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PLAYTIME'S OVER BITCHES!!
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Discussion Starter · #1 ·
what is your thought on what should come first?
i see people send their jugs off to have them ported and then get them bored.
i always send out the jug to get bored first, and then have it ported. having it ported afterwards insures that ( in the right hands of course) your ports will be chamfered properly and wont snag a piston ring...agreed?
ir you have your cylinder ported first, there is a certain angle the porting leaves behind. this is done for a reason by the port man. if you bore it afterwards, then it takes a small part of that angle away and in my oppinion, is no longer at the specs the port man left behind. thus changing things slightly.

thoughts anyone?
 

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I like to port my cylinders first to ensure there are no burs in the cylinder, especially if its a sleeved cylinder.

I think its more personal preference than any thing
 

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i think port first, so when it does go you have those extra bores :D. you do have a point though scott, never thought of it that way
 

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port and then bore is how I would do it... what if the guy sneezes when he is porting and puts a mark on the inside of your fresh bored honed cylinder? I dont think you are changing the angle and most guys that bore and hone chamfer the ports as part of there service. at least the shop that I use does....
 

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PLAYTIME'S OVER BITCHES!!
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Discussion Starter · #5 · (Edited)
port and then bore is how I would do it... what if the guy sneezes when he is porting and puts a mark on the inside of your fresh bored honed cylinder? I dont think you are changing the angle and most guys that bore and hone chamfer the ports as part of there service. at least the shop that I use does....
i must be backwards then. i know that the port guy will do a better job of chamfering the ports than the machine shop will. i've seen this a ton of times. if the guy sneezes, then he shouldnt be porting while his alergies are acting up.:Laugh8:
also, i dont think that the machinist should be in there messing around with the porters work, which is what he's doin while chamfering...correct? what if he sneezes while chamfering? there goes your expensive port work,lol!!
 

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i must be backwards then. i know that the port guy will do a better job of chamfering the ports than the machine shop will. i've seen this a ton of times. if the guy sneezes, then he shouldnt be porting while his alergies are acting up.:Laugh8:
also, i dont think that the machinist should be in there messing around with the porters work, which is what he's doin while chamfering...correct? what if he sneezes while chamfering? there goes your expensive port work,lol!!
I am with you on this one bro.I always bore first and then send the new piston and cylinder to the porter to get done.I see the differences both ways and I guess it is personal preference.I will still stick to my guns and get it bored first,it has worked every time so far so why change.lol
 

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PLAYTIME'S OVER BITCHES!!
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Discussion Starter · #9 ·
to clear this up some. im talkin about if you have a set of juggs ( or one jug) that needs boring and you would like to have it ported as well before putting it back together. we all know that boring is'nt a performance mod to a two stroke.
 

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Port first is the way to go. Ports on almost all cylinders from the factory have some pretty sorry flow to them where as a new cylinder almost always has a good bore with a lot of mileage left to go before a new bore job must be done.
 

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to clear this up some. im talkin about if you have a set of juggs ( or one jug) that needs boring and you would like to have it ported as well before putting it back together. we all know that boring is'nt a performance mod to a two stroke.
Depends on how much we are talking about boring. If your taking a stockish 250 cylinder which is around 67mm and you want to go right to the max around 69mm, I would bore it first and then port it because as you increase your bore the effective area of your ports get smaller and needs to be corrected. So your port job that you got for that 67mm bore is now too small to flow effectively at 69mm. This sometimes accounts why smaller engines out perform larger ones. If you are talking taking the cylinder to just the next oversize then you are OK porting and then boring, as long as you make sure that whoever does the boring does a chamfer on the ports. To answer your question, Yes you are actually messing with the porter's work if you have the machinist chamfer the ports, becaue you can actually 'play' with the chamfer to get a little more flow out of the ports and make them 'act' larger then they actually are.

