Engine Porting - Gases out, Fuel Air in

[GearNut]

There are 3 known factories in China that make these engines. Each factory makes slightly different internal parts than the next one.

All the engines look pretty much identical on the outside, the internals are different enough to not allow easy parts swapping.
Some connection rods are longer or shorter than the next one requiring a matched piston to allow the correct compression ratio and port timing.

 

[Rconce01]

Ohh man seriously?

Yeah i started to notice that when all of you talk about 47mm bore and my engine looks just like those yet it has a 35 mm bore? the piston is a little over 1 5/16" diameter.

So how do i buy my replacement piston?

There are 3 known factories in China that make these engines. Each factory makes slightly different internal parts than the next one.

All the engines look pretty much identical on the outside, the internals are different enough to not allow easy parts swapping.
Some connection rods are longer or shorter than the next one requiring a matched piston to allow the correct compression ratio and port timing.

 

[GearNut]

Find out who made your engine. Where did you buy it from?

You might get lucky and a vendor or 2 may measure a new piston to compare it to yours.

Piston diameter as measured at the skirt, the distance between the center of the wrist pin to piston crown and diameter of the wrist pin are what you need to match up.

 

[Rconce01]

Ok great, wow man thanks your really good at this stuff.

Bout it on ebay *80cc bike motor"

How many different diameters are out there?
I'm gonna pull the little sucker out now and measure it up.

Find out who made your engine. Where did you buy it from?

You might get lucky and a vendor or 2 may measure a new piston to compare it to yours.

Piston diameter as measured at the skirt, the distance between the center of the wrist pin to piston crown and diameter of the wrist pin are what you need to match up.

 

[GearNut]

I wish I knew.
I have never seen a listing of all the different dimensions out there.
I have 3 engines, 2 are the same. I have no idea who made them though.
When the day comes that I need a new piston or cylinder I will be in the same boat as you are right now.
I'll probably just wing it and modify whatever I get to run.

 

[Rconce01]

i just pulled apart both motors.

Both pistons are 47mm.

 

[oologah]

They said the rod was shorter and the piston longer on the Grubee, or the other way around. It plain don't fit.
These engines are NOT all the same. I know that and am not going to order the wrong part and be out the money.
Hey, all these cars built in the US must all be the same, Just jokin.
E-mail the different venders and ask them about it.

A good note, if you ever lose a G clip when putting a piston on, don't assume it isn't in the engine. Mine was, put it all together and it ran for 15 sec. or so before the clip found its way between the piston and the cylinder wall.

 

[Rconce01]

They said the rod was shorter and the piston longer on the Grubee, or the other way around. It plain don't fit.
These engines are NOT all the same. I know that and am not going to order the wrong part and be out the money.
Hey, all these cars built in the US must all be the same, Just jokin.
E-mail the different venders and ask them about it.

A good note, if you ever lose a G clip when putting a piston on, don't assume it isn't in the engine. Mine was, put it all together and it ran for 15 sec. or so before the clip found its way between the piston and the cylinder wall.

Whow sorry to her you had that engine failure!

Haha yeah dude all us cars are the same, I own like 5 built gy General Motors other wise known as govt. motors, all parts are interchangeable.

Right now I am going to take a shot at the piston justin over at pirate cycles sells. worse case i loose 15 bucks.

Has anyone actually provided proof as far as two different types of stroke length for engines with the same 47mm bore??

I pulled both of my engines apart that were bought on ebay about 3 yrs apart from different sellers and dimensioned off the pistons and the stroke and its exactly the same.

by the way whenever I loose something on the engine i assume worse case scenario and i pull it aprt and make sure its not inside. That ws just a little 100 dollar engine you ruined, i've seen people ruin v8's, jet ski engines, even some lawmowers back in auto tech class in high school.

Its better to be safe than sorry. I hope that was a lesson learned for you and hopefully you will keep that from happening to others.

As for me I'm going to start playing with my pistons ad report back to you guys. Thanks for all the good feedback.

 

[GearNut]

I have no link to the thread, but yes, someone posted pictures of 2 cranks side by side showing the different rod lengths, and 2 pistons side by side showing the different heights and wrist pin placements.
It may have been on this site or the "other site".

 

[strlnperf]

My father does engine mods on Whizzers . Goes by the name Whizzer performance. He offers carb kit upgrades and exhaust kit upgrades. Give him a shout if you have any questions. His name is Jay telephone number is 1(562)404-7114. He has a Whizzer now that will do 60+ based on the the stock Whizzer flathead design.

Eric