Welcome to the Roketa Café - Page 2

FastDoc · 11-18-2013, 11:45 AM

Excellent plan, sounds technically challenging but that's right up your alley!

Looking forward to the pics. Is this bike going to Bonneville?

SpudRider · 11-18-2013, 12:47 PM

We eagerly await further updates!

Weldangrind · 11-19-2013, 12:10 AM

Quote:

Originally Posted by FastDoc

Excellent plan, sounds technically challenging but that's right up your alley!

Looking forward to the pics. Is this bike going to Bonneville?

It just might!

Weldangrind · 11-19-2013, 11:57 PM

Since this bike will no longer be suitable for off-road, I've moved it to the Street category.

katoranger · 11-20-2013, 09:35 AM

Where are the pics?

Weldangrind · 11-20-2013, 10:47 AM

Don't have much to show yet. Bro in Law lives in Calgary, so we're lucky to get time once a month on this bike. He doesn't want me to proceed on my own, since he appreciates the learning curve. It's his first bike and first fabrication project.

We're still in the process of de-tabbing the frame and figuring out what changes to make. I find this shot to be particularly interesting, since it compares the Roketa frame with an '81 XR200 (not the R version). You can see how we've removed the seat base metal and cut the gussets. We then heated the steel and bent the seat hoop down until it was in line with the area that is forward of the seat.

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Views: 326
Size: 96.5 KB

This shot shows how I've yet to fabricate the mounts for the rear shocks, which were donated by the XR200, as was the swingarm.

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There is much to be done, and we're now focused on the motor, since it's easy work to do inside the shop during cooler and wetter weather. Stay tuned.

SpudRider · 11-20-2013, 01:31 PM

All right! Brother Tom is working the angle grinder!

SpudRider · 11-20-2013, 01:43 PM

I can hear the neighbors.

"What are they doing over there now?!

Weldangrind · 11-21-2013, 01:34 AM

Quote:

Originally Posted by SpudRider

I can hear the neighbors.

"What are they doing over there now?!

They're very used to me. They also appreciate that I'm always ready to lend a hand.

SpudRider · 11-21-2013, 01:39 AM

Quote:

Originally Posted by Weldangrind

They're very used to me. They also appreciate that I'm always ready to lend a hand.

I was kidding, of course.

I'm sure your neighbors were not disturbed, and they appreciate your willingness to help.

Weldangrind · 11-21-2013, 10:46 AM

Further to the displacement discussion, I remember being quite puzzled by the markings on the Roketa motor when I first brought it home (page 3 http://www.chinariders.net/showthrea...=roketa&page=3 ). I couldn't wrap my mind around how 125cc was indicated, yet it was badged as a 200. I'm still not sure why the markings are as they are, but I have the answer about actual displacement.

With this 200cc OHC motor, the bore is a whopping 68.5mm, and the stroke is a tiny 52.5mm.

The standard-issue 223cc OHC motors use a 65.5mm bore and a 66.2mm stroke.

My 200 would rev nicely, but make very little power down low. The 223 would have more low-end grunt, but would max out at a lower rpm. I'm very hopeful that I can combine the 68.5mm bore with the 66.2mm stroke for an unprecedented big bore and stroke China motor. I'm about to pull the trigger on some parts from Taobao to do the deed.

For the sake of interest, I compared the OHC Roketa parts with Honda XR200 parts, and found very little that would swap over. The stud spacing is considerably larger on the Roketa, so you can't put a China cylinder and head on a Honda bottom end. Even the valvetrain is different. What remains to be seen is if I can stuff a monster crank in an XR200 motor to create an awesome stroker; that, mixed with the 10:1 Wiseco piston I have would be lots of fun. I know that the China crank has a different flywheel taper, but I could likely overcome that by using a China flywheel and electrics.

I can't answer that at this time, because the flywheel requires a 28mm female puller that I've never seen. That'll come from Taobao as well.

edtardo · 11-21-2013, 02:16 PM

this thread brings me so much joy

katoranger · 11-21-2013, 09:02 PM

Quote:

Originally Posted by Weldangrind

They're very used to me. They also appreciate that I'm always ready to lend a hand.

