 390 main and 32.5 pilot still rich.i pulled the choke up on it while it was running the other day and all it did was die right away and caused the plug to foulout.took the plug out shined light down the plug hole and piston looks spotless just to rich.

i ran the electrical checks on the throttle position sensor last night and the manual told me what wires to hookup to my meter.it said when hookedup to meter you should see a low number at idle and as you take the throyttle to full throttle numbers should increase.
it did the opposit at idle the number was high and as i turned the throttle the numbers whent lower (dont understand this)
if i put my meter on two different wires on this plug it reads right,but not the 2 wires the manual says to check for this.

can i run this bike with the rc valve disconected?
how will this run without it?

thanks guys for the help im not giveing up on it yet (just want it fixed and willing to spend whatever it takes)

i have to fix my compression tester-last night i screwed it in and kicked the bike about 7 times real fast and compression whent to 155 lbs but i think it was leaking down real fast.i have the releif valve leaking on the gauge so it leaked out that some but i dont think it is holding pressure.
would this be the crank seals?

could it be bad crank seals and the center cases leaking somehow?
 
E

EncyclopediaRonnie

Member
Nov 8, 2010
142
0
comp sounds pretty good and you cant test crank seals with just a comp tester as a comp tester stores no presure in the crancase just reads what the motor can compress. the leaking of preasure will be past the relief valve on the tester.

for a leak down test you gotta remove exaust carb and block it alkl up lol
 
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