74mm big bore kit

[Thumper]

Originally Posted by XLsior

the 200cc* cg bikes will have the 163-FM


250cc* should have the 167-FM

The 167FM engines are actually 229cc. This is the common "CG250" clone in the Storm, Hawk... There is some variability in bore and stroke on these clones, but here is a good, and accurate displacement calculator to see what real displacement should be:
https://spicerparts.com/calculators/...ent-calculator

Select metric, then enter these bore and stroke numbers from various listings for engines. I copied the info from 2 engines from AJ1, and 2 listings from ebay. I was surprised to find that they were all accurate claims when I entered the bore and stroke numbers on the listings.

But I noticed something interesting. The Zongshen ZS174MN watercooled engine at AJ1... 74mm bore is like the OTOM kit I got, and if you use my stroke (61.4mm for the ZS172FM) you get 265cc, but if you use the stroke from the ZS174MN (65mm), you get 280cc. I think the OTOM kit assumes a 65mm stroke!

Here they are:
AJ1 Zongshen CB250F, ZS172FMM-3, 20hp
bore x stroke
72mm x 61.4mm
249.9cc
Spicer 249.99

AJ1 Zongshen CBS300, ZS174MN watercooled, 25hp
bore x stroke
74mm x 65mm
279.5cc
Spicer 279.56

Ebay lifan (Cleveland Cycleworks) 14hp
167FMM
67mm x 65mm
229cc
Spicer 229.17

Ebay lifan 163FML
bore x stroke
63.5mm x 62.2mm
197cc
Spicer 196.98