Added a boost port tonight *pics*

Havent ran it yet just got the engine all back toghter last night still havent put the body work back on it yet ,but ill let ya guys know how the bike performs for sure

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Great pics and better informatiom. But could anyone post pics of the tools/burrs used. Maybe my fingers are just too fat but I can't imagine getting a dremel down the bore and having any room to shape the roof of the boost port. Thanks

hurry up and get that beast out on the track so I can hear about the results.

I acually started working on my hf fairing bike tonight to fix the sticking throttle problem so i got no where on my ff bike that im doing all the work to lol..

Hopefully tommrrow ill fire it up and try to get it dialed in with the jetting and hopefully do some speed testing this week i usally have to wait till the weekedns to get the bikes out for rides cause its dark by the time i have any free time then ill see if all my free mods were worth the work!

Ill try to take a picture of the things i used to do what i did

OK guys, not being a porting guru, but knowing more than a little bit about it, let me attempt to explain. Also, what I can't explain can be gleaned from hours of reading here: http://www.macdizzy.com/cyl_primer.htm Make yourselves smart here, then you can answer the questions...

If you look at the main transfer ports, it's obvious that they are presenting the fresh fuel-air mixture towards the TOP REAR area of the cylinder, opposite the exhaust port. This is called LOOP CHARGING. The fresh fuel air mixture loops towards the top rear to SCAVENGE the spent exhaust gasses from that area first, then continues to loop around the cylinder, hopefully getting rid of as much of the spent gas as possible. Then, hopefully, the piston will close off the exhaust port BEFORE any of the fresh fuel-air mixture exits out the exhaust. But this is the real world. Thank GOD for tuned expansion chambers. The rear boost port or ports continue and enhance this scavenging process, but we don't want to totally DISRUPT this process.

The first thing that has to happen, is that there has to be enough BLOWDOWN time to let the transfer process happen. Blowdown time is the time it takes for cylinder pressure to decrease enough after the engine fires to let transfer take place. Raising the exhaust port, thus opening it sooner increases it's open time and decreases blowdown time. Widening it decreases blowdown time. Get the bad out and the good in as fast as possible. A taller exhaust also decreases the corrected compression ratio, so you have to give in order to get. Once the transfer process starts happening, you want it to be INITIATED by the MAIN TRANSFERS in order to get the loop started towards the top rear of the cylinder. If the boost port or ports open first, then they will be working AGAINST the main transfers, and if their roof angle is too straight they will be trying their darndest to force all of that nice fresh fuel air mixture STRAIGHT OUT THE EXHAUST! (That's what they are facing, remember?) They (it) should open just slightly AFTER the main transfers, and they should have a fairly steep (40-60deg.) roof angle to pretty much blow straight up at the combustion chaimber. They are boosters, and their job is to enhance scavenging, not counteract it.

ScooterWiz

Or it’s to pack the last bit of fuel right at the plug... Which would mean it would be the last intake port to close. There are 101 different ways to tune. Don't get wrapped up in Mcdizzy, its great info, and a great place to learn DIFFERENT techniques, but it’s by far the book of perfection.

Also, it all depends on the main transfer port defection as to if a high boost port will negatively affect the process or enhance it. You can not assume that your statement will be true in all conditions either, as I have proven time and time again that it is not.

I love how this thread has developed. All of our contributions are inspiring those new to 2-stroke tuning to give it a try and research and experiement. B3 is right macdizzy is a good source to learn some techniqes but like he and I have stated before, everyone tunes 2-strokes differently and that's the great thing about 2-strokes. Thats why I really like this thread, it just proves that point and encourages experiementation. Pay close attention to what Scooterwiz mentioned about the exhaust port. There are some very good and bad points to making adjustments to the exhaust port. I have heard people complain about loosing all bottom end from porting the exhaust. This is simply b/c they don't know what they are doing and did it incorrectly. There is plenty of power to be harnessed from these little engines if you are willing to research and experiement. I laughed my azz off this weekend at the track when my 40.2cc L7 Cag spanked the big bore bikes all the way around the track. It's all in the tuning boyz and girlz!

I was suprised to see my thread came back lol im still messing with my cyl ,i just put it back on a few days ago after doign a few diffrent things to it to pull more top end outta it hopefully the wife will let me off house painting detail long enough to try it out lol

Hey have you tried out the port job yet?...I am anxious to see...

Post up when ya get a chance!

you cant keep us all in suspense like this, gotta test it out soon.

what does a boost port do and is it worth the time and effort

lol did you even read the thread? i think if you look around in the early pages,i think around 4 the same question was ask and answered. id suggest you read this whole thread as it will provide you with a better understanding of what a boostport is and how you can port your own.

Well I read the entire thread and I only heard controversy. The guy that started the thread never even gave any implies if it helped or not. It was always I am going to post asap but he never did.....If it was such a great job he would have told us about it.
I believe bartw had it correct the boost ports should not travel past the transfer ports or turbulence will cause an adverse effect.

yea your right he did never reply back on the results

wouldnt it be better to make a boost port with a pillar drill? got loads of machines at work that will do most engineering work. will i also need to make a hole in the piston skirt? or can i just do the boost port?

u can just add the port....the hole in the skirt wont change anything....i have had it both ways....it doesnt matter....i feel no hole is better cause the piston is stronger

if you boost port the cyliner head do u have to boost port the piston to or is that optional/ stupid question i know

look up man...i just posted it....u dont need to unless u want to waste time