Pocketbike Forum banner
1 - 12 of 12 Posts

·
Registered
Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
Joined
·
45 Posts
Discussion Starter · #1 ·
Hey guys,
So I picked up this C1 and started tearing it down, as it wasn't running right. Only on choke it would run. So first cleaned the carb, but that didn't help much. Now I have the engine out and all but split the cases, as the waterpump area looks clean and I can't feel much play on the crank.

I reckoned the bad running might be the piston and rings or otherwise leaking crank bearings. So I took the cilinder off and it has some marks of blow by the rings and the plug is pretty black. As I am rather new to 2 strokes, could anyone assess the state of my piston/? What does this brown markings tell?
Drinkware Food storage containers Cookware and bakeware Tableware Gas
Drinkware Cookware and bakeware Lid Food storage containers Cylinder
Household hardware Wood Art Auto part Screw

As you can see I have quickly measured the squish at one place. It was.76mm. Broke off one of the skirts, don't ask....

I think the rings might be the problem, so I am ordering a new piston with rings. I also took all gaskets and needle bearing to a local shop to have them match them up. Already been some time now, so I think they have a hard time finding the right parts.
 

·
Registered
Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
Joined
·
45 Posts
Discussion Starter · #4 ·
The cilinder looks to be okay. No signs of wear as I can tell. so I am trying the piston and rings first. What would be a reason for changing the cilinder too?
 

·
Administrator
Joined
·
3,630 Posts
If you get all three parts together as a kit you won't have to worry about the cylinder and piston not having a good fit
 

·
Registered
Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
Joined
·
45 Posts
Discussion Starter · #6 · (Edited)
Well well, it took the local shop some time to match up the gaskets and seals, but they are finally here. Also got the new piston in and it is quite different from the original one.

The old one has two piston rings, the new piston only one. Not a big deal, but the ring might need to be replaced a little earlier. However the material is completely different (it looks like light alloy vs aluminium) and the original piston weighs 63 grams (0.139lb). The new piston is a mere 36gr (0,079).
Would you expect more wear from the new piston due to the lighter material or will it make no difference?
Material property Cylinder Gas Household hardware Auto part


Furthermore the bearing is a wider 15mm version, so would not need the spacers. I ordered a original spec 12mm quality NTN roller bearing. I think I am going to use the quality one with the spacers. Or would the wider one be the best choice? But I don't know the quality of that one.
 

·
Registered
Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
Joined
·
45 Posts
Discussion Starter · #7 ·
The new piston is of a different material and is about 0.05mm smaller in diameter as the original heavier piston. That might be as the alu piston will expand more from heat?

I am measuring the cylinder and pistons to determine clearence, but does anyone have some maintanance figures on piston sizes? Or the bore size of a new C1 cylinder? I couldn't find anything in the Blata manual.
 

·
Administrator
Joined
·
3,630 Posts
The best way to fit a piston in a cylinder is to oil the piston with 2 stroke oil and put the piston in the cylinder and let it fall it should fall slowly if it falls right through the Piston is too small if gravity is not enough Force to take the Piston down the cylinder then it is too tight.

Obviously if the person is too small then you will need to replace it.

If the Piston is a slight hair too big and does not free fall but wants to you can hone the cylinder a few passes and try again.

If your cylinder has a coating inside of it or a heat treatment you cannot hone the cylinder!

Try polishing the piston ☝.
 

·
Registered
Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
Joined
·
45 Posts
Discussion Starter · #10 ·
Ah that's a good trick MrKitty. I'll try that one.
I will keep you posted when I have rebuild the engine.
 

·
Registered
Joined
·
300 Posts
Hey guys,
So I picked up this C1 and started tearing it down, as it wasn't running right. Only on choke it would run. So first cleaned the carb, but that didn't help much. Now I have the engine out and all but split the cases, as the waterpump area looks clean and I can't feel much play on the crank.

I reckoned the bad running might be the piston and rings or otherwise leaking crank bearings. So I took the cilinder off and it has some marks of blow by the rings and the plug is pretty black. As I am rather new to 2 strokes, could anyone assess the state of my piston/? What does this brown markings tell?
View attachment 161631 View attachment 161632 View attachment 161633
As you can see I have quickly measured the squish at one place. It was.76mm. Broke off one of the skirts, don't ask....

I think the rings might be the problem, so I am ordering a new piston with rings. I also took all gaskets and needle bearing to a local shop to have them match them up. Already been some time now, so I think they have a hard time finding the right parts.
Just out of curiosity, mind if I ask what you paid?
 
1 - 12 of 12 Posts
Top