XR200 vs XR200R Piston

Weldangrind · 05-19-2010, 08:19 PM

The XR200R piston from '81 to '83 is a 10:1 compression piece vs. 9.2:1 in a similar year XR200. I'd love to stick one of these XR200R pistons in our Beast!

The XR200R piston is in the ring compressor, but you get the idea:

SpudRider · 05-20-2010, 12:59 AM

Can you just exchange the piston head, or do you need to exchange other parts, also?

Spud

Weldangrind · 05-20-2010, 02:25 AM

Not sure. I do know that the ATC (three wheeled) stuff from the eighties was 0.5mm smaller in bore, so it's anybody's guess what bore the clone stuff is. If the bore on my Zong Honda clone is 65.5mm, it would bolt right in.

I'd also be curious to learn whether or not the valves are the same size. Maybe my quad will blow up one day, and I'll be able to answer these questions.

katoranger · 05-20-2010, 08:55 AM

I the R piston domed? I can see that the valve relief is much deeper.

Allen

Weldangrind · 05-20-2010, 10:38 AM

Yep, considerably domed.

FastDoc · 05-20-2010, 11:11 AM

Quote:

Originally Posted by katoranger

I the R piston domed? I can see that the valve relief is much deeper.

Allen

That's what I was wondering. In the pic the 'R' piston looks lower compression. :?

Weldangrind · 05-20-2010, 11:25 AM

Sorry guys, I didn't notice the optical illusion. I can't seem to get close up with my crappy old camera, but maybe this shows the difference a bit better:

TurboT · 05-21-2010, 02:44 AM

Thats funny! When I looked at those pics last night I thought, "That's weird, the piston looks like its indented not raised.." I was going to comment, but thought my late night brain was not computing.

Very strange how the camera did that.

..makes sense the valve notches are bigger, since it'd be closer to the valves on it's stroke.

Why do I feel like I read our Beast motors are 63.5mm somewhere?

Weldangrind · 05-21-2010, 12:00 PM

Not sure. I wouldn't be satisfied until I could measure one myself, though.

05-19-2010, 08:19 PM	#1
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	XR200 vs XR200R Piston The XR200R piston from '81 to '83 is a 10:1 compression piece vs. 9.2:1 in a similar year XR200. I'd love to stick one of these XR200R pistons in our Beast! The XR200R piston is in the ring compressor, but you get the idea: __________________ 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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05-20-2010, 12:59 AM	#2
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	Can you just exchange the piston head, or do you need to exchange other parts, also? 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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05-20-2010, 02:25 AM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Not sure. I do know that the ATC (three wheeled) stuff from the eighties was 0.5mm smaller in bore, so it's anybody's guess what bore the clone stuff is. If the bore on my Zong Honda clone is 65.5mm, it would bolt right in. I'd also be curious to learn whether or not the valves are the same size. Maybe my quad will blow up one day, and I'll be able to answer these questions. __________________ 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

05-20-2010, 08:55 AM	#4
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	I the R piston domed? I can see that the valve relief is much deeper. Allen __________________ You meet the nicest people on a Honda Clone.
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05-20-2010, 10:38 AM	#5
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Yep, considerably domed. __________________ 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

05-20-2010, 11:25 AM	#7
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Sorry guys, I didn't notice the optical illusion. I can't seem to get close up with my crappy old camera, but maybe this shows the difference a bit better: __________________ 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

05-21-2010, 02:44 AM	#8
TurboT Join Date: Sep 2008 Location: Surrey, B.C., Canada Posts: 2,185	Thats funny! When I looked at those pics last night I thought, "That's weird, the piston looks like its indented not raised.." I was going to comment, but thought my late night brain was not computing. Very strange how the camera did that. ..makes sense the valve notches are bigger, since it'd be closer to the valves on it's stroke. Why do I feel like I read our Beast motors are 63.5mm somewhere?
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05-21-2010, 12:00 PM	#9
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Not sure. I wouldn't be satisfied until I could measure one myself, though. __________________ 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