I'm an idiot.

FastDoc · 01-06-2011, 11:15 PM

The Zong's got poor compression. I should have checked that first before dumping $200 in parts and a lot of time into it.

I can easily hold my thumb over the spark plug hole while cranking the motor. Adding some oil to the cylinder did not help so I think it's the valves. They are adjusted so that's not it either.

I have $400 into it. Anyone wany a $200 project bike? Maybe Spud can get you a new motor inexpensively and you'd have a like new bike.

As for me, I'm done with it.

Weldangrind · 01-06-2011, 11:46 PM

If you send me the head, I can try replacing the valves for you. Alternatively, maybe you can find a Yamaha head that fits, like Spud did.

FastDoc · 01-07-2011, 11:34 AM

Thanks, buddy but I think I'm gonna cash out. I'd rather not put more time into the bike, although it may be a simple bad valve and fixable very cheap. My heart's not into it, I won't turn a profit on it, so I'd just as soon let it go.

01-07-2011, 11:06 PM

oh that sucks man, I shouldv thought of that ! whenever I was working on my RM250 or my TZR250 I uselly always check the compression !!! it actually makes perfect sense with all the symptoms you had on your bike !
Anyway I'll see if anyone around here wants it. Good luck with the sell !

Reveeen · 01-08-2011, 03:04 PM

Of course you realize: that a head gasket, blown between the cylinders (or the timing chain cavity), would cause the problem you describe?

Ok, I know, too easy, right? (nothing EVER works out that easy for me)

For the want of a $6 gasket it's worth a look!

Weldangrind · 01-08-2011, 03:10 PM

My thoughts exactly.

And a buch of China Rider enablers will needle you until you take it apart.

katoranger · 01-08-2011, 03:17 PM

Just do it. No cost involved in a top end tear down. Do it for the sake of future information for others.

Call it research.

Also check into the yamaha sr250.

Weldangrind · 01-08-2011, 03:27 PM

And take pictures. Lotsa pictures.

SpudRider · 01-08-2011, 09:30 PM

Quote:

Originally Posted by katoranger

Just do it. No cost involved in a top end tear down. Do it for the sake of future information for others.

Call it research.

Also check into the yamaha sr250.

X2! As with your "Dirt Rat" restoration, you have broken new ground with the Zongshen 250GS project, Doc! If you have space in your garage, I strongly encourage to stick with this project a little longer.

All of us have enjoyed watching your work on this project, and we have learned a lot from you.

Spud

FastDoc · 01-11-2011, 10:06 PM

Another update.

I (tried to) pull the head. The valves look OK but there are vertical scoring marks on the cylinder so I think that's the problem. I was unable to pull the head all the way off. It does not seem possible with the motor still in the frame.

I'm not sure I want to hone and re-ring or install an oversize piston. I'm still inclined to part it out.

What's a motor for one of these cost, Spud? Are oversize pistons available?

FastDoc · 01-12-2011, 12:10 PM

It came to me this AM how to remove the head with the motor in the frame. Will decide what to do based on Spud's avalibility of parts.

katoranger · 01-12-2011, 07:29 PM

It may be possible to use yamaha parts. Let us know if it appears to has a broken ring or what went wrong.

Allen

FastDoc · 01-12-2011, 07:55 PM

I looked at it again. No way to get the head off without pulling the motor and the swingarm/rear suspension. :evil: The head looks identical to the Yamaha. I don't know what's wrong. the cylinder is very lightly scored but otherwise it and the valves look OK.

Weldangrind · 01-13-2011, 02:18 AM

Does it have a decompression device like a Honda? Maybe that's hanging open.

You could always hook up an airline to the spark plug hole and see where the air goes. That'll tell you where the horsepower is leaking.

Cal25 · 01-13-2011, 09:02 AM

Any chance of a valve stuck partially open?

01-06-2011, 11:15 PM	#1
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	I'm an idiot. The Zong's got poor compression. I should have checked that first before dumping $200 in parts and a lot of time into it. I can easily hold my thumb over the spark plug hole while cranking the motor. Adding some oil to the cylinder did not help so I think it's the valves. They are adjusted so that's not it either. I have $400 into it. Anyone wany a $200 project bike? Maybe Spud can get you a new motor inexpensively and you'd have a like new bike. As for me, I'm done with it. __________________ Happy to serve.
	0

01-06-2011, 11:46 PM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	If you send me the head, I can try replacing the valves for you. Alternatively, maybe you can find a Yamaha head that fits, like Spud did. __________________ 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

01-07-2011, 11:34 AM	#3
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Thanks, buddy but I think I'm gonna cash out. I'd rather not put more time into the bike, although it may be a simple bad valve and fixable very cheap. My heart's not into it, I won't turn a profit on it, so I'd just as soon let it go. __________________ Happy to serve.
	0

01-08-2011, 03:10 PM	#6
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	My thoughts exactly. And a buch of China Rider enablers will needle you until you take it apart. __________________ 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

01-08-2011, 03:17 PM	#7
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	Just do it. No cost involved in a top end tear down. Do it for the sake of future information for others. Call it research. Also check into the yamaha sr250. __________________ You meet the nicest people on a Honda Clone.
	0

01-07-2011, 11:06 PM	#4
Guest Posts: n/a	oh that sucks man, I shouldv thought of that ! whenever I was working on my RM250 or my TZR250 I uselly always check the compression !!! it actually makes perfect sense with all the symptoms you had on your bike ! Anyway I'll see if anyone around here wants it. Good luck with the sell !
	0

01-08-2011, 03:04 PM	#5
Reveeen Join Date: Jun 2009 Location: orbital platform Posts: 741	Of course you realize: that a head gasket, blown between the cylinders (or the timing chain cavity), would cause the problem you describe? Ok, I know, too easy, right? (nothing EVER works out that easy for me) For the want of a $6 gasket it's worth a look!
	0

01-08-2011, 03:27 PM	#8
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	And take pictures. Lotsa pictures. __________________ 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

01-11-2011, 10:06 PM	#10
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Another update. I (tried to) pull the head. The valves look OK but there are vertical scoring marks on the cylinder so I think that's the problem. I was unable to pull the head all the way off. It does not seem possible with the motor still in the frame. I'm not sure I want to hone and re-ring or install an oversize piston. I'm still inclined to part it out. What's a motor for one of these cost, Spud? Are oversize pistons available? __________________ Happy to serve.
	0

01-12-2011, 12:10 PM	#11
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	It came to me this AM how to remove the head with the motor in the frame. Will decide what to do based on Spud's avalibility of parts. __________________ Happy to serve.
	0

01-12-2011, 07:29 PM	#12
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	It may be possible to use yamaha parts. Let us know if it appears to has a broken ring or what went wrong. Allen __________________ You meet the nicest people on a Honda Clone.
	0

01-12-2011, 07:55 PM	#13
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	I looked at it again. No way to get the head off without pulling the motor and the swingarm/rear suspension. :evil: The head looks identical to the Yamaha. I don't know what's wrong. the cylinder is very lightly scored but otherwise it and the valves look OK. __________________ Happy to serve.
	0

01-13-2011, 02:18 AM	#14
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Does it have a decompression device like a Honda? Maybe that's hanging open. You could always hook up an airline to the spark plug hole and see where the air goes. That'll tell you where the horsepower is leaking. __________________ 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

01-13-2011, 09:02 AM	#15
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	Any chance of a valve stuck partially open?
	0