250cc gearing recommendations

[crackerjac]

I'm building a project dirt bike and would like some recommendations on gearing.

Bike will have an all aluminum twin spur design frame and an air cooled Zongshen 250cc ZS169FMM engine. I currently have a set of 19"/16" rim and tires to use, I'm only 5'7" 160lbs so the bike can't be too high, lol. The bike will be obviously lighter than a steel frame China 250cc.

What would you recommend for a front and rear sprocket ratio combo? It will be mostly a trail bike, some sandy trails, and open field areas so a bit of everything. I live on the prairies so not many hills to climb but I'd also not want it to bog to much if the opportunity presented itself. Just looking for an all around good ratio for this motor's power band.

I think it has a 15T front and 37T 428 rear which seems a bit high geared to me. Thoughts?

[timcosby]

Originally Posted by crackerjac

I'm building a project dirt bike and would like some recommendations on gearing.

Bike will have an all aluminum twin spur design frame and an air cooled Zongshen 250cc ZS169FMM engine. I currently have a set of 19"/16" rim and tires to use, I'm only 5'7" 160lbs so the bike can't be too high, lol. The bike will be obviously lighter than a steel frame China 250cc.

What would you recommend for a front and rear sprocket ratio combo? It will be mostly a trail bike, some sandy trails, and open field areas so a bit of everything. I live on the prairies so not many hills to climb but I'd also not want it to bog to much if the opportunity presented itself. Just looking for an all around good ratio for this motor's power band.

I think it has a 15T front and 37T 428 rear which seems a bit high geared to me. Thoughts?

in the classified section a guy has a oem 50 tooth that should be just right for trail riding if it will fit your wheel

[crackerjac]

Originally Posted by timcosby

in the classified section a guy has a oem 50 tooth that should be just right for trail riding if it will fit your wheel

It appears he is only selling everything as a package. :(


Thoughts on a 15T/56T or 13T/37T for this particular motor for offroad mostly flat trail riding in the bush but some sandy areas as well?

Anyone know why these come from the factory as dirt bikes with such high gear ratios? They come with 15T/37T for a 250cc dirt bike. Most other manufacturers of this cc are more like 13T/50T

[ChondaChondaChonda]

I have the same motor (Zongshen 169FMM) and ended up running 14/45. It is a little higher than I like in first gear on steep stuff, but just right on the top end.

Gearing seems much lower and narrower than a Honda 230.

My stuff ended up piled over in introductions:
http://www.chinariders.net/showthread.php?t=17694

[crackerjac]

Originally Posted by ChondaChondaChonda

I have the same motor (Zongshen 169FMM) and ended up running 14/45. It is a little higher than I like in first gear on steep stuff, but just right on the top end.

Gearing seems much lower and narrower than a Honda 230.

My stuff ended up piled over in introductions:
http://www.chinariders.net/showthread.php?t=17694

Cool, I'm not the only outcast installing a Zong in a brand name bike. I'm going to upset a lot of Honda owners but I have a 05 CRF450X frame just sitting there and the Zong ZS169FMM motor and I like to tinker so it should be interesting. Really light weight aluminum frame and the gear sets in these are a lot lower than the CR230s. It should be interesting. Down side is it's going to be trial and error on the ideal sprocket ratios as there is nothing to reference it to. It's a budget bike but I guess I'll order a couple different sprockets close to what I think it should be and go from there. Do you think a 14/48 or 13/45 would be better for trail riding but still have enough top end? I'll read through your intro link when I get a moment.

Anyone know a guy on the Thumpertalk forum named "CharlieT"? It looks like he did a similar Honda 200cc into a similar frame but it was 8~12 years ago. That motor shares the same case design as the Zong 250 as far as I can tell.