For a 250cc 2 stroke engine that only has boyesen reed and exhaust (no porting) what would be a better carb to get a 36mm or a 38mm. Currently my trike has the stock 32mm Mikuni. What do you guys think?

 

If you haven't done anything else to your engine, the stocker is just fine. If you go larger it may help with top-end power at the expense of bottom-end. The smaller carb will help with bottom-end. Another option is a taper bore, this will give you advantages of both. For a stock engine, the 38mm will be too much. I still run the stock 34mm on my 250R due to the fact that the motor isn't ported or bored out. I've even seen 34mm on 300cc 2 strokes and they're just fine.

 

I just dropped a 38 into my R with no visible loss in botton end from a stock 34. The bike does have some port work though.

 

I have a Sudco racing Keihn 38MM on my R.. It works really well, but I have mid-porting. I agree with trapper, unless you have motor work done, dont get a different carb.

Is something wrong w/your Tri-Z? Is that why you're asking?

 

There is nothing wrong with my Z. I am just trying to decide what will be my next mod. I think I have too tall gearing and I thought that if I get a bigger carb and an exhaust I will be able to pull stronger with my current gearing istead of removing a teeth or two at the rear sprocket. I think my stock is too small, it is a 32mm Mikuni (not a 34) like most 250s. I also notice last week that if I do not close the fuel gauge I can see some fuel going out of one of hte car hoses but maybe it has been like that I and just notice it now. I am leaning toward a 36mm but I am not sure yet.

 

I have a Duncan Racing/Keihin 36mm on my R. I love it. It actually improved bottom. I am running FMF Torque reeds and a fatty pipe (stock bore, no porting). I would reccomend the Duncan/Keihin 36mm.