125 Pit Bike Oil Leak Repair

Weldangrind · 03-30-2009, 02:31 AM

My son's 125 developed an oil leak out of the left side, and I presumed it was a shifter seal leak until I started investigating further. I figured that the leak was caused by excessive crankcase pressure, so I added a valve cap vent. That seemed to free up some power, but the leak remained.

The photos below show the removal of the flywheel, stator plate and o-ring. The replacement o-ring, part number 91301035003 was about $7 at the local Honda dealer. No more leaks.

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warrior91 · 03-30-2009, 12:30 PM

Nice. If all of us can do this once per maintenance item we will have a good tech resource for the novice or the mechanically inclined but forgetful kind.
We should sticky this as soon as you ad honda part# and engine modle...although 125 china horiz. engine says it all

Weldangrind · 03-31-2009, 02:01 AM

I edited the post to include the part number.

Cheers!

SpudRider · 06-20-2010, 02:13 PM

I'm sorry I missed this post when you first wrote it, W&G. As usual, your writeup is great, and the photographs are wonderful.

If I ever get a Honda engine, I am certain I will spend a lot of time reviewing your excellent posts!

Spud

Weldangrind · 06-20-2010, 03:38 PM

Thanks Spud.

Jim · 06-20-2010, 08:28 PM

Me too, thanks

You should add it to the tech stickies.

FLASHLIGHTBOY · 07-18-2010, 12:28 AM

Is that a tool for removing the pulley?? if so does it work on all the motors???

Weldangrind · 07-18-2010, 01:36 AM

So far, it has worked on XR200R engines from the early eighties, a GY6 ATV and a 125 pit bike Honda clone.

Thumper · 02-21-2023, 02:22 PM

Quote:

Originally Posted by Weldangrind

My son's 125 developed an oil leak out of the left side, and I presumed it was a shifter seal leak until I started investigating further. I figured that the leak was caused by excessive crankcase pressure, so I added a valve cap vent. That seemed to free up some power, but the leak remained.

The photos below show the removal of the flywheel, stator plate and o-ring. The replacement o-ring, part number 91301035003 was about $7 at the local Honda dealer. No more leaks.

I guess this is pretty obvious, but does that gear on the crankshaft drive a counterbalancer with that chain?

dirtbkr188 · 02-21-2023, 04:01 PM

No, it doesn't, Thumper, it only drives the oil pump shaft, there is no counterbalancer. At the other end is the cam sprocket

03-30-2009, 02:31 AM	#1
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	125 Pit Bike Oil Leak Repair My son's 125 developed an oil leak out of the left side, and I presumed it was a shifter seal leak until I started investigating further. I figured that the leak was caused by excessive crankcase pressure, so I added a valve cap vent. That seemed to free up some power, but the leak remained. The photos below show the removal of the flywheel, stator plate and o-ring. The replacement o-ring, part number 91301035003 was about $7 at the local Honda dealer. No more leaks. \ __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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03-30-2009, 12:30 PM	#2
warrior91 Join Date: Nov 2007 Location: N.E. Saskatchewan, Canada Posts: 679	Nice. If all of us can do this once per maintenance item we will have a good tech resource for the novice or the mechanically inclined but forgetful kind. We should sticky this as soon as you ad honda part# and engine modle...although 125 china horiz. engine says it all __________________ '91 Yamaha Warrior- stage 2 '83 Honda ATC 70 '08 Yongjiang 125cc mx (Loncin) '08 Yongjiang 150cc atv (Jinlong)
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03-31-2009, 02:01 AM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	I edited the post to include the part number. Cheers! __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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06-20-2010, 02:13 PM	#4
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	I'm sorry I missed this post when you first wrote it, W&G. As usual, your writeup is great, and the photographs are wonderful. If I ever get a Honda engine, I am certain I will spend a lot of time reviewing your excellent posts! Spud __________________ Spud "Never argue with an idiot. He will drag you down to his level, and beat you with experience." Mark Twain 2015 Zongshen ZS250GY-3 (RX3) 2006 Zongshen ZS200GY-2 (Sierra 200) 2005 Honda XR650L 2004 Honda CRF250X 1998 Kawasaki KDX220 Mods made to my Zongshen ZS200GY-2: http://www.chinariders.net/showthread.php?t=6894
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06-20-2010, 03:38 PM	#5
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Thanks Spud. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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06-20-2010, 08:28 PM	#6
Jim Join Date: Mar 2007 Location: Abbotsford, BC, Canada Posts: 4,880	Me too, thanks You should add it to the tech stickies. __________________ "Be excellent to each other" "We are all human. Let's start to prove it!"
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07-18-2010, 12:28 AM	#7
FLASHLIGHTBOY Join Date: May 2009 Location: SASKATOON Posts: 1,161	PULLEY REMOVAL Is that a tool for removing the pulley?? if so does it work on all the motors???
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07-18-2010, 01:36 AM	#8
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	So far, it has worked on XR200R engines from the early eighties, a GY6 ATV and a 125 pit bike Honda clone. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

02-21-2023, 04:01 PM	#10
dirtbkr188 Join Date: Aug 2009 Posts: 588	No, it doesn't, Thumper, it only drives the oil pump shaft, there is no counterbalancer. At the other end is the cam sprocket
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