Yamaha YZ400F - Page 4

Weldangrind · 03-02-2012, 11:25 AM

I've changed many valve stem seals on cars with the heads in place, and it works quite well. What stops you from performing the same procedure on a bike is that there's no room for the valve spring tool in such a confined space. The only solution is to use a c-clamp style valve spring compressor that holds the valve from the back side. They're reasonably priced.

BTW, I wouldn't disturb the piston; I'd just remove the head and change the seals. If it makes good compression, I wouldn't even remove the valves. That means no farming out at all.

dmmcd · 03-02-2012, 11:41 AM

Plus on a bike it is like 4 bolts and the head is in off and in your hand. The only pain is getting the cam off (don't drop the cam chain into the lower end or you have to pull the case covers off... been there) and back on and timed correctly. I thought the seals had to be pressed into and out of the head, also, which requires having the head off the engine.

Depending on how many hours your bike has, the piston is probably fine. I got a great deal on the new piston, and didn't know the history of my bike so I did the piston while I was in there. The manual for the CRF says to replace the piston every 50 hours or something like that. The ceramic bore likely doesn't score, so it probably wouldn't need any attention if you decided to replace the piston.

FastDoc · 03-02-2012, 11:41 AM

If that's the case Weld it may not be so bad. 2 hours to remove the head, another 2 to replace it, $30 or so for the seals, another $50 or so for the gasket, and maybe $75 for Andy to R&R the seals.

One afternoon and $155?

SpudRider · 03-02-2012, 03:05 PM

Quote:

Originally Posted by FastDoc

...I think with a car it'sossible to replace the valve seals with the head still on. Use air pressure or a rope to keep the valves from falling into the engine and pull the old seals and replace them somehow. I guess the same does not apply to a bike, and mine has 5 valves too.

Yes, it's possible to use air pressure, or the rope trick, to replace the valve stem seals on your motorcycle.

However, if I am replacing the valve stem seals, I prefer to remove the cylinder head. Not only does this make the job easier, I want to inspect the cylinder whenever the valve stem seals need to be replaced.

Spud

MICRider · 03-02-2012, 06:30 PM

My 2 cents... If it's running good and not smoking like a banshee (or a two stroke) when your riding it I would just leave it alone until they get worse. Oil's cheap if you have to add a little here and there

FastDoc · 03-02-2012, 06:37 PM

It only smokes a couple of minutes on startup if its not been run for a couple of weeks or more.

It just annoys my OCD more than anything else. No oil on the plug or in the exhaust outlet at all. The smoking all goes away when it's riding or has been recently ridden.

MICRider · 03-02-2012, 06:55 PM

I've had Chevy pickups that did that for years, never hurt anything

I can see it getting on the OCD though, guess it all depends on how much it bugs you.

FastDoc · 03-02-2012, 11:53 PM

OK here are some of the promised pictures of the YZ. It's in Andy's shop. We'll leaave from there Sunday to the dunes so I left it there. It's all fixed up and good to go. :P

Sorry for the pic quality but it will do for now.

New chain and sprockets and Trail Tech kickstand.

Pretty nice looking bike I think. That FMF pipe is like an air cannon. It really barks. 8)

God willing this will be a good motorcycle I will be able to enjoy for years to come. I certainly will never outgrow its performance. :P

This is Andy's KZ125 racebike. Heavily modified and show quality. Polished and powdercoated. You could look at this thing with a magnifying glass and not see an imperfection.

It is stupid fast but very difficult to stay on top of the powerband without blowing off the bike, its an expert only machine, IMHO.

SpudRider · 03-03-2012, 12:27 AM

Thanks for posting the long-awaited photos, Doc! Your YZ looks great!

Spud

FastDoc · 03-03-2012, 12:32 AM

Thank you Brother Spud!

Here's a short video of Andy on his KZ. Since we'll be going desert riding Sunday I'll have more pics of him then.

SpudRider · 03-03-2012, 01:13 AM

Quote:

Originally Posted by FastDoc

Thank you Brother Spud!

Here's a short video of Andy on his KZ. Since we'll be going desert riding Sunday I'll have more pics of him then.

You've got to love those 2 stokes! Thanks for posting the video, Doc!

Spud

FastDoc · 03-03-2012, 12:10 PM

Two Strokes are the best Spud. Your KDX will run with anything and be very cheap and easy to maintain. No valve seals! Heck, no valves!

I'd have gotten a KDX for myself but I'm afraid I passed the best deal on one to my good friend in Idaho! 8)

I've not seen one as good as your's efore or since on CL. :wink:

The YZ is easier to ride for me though. Power all over, right off idle. It's easier in the technical and slow stuff.

Weldangrind · 03-03-2012, 02:16 PM

Great blue mountain of power! That's an awesome looking machine. 8)

I've never seen aluminum guards like yours (above the kickstand and behind the brake pedal). I've only seen plastic there, but I like yours much better. Looking forward to action pics after this weekend.

FastDoc · 03-03-2012, 03:10 PM

It came with the guards. I believe they are made by Devol.

This time tomorrow hopefully I'll be blasting around the desert on it with my friends.

I'll be sure to take pictures. Supposed to be mid 60's and sunny.

Praise God.

FastDoc · 03-04-2012, 10:19 PM

Check the Ride Report section for some pictures of The Beast for today.

I'm happy to say that after it runs about one minute there's no smoke and A LOT of power. 8O

With that said riding it back to back with Roger's new KX450 I have to say 4 stroke motocrossers have come a long way in 11 years. His fuel injected engine has more power, faster and smoother than the YZ. It's like the YZ has 200% of the power I could ever use, and his bike has another 15%. 8)

His bike is also about 15 pounds lighter. You wouldn't think you'd notice that amount but you do.

