167FMM mods

[Mudflap]

It's good to have oil temps over 212° f so any moisture boils off.

[Thumper]

Everywhere I have looked, I hear 65mm stroke for this engine. So if the cylinder is 67mm:

Use the Spicer engine displacement calculator or equivalent to determine true displacement:

https://spicerparts.com/calculators/...ent-calculator
67mm bore x 65mm stroke = 229.17

[Megadan]

Originally Posted by Thumper

Everywhere I have looked, I hear 65mm stroke for this engine. So if the cylinder is 67mm:

Use the Spicer engine displacement calculator or equivalent to determine true displacement:

https://spicerparts.com/calculators/...ent-calculator
67mm bore x 65mm stroke = 229.17

Yes. That is known to most of us. A 70mm bore makes it as close to a true 250 as you get. It's just like the 200cc GY6 scooter engines are 168cc. Just marketing bullhooey

[crackerjac]

Originally Posted by Megadan

Yes. That is known to most of us. A 70mm bore makes it as close to a true 250 as you get. It's just like the 200cc GY6 scooter engines are 168cc. Just marketing bullhooey

Reviving an old post.


Has anyone installed one of these 70mm kits?


What about the 72.5mm (268cc advertised as 350cc) they appear to require some clearancing of the case, obviously, as the jug is 76mm wide!

[Lakamla]

Salut a tous, moi je suis sur un petit trail de la marque zongshen en 200cc ... équivalent a la cyclone RX1 ... j'aimerais bien augmenter la puissance mais bon ...c'est pas évident manque de pièces de rechange.... J'ai installé un refroidisseur d'huile, ...vires le carbu a dépression d'origine et j'ai installé un PWK 30 avec un filtres a Air corné.... C'est galaire a réglé c'est carbu

[XLsior]

70mm kits are about as large as you can go into a 167fmm case. Any larger and you would have to open the case hole, At which point the return on investment evaporates unless you have the tooling/equipment to do it yourself.


However I'm not even sure it can be done without impacting headstuds and oil galleys.


So IMO anything over a 70mm bigbore kit would be better spent on an entirely new better in class engine.

[slithica]

Originally Posted by crackerjac

Reviving an old post.


Has anyone installed one of these 70mm kits?


What about the 72.5mm (268cc advertised as 350cc) they appear to require some clearancing of the case, obviously, as the jug is 76mm wide!

I installed a 70mm kit, so far it's working well. Hilariously enough it says 300cc on the jug and it's marketed as such by most places but it's actually 249cc now... so it's just an actual 250cc now. On the bright side it makes slightly over 20hp now.


I installed new roller rocker arms and a fatter cam lobe at the same time.



The 72.5 is not worth it, nor will it happen reasonably.


You would need to pull the engine and have it machined out to fit the larger jug. You would be better off just buying a better/larger engine.