cylinder boring

[00sheerzr]

i want to rebuild my quad in the spring or summer because i like the snow lol i have a boring machine but never bored a 2 stroke cylinder with ports in it, do i just adjust and start cutting but then after that i hear something about making sure the rings dont get caught in the ports after you bored it, my father has tons ef experience boring cylinder in 4 strokes but not 2 strokes, so if anyone has ever done this id love some help

[papa_smurf49319]

You have to chamfer the ports that way the rings dont catch on them.

[00sheerzr]

You have to chamfer the ports that way the rings dont catch on them.

 

now what exaly is chammfering how do you do it

[volcrano]

now what exaly is chammfering how do you do it

not trying to be a dick dude-but if ur asking these questions u might want to have someone else do it.chamfering means cleaning up the rough edges around the ports so it is smooth so rings wont get caught.

[00sheerzr]

not trying to be a dick dude-but if ur asking these questions u might want to have someone else do it.chamfering means cleaning up the rough edges around the ports so it is smooth so rings wont get caught.

 

believe me i know what doing when it comes to boring cylindersa on 4 strokes, ive rebuilt over 15 harely davidson engines,2 warriors 1 400ex , a raptor and 250f dirtbike, i usually send out 2 stroke cylinders to get replated but banshee cylinders dont have nikasil plating so im planning on boring them myself, i have all the tools to do it and tons of experience but it doesnt hurt to ask questions thank you very much

[blowit]

believe me i know what doing when it comes to boring cylindersa on 4 strokes, ive rebuilt over 15 harely davidson engines,2 warriors 1 400ex , a raptor and 250f dirtbike, i usually send out 2 stroke cylinders to get replated but banshee cylinders dont have nikasil plating so im planning on boring them myself, i have all the tools to do it and tons of experience but it doesnt hurt to ask questions thank you very much

 

 

You seem competent enough to do the job. Just remember that 2 pokes like to taper because of the all the holes in the cylinder so you may spend more time at one end than the other. Chamfer is critical and probably the most over looked aspect of an 2 poke and a high ranker in my rebuild customer list. I guess if you miss it, you will have to skills to do it over. I will admit that there are plenty of crazies, that know nothing about engines, boring 2 pokes and putting on a half ass chamfer and getting away with it. If you plant to rebuild every year, it might not matter. Most of our motors run for many years though.

 

We just do NOT agree with the "break in like you are going to run it" theories. Engines that are new have higher CF factors (coefficient of friction) than run in motors. That friction translates to heat and must be carefully monitored if you want an engine to last. Hot metal will melt, cause glazing, glazing causes poor lubrication from lack of oil retention, and the cycle continues. Where I am going with that is cylinder finish. It is rather important on a 2-poke since you do not get near the lubrication compared to that of a 4 poke with pressurized oil, oil rings, etc, not to mention a MUCH smaller piston surface area.

 

Mull Engineering

[rb0804]

You seem competent enough to do the job. Just remember that 2 pokes like to taper because of the all the holes in the cylinder so you may spend more time at one end than the other. Chamfer is critical and probably the most over looked aspect of an 2 poke and a high ranker in my rebuild customer list. I guess if you miss it, you will have to skills to do it over. I will admit that there are plenty of crazies, that know nothing about engines, boring 2 pokes and putting on a half ass chamfer and getting away with it. If you plant to rebuild every year, it might not matter. Most of our motors run for many years though.

 

We just do NOT agree with the "break in like you are going to run it" theories. Engines that are new have higher CF factors (coefficient of friction) than run in motors. That friction translates to heat and must be carefully monitored if you want an engine to last. Hot metal will melt, cause glazing, glazing causes poor lubrication from lack of oil retention, and the cycle continues. Where I am going with that is cylinder finish. It is rather important on a 2-poke since you do not get near the lubrication compared to that of a 4 poke with pressurized oil, oil rings, etc, not to mention a MUCH smaller piston surface area.

 

Mull Engineering

 

Very well put, but there is two things that I did not see so I am going to chime in. The first being that carbide does not like interupted cuts (the starting and stoping of going through the ports) so if you take a big cut with a carbide bit you will most likely break it (you may break it anyway). The other bing if you do not chamfer the ports, not only do you run the risk of catching a ring on the sharpness of the port window, but the 90* edge of the port window acts as a scraper actuall removing the oil for the piston which is a very bad thing. Can you say seizure?

[Larry's Shee]

Think of chamfering as a slight taper from the port into the cylinder to gently ease the rings back into the cylinder after they pop into port. You can get specifics on angle from Gorden Jennings Two Stroke Tuners Handbook or on the blaster forum there is a link to McDizzy that might show it.