I have done the searches, and have read almost all of the posts concerning 250R Engines on this site. Now I still can't make up my mind. I have an '86 250R (short rod with a good bottom end) I would like to get a new cylinder when it is time to rebuild my top end. I would also like more power, something in the range of the new Yamaha 450's (200 yard drag). These are my choices:

Re-port my 86 cylinder

Get a 88-89 cylinder and have it ported with a cool head, 38 mm carb, and a ESR TRX 5 pipe.

Or get an ESR 310 bolt on kit, TRX 5 porting, 38mm carb, and a ESR TRX 5 pipe.

What, from real world experiences would be the best. I like the idea of a sleeper (stock 250R Cylinder), but I like the ideas of out running some faster bikes too. Any suggestions?

 

Here, by mine:
ESR310 motor

 

what is the reserve?

310 is capable of more power generally

 

If you got the money and want a sleeper take the cylinder and get it re- sleeved wth a 295 sleeve. then get it re ported. After that you can get the bolt on products. (carb, reeds, pipe, ect). BUT a bolt on 310 kit (just a aftermarket cylinder with a 295 sleeve) has better cooling, and are capable of a little more porting, and also usually have no problems with.

 

Reserve is mid teens.

 

thats fair.

 

Correct me if i'm wrong, But i don't think you can do the 310 kit with the short rod (86). You have to have the 87-89 rod. So if Nicname wants to go that big, He will have to split the cases. Personally I don't think you gain that much from the 310 over the 265. I would probably just go that way. But when you go 330, It's a whole different story.

 

310 pro-x barrel has bigger water jackets, and bigger transfer area. All this creates a better motor for both cooling and hp.

 

im thinking of going to a 330 but i really want a 350. i have a ct 310 and want more speed (sand) i know esr have sick motors but im keeping this bike ct. im looking into an 88 or 89 250r quad and go esr with that one. my question, should i keep with ct racing or go esr with my trike?

 

250R4LIFE, the ESR 310 bolts on to a short rod fine, I have one. Their 330 kit bolts on without case mods to a longrod throught the use of a spacer. You can also run a 330 and 350 on a short rod but it would requires case mods.