After riding today i decided that the port job i did last weekend wasent cutting it so off came the cyl again and i added the boost port and below are pics of how i made my boost port map,i used a carbide dremel bit then cleaned it up with a sanding stone,i also didnt use a gasket on the cyl just some yamabond to bump the compression up a lil.
tommrrow im porting the carb the reed cage, tapering my needle and lighting the flywheel.
For anyone that missed my port pics before i added them in,that port job alone with out the boost port provided a killer low mid range.
first pic with the blue tape is how i mapped out my boost port i then traced out the port with a sharpie,2nd pic is after i removed the tape and the sharpie remains where i cut out.
last pic is where i removed the box with the sqiggly lines and put my 42F sig on it .
Did you do all of this with a dremel? I've got a dremel and love metal working just always get scared of sparks for some lame reason haha. Hopefully I can overcome that real real soon.
Im gonna play with porting my stock head and adding the boost port and see how good I can do and if I mes anything up before I go to work on my B head. I think I am going to wait on the BB kit until I buy a FCS ctrank and get that sucker in to play with porting more, then work up to the BB kit. whats a die grinder, I thouhgt it was what you hold in your hand and it has like a 5 insh grinding wheel but I dont see what kind of headowrk you could do with that so I assume I am dead wrong.
Here is a stupid question, why would the boost port go up exactly as high as the transfer ports? Of course I am asking this because I think something different but tell me your guys theory.
yes the boost port goes up as high as the transfer ports,i used a dremel on the boost port and a die grinder on the rest.
Ok cool. I think I am going to port my exhaust port and carb. Should I use a die grinder for the carb too? Also how do I know how much to take off on the exhaust and carb?
Here is a stupid question, why would the boost port go up exactly as high as the transfer ports? Of course I am asking this because I think something different but tell me your guys theory.
I guess everyone is doing the boostport differently.I think rexracer,PBU and a couple of other people go the same lenght as the transfer ports.But some people dont.Which one is more benificiall?back your opinion up?
wow so many questions let see if i can cover them all lol ,when i said die grinder i shoulda said mini die grinder lol its alot smaller but a die grinder is bascially like a dremel but runs off my air compressor.
I have started work on my carb and im using the dremel on it..
how wide i made it is approx a 1/4 inch wide maybe a lil more more i didnt measure it and the depth is as far down as u can go without going threw the cyl
...B3... u said the boost port shouldnt go as high as the transfer ports care to go a little further and explain?
I havent rode it yet because im still working on the carb today im going to check the compression and see what i got compared to what i had before
Im by no means a porting guru i mess around with everything i own im 31 and have had alot of 2 strokes and i do performance work to them all and have allways made gains from the things i do.
A boost port alone adds 1K to the top end RPMs. That was tach'd with my GPT tach on a completely stock bike. Before the boost port, 96-9700. After boost port, I consistently hit 10600-10700 RPMs. A simple rejet was needed as well.
Doing a 4 port (porting the 2 intakes, exhaust, and boost port), should net you close to 11K. But if you're using the stock pipe, you're limited to its potential. Get an IP2 or polini 6.2 pipe, add some CF reeds, port the carb, and you should be getting around 12,700 RPMs. Not bad for a cag eh? Your low end wont be as good as a stock cag (maybe add a reed spacer to help out this area. I haven't tried it), but your top end will be screaming. Also, try to get some clutch springs to take advantage of the mods. I've seen other boost ports that are larger in width. They all basically work the same. It fakes the engine to think there are 2 exhaust ports instead of one. Fuel and air enter the head more than stock. You'll get an increased combustion...that equals more power.
Quote:
Originally Posted by 42F67N
wow so many questions let see if i can cover them all lol ,when i said die grinder i shoulda said mini die grinder lol its alot smaller but a die grinder is bascially like a dremel but runs off my air compressor.
