New engine or fixing old one

[Tyler6357]

Yeah crank rotates normaly and everything but cylinder is bad. Im thinking about buying zeda 80 triple 40. But on the other side like you said I can just buy all upper parts. One question. Are engines like zeda and mine chinagirl same except this one has ported cylinder or there are some other differences?

The main differences in cylinders besides porting is that some have a 40mm intake port while others have a 32mm intake port. In the old days they all had 32mm intakes, the 40mm ones came later as an upgrade for speed mods like reed valves. Also, there are 2 types of pistons, ones have a lower wrist pin location and ones that have a high wrist pin location.


Looking at the picture you posted, I think you have a high wrist pin location, some call them Type A and other's call them Type B. If your crank rotates okay there is probably no damage to the bottom end. you might need a new needle bearing and wrist pin, you have to remove the piston to find out if they are damaged. Often these things come with the piston anyhow, it's a good idea to put a new head gasket on too. You can find all this stuff sold together or you can buy them separate. Something like this except this one has a low wrist pin piston---> https://www.ebay.com/itm/66cc-80cc-...710780&hash=item1a33a8deaa:g:8EcAAOSw0lhckKbD

Maybe this but it has no gaskets--->
https://www.ebay.com/itm/47mm-66-80...418481?hash=item2ca38bf131:g:SLkAAOSwe-FU94~q
You will have to shop around.

Also, like I said, if the cylinder is damaged you will need a new one, stock ones cost about $20.

 

[Tyler6357]

I recommend watching these 2 videos from Fred at CRMachine. They are kinda old but still relevant. Fred is the original designer of the "FredHead" upgraded high compression heads.---> https://crmachine.com/

These videos will help you understand the differences between the different china girl engines. Also, I recommend watching his other videos for just about everything you wanted to know about your china girl engine. They are very simple engines and are surprisingly easy to fix.

Frederic Chelminski youtube channel--> https://www.youtube.com/user/turrettooling1968/videos

 

[Carlos motors]

I recommend watching these 2 videos from Fred at CRMachine. They are kinda old but still relevant. Fred is the original designer of the "FredHead" upgraded high compression heads.---> https://crmachine.com/

These videos will help you understand the differences between the different china girl engines. Also, I recommend watching his other videos for just about everything you wanted to know about your china girl engine. They are very simple engines and are surprisingly easy to fix.

Frederic Chelminski youtube channel--> https://www.youtube.com/user/turrettooling1968/videos

Thanks Tyler for videos and explanation. Few shorts questions.
First do you think I should rebuild the whole engine or just changing upper parts will do?
Second what do you think about this head

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Third can you explain me in short lines what is port timing. If I understood porting is when you trimm bit of metal from intake and exhaust port to maximize inlet and outlet of fuel and exhaust fumes.

 

[Tyler6357]

Thanks Tyler for videos and explanation. Few shorts questions.
First do you think I should rebuild the whole engine or just changing upper parts will do?
Second what do you think about this head

Silver CNC Cylinder Head&Gasket Set Fit 80cc Motorized Bicycle Bike Motor Engine | eBay

Find many great new & used options and get the best deals for Silver CNC Cylinder Head&Gasket Set Fit 80cc Motorized Bicycle Bike Motor Engine at the best online prices at eBay! Free shipping for many products!

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Third can you explain me in short lines what is port timing. If I understood porting is when you trimm bit of metal from intake and exhaust port to maximize inlet and outlet of fuel and exhaust fumes.

(1) Well, it doesn't sound like the bottom end is damaged but the top end is history, so, yeah, I think a new top end will get it running again, a new stock top end will cost you about $30.
(2) I think that head is much better than a stock one. The larger fins and large base will dissipate the heat much better letting the engine run much cooler and will make it last longer. I assume it has a 6cc volume which won't really add much extra compression. It will seal much better than a stock head too. I would say "yes".
(3) No, I can't explain it in short lines, haha. Fred has a video but there are tons of other videos on the subject at youtube.

 

[Frogslayer]

I disagree with your statement #2. If your jetted correctly and not racing heat won't be an issue and you can't seal better than sealed. Only if you needed a different shaped combustion pocket on the head would it be worth changing it in my opinion.

 

[Carlos motors]

(1) Well, it doesn't sound like the bottom end is damaged but the top end is history, so, yeah, I think a new top end will get it running again, a new stock top end will cost you about $30.
(2) I think that head is much better than a stock one. The larger fins and large base will dissipate the heat much better letting the engine run much cooler and will make it last longer. I assume it has a 6cc volume which won't really add much extra compression. It will seal much better than a stock head too. I would say "yes".
(3) No, I can't explain it in short lines, haha. Fred has a video but there are tons of other videos on the subject at youtube.

Is this cylinder any good?

Rectangle Exhaust Ported cylinder

Photographed is an unported cylinder. The cylinder you are purchasing is fully ported! should make around 4.5-5.5hp Add tons of power to your stock motor by putting this Zeda80 ported cylinder on your engine. It will gain a lot of power all around. A killer up grade to a zeda engine.

zedamotorsports.com

Or should I buy just a regular one
Also do I need new clutch pads

 

[Carlos motors]

Is this cranck corrosion problem?

 

[Tyler6357]

I disagree with your statement #2. If your jetted correctly and not racing heat won't be an issue and you can't seal better than sealed. Only if you needed a different shaped combustion pocket on the head would it be worth changing it in my opinion.

Hey, I've seen those thin stock heads warp from the heat causing air leaks around the head gasket. The Chinese metal is made so weak and soft that it can become all but useless. There is no doubt that that head will be far better than stock and it will certainly keep temps down better than stock.

 

[Tyler6357]

Is this cylinder any good?

Rectangle Exhaust Ported cylinder

Photographed is an unported cylinder. The cylinder you are purchasing is fully ported! should make around 4.5-5.5hp Add tons of power to your stock motor by putting this Zeda80 ported cylinder on your engine. It will gain a lot of power all around. A killer up grade to a zeda engine.

zedamotorsports.com

Or should I buy just a regular one
Also do I need new clutch pads

I don't know how well they ported that cylinder, if it was done right, it's a good deal. I personally usually just get stock one and port it myself, so I really don't know if that's a good deal or not, $34.50 seems like a decent price for a ported cylinder though.

The clutch pads don't look too bad, I've seen worse.

 

[Carlos motors]

I cant find anywhere on ebay piston type B (30mm) that ships to croatia... Every piston is 25mm