You probably fix all their broken stuff too.

Weldangrind · 11-21-2013, 10:56 PM

Quote:

Originally Posted by edtardo

this thread brings me so much joy

I presume that you're not giving me a hard time.

I totally geek out over engine building, especially when I can manipulate the rod / stroke ratio and stuff like that.

Weldangrind · 11-21-2013, 10:58 PM

Quote:

Originally Posted by katoranger

You probably fix all their broken stuff too.

I've been known to. Doesn't hurt to stay on the neighbour's good side, especially when your son and his friends fire up the dirt bikes when you're not home.

11-18-2013, 11:45 AM	#16
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Excellent plan, sounds technically challenging but that's right up your alley! Looking forward to the pics. Is this bike going to Bonneville? __________________ Happy to serve.
	0

11-18-2013, 12:47 PM	#17
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	We eagerly await further updates! __________________ 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

11-19-2013, 11:57 PM	#19
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Since this bike will no longer be suitable for off-road, I've moved it to the Street category. __________________ 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

11-20-2013, 09:35 AM	#20
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	Where are the pics? __________________ You meet the nicest people on a Honda Clone.
	0

11-20-2013, 10:47 AM	#21
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Don't have much to show yet. Bro in Law lives in Calgary, so we're lucky to get time once a month on this bike. He doesn't want me to proceed on my own, since he appreciates the learning curve. It's his first bike and first fabrication project. We're still in the process of de-tabbing the frame and figuring out what changes to make. I find this shot to be particularly interesting, since it compares the Roketa frame with an '81 XR200 (not the R version). You can see how we've removed the seat base metal and cut the gussets. We then heated the steel and bent the seat hoop down until it was in line with the area that is forward of the seat. This shot shows how I've yet to fabricate the mounts for the rear shocks, which were donated by the XR200, as was the swingarm. There is much to be done, and we're now focused on the motor, since it's easy work to do inside the shop during cooler and wetter weather. Stay tuned. __________________ 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

11-20-2013, 01:31 PM	#22
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	All right! Brother Tom is working the angle grinder! __________________ 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

11-20-2013, 01:43 PM	#23
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	I can hear the neighbors. "What are they doing over there now?! __________________ 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

11-21-2013, 10:46 AM	#26
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Further to the displacement discussion, I remember being quite puzzled by the markings on the Roketa motor when I first brought it home (page 3 http://www.chinariders.net/showthrea...=roketa&page=3 ). I couldn't wrap my mind around how 125cc was indicated, yet it was badged as a 200. I'm still not sure why the markings are as they are, but I have the answer about actual displacement. With this 200cc OHC motor, the bore is a whopping 68.5mm, and the stroke is a tiny 52.5mm. The standard-issue 223cc OHC motors use a 65.5mm bore and a 66.2mm stroke. My 200 would rev nicely, but make very little power down low. The 223 would have more low-end grunt, but would max out at a lower rpm. I'm very hopeful that I can combine the 68.5mm bore with the 66.2mm stroke for an unprecedented big bore and stroke China motor. I'm about to pull the trigger on some parts from Taobao to do the deed. For the sake of interest, I compared the OHC Roketa parts with Honda XR200 parts, and found very little that would swap over. The stud spacing is considerably larger on the Roketa, so you can't put a China cylinder and head on a Honda bottom end. Even the valvetrain is different. What remains to be seen is if I can stuff a monster crank in an XR200 motor to create an awesome stroker; that, mixed with the 10:1 Wiseco piston I have would be lots of fun. I know that the China crank has a different flywheel taper, but I could likely overcome that by using a China flywheel and electrics. I can't answer that at this time, because the flywheel requires a 28mm female puller that I've never seen. That'll come from Taobao as well. __________________ 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

11-21-2013, 02:16 PM	#27
edtardo Join Date: Mar 2012 Location: Altoona, Fl Posts: 158	this thread brings me so much joy __________________ NewStar DB 200 Facts are meaningless. You could use facts to prove anything that's even remotely true! --Homer Simpson
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