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AM6 Needle Bearing Specs / Availability

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doubl3clutch
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AM6 Needle Bearing Specs / Availability

Post by doubl3clutch » Mon Aug 05, 2019 4:47 pm

Hi All,

I have a 99 GPR75, 2000 RS50, and a 2003 SM50. Am I correct in assuming these all have the exact AM6 Engine, other than the GPR75 top end? I'm ordering new top end kits and keep seeing different size needle bearings listed. Would the cranks be different by chance?

Can someone confirm the correct size Needle Bearing Size? Will Venmo ya a beer!

Thank you,
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toratora
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Engines and Bearings

Post by toratora » Mon Aug 05, 2019 6:39 pm

The Derbi bikes do not employ the Minarelli engines. Derbi makes its own two stroke engines for these bikes. One notable exception was the 2006 GPR125 2T which employed the Yamaha DT engine. The Derbi 125 four stroke engines appear to have been designed by the Derbi engineers, and built in China by Piaggio Zongshen motorcycles.

If you look on the Derbi engine just above the serial number you’ll find a part number. On the 075 engine it will be EBE075. This is similar to the Derbi EBE050, EBS050, and SendaH engines. As a class these are generally referred to as Euro2. However the 075 is quite a bit different in some ways—most notably the cases. It also employs a 43mm stroke crank, rather than the 40mm stroke found on the 50cc variants.

In the Red Power thread you’ll find a fair amount of information on the EBE075 engine. I have a few bikes with that engine, and that thread is basically where I post my exploits. Eventually when I am more confident with my findings I’ll make a proper post on the EBE075 in the Tutorial Resources section.

As to needle bearings. These are greatly dependent upon the crank. With the AM6 it is general consensus that if you are installing a BBK (Big Bore Kit) you should upgrade the crank to a performance item. On the Derbi engine this depends more on which BBK (or even performance 50cc kit) you are installing. The stock Derbi crank is more robust than the stock AM6 crank. This is one of the reasons the Derbi engine is generally considered a better design.

Many of the stock 50cc engines run a 12x15x15 little end bearing including the AM6, and EBE050. The EBE075 however employs a larger bearing—12x16x16. Most performance cranks employ lager bearings too, but they are dependent on which crank so it would be difficult for me to say without knowing the crank. :paw_prints:
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