GY6 50cc 139QMB specs. 50cc vs 80cc By dmartin95 (Read 3,358 times)

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GY6 50cc 139QMB specs. 50cc vs 80cc by: dmartin95 - Jan 24, 2015 13:34:13 GMT -5

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Post by dmartin95 on Jan 24, 2015 13:34:13 GMT -5

Ok, the stock bore and stroke of these two motors are as follows:

GY6 50cc Original Size: 39mm*41.4mm (49.4cc)

GY6 80cc Original Size: 47mm*41.4mm (71.8cc)

Now, almost all GY6 50cc parts are listed for the 139QMB. The 39 in that number is for the piston displacement size.

I'm also finding parts for the GY6 80cc, however I can not find a base engine stamp. Based on the size of the components, it should be a 147QMD, but I can not find an engine with this stamp.

When it comes to the bigger 150cc, there are some that have 54mm stud spacing and other with 57mm... Hence, the a and b case engines... I'm wondering if the 50cc's have a similar difference...

When it comes to the 50cc range, does anyone know any other stamps besides 139QMB?

Bintelli - Havoc - 150cc x 2
Yamaha 2015 S MAX (XC155)
TaoTao ATM-50
BMS Heritage - Taida 191cc
DF moto / Sunny (hunter/phantom style) 155cc (4 valve)
Taotao Quantum Tour - 232cc, 4 valve water cooled Taida

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GY6 50cc 139QMB specs. 50cc vs 80cc by: JerryScript - Jan 24, 2015 15:45:11 GMT -5

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Post by JerryScript on Jan 24, 2015 15:45:11 GMT -5

I have the BN139QMB, it has standard stud spacing, but has the taller head with valves that are 3mm taller requiring a different set of rocker arms (found out last month when I did a head swap on the side of the road).

There is a 16" wheeled 50cc, though I haven't found a source for new ones in the US, I think they were last sold in the US pre-2010, and I have no idea what the engine stamp says. There is a forum member here that owns The Tomos Twister, which is one 16" 50cc model, and most likely has a different engine, I don't think the standard long case can handle 16" wheels. I can't think of the member's name, but I will keep a look out for his avatar which is a pic of his Tomos Twister, and I'll PM to ask about the engine stamp.

Icebear PMZ50-4J