Misleading 250R Big Bore Info

[Mr. Sandman]

The following is a revelation to me and may be to some of you as well or it may be common knowledge but either way, I thought I'd share.

I recently rebuilt the top and bottom ends of my 85 250R that has been set up with an ESR/Pro-x 310cc big bore kit for the last few years. I sent the cylinder off to ESR for boring and a new piston. When I got it back, I noticed the piston size as being 72.5 mm. Since there's no replacement for displacement, I was curious about how many cc's I gained by going to the next size overbore so I rung up my trusty displacement calculator, entered the figures and came up with 297 cc's. 297 cc's? I must have made a mistake! I ran the figures again, same answer. Hmmm....interesting. I ran the figures using the previous 72mm bore and came up with 295 cc's. This just doesn't make sense. Maybe they sold me a mislabled 295cc cylinder by mistake and not the 310 I ordered. So.. I called ESR and come to find out the stock bore of their 310 kit is 72mm's and that you don't get to 310cc's until you reach the 5th and final bore of 74mm's.

I know a motor is not always the exact displacement as what it's labled as (a 250R is acutally 246cc's) but that's false advertising on ESR's part if you ask me, however, if I keep my R another 20 years I might reach 310cc's eventually.

[atcsteve]

Thats true,but Ive changed the bore from the first to the last,and no real power gains,so,I bore as needed now!!

[max]

I always thought I had the 295 kit. I just did the last bore on mine, my piston is 73.5mm. La Sleeve tells me thats as big as they go, which is where I got my piston from. So from what your telling I have a 310. We'll thats sweet. Ive heard this info from someone else too. That suck that you were totally mislead. Sounds like you just have the 295 sleeve like me. Wonder if La Sleeve is where ESR got their kits from?

[deathman53]

310's are 295, most 330's are 320 or so, a 80 over is really a 262 not 265. most of you bikes aren't accurite either, 83-85 200x is 190cc, 300ex is 282, 250ex is 229

[gotballs 250r 82]

I know you could always buy a bigger esr. But you would need a fat stack of cash. Well you learn somthing new every day here @ 3 wheelworld.

[jason 32]

not cool!!
take the bore x the bore x the stroke x .7854,and you will have your cc's
it should be a true 310,from them!!!!!!,thats a **** deal,and over priced too
its like every one wants a fotune for there stuff,and they expect people to afford it
and im not talking just about esr

[deathman53]

you can bore it out a 310, but its at the last bore.

[Mr. Sandman]

not cool!!
take the bore x the bore x the stroke x .7854,and you will have your cc's

I use this link for cc calcs. http://www.straightliners.co.uk/calcs/eng-disp-calc.htm

[3WW Star-Yamahondaman]

the "295's" are the "310's" ....... 72 mm piston

[88 Turbo Coupe]

So if you want a 310 you have to buy a 330 kit on the first bore??

[hrc85250r]

god you guys are ridiculous. a 310 kit is a 295 until the last bore which is a 310. 330's are about 320cc's on the first bore and 330 on the last. on and on and on for all of the cylinder kits, and if you havent noticed, ESR has the cheapest pro-x cylinder kits around.

[Red Rider]

god you guys are ridiculous. a 310 kit is a 295 until the last bore which is a 310. 330's are about 320cc's on the first bore and 330 on the last. on and on and on for all of the cylinder kits, and if you havent noticed, ESR has the cheapest pro-x cylinder kits around.

Hey Einstein, they're not talking about the price here. The point being made here is that you're not getting the product (displacement) that you thought you were. It doesn't matter if it's the cheapest cylinder around. If I buy a 310, I want a 310, or at least a 306. You don't round 295cc's up to 310cc's. If they want to round up, it should be sold as a 300, not a 310.

[jason 32]

they should specify it as the last bore!!!
untill that- it isnt a 310=thats the point!!,we are not rediculas

[88 Turbo Coupe]

I guess in this case ESR is not too HONEST. Hmmm

[250r'en +TCB]

I guess in this case ESR is not too HONEST. Hmmm

It's not just ESR, all the companies who make big bores do this.......