I have started work on my carb and im using the dremel on it..
how wide i made it is approx a 1/4 inch wide maybe a lil more more i didnt measure it and the depth is as far down as u can go without going threw the cyl
...B3... u said the boost port shouldnt go as high as the transfer ports care to go a little further and explain?
I havent rode it yet because im still working on the carb today im going to check the compression and see what i got compared to what i had before
Im by no means a porting guru i mess around with everything i own im 31 and have had alot of 2 strokes and i do performance work to them all and have allways made gains from the things i do.
It should... and here's why. The boost port is allowing the engine to force more fuel and air into the combustion chamber upon it's downstroke utillizing all three ports; the two transffers and the boost ports. This requires the top of the port to extend past the piston rings at BDC(bottom dead center). It also helps to bevel the top of the port in order to aim the air/fuel mixture up towards the spark plug. The boost port also increases the volume of the crankcase for the duration of the upstroke.
If, however the boost port does not extend past the rings, you will simply be increasing the volume of the crankcase which will allow for the air/fuel mixture to be forced through the transffer ports at a greater velocity.
So which one is the correct way to make a boost port? Well why go through the trouble of simply increasing crankcase volume with a boost port when that can be achieved much easier by simply adding reed block spacers. Reed block spacers increase the amount of volume in the crank case achieving the same effect as a boost port that does not extend past the rings. So if thats what you're after, save your rings and just add a reed block spacer.
So does making the boost port extend past the rings add any performance over just increasing crankcase volume? Well it's debatable. It allows for better mixture of the air/fuel mixture by swirling the mixture around the combustion chamber through 3 ports. It removes some drag from the piston ring/cylinder friction, thus possibly the increase in rpms. It too is increasing crankcase volume, allowing for a slight bump in compression, also resulting in more rpms.
Basiclly the whole thing depends on what you wish to achieve in the end. The great thing about tuning an engine is you can talk to the top 50 engine tuners in the world and they will all have different tip and tricks. Everyone has their own methods for achieving the same end result... more power, more speed!
Just to note: I ran reed block spacers before I ported my head, it helped alot! I ported my head(boost past the rings) and it helped more! Together they make for an awsome combination!
No, it should not be the same height.
Most of the time it will be open for about 1 degree longer than the side transfers. For a boost port to work properly, as its main intention is to pack the mixture at the plug area, its journal roof must be at a pretty steep angle, usually in the neighborhood of 30-40 degrees.
No, it should not be the same height.
Most of the time it will be open for about 1 degree longer than the side transfers. For a boost port to work properly, as its main intention is to pack the mixture at the plug area, its journal roof must be at a pretty steep angle, usually in the neighborhood of 30-40 degrees.
Yes you are correct. I thought you said not to go past the piston rings at BDC. If you make it too long it will force some of the mixture out of the combustion chamber before it's ignited, thus robbing power from the engine. You are exactly right about the angle of the journal roof. As for the length of the boost port I do not recomend any amateurs attempting to make the journal extend past the transfer ports. You could easily ruin the head of your engine if you go too far. B3... this is why I did not specify a length on the boost journal, I simply stated that it must be past the rings at BDC. Their are alot of amateurs on this board that don't understand how to make a journal 1 degree longer than the transfers. Maybe we should start a thread about timing?
Originally Posted by bartw
Here is a stupid question, why would the boost port go up exactly as high as the transfer ports? Of course I am asking this because I think something different but tell me your guys theory.
He said "exactly", and thats why I said "it should'nt".
No big deal, just a bad choice of wording on my part I guess.
*edit*
on your question about making a thread about port timing. There are so many sites now that have almost every senerio out there, if someone is of the right mind to even do motor work correctly, they would also be of the right mind to find the info and decide what they believe through their own trial and error. Its not that I do not want to help others, its the fact that I do not want to waste my breath as I have done so many times in the past, then when someones engine does not work they blame the person who told them how to do it, and do not take into consideration that they are the ones in fact who did it wrong or did not understand when they said they did.
