SlowMoe

Sorry, bike did not come with one

I'm not sure if I have read any data suggesting just how wide you can go with the auxiliary exhaust ports, but I would imagine there is a significant amount of material that can be taken off and a significant amount of blowdown volume to be obtained..

One would think that the transfer ports on an as cast serval cylinder would be pretty optimal as far as where the charge is aimed. Are you suggesting somewhat of a re-design of the transfer port discharge, or optimizing the sir rent angles by checking and removing any flaws?

Ive been looking at a lot of graphs for stock serval vs ported serval and the gains seem very impressive, especially since typically there is no sacrifice in bottom to midrange power, just gains across the entire powerband, especislly up top. This leads me to believe the port timings arent changed much, if at all. So what is being done to these things? The only thing I can think is that maybe the exhaust is re-shaped/ enlarged some and possiblythe auxilliary exhaust ports are widened and the tunnels hogged out some. Any thoughts?

Well I've heard people say some off the wall things, such as they help the reeds close faster and other things, but didnt make too much sense to me at the time

I assume these are just to a) Increase "intake" area when the piston is traveling up Increase transfer area (to feed boost port) when the piston is traveling down Does that about sum it up?

Those are some teeny weeny boysen ports. I usually stack 2 or 