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Discussion Starter · #1 ·
Ok so i have a Gs-12 pocket bike which i believe is a 49cc 2 stroke engine. it has lights,horn,blinker,and a electric start. Now the problem i have is i get great spark and gas is going to carb but its not starting. so i took the whole thing out and did a compression test and got 75psi after 5 pulls. is this good or bad, should i tear into engine or buy a new one? i dont know help!
 

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Sounds low. You may need new piston rings AND/OR a cylinder head. If you do that is about $40. I would pour a bit of oil down the spark plug hole and then take another compression test. If you get a higher PSI then your rings/cylinder are prob worn out.
 

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Discussion Starter · #3 ·
Sounds low. You may need new piston rings AND/OR a cylinder head. If you do that is about $40. I would pour a bit of oil down the spark plug hole and then take another compression test. If you get a higher PSI then your rings/cylinder are prob worn out.
Hey i just did what you said and after i poured oil in my psi got up around 100psi. so with that being done what should i replace and where do i buy it?
 

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Can you take a picture of your engine and upload it? Also you will need to take your cylinder head off. Which is REALLY easy. Should just be 4 bolts and take the spark plug boot off. Then you will need to measure the diameter of the piston. But I need to see a pic of the engine. I think after 3 posts you should be able to upload a photo. Here is a pic of an engine that I think is yours. And you dont need to buy whats in the links theyre just pictures.

http://www.racemotorparts.com/product_info.php?products_id=311

Also here is a diagram. I think it is your engine(correct me if I'm wrong). Just have to scroll down a bit. And the cylinder head is labeled 51 .

http://www.pocketbikeplanet.com/showthread.php?t=54921
 

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Discussion Starter · #5 ·
Can you take a picture of your engine and upload it? Also you will need to take your cylinder head off. Which is REALLY easy. Should just be 4 bolts and take the spark plug boot off. Then you will need to measure the diameter of the piston. But I need to see a pic of the engine. I think after 3 posts you should be able to upload a photo. Here is a pic of an engine that I think is yours. And you dont need to buy whats in the links theyre just pictures.

http://www.racemotorparts.com/product_info.php?products_id=311

Also here is a diagram. I think it is your engine(correct me if I'm wrong). Just have to scroll down a bit. And the cylinder head is labeled 51 .

http://www.pocketbikeplanet.com/showthread.php?t=54921
Ok i have taken a couple of photos but i cant upload them. it wants me to put in a url. i cant find any other way
 

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Discussion Starter · #6 ·
IMG_5926[1].jpg

IMG_5925[1].jpg

IMG_5924[1].jpg


Ok so here are some photos of the engine. i have taken the head off the engine to find a black crusty looking piston. the piston measure 1 3/4inch across.
 

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Ok so its a 44mm piston and head. You might be able to get away without getting a new cylinder head but I highly recommend it becuase chances are you piston rings as well as the head is worn at its only $30. Here is what you should order.


Cylinder Head:
https://www.pocketbikeparts.com/fs529-pocket-bike-cylinder-49cc-44mm.html

Here are the piston and ring sets. But BEFORE YOU ORDER.Measure the wrist pin on your engine. If you dont know what a wrist pin is look at this picture down below.

http://puredieselpower.com/dodge-products/04.5-07-5.9l-cummins-diesel-wrist-pin.html

The wrist pin is labelled the number 5. Measure that. The two different sizes are 10 or 12mm. So make sure you measure it right. Once you measured then order which one you need.

Here is the 44mm piston with 12mm wrist pin and rings:

https://www.pocketbikeparts.com/pocket-bike-piston-rings-set-49cc-44mm-12mm-wrist-pin.html


And here is the 44mm piston with a 10mm Wrist Pin and rings:

https://www.pocketbikeparts.com/pocket-bike-piston-rings-set-49cc-44mm-10mm-wrist-pin.html

If you have the head off you will be able to measure the wrist pin without removing anything else. And you will also need a gasket set.

Gasket set:

https://www.pocketbikeparts.com/fs5...g-set-x7.html#product_tabs_description_tabbed

Also if you decide to get the parts make sure you heat cycle the engine properly. You can send EPR a PM for the proper heat cycling method. And use the discount code 3030110 for 10% off. Good luck.:thumbsup:
 
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