Bog at low revs - Husqvarna WR 125 03

huskyjack1999
My bike has developed a bog when throttling from idle (well the bike doesn't idle at all but you know what I mean) around 2/3 throttle it kicks in. I am running a 390 main and a 35 pilot, I purchased a jet Mikuni pilot jet kit because I am running stock carb of course, it includes 35 to 52. I thought if I make my pilot richer it may fix the bog, which I believe a bog means 'too lean'. The spark plugs are reading black and dry then the occasional ride it would be black and oily.
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Paw Paw 271
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Benton, LA US
Paw Paw 271 4/28/2017 2:16pm
4/28/2017 2:16pm Edited Date/Time 4/28/2017 2:20pm
It's time for a compression and leak test. It seems your plug readings are confusing.
When was the last time the cranks shaft seals were changed?
When was the last top end done?

Paw Paw
Dtat720
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Flowood, MS US
Dtat720 4/28/2017 5:23pm
4/28/2017 5:23pm
If your plug is black, you are already rich and need to lean it out. But, as Paw Paw said, check your crank seal on the clutch side, could be starting to leak and sucking oil in. Rings could be toast as well.

Are you getting black soot out of the silencer?
xnationalwrench 4/29/2017 6:07am
4/29/2017 6:07am
Has the bike been sitting very long? What kind of gas are you using? What do you have the air mixture screw set at?
huskyjack1999 4/29/2017 7:05am
4/29/2017 7:05am
Update: fitted brand new oiled air filter and it seems to be back to life!

I get the occasional black soot out of the silencer, but I've been told low rpm riding can cause that symptom. So I guess I rode a bit harder instead of keeping the throttle in one place like you'd do on a 4 stroke, I throttle it for bursts of power. Seemed to do the job as I rarely get it that often, I am going to repack the silencer soon.

I have the stock TMX carb it's screwed out 3 x full turns, my clip is set at the forth notch on the throttle needle. I'm currently running 50:1, using a good Castrol fully synthetic oil. Unsure on how many hours it has on the top end, checked the piston condition through exhaust ports, it seemed ok not too worn and rings look good. I have compression, but I honestly think it's the carb. My elevation is around 5m and the weather around 40f - 55f.

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huskyjack1999 5/6/2017 3:38am
5/6/2017 3:38am Edited Date/Time 5/6/2017 8:03am
I'm going to fit a 32.5 pilot in with a clean air filter, if that doesn't effect anything I'll try a 30. The bog is straight off idle but evens out at 1/3 of a turn. Would the problem be pilot jet related? I don't really wanna buy an airstriker when this problem could possibly be fixed by a little bit of cheap brass.
huskyjack1999 5/6/2017 3:41am
5/6/2017 3:41am
xnationalwrench wrote:
Sounds like you need to go smaller on the pilot jet then readjust the air screw.
Can I ask how you set your air screws? My bike doesn't idle can this be a problem for adjusting my air screw?
huskyjack1999 5/7/2017 2:08pm
5/7/2017 2:08pm
UPDATE: Fitted a 32.5 pilot seemed to be better more crisp in the 1/4 throttle and air screw is functional. So my air screw setting is at 2 & 1/2 turns. Took a part my reeds and I was sadly disappointed, my reeds were fine but my crank and lower cylinder wall have some serious wear spots. Also I found a miniature hole in my reed housing. Here I'll upload a few pictures.





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