Zongshen 200GY-2: Engine Rebuild at 51,687 Miles

[SpudRider]

Originally Posted by wilserchinarider

Spud, I am intrigued w/ this photo, and find it surprising the Zong was running w/ such a worn rocker?

Prior to the rebuild, did you notice constant valve adjustments were required for the exhaust valve to compensate for the wear that was occurring? Or do you think this happened over many miles and was just slowly compensated for in your routine valve adjustments?...

My Zong ran very well with the worn, exhaust valve rocker. The exhaust valve held its clearance well. I did not have any indications anything was wrong until I noticed a concerning noise emanating from the cylinder head.

Incidentally, I will restate, this was a Yamaha rocker which came inside the XT200 cylinder head I installed.

Spud

[SpudRider]

Here's a photograph of my valve spring compressor which I bought on eBay for a very reasonable price.



With the cylinder head removed, here's how you attach the tool to compress the valve springs, and remove the valves. For illustrative purposes, I have the tool attached to a 1982, XT250 cylinder head.



One end of the tool is centered on the bottom of the valve.



The other end of the tool compresses the valve spring as the handle is turned. The open adapter on this end of the tool allows you to remove, and install the valve retainers more easily.



I have removed the valve rockers as well as the camshaft from this cylinder head, so I have a lot of room to work.



You must remove the camshaft, or you won't be able to compress the valve springs. However, you can use the tool with the valve rockers installed, as shown below. However, you have less room to access the valve retainers.



After the valve springs are compressed sufficiently, I use a magnet to remove the valve retainers, as shown in the following video.



I prefer to lap the valves using a short section of hose connected to the valve stem with a small hose clamp. Even old, dirty valves are easy to lap using this method. However, the rockers must be removed to attach the hose to the end of the valve stem.



Here's a closeup view of my valve lapping tool attached to the valve stem.



Spud

[SpudRider]

I changed the engine oil approximately 500 miles after my engine rebuild. The oil filter was a little dirtier than usual. I also cleaned some tiny, metal specks which were deposited in the oil filter cavity. However, nothing was unusual in this regard. I plan to recheck the valve lash in the next several days. My Zong's engine is running strongly and smoothly. I am pleased to report I don't have any oil leaks, and my bike is not burning motor oil.

Here are several photographs I took during today's ride.









Spud

[Weldangrind]

Was your bike using much oil before the rebuild?

[SpudRider]

Originally Posted by Weldangrind

Was your bike using much oil before the rebuild?

Yes, it was. I think my current machinist bored my Honda XR650L cylinder better than my last machinist bored my Zong's cylinder. :roll: Therefore, when I discovered the damaged valve rocker, I had my new machinist bore the Zong's cylinder as well.

Spud

[FastDoc]

Thanks again for the pics Spud. You put a lot of work into this project and researching how to do it. We all appreciate your sharing with us. The Zong is a GREAT trailbike and deserves the work you have put into it. We Chinariders should have bought a container of them when they were under a grand delivered! :wink:

[SpudRider]

Thank you, Doc. Today I checked the valve lash; it was approximately 1,200 miles after my top end rebuild. The valves were still in specification, but a little looser, so I tightened them into the middle of the specified range. My Zong is purring like a kitten.



Spud

[Weldangrind]

Your Zong looks great, Spud. I'm glad that we were all able to watch as you slowly changed it into what it is.

Do you still have the old cylinder? What does your machinist think the outer limits would be? It would be interesting to learn if you could gain more cc's by boring and choosing a Wiseco piston.

[SpudRider]

Originally Posted by Weldangrind

Your Zong looks great, Spud. I'm glad that we were all able to watch as you slowly changed it into what it is.

Do you still have the old cylinder? What does your machinist think the outer limits would be? It would be interesting to learn if you could gain more cc's by boring and choosing a Wiseco piston.

Thank you, Weld. As well as the added protection, I think the orange handguards added just the right amount of color to the Zong. I no longer feel the impulse to add additional striping to the fuel tank.

I have the original cylinder, bored to 4th oversize, which is +1.00 mm. I can't find an appropriate Wisceo piston which is larger. However, my Zongshen 210 is running stronger than ever with the addition 6cc of engine displacement from the two cylinder borings.



Spud

[FastDoc]

How much longer do you think the weather will allow you to ride at that altitude, Spud?

We're cooling off here. Highs still in the 80s but getting dangerously close to the 30's at night.

Winter is not worth living through...

[Weldangrind]

That tells me that a TTR-230 (or similar) engine would have to give up its crank for larger displacment than what you have now. Would you do that, or just search for a complete 230 motor?

[SpudRider]

Originally Posted by FastDoc

How much longer do you think the weather will allow you to ride at that altitude, Spud?

We're cooling off here. Highs still in the 80s but getting dangerously close to the 30's at night.

Winter is not worth living through...

I'm hoping I can ride the mountain trails for another month before the snow closes them off.

Spud

[SpudRider]

Originally Posted by Weldangrind

That tells me that a TTR-230 (or similar) engine would have to give up its crank for larger displacment than what you have now. Would you do that, or just search for a complete 230 motor?

With the proper jetting and sprocket ratios, the Zong is a pretty good trail bike with a 200cc engine. However, I would install an XT225, TT-R225, or TT-R230 engine if I found a good deal on one. The 223cc Yamaha engine would bolt right into the Zong's frame, and the sprockets would align perfectly.

Spud

[hect75]

Spud,
The cylinder head and cylinder block are liking oil (small amount) and need to take them off. However, I tried but the 4 studs (2 attached in the left and 2 right crankcase that hold these cylinders) are impossible to remove. I check your thread posted in Sept 2012 about the engine rebuild and learned you remove the studs. The pic 3 you installed the cylinder block with no studs and wonder how you did it. Need your experience because I don't know how to remove them and don't want to drop by the Yamaha's shop to do the job. I pretend to seal these cylinders with RTV silicone because gaskets are way too difficult to get them.

[SpudRider]

Originally Posted by hect75

Spud,
The cylinder head and cylinder block are liking oil (small amount) and need to take them off. However, I tried but the 4 studs (2 attached in the left and 2 right crankcase that hold these cylinders) are impossible to remove. I check your thread posted in Sept 2012 about the engine rebuild and learned you remove the studs. The pic 3 you installed the cylinder block with no studs and wonder how you did it. Need your experience because I don't know how to remove them and don't want to drop by the Yamaha's shop to do the job. I pretend to seal these cylinders with RTV silicone because gaskets are way too difficult to get them.

You can must remove the four studs before you can remove the cylinder. Tighten two bolts on top of each stud, or use a pair of vise grips to grab the studs to remove them. In order to make subsequent engine work easier, I replaced the stock Zongshen studs with studs from a Yamaha XT200 engine. These studs are part #9 in the following diagram, and only cost $2.21 apiece.



http://www.cyclepartswarehouse.com/f...83&fveh=177068

You will need to replace both gaskets with new gaskets, or you will definitely have engine problems. You can buy Zongshen gaskets from Taobao, or you can use Yamaha TW200 gaskets.

http://www.cyclepartswarehouse.com/f...13&fveh=204271

http://www.cyclepartswarehouse.com/f...13&fveh=204271