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10642
Joined
7/21/2009
Location
Harrisburg, OR
US
Edited Date/Time
7/1/2015 7:43pm
Figured I'd start our own thread.
The mint '05 she picked up has been sitting for a long while. It's definitely getting too much air on the pilot circuit. The idle doesn't hang or anything so it doesn't seem like a general air leak. The carb also leaks out the overflow. I've taken the carb apart and cleaned it. There's a small amount of corrosion on all the brass pieces.
In this pic, where the middle hole is, that's the pilot jet hole (the circuit that is causing the bog). Behind the threads there's a brass piece that the long end of the pilot syncs up with. The outer edges of this brass fitting are a little gouged. Not sure if that could be causing it to run lean on that circuit. Seems plausible.
We're trying to get it to work before ordering a new carb. Everything else on the bike is pretty much un-touched, but that doesn't mean a gasket or seal could be bad in the many years it's been stagnant.
The mint '05 she picked up has been sitting for a long while. It's definitely getting too much air on the pilot circuit. The idle doesn't hang or anything so it doesn't seem like a general air leak. The carb also leaks out the overflow. I've taken the carb apart and cleaned it. There's a small amount of corrosion on all the brass pieces.
In this pic, where the middle hole is, that's the pilot jet hole (the circuit that is causing the bog). Behind the threads there's a brass piece that the long end of the pilot syncs up with. The outer edges of this brass fitting are a little gouged. Not sure if that could be causing it to run lean on that circuit. Seems plausible.
We're trying to get it to work before ordering a new carb. Everything else on the bike is pretty much un-touched, but that doesn't mean a gasket or seal could be bad in the many years it's been stagnant.
05 YZ125 Lean Bog - More Motocross Videos
The Shop
The shock spring was free to spin around the shock body. I moved the adjusters down to put tension on the spring, is that a normal thing? We're gonna get it resprung and set the sag for her when she's here in a couple weeks.
The front brake is pretty mushy, I bled it and topped it off. Was just wondering if that '05 brake is just shitty in stock form.
The main seals may have dried up from sitting. Couldn't hurt to throw some new ones in.
How does the needle and seat look? They are replaceable on this carb.
Lots of people think the YZ brakes suck but when they are bled and functioning properly they can have a very firm lever and plenty of stopping power.
The needle and seat looked good to me, passed the eye test.
The lever is definitely not firm and stopping power is pretty lax. I'll put some new pads on and re-bleed it.
I was going to suggest it may be too rich also, I had the same thing happen with my RM125 when I first got it.
Play with the air mixture screw. Can you eliminate that bog by going to an extreme in or out? This would indicate where you need to be with the pilot size.
What does the slide and carb body look like? Can you post a picture of both?
Have you checked the reeds for cracks and or chips?
I would do and check all of these items before I put seals in it.
Well it got better when I richened the needle, and the bottom end bog seems to get better when I choke it. Seems lean.
http://www.vitalmx.com/forums/Race-Shop,42/2005-YZ125-bog-issue-with-vi…
Purchase or fab up a leak-down kit, that and a defective carb ended up fixing my problems.
The intake manifold was leaking on mine, but only after it warmed up. Oddly enough, it wouldn't change rpms if that area was sprayed with WD-40, Ether, or carb cleaner while the engine was running. Soapy water and the leak-down tester finally revealed the issue. Some Hondabond on both sides of the gasket fixed it right up.
Pit Row
I bought a nearly brand new 2011 while my 2008 was my primary race bike.
The 2011 dripped gas and felt lean.
So I think they ran pump premium due to the slight corrosion of brass parts.
The bike NEVER ran as well as my 2008 did. It felt lean on top and acted funny in the main event of the Dream Race last year.
I almost swapped carbs but decided to pay the $17 to Yamaha for a new float needle/seat set.
Now she rips!
If your bike is dripping fuel, replace the needle and seat set first.
By the way, the stock 2008 jetting works extremely well with a VF3 reed and FMF pipe.
Get some good ethanol free fuel in there. Pump gas kills two strokes.
JW, we have a 2006 YZ125. Never had any bog issues, but it did leak fuel out of the carb bowl. The needle set was worn out. Beyond that, I've got nothing because the advice you've already received is a great start. Good luck!
On another note thanks for your input everyone. You guys rock.
TM
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