td center

Member
Apr 26, 2004
35
0
I have a 2000 CR125 with a new PWK 35mm carb conversion, stock exhaust, pretty fresh motor, and Rekluse auto clutch.

I swapped out the Mikuni TMX carb for the Keihin after having constant jetting problems...now that I put on the PWK I am having the same problems.

I am at about 200' above sea level. I have a freshly packed silencer, clean and oiled air filter, new BR9EG plug, and 32:1 premix with Mobil1 MX2T and shell 93 octane pump gas.

In the 35mm PWK I have:
Pilot Jet - #58
Needle - Keihin DGJ needle
Clip Position - 3rd
Main Jet - #168

The bike runs fine if I slowly roll on the throttle in first, and then runs strong throughout all the other gears. When I crack the throttle WFO from a standstill or even moving slowly it bogs real bad and dies...everytime!
I followed Spanky's Jetting Guide and tried a #55 pilot. The thing is, my airscrew is not having much affect on the idle. I never need the choke to start the bike, but when I do put it on while the bike is running, the idle drops a bit.
I have spooge ALL over the exhaust manifold running down the front of the case, and even out of the top of the cylinder where the plug is (unless it is just splashing up but it looks like it is actually squeezing it's way past the plug which is pretty snug).
Like I said, besides the WFO from a standstill, the bike runs good.
any help is REALLY appreciated!!! Thanks. :cool:
 

td center

Member
Apr 26, 2004
35
0
I wish that's all it was, but I had cleaned and oiled the air filter (Twin Air with only 1 use). Even after squeezing out the excess oil I let the air filter sit overnight to dry out even more to prevent any filter oil from being sucked into the intake.
 

BJAWES

Member
Mar 22, 2004
59
0
Spooge? Oil? Black? You could have a bad crank seal on clutch side that's letting trans oil into the crankcase. Was your previous silencer packing soaked with wet spooge too?
 
Mar 1, 2005
231
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The bike runs fine if I slowly roll on the throttle in first, and then runs strong throughout all the other gears. When I crack the throttle WFO from a standstill or even moving slowly it bogs real bad and dies...everytime

my bike is having the EXACT same bogging issue. from what ive been told its a lean condition..makes sense.if theres not enough fuel present for the bike to accelerate,its gonna bog and die.try richening you pilot circuit,it should help.ive richened mine and it helped but it still bogs like yours.im gonna try richening it somemore and hopefully that will cure the prob.some people may try to tell you that its normal since its a 125 as they dent have much low end but the bike shouldn't bog weather it has much low end power or not.one other thing you can try is to engage your choke then try it again and see if its better.if so,then that confirms a lean condition.
 

td center

Member
Apr 26, 2004
35
0
BJAWES said:
Spooge? Oil? Black? You could have a bad crank seal on clutch side that's letting trans oil into the crankcase. Was your previous silencer packing soaked with wet spooge too?

The previous silencer packing was filled with a bit of spooge, but that's also because I had not changed it in quite a while. The engine is still pretty fresh (EG did a full rebuild, top and bottom end with new crankseals).
Can the seal go that quickly?
 

td center

Member
Apr 26, 2004
35
0
2-strokes-4-life said:
The bike runs fine if I slowly roll on the throttle in first, and then runs strong throughout all the other gears. When I crack the throttle WFO from a standstill or even moving slowly it bogs real bad and dies...everytime

my bike is having the EXACT same bogging issue. from what ive been told its a lean condition..makes sense.if theres not enough fuel present for the bike to accelerate,its gonna bog and die.try richening you pilot circuit,it should help.ive richened mine and it helped but it still bogs like yours.im gonna try richening it somemore and hopefully that will cure the prob.some people may try to tell you that its normal since its a 125 as they dent have much low end but the bike shouldn't bog weather it has much low end power or not.one other thing you can try is to engage your choke then try it again and see if its better.if so,then that confirms a lean condition.

I guess it really does make sense to be a lean condition. So I guess I may have gone in the wrong direction by switching from a #58 to a #55 pilot.
I keep reading different things though where some say it is lean and some say rich.

Also, have you heard anything about changing to a larger diameter bushing (7mm) for the power valve?

I am at a REAL loss here, and not sure what else to try at this point. 2-strokes-4-life, if you or anyone else have any ideas...I am all ears! :cool:
 

kartstar

Member
May 24, 2006
14
0
The pilot jet only controls mixture up to about 1/2 throttle, so if the slow roll-on is OK, it may not have much to do with the pilot jet. Do you have new reeds with your new top/bottom end? also, 168 main at sea level sounds pretty lean...but my 125 experience is limited to 40HP kart engines.
 
