What are the pros and cons of bored out engines?

Question

1990 polaris trail boss 250 that was bored out

What should i watch for when buying a second-hand bored out bike?

Details.

Will it fit in the back of a 1991 GMC Jimmy?

Answer 1

a bored out bike doesn't increase it's size in anyway... it only increases the sizes INSIDE the engine... it would literally be impossible to put two fo the same bikes next to each other, one bored, one not and figure out which one it is....

when you bore it out, you thin the walls, which means more heat, more quickly, your engine will also wear out slightly faster.... it'll use more gas too

the pros are pretty obvious, more power/speed.... (there's not a whole lot of upsides to boring, it's basicly done just to increase power)

Answer 2

The advantages are larger displacement and a fresh, true cylinder for the piston and rings to run up and down in. The disadvantage is a thinner cylinder wall resulting in a very slightly higher operating temperature.It's probably only bored 10-20 thousands of an inch over, which is nothing. Most cylinders can be bored oversize once(some even more) quite easily. If your talking Jimmy, as in Blazer, you'll obviously have to remove the back seat. You may also have some height clearance issues with the top on, and I doubt the tailgate will close. If you mean the smaller size Jimmy/Blazer(S-10 based), then no, it won't fit.

Answer 3

More CCs= more power. More CCs = thinner cylinder walls which= more heat.

Answer 4

Depending on the bore of the cylinder. You'd have to take the cylinder head off and look at the cylinder itself, there is a darker ring, the sleeve, that can be seen from the outside, depending on how much of that is left is how much bore you have available (you could measure with tools however). If the sleeve is worn out(not much sleeve left/seen from outside/inside), then if you "blow it up", you will have to get a new cylinder, which will run you about 150-200 aftermarket. The pros? Having a faster motor!

It all depends on how the bore job was done, was it ported and polished, etc...Polaris engines do not cost that much to replace, but it just depends.

The only thing about it fitting in the Jimmy would actually be the height, Polaris' are very tall quads!

Good luck with your shopping.

Answer 5

most will fit in full size beds, or at least the 6 footers, bored out should give more power as volumn in cyclinder is increased, like taking your 250cc and making it a 280cc. if done right you dont need to worry about anything.

Answer 6

Pros: more displacement gives the potential for slightly more power and more displacement with the same size combustion chamber means a slightly higher compression ratio.  After boring, a nice, new cylinder with new piston and new rings can make for a good running engine that doesn't use oil with new from the factory power output.

Cons, higher compression ratio could cause detonation problems and require higher octane fuel.  The tiny bit of extra hp could cause extra heat to be produced, but if it's just an overbore, it will be so slight that you'll never notice.  

A good overbore is better than a worn out standard engine any time.