I plan on getting the FST 265cc big bore kit for my 1985 LT230S. I was wondering how the transmission will hold up to the extra power. Also, I already have a DG Excellerator exhaust, K&N filter w/ no air box lid, and a jet kit, what aftermarket cam shaft would work best with this engine setup (including the big bore). One more thing... I am running a 12 tooth front sprocket with a 41 tooth rear sprocket and I am always riding in 4th or 5th gear, what sprocket setup will give me more top end through the gears?

 

How much is the big bore kit?

 

The kit itself is $250. To get it installed would be around $300-$400.

 

hey hey.. let us know how it works out if ya will. I saw that kit listed before and thought about it but then i thought isnt it overkill for a sport util that old.. also Web Cam's are pretty nice for those, i have a mid ranged cam from them and mine runs pretty smooth in 3rd and 4th. I ride pretty hard through the woods and it never seems to run out of power..

 

Have you had any progress with your mod?

 

I have a 230s bored to a 250 and it has plenty of power. So I would go for the 265 if I could. My machine just lifted to do a wheelie the other day in 3rd gear. The only problem is that other parts start to fall off, depending how old it is. Oh and I also have a super loud DG Megaphone on mine.

 

what exactly did you do to get it to a 250? please dont say you got it bored twenty over, .020

v581

 

All I know is that someone rebuilt my motor and bored it out with an oversized piston in it which I believed made it a 250. Its definitely not stock and it goes faster than what it did. The piston I believe is a .020 Wisesco Piston made for the Lt230s. If there is a 265 kit, which I have heard of, I should be able to have a 250. The motor I now have may not be available as a kit but motorcycle shops will rebore your machine with an oversized piston.

 

I could sit here LMAO and post a comment of that nature but i think its about time you kids learned the math if your going to be digging in the motors.

Lets start with the concept of general over bore pistons. When you said .020 wiseco piston what you really mean is .020 inches over the standard bore! not 20cc's of displacment. With that said lets consider what the bore of your lt230 is stock. A quick look on the net and we have 66mm (millimetters).

Ok now we have our first problem. your bore is now 66mm + .020 inches. this is the reason you should get way from using inches when describing getting your cylinder bored. When you look at wiseco's catalogue you will not see a piston listed as .020 inches over, you will however see on the is .5 mm over bore. So... .020 inches = .5 mm.

Now here comes the hard part. in order to find out how many cc's your engine will be come from a bore increase we need to know the stroke which in your case is 67 mm.


The formula fo figuring out your displacement is really simple and only requires multiplication and division (or knowledge on how to work a calculator).


Just get the numbers you need which is bore and stroke

Your bore is 66.5mm
your stroke is 67mm

just so we are on the same page:

* means multiply

/ means divide

Do things in parens first!
Here's the formula

(0.7853982 * bore * bore * stroke) / 1000 = displacement (number of cc's)


So now lets see what your .020 bored lt230 is

(0.7853982 * 66.5 *66.5 *67) / 1000 = 232.71 cc's

Congrats you now have a 233! Not very close to that 250 you thought you had.

Want some homework? What bore size do you need to be at to make it a 250?

 

.020 over piston is definitely not going to make your quad a 250. closer to a 235 if anything.