Zongshen 200GY-2: Top End Rebuild at 31,656 Miles

[SpudRider]

Originally Posted by katoranger

Spud, could you have used an xt225 cylinder for more ccs? Just a thought I had.

Allen

Yes, I probably could have used an XT225 cylinder, but I would not have gained much, if any, additional power for the added expense, and trouble.

The XT225 cylinder has a longer stroke, as well as a bigger bore. Therefore, to get the extra 25cc displacement, I also would have needed to install a longer connecting rod. Since the XT225 barrel is longer, I would have lost some compression if I had not installed a longer connecting rod.

However, the complete XT225 engine might bolt directly into the Zongshen frame with few, or no modifications required.

Spud

[katoranger]

That makes sense. Not worth the extra cost of a crank and rod.

Lets see another 30K now.

Allen

[SpudRider]

Originally Posted by katoranger

...Lets see another 30K now.

Allen

I'm working on it, Allen. I have over 32,000 miles on the odometer right now.





Spud

[FastDoc]

It occurs to me youre Yamazong is leaning further and further to being a Yamaha more than a Zong!

[SpudRider]

Originally Posted by FastDoc

It occurs to me youre Yamazong is leaning further and further to being a Yamaha more than a Zong!

There is not much difference, Doc. However, the Zong is much less expensive to purchase, and to operate.

Spud

[mizke]

Originally Posted by SpudRider

There is not much difference, Doc. However, the Zong is much less expensive to purchase, and to operate.

Spud

best part is tho, sometimes when a common part needs to be replaced. you could throw the yamaha part on it, better quality and will prolly last a little while longer..

[SpudRider]

Originally Posted by mizke

best part is tho, sometimes when a common part needs to be replaced. you could throw the yamaha part on it, better quality and will prolly last a little while longer..

In my experience, the Zongshen part is just as good as the Yamaha part, only the Zongshen part is much less expensive.

Spud

[allanc7]

Spudrider
Hello from Oz. Thank you for all your wonderful write-ups.

With the top end rebuild, can I ask:
*did you use a new Yamaha cam chain and sprockets or Zongshen?
*Has your friend Andy expressed an opinion as to why the inlet valve recessed into the head?
*Apart from the stutter at WFO, were there any other signs that led you to check inlet valve clearance every 500 miles?

Regards
Allan

[2LZ]

I have to say I'm thoroughly impressed with the cleanliness of the engine internals. No doubt a symptom of your excellent maintenance ....and the fact you got over 30,000 'basically flawless' miles out of a small displacement "dirt bike" is a great trumpet for the quality of the Zong, especially concidering the cost differential between the China and Japanese alternative.. 8O

The valve issue you were speaking of is how the pushrod Harley's I've had experience with have worn. Valves don't loosen....they tighten..... First sign, harder starting. When my old Ironhead chopper took more than 4 or 6 kicks....something was amiss. Odds are, the intake needed setting.

As the valve pounds into the seat..along with the heat.....and the unleaded fuels came into play for lack of top end cooling and lube.....the valve seats would wear creating a sink hole. As the 'hardened' finish wore off....the more frequent you had to reset them.

[SpudRider]

Originally Posted by allanc7

Spudrider
Hello from Oz. Thank you for all your wonderful write-ups...

Welcome to these forums, Allan. We are very pleased to have you join us from "down under." Thank you for your kind words; I always appreciate it when someone takes the time to let me know he enjoys my posts.

Originally Posted by allanc7

...With the top end rebuild, can I ask:
*did you use a new Yamaha cam chain and sprockets or Zongshen?
*Has your friend Andy expressed an opinion as to why the inlet valve recessed into the head?
*Apart from the stutter at WFO, were there any other signs that led you to check inlet valve clearance every 500 miles?

Regards
Allan

I used a new, Zongshen camchain for my top end rebuild. Since it was practically new, I used the camshaft sprocket from the Yamaha, XT200 cylinder head. The Zongshen camshaft sprocket would work as well; it appears to be identical to the Yamaha, TW200 camshaft sprocket.

My friend Andy has not expressed an opinion regarding the wear on the intake valve, other than the engine had delivered 31,656 miles of good service. However, I have read of this phenomenon occurring with the valves on other engines. I will note the Zongshen exhaust valve, which is exposed to higher temperatures, was in good condition.

After riding my Zong for almost 32,000 miles, I had become very familiar with its idiosyncrasies. Therefore, I had noted my Zong would start very easily, with a rapid push of the starter button, when the valve lash was properly adjusted. I usually check my Zong's valve lash every other oil change. During these inspections I had noted the exhaust valve held its adjustments very well for 30,000 miles. However, I discovered my intake valve was invariably tight.

As I became more familiar with my bike, I noted my Zong would become harder to start when the intake valve clearance had tightened. Therefore, whenever my Zong became even slightly harder to start, I would always check the valve lash. As the mileage on my engine increased, I noticed this starting idiosyncrasy occurred more frequently. In addition, I was even more diligent with my maintenance schedule as the odometer numbers increased.

Because I checked the valve lash regularly, and became familiar with the idiosyncrasies of my engine, I was able to detect the accelerated wear on the intake valve, and correct the problem before my engine was damaged.

