06 CR125 Problems.

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8/3/2018 2:54 PM

Hey guys. Picked up an 06 cr 125 a few months ago for my girlfriend. The seller is an "apprentice mechanic" at his local Honda shop. He bought it from a friend and it was blown up and said he rebuilt the top and bottom end. It ran rich AF and was pretty boggy when I tested it, but we were on a time crunch to pick the bike up and nothing seemed too off in how the engine was running. (I was thinking just some jetting). From the get go it has always bogged really bad off the bottom and under load. It almost won't run.

I fixed a few parts in the carb that needed replacing and re-jetted it. It runs better, but didn't fix the bog. Installed my carb (Keihin), ran a little better, but same problem persisted.

Reeds are brand new.

The power valve was not hooked up correctly (chicken wire), but got the parts and put it together. The problem still persisted.

Clutch is missing a spring and a bolt and seems to not be working very well, but still works.

Bought ether and sprayed all over the engine and inside the ignition side, didn't rev up or show any leaks.

Just did a compression test with a new tester, so I don't know how calibrated it might be, but the test was just under 120 psi.

I have taken a look inside the cylinder before and you can see the cross hatching and it looks good and new, but I haven't pulled it all apart yet.


If it helps, once it is revved up it seems to almost run normally. Just from a stop or slow start or under load and/or low revs it bogs really bad, almost dies.

My next step was to pull the top end and inspect and was wondering if there is a way to check/inspect the clutch side crank seal.

Any help would be appreciated! My local shop is at a loss of where to go from here as well.

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8/3/2018 4:38 PM
Edited Date/Time: 8/3/2018 4:38 PM

120 psi is low. Low compression will make it act like it is overly rich.

Paw Paw

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8/3/2018 11:25 PM

"If it helps, once it is revved up it seems to almost run normally. Just from a stop or slow start or under load and/or low revs it bogs really bad, almost dies."


Had the same when i picked up a cr85 07. Was a new piston in it, original one. After changing the main ,slow and needle and adjust the float valve It was still bogging out of a corner . Got the piston out and put a vertex piston in it. With that i had to go from main 158 to main 150 ,slow from 42 to 40 and needle the same.. Problem solved



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8/5/2018 7:30 PM

Are you getting any fuel running out of your carb overflow lines when the bike is leaned over SLIGHTLY before you should normally see fuel running out? I'm wondering since the problem seems to clear up once you've revved it a bit and you've dropped the level in the float a little whether your float level is wrong or if you've got a seal issue associated with the float section of the carb that's allowing fuel to sneak into the float even if its adjusted properly.

Personally I would do the leaning the bike over fuel overflow check a couple times..... both right after its been running and also after maybe 30 minutes or so without running the bike at all with your fuel petcock left open to see if fuel is trickling into the carb over time. If after 30 minutes you either have fuel dripping out without leaning the bike or you get fuel out of the vent lines when you barely lean it over you probably have an issue with the float section.

You can also use some fresh fuel line and blow into the carb with the FLOAT FULL to feel whether it's sealing off correctly or letting anything by.

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8/5/2018 9:12 PM

I pulled a ktm 125 apart recently and the Piston was in backwards, and it's not the first time it's happened.

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8/6/2018 7:05 AM

You-n-Gs-town born & bred wrote:

Are you getting any fuel running out of your carb overflow lines when the bike is leaned over SLIGHTLY before you should normally see fuel running out? I'm wondering since the problem seems to clear up once you've revved it a bit and you've dropped the level in the float a little whether your float level is wrong or if you've got a seal issue associated with the float section of the carb that's allowing fuel to sneak into the float even if its adjusted properly.

Personally I would do the leaning the bike over fuel overflow check a couple times..... both right after its been running and also after maybe 30 minutes or so without running the bike at all with your fuel petcock left open to see if fuel is trickling into the carb over time. If after 30 minutes you either have fuel dripping out without leaning the bike or you get fuel out of the vent lines when you barely lean it over you probably have an issue with the float section.

You can also use some fresh fuel line and blow into the carb with the FLOAT FULL to feel whether it's sealing off correctly or letting anything by.

Last paragraph... cool trick!

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8/21/2018 12:16 PM

You-n-Gs-town born & bred wrote:

Are you getting any fuel running out of your carb overflow lines when the bike is leaned over SLIGHTLY before you should normally see fuel running out? I'm wondering since the problem seems to clear up once you've revved it a bit and you've dropped the level in the float a little whether your float level is wrong or if you've got a seal issue associated with the float section of the carb that's allowing fuel to sneak into the float even if its adjusted properly.

Personally I would do the leaning the bike over fuel overflow check a couple times..... both right after its been running and also after maybe 30 minutes or so without running the bike at all with your fuel petcock left open to see if fuel is trickling into the carb over time. If after 30 minutes you either have fuel dripping out without leaning the bike or you get fuel out of the vent lines when you barely lean it over you probably have an issue with the float section.

You can also use some fresh fuel line and blow into the carb with the FLOAT FULL to feel whether it's sealing off correctly or letting anything by.

I will try this, but I put my kehin carb on there and the same problem persisted...

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8/22/2018 9:54 PM

Does the cylinder have a sleeve?
Is the power valve not closing all the way?

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