TRX250R.ORG

Workshop => Engine and Bottom End => Topic started by: liv2ride on July 27, 2013, 03:35:37 PM

Title: Engine Displacement Math
Post by: liv2ride on July 27, 2013, 03:35:37 PM

What is the formula for figuring engine displacement?
78MM Bore X 76MM Stroke

Title: Engine Displacement Math
Post by: yaegerb on July 27, 2013, 03:41:04 PM

Quote from: liv2ride;6040

What is the formula for figuring engine displacement?
78MM Bore X 76MM Stroke

bore x bore x stroke x .7854

so if you convert it to CC's your equation is 7.8 x 7.8 x 7.6 x .7854 = 363.15 or 363 for rounding purposes.

Title: Engine Displacement Math
Post by: Pumashine on July 27, 2013, 04:49:49 PM

What is stock stroke for the 250r? I was wondering how you got the 76mm stroke?

Title: Engine Displacement Math
Post by: yaegerb on July 27, 2013, 05:07:19 PM

I know the stock stroke on the 85 and 86 engines but not the 87-89

85 and 86:  72MM

if it was one of the above model engine, he must have added a +4 rod.

Title: Engine Displacement Math
Post by: liv2ride on July 27, 2013, 05:25:22 PM

Correct. '86-'89 are all 66X72

For this (350PV) build I added a +4mm crank.

Hindsight shows me my $ would have been better spent on good quality port work. My 330 non-PV outperforms the 350PV in every aspect of performance.


IMO the extra stroke takes away the engines ability to get into the real high RPM's. That's what I love about the R's

Title: Engine Displacement Math
Post by: Polonda on July 27, 2013, 06:13:36 PM

http://www.csgnetwork.com/cubicinchcalc.html

make sure to select mm and 1 cylinder obviously.  Enter bore and stroke.  Leave the rest blank.