whats up guys!!......I have a 1986 250 quadracer and am gonna be doing a complete rebuild on it and was thinking about port and polish.....is it worth it..how much noticiable is the differences?????do i need to run racing fuel when i port and polish??...should i just polish??how much does this procedure cost??..i am going with weisco piston rings ,uni filter, boysen power reeds and rejet.....let me know thanks!!!!!!!!!!

 

doesnt anybody know??

 

Just cleaning up your ports, and polishing your exhaust port, would help more then you think. And by doing that doesnt mean you have to run race gas.

 

It cost between 200-400 dollars to have a good shop do it, just depends on the shop. I've never had a cylinder ported, but to answer your question it will make a big difference. However it is usually the last thing that people have done, so unless you have a pipe and larger carb you won't notice much.

Generally you do need to run race fuel after a full on port and polish, or at a minimum a blend.

 

I am no expert, but I have read not to over polish the intake. You want it slightly rough to better atomize the fuel.

 

i run an fairly modded 88 lt 500. it has been ported and polised by two different shops T&N did the first for $220 and DAB did the second for $200. and to be honest with you i could not tell a diference between the stock porting or either one of the after market jobs. and to answer your question about running race fuel after porting the answer is no because porting does not change your compresion at all what it changes is the size of your ports (bigger) and your timeing which is when the fuel and air mix enters the cilinder and the exhaust exits. the way the timing is changed is by raising or lowering the intake and exhaust ports so that the fuel and air mix enters and exits earlyer or later respectively. what polishing does is is smoothes up the exhaust port in order to get rid of the trubulence created buy the rough surface of the stock cast port. the intake is smoothed a little but not to much this is because it does help the atomization of the fuel a little but is more to keep the atomized fuel from condensing on the smooth surface of the polished intake port. and in therory this will make a big difference but in my personal experience i didn't notice anything but then again a lot of people do notice the difference. i hope this helps

 

He makes a good point, go with a shop that knows what they are doing. I.e, Duncan, CT, FTZ, or foward motion.

But you are wrong in that saying porting doesn't increase/change your compression on a two stroke. On a four-stroke it has no bearing on compression. But because it does change the timing events the compression is changed, simply because the distance from the top of the exhaust port to the top of the jug is different. More complexly because more fuel/air enters the cylinder when it's running both from the intake and what is forced back throught the exhaust port.
Also when a cylinder is ported properly the chamber of the head is matched to the port work, and this usually involves a reduction in chamber size which increases compression.

And the intake is not poshished it is usually given a cartridge roll finish. The exhaust port and combustion chamber are polished.

 

You should have noticed a HUGE difference b/w stock and a ported jug... The LTs are EXTREMELY detuned. Granted the smaller reed (88+) motors won't make quite as much HP as the 87, but I'd venture to say "Something is wrong"
Where you at in Wester Utah?

 

 

i'm actualy in northern utah near ogden the name of the town is farr west and your right i would have thought that porting on a 500 would have helped thats why i had two different shops do it but i could not tell a difference what so ever. the mod that i could fell the most change with was raising the compresion and that made a big difference and useing a paul turner pipe helped a lot to