Spud

[SpudRider]

Originally Posted by 2LZ

I have to say I'm thoroughly impressed with the cleanliness of the engine internals. No doubt a symptom of your excellent maintenance ....and the fact you got over 30,000 'basically flawless' miles out of a small displacement "dirt bike" is a great trumpet for the quality of the Zong, especially concidering the cost differential between the China and Japanese alternative.. 8O ...

Thank you, 2LZ; I am a firm believer in good maintenance. After riding my zong almost 33,000 miles, I am very impressed with its quality of manufacture; I consider the Zong an exceptional value.

Originally Posted by 2LZ

...The valve issue you were speaking of is how the pushrod Harley's I've had experience with have worn. Valves don't loosen....they tighten..... First sign, harder starting. When my old Ironhead chopper took more than 4 or 6 kicks....something was amiss. Odds are, the intake needed setting.

As the valve pounds into the seat..along with the heat.....and the unleaded fuels came into play for lack of top end cooling and lube.....the valve seats would wear creating a sink hole. As the 'hardened' finish wore off....the more frequent you had to reset them.

Your experience with your pushrod engine, Harley Davidson motorcycles exactly parallels my experience with my Zong, 2LZ. As always, thank you for sharing your insights.

Spud

[TurboT]

Ok, haven't had much time to read the forums so I've been sticking to the ATV one for the last bit for the most part.. just had some time to read through this.

Good work Spud... I do have questions!

I'm curious why you chose a .50mm piston and not the .25? You did mention it was the '2nd oversize' so I assumed a .25 would be available?

You only have one picture of the actual cylinder after machining, and perhaps it's the picture quality but I didn't see much of a cross hatch pattern in the bore. I'm curious if you know how your machinist opened up the hole? Small barrels like that can be a bit tricky to machine that amount of material out of at once... especially two oversizes. Was this a specific motorcycle machine shop or other?


My .02c on the head, good choice to use the other one. Just from eyeballing it looks like you'd may have needed a new valve seat and possibly a valve. The machining on the seat would've set you back a bit...and I would say installing valve seats in an aluminum head is a bit scary. 8O

Overall looks like a bit of fun! You did a great job I'm just curious about the process and stuff.

-T

[SpudRider]

Originally Posted by TurboT

…Good work Spud... I do have questions!

I'm curious why you chose a .50mm piston and not the .25? You did mention it was the '2nd oversize' so I assumed a .25 would be available?…

Thank you, Turbo. I searched the internet, but I could not find either a 0.25mm, 1st oversize piston, or 1st oversize piston rings. Also, I only found references to the 2nd oversize piston on the TW200 forum. Therefore, I bought the smallest oversize piston, and rings, I could find for sale.

Originally Posted by TurboT

…You only have one picture of the actual cylinder after machining, and perhaps it's the picture quality but I didn't see much of a cross hatch pattern in the bore. I'm curious if you know how your machinist opened up the hole? Small barrels like that can be a bit tricky to machine that amount of material out of at once... especially two oversizes. Was this a specific motorcycle machine shop or other?…

My good friend Andy has been a professional mechanic for thirty years. Andy is currently a Maintenance Supervisor, and he referred me to a local, independent machinist he employs for jobs at his shop. Andy also recently employed this machinist to rebore a cylinder for one of his own motorcycles. I trust Andy’s judgement, so I didn’t question the machinist about the job. Since Andy works near the machinist’s shop, I also stopped, and showed Andy the cylinder before I installed it on my motorcycle.

Originally Posted by TurboT

…My .02c on the head, good choice to use the other one. Just from eyeballing it looks like you'd may have needed a new valve seat and possibly a valve. The machining on the seat would've set you back a bit...and I would say installing valve seats in an aluminum head is a bit scary. 8O…

Thank you for the feedback, Turbo. I consider myself blessed that Andy gave me the Yamaha, XT200 engine, and the cylinder head was in such good shape! I learned a lot from doing this top end rebuild, and my engine is now running better than ever. I enjoy being able to maintain my own motorcycle. However, I must admit, I would much rather ride my Zong, than wrench on it!

Spud

[TurboT]

Hey Spud I didn't mean to imply the machining was done incorrectly. I just didn't see a cross hatch in the photo (possibly just because it didn't focus on the bore) and was curious about it.

I have some experience with that type of thing, and my hands get sore just thinking of my time honing motorcyle barrels in our machine which was designed for connecting rods. (small diameter motorbike cylinders did not fit in the machine for honing car blocks)

I think you're fortunate on the replacement head being available and in such good shape too. Not that yours wasn't fixable, but certainly a time and $$$ saver.

I think you're good to go for another 30,000.

[SpudRider]

Originally Posted by TurboT

Hey Spud I didn't mean to imply the machining was done incorrectly. I just didn't see a cross hatch in the photo (possibly just because it didn't focus on the bore) and was curious about it...

I didn't take it that way, Turbo. Please know I was not offended. The simple truth is, I completely trusted Andy's professional judgement concerning this cylinder rebore. Subsequent to this top end rebuild, my Zong has never run better, so I believe my faith was not misplaced.

Originally Posted by TurboT

...
I think you're fortunate on the replacement head being available and in such good shape too. Not that yours wasn't fixable, but certainly a time and $$$ saver.

I think you're good to go for another 30,000.

Amen! I certainly hope you're correct about the additional 30K miles. I now have my Zong modified almost perfectly to suit my riding needs. I hope am blessed to continue riding my Zong safely for many more miles.

Spud