Engine Trouble Crankshaft won't spin

[justakid108]

I recently replaced the head/piston head on my bike because the last one was shredded. So now we have another problem... The crankshaft gear is bound up. Idk why, but any help would be nice...

The piston like "locks" at the bottom. It clicks, then stops...

 

[wagel]

Is the piston with same pin height as the old one?

 

[gary55]

Good chance you got the wrong top end. The piston on the left is type A. The right is B. The A type engine has a 2 mm shorter rod, and a 1mm taller cylinder allowing for the 3mm lower wrist pin. The type b piston will hit the balance wheels of the crank of a type A engine. If the old one was shredded you may also have metal in the case causing the bind. At any rate the crank case needs to be thoroughly flushed of all foreign matter. To get everything out you need to remove the engine, remove the magnet from the crank, and you should remove the magneto as well so you can flush the case with gasoline, blast the case out with water hose, and use fuel oil mix for the final flush. If you just order a type A piston and the new cylinder is a type B you may have piston to head clearance problems. If not you will have insanely high compression.

 

[gary55]

This is a type A engine with a type B cylinder. The top edge of the piston is even with the top of the cylinder without being torqued down. I am almost certain it will bounce on the head if assembled.

 

[justakid108]

This is a type A engine with a type B cylinder. The top edge of the piston is even with the top of the cylinder without being torqued down. I am almost certain it will bounce on the head if assembled.

So how do I tell what mine is???

 

[justakid108]

This is a type A engine with a type B cylinder. The top edge of the piston is even with the top of the cylinder without being torqued down. I am almost certain it will bounce on the head if assembled.

Well, I got the piston AND Cylender... so would that be a problem???

 

[boss4457]

Im having the same problem i replaced the cylinder but when i torque the head down the motor wont turn in a certain spot i think the piston is hitting the head. Can i run double head gaskets or do i need another cylinder.

 

[gary55]

You guys need to invest in a micrometer. they are dirt cheap at harbor freight, but in the mean time you need to compare the old parts with the new ones to see if they are different. If you only purchased a cylinder and the piston is hitting the head than you can double the gasket, and probably get the needed clearance

Well, I got the piston AND Cylender... so would that be a problem???

If the piston has a higher wrist pin whole than the one you took out than yes that will be a problem. When replacing individual components you have to make sure that they are the same as the original.

 

[justakid108]

You guys need to invest in a micrometer. they are dirt cheap at harbor freight, but in the mean time you need to compare the old parts with the new ones to see if they are different. If you only purchased a cylinder and the piston is hitting the head than you can double the gasket, and probably get the needed clearance

If the piston has a higher wrist pin whole than the one you took out than yes that will be a problem. When replacing individual components you have to make sure that they are the same as the original.

Yup... that was it... I need a type A piston. Can you put a link to where I could buy one???

 

[justakid108]

You guys need to invest in a micrometer. they are dirt cheap at harbor freight, but in the mean time you need to compare the old parts with the new ones to see if they are different. If you only purchased a cylinder and the piston is hitting the head than you can double the gasket, and probably get the needed clearance

If the piston has a higher wrist pin whole than the one you took out than yes that will be a problem. When replacing individual components you have to make sure that they are the same as the original.

Also, if I just got a piston, can I use the same head???