i am lost

[84200s/m]

how do i tell if my bike been bored out already

[250sx]

measure the cylinder and go to wiseco.com to look up the specs for your bike

[Fuzzy]

If you have it apart allready. There should be some markings on the piston. Stock honda and weisco both have the size on the top of the piston usally. I have seen some 200s pistons that diddnt say the size on them. If that is the case then you will have to measure it. Or take it to a shop and have them measure it for you. If you dont have a micrometer.

[84200s/m]

mine has numbers on each side of the piston right by where the pin goes through

[Fuzzy]

I know the ones you are talking about. But i think thoes are just casting numbers.


If you have a tape measure handy. Try to measure the piston. Stock was 2 1/2 inches. Any over that then you know for sure it was over sized and probable have to have it measured to be acurate.

[84200s/m]

ok thanks fuzzy i checked it is 2 1/2 in
the numbers are 958z than 3(eor f)than on the other side hon da
and on the top of the piston there is in and 2 little indents by it

[Fuzzy]

I have one in my hand with the same numbers on it. It is the stock one out of my 82 200. That is a stock 65mm piston then. So the cylinder has never been bored.

[84200s/m]

ok thanks for the help next ? how big should i bore it i would like some more power

[Fuzzy]

If the cylinder is in good shape i wouldnt bore it at all. I would replace that stock piston with a 200x piston and rings. That will increase your compression from 7:9-1 to 10:0-1. You will notice the difference.

[dads]

If you have to bore, start small. unless you do not care if you have to buy a new cylinder next time. That way you can get several bores out of a stock cylinder. and do like Fuzzy said , go to a highter compression piston each time you bore.

[84200s/m]

i have 2 cylinders and i only need it to last for the winter how big should i go i was thinking 0.50 or something like that with a high comp piston

[Fuzzy]

If it is for proformance that you are boring it then dont. The few cc`s you gain by boring it wont even be noticable. Your money would be better spent on a 200x head and cam and going with the 200x piston they it would be to shave the cylinder. Like i said before if the cylinder isnt all scratched up and gouged i wouldnt bore it. I would just hone it out and get new rings.

You cant run too high of compression on a 200s because you wont be able to pull it over with the pull rope. And with a 200x piston and cam it will really bring that 200 to life.

[84200s/m]

i have to bore it and i need a piston so i want to get the most power can i dont have enuff money to buy a new head and
u saying i cant pull start it if i get a high comp piston is that because the pull rope will break or is it just had to pull
also wouldn't my decompression cure that

[84200s/m]

what should i do:confused:

[Fuzzy]

It is not so much that you wont be able to pull it over but that it will rip your arm out of the socket if it kicks back. So i wouldnt run more then a 10:0-1 piston in it. And as far as how big to go. The price for the piston and rings are the same no matter what size you go with. So the big thing is boring. The more they have to take off the more it costs. So contact your local machine shop and get prices for boring. But no matter how much you take off it wont be enough to be noticable. On a 350 chevy v-8 bored to .030 over works out to be a 355. So on a single cylinder machine that is 198 cc or so. It works out to be a 200 cc even it you go like .050 over. So instead of spending $50.00 on the boring i would buy a 200x head and cam off of ebay you would notice a much better increas of power over a 2 cc bore job.

[84200s/m]

yes i know but what i am sayin i want a bore not a head i only plan on getting it going to last me till i can buy a better one
what bore size will be best for me i want it to work good and last
as for pull starting it that dont bother me
also for the boreing its $45 to be done no matter how much
and the reason i want to bore it out alot it to make sure that it will be perfact so i have no compression loss or burning oil

[dads]

And the other thing Fuzzy should have said is the pull starts don't hold up to stock eng's so they will go to h ell quicker if you rase the compression.

Check for new pistons for it , see if they max out at 80 over.

[Fuzzy]

Good point dads.

So basicly what you are asking is. How big do you have to go to make sure it is perfectly round. I would think if there are no gouges in the cylinder then .010 over would be enough. But if it is gouged up pretty good. Then .030 would take care of it.

Any more then that you start running into heating problem and piston melt down. But if you want to go wild and get as much as you can for the money. Then go with the .080 over And you can be darn sure it will be round.

[84200s/m]

how would 0.050 over do would i have heating problems

[Fuzzy]

When the engines are designed they are made to run the way they were built. Meaning the more stock it is the more reliable it is. And boring was a option to fix cylinders that got messed up and couldnt be just honed.

But beings how they are air cooled engines there cylinder walls wernt that thick to begine with. So that they could tranfer heat easy. And the thinner you make the cylinder wall the more chances you have of overheating and melting down the piston. Because there isnt enough metal to tranfer the heat out of the motor. And also the more sensitive the engine becomes when splashing cold water on it like going through a puddle.

I am sure many people have have ran them at .050 over. But i am not going to be the one to tell you to do it. Becuase i dont want to be responable if it melts down. So any more then .010 over you start messing with its cooling. And oil suply becomes cruital. So i am sure you could run it at .050 over.But do it at your own risk. If the piston melts down and sticks to the cylinder wall it could snap the connecting rod and then you are looking at a total tear down and overhaul.

So i real good rule of thumb is to never bore then more then you need to.

[84200s/m]

ok thanks your good help

[84200s/m]

opps

[84200s/m]

1981-86 ATC200S. Part number 4156P2, .50 over, 66mm is that an good piston for my bike

[Fuzzy]

Yep that is a 10.25:1 piston set. But it would acutally be a 65.5mm not 66mm. Stock bore is 65mm. So .050 over makes it 65.5mm.

It would be a big improvment over the stock one.

[84200s/m]

the part number says its an 66mm piston

[Fuzzy]

the 4156P2 is a 1.00 overboar 66mm.
the 4156ps is a .050 overboar 65.5mm.

So you have the right part# for a 66mm but it would be 1.00 over instead on.050.