For the record boring is a performance mod on a two stroke because you are increasing the displacement of the engine. Just going to the next oversize, is not going to do much for power. Like I stated before, as you increase the bore, the ports effectively become smaller so they need to be corrected to get the maximum out of your setup. This is usually not cost effective (bang for the buck) so it hardly ever gets done. Port jobs are usually a one and done type of mod. Different shops port different ways. Some shops may not worry about messing around with the port area as it enters the cylinder or the angles if it is a trail port. Nickisil cylinders have an advantage over the iron liner (besides from the reduced friction and better heat transfer) because the porting stays the same and you just slap in new pistons of the same bore in it unless you somehow manage to hurt the plating.
 

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PLAYTIME'S OVER BITCHES!!
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Discussion Starter · #14 ·
For the record boring is a performance mod on a two stroke because you are increasing the displacement of the engine. Just going to the next oversize, is not going to do much for power.
thats kinda what i ment by that statement really. i dont know of anyone that would just punch one out to the max thinking it's going to give an incredible power increase. flow is where it's at on a two stroke.
 

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thats kinda what i ment by that statement really. i dont know of anyone that would just punch one out to the max thinking it's going to give an incredible power increase. flow is where it's at on a two stroke.
I know a guy that'll do that.........my brother. He had a nice ATC250R cylinder, stock 66mm bore. He sent it off and had it bored .80 over. I tried to talk him out of it at the time, but he wanted a bigger piston. IMO that is wasting bores.

If a cylinder has never been ported on, I say bore it first, then port it.
 

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this is how i usually do it : first i scribe my lines out ,i do all my hogging with 1/4 carbide and get it fairly close t o size and shape im hunting for ..then ill bore/hone it to size ... now i have the final bore diamater to calculate my chordial widths and i got something to work with and by this time the roughing stage is all done and i stepped down to using 1/8 carbide cutters anyways so theres no concern of a slip causing any gouge issues ,after the porting is all wrapped up i chamfer all my ports vertical and horizontal then lube it good and run a light flex ball hone to insure theres no chance of a snag on the ring or a sharp port edge that skims oil off . i like saving that last 25% of the porting process after its bored .it lets me fine tune things and having a clean fresh bore to work with makes scribing and laying out the map easier too.i would say if you had to pick one id port then bore unless its a drastic increase in bore size ..as rb0804 mentioned it can screw up chordial widths
regardless of what order you should always chamfer the ports before final assembly ,a sharp port edge is dangerous and shortens the life of your topend



 

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PLAYTIME'S OVER BITCHES!!
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Discussion Starter · #17 ·
my reason for this thread is to really find out if there is scientific fact why one should be done before the other. it almost seems that it is more of personal preferance.
obviously, mine is porting after boring so i know that my ports being fine tuned is the last thing that happens.
 

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thats kinda what i ment by that statement really. i dont know of anyone that would just punch one out to the max thinking it's going to give an incredible power increase. flow is where it's at on a two stroke.

You should read this article. For those class racing at the 265/270cc limit it is worth it. When is the last time you had a stock bore (66-67mm) 250 pull around 60 horse? This cylinder came right out of the box and went right to the max. It's a bang for the buck thing. Why not go with a bigger bore if you can get the piston weight close to a stock piston so it revs and vibrates about the same?

http://www.macdizzy.com/sixtynine.htm



regardless of what order you should always chamfer the ports before final assembly ,a sharp port edge is dangerous and shortens the life of your topend
This is so true, not only do you run the risk of catching the piston ring in one of the ports, the sharp edges of the port widow act as a scraper robbing the piston of the lubrication that it needs to function properly.
 

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my reason for this thread is to really find out if there is scientific fact why one should be done before the other. it almost seems that it is more of personal preferance.
obviously, mine is porting after boring so i know that my ports being fine tuned is the last thing that happens.
always bore first ,
The answer two your question is YES there is facts about this but the porters will tell you bull shit if they really don't know
DMZ
 
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