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BJAWES

Member
Mar 22, 2004
59
0
Packing "filled" with a "bit" of spooge? And you're bogging at WFO (main jet)? I'll agree that you have a air/fuel problem, and I didn't know you had a complete rebuild. I said "crank seal" because you could be sucking in air as well as trans oil, but yes doubtful seeing as it was just rebuilt.
 

td center

Member
Apr 26, 2004
35
0
BJAWES said:
Packing "filled" with a "bit" of spooge? And you're bogging at WFO (main jet)? I'll agree that you have a air/fuel problem, and I didn't know you had a complete rebuild. I said "crank seal" because you could be sucking in air as well as trans oil, but yes doubtful seeing as it was just rebuilt.

Well, that's the strange thing...WFO after rolling it on in first is fine. I can go through all the gears with the throttle pinned in each gear and the bike feels pretty good.
It's just when I am either at a standstill or just creeping along and twist the throttle wide open that it bogs so bad it dies. :fft:
 

skipn8r

Member
Mar 10, 2004
145
0
td center said:
The thing is, my airscrew is not having much affect on the idle. I never need the choke to start the bike, but when I do put it on while the bike is running, the idle drops a bit.
I have spooge ALL over the exhaust manifold running down the front of the case, and even out of the top of the cylinder where the plug is (unless it is just splashing up but it looks like it is actually squeezing it's way past the plug which is pretty snug).
If you're sure the rest of the engine is OK, these are classic symptoms of a slow jet that is too large. If your air screw has no effect with a 55, keep stepping down until it does. If all is well, the engine should idle and respond best at around 1.5 - 2 turns out. Seems to me you should be in the 40 range or so, but I'm not very familiar with 125's.

BTW, a 35 mm carb is on the small side for a 125; '01 was a 36 mm and current models use a 38 mm. In general, when you install a smaller carb, the jetting sizes should also be smaller than with a bigger carb.
 

td center

Member
Apr 26, 2004
35
0
Well, I went out and bought some leaner jets today. I checked the reeds to make sure they were OK, and they are fine.
I put in a leaner jet and went for a test spin, the bog was still bad when pinning the throttle from a standstill or slowly rolling.
I decided to try with the choke on...it worked perfectly for take off, of course once past the inital go it was crappy since it was now richening everything.
I went to the richest pilot I had (#58) and it was still bogging a bit, but a little better.
The only problem now is it actually is loading up until I clear it as though it's too rich but once I rev a few times to clear it, it gets better. I want to try the next richer pilot since running with the choke on really helped the throttle off the line, but why would it be loading up?
Thanks!
 

Uchytil

LIFETIME SPONSOR
Jun 29, 2003
814
9
I read through most of this and have to say this is a so common problem with the CR. I bought a CR125R in 01 and it had the exact same issues, bog on standing accel, etc. I went through jetting, slide mods, PC pipe, exhaust head spacer, with no joy. The stock reeds are CF and fairly stiff so I tried Boyseen power reeds which are dual stage fiberglass. I also put the bike back to stock trim with the only change being reeds. I got rid of the bog down low but lost it on the top (very top) so I was happy. Of course this was on a brand new engine. Other than that simple fix I would have the engine tuned by Eric Gorr if I was really concerned. Too bad but the CR125 00 and on is a roach, my opinion.
 

johnnymic

Member
Mar 6, 2004
1
0
If you get no response in idle while adjusting your mixture screw, than your cab is dirty on the inlet side. I had the same condition with no response with mixture screw and every time I looked at the carb it looked perfect so I didn't clean it. Well, the other day I cleaned it anyway with half a can of carb cleaner and compressed air. "Holy Crap" did that make a difference. The mixture screw now will raise and lower idle when adjusted (like it should). But now I'm having the sluggish off the start problem and good after the roll, same as you. I know the bike is running too lean since now it's getting air from the mixture screw so I'm in the process of jetting. The bike is a 94 CR125...62 pilot, 170 main and needle on 3rd clip, I'm presently waiting for my new 65 pilot to arrive this Friday. Did you ever get your problem fixed?
 

pbforlife3

Member
Jan 1, 2005
46
0
i know this isnt for the same bike but my 01 yz 125 does the same thing....if im just sitting there i have to keep the gas on to idle...i never adjusted to idle cause it didnt bother me i liked it cause if i lost the bike it would shut off....however....i was running my bike and it just started chugging and bogging down then shut off....in all attempts to get it to run again i finally did by bump starting it...however i had no low end power whatsoever and no power to go up the smallest incline i cleaned my airfilter cleaned the carb and retried just kick starting the bike and have had no luck since....i was running the bike at 32:1 and have changed back to 40:1 now but still no luck...any suggestions?

PS: top end is fresh and bike only has about 15-20 hours ride time on it since top end work
 

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