I am very pleased to have the YZ to ride.

03-02-2012, 11:25 AM	#46
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	I've changed many valve stem seals on cars with the heads in place, and it works quite well. What stops you from performing the same procedure on a bike is that there's no room for the valve spring tool in such a confined space. The only solution is to use a c-clamp style valve spring compressor that holds the valve from the back side. They're reasonably priced. BTW, I wouldn't disturb the piston; I'd just remove the head and change the seals. If it makes good compression, I wouldn't even remove the valves. That means no farming out at all. __________________ 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

03-02-2012, 11:41 AM	#47
dmmcd Join Date: Apr 2011 Location: Souderton, PA Posts: 367	Plus on a bike it is like 4 bolts and the head is in off and in your hand. The only pain is getting the cam off (don't drop the cam chain into the lower end or you have to pull the case covers off... been there) and back on and timed correctly. I thought the seals had to be pressed into and out of the head, also, which requires having the head off the engine. Depending on how many hours your bike has, the piston is probably fine. I got a great deal on the new piston, and didn't know the history of my bike so I did the piston while I was in there. The manual for the CRF says to replace the piston every 50 hours or something like that. The ceramic bore likely doesn't score, so it probably wouldn't need any attention if you decided to replace the piston. __________________ 2008 Yamaha WR250x 2006 Honda CRF250R Sold: 2002 Suzuki SV650S, 2009 Qlink XF200
	0

03-02-2012, 11:41 AM	#48
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	If that's the case Weld it may not be so bad. 2 hours to remove the head, another 2 to replace it, $30 or so for the seals, another $50 or so for the gasket, and maybe $75 for Andy to R&R the seals. One afternoon and $155? __________________ Happy to serve.
	0

03-02-2012, 06:37 PM	#51
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	It only smokes a couple of minutes on startup if its not been run for a couple of weeks or more. It just annoys my OCD more than anything else. No oil on the plug or in the exhaust outlet at all. The smoking all goes away when it's riding or has been recently ridden. __________________ Happy to serve.
	0

03-02-2012, 11:53 PM	#53
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	OK here are some of the promised pictures of the YZ. It's in Andy's shop. We'll leaave from there Sunday to the dunes so I left it there. It's all fixed up and good to go. :P Sorry for the pic quality but it will do for now. New chain and sprockets and Trail Tech kickstand. Pretty nice looking bike I think. That FMF pipe is like an air cannon. It really barks. 8) God willing this will be a good motorcycle I will be able to enjoy for years to come. I certainly will never outgrow its performance. :P This is Andy's KZ125 racebike. Heavily modified and show quality. Polished and powdercoated. You could look at this thing with a magnifying glass and not see an imperfection. It is stupid fast but very difficult to stay on top of the powerband without blowing off the bike, its an expert only machine, IMHO. __________________ Happy to serve.
	0

03-02-2012, 06:30 PM	#50
MICRider Join Date: Oct 2009 Location: Alberta, Canada Posts: 3,274	My 2 cents... If it's running good and not smoking like a banshee (or a two stroke) when your riding it I would just leave it alone until they get worse. Oil's cheap if you have to add a little here and there
	0

03-02-2012, 06:55 PM	#52
MICRider Join Date: Oct 2009 Location: Alberta, Canada Posts: 3,274	I've had Chevy pickups that did that for years, never hurt anything I can see it getting on the OCD though, guess it all depends on how much it bugs you.
	0

03-03-2012, 12:27 AM	#54
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	Thanks for posting the long-awaited photos, Doc! Your YZ looks great! 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
	0

03-03-2012, 12:32 AM	#55
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Thank you Brother Spud! Here's a short video of Andy on his KZ. Since we'll be going desert riding Sunday I'll have more pics of him then. __________________ Happy to serve.
	0

03-03-2012, 12:10 PM	#57
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Two Strokes are the best Spud. Your KDX will run with anything and be very cheap and easy to maintain. No valve seals! Heck, no valves! I'd have gotten a KDX for myself but I'm afraid I passed the best deal on one to my good friend in Idaho! 8) I've not seen one as good as your's efore or since on CL. :wink: The YZ is easier to ride for me though. Power all over, right off idle. It's easier in the technical and slow stuff. __________________ Happy to serve.
	0

03-03-2012, 02:16 PM	#58
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Great blue mountain of power! That's an awesome looking machine. 8) I've never seen aluminum guards like yours (above the kickstand and behind the brake pedal). I've only seen plastic there, but I like yours much better. Looking forward to action pics after this weekend. __________________ 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

03-03-2012, 03:10 PM	#59
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	It came with the guards. I believe they are made by Devol. This time tomorrow hopefully I'll be blasting around the desert on it with my friends. I'll be sure to take pictures. Supposed to be mid 60's and sunny. Praise God. __________________ Happy to serve.
	0

03-04-2012, 10:19 PM	#60
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Check the Ride Report section for some pictures of The Beast for today. I'm happy to say that after it runs about one minute there's no smoke and A LOT of power. 8O With that said riding it back to back with Roger's new KX450 I have to say 4 stroke motocrossers have come a long way in 11 years. His fuel injected engine has more power, faster and smoother than the YZ. It's like the YZ has 200% of the power I could ever use, and his bike has another 15%. 8) His bike is also about 15 pounds lighter. You wouldn't think you'd notice that amount but you do. I am very pleased to have the YZ to ride. __________________ Happy to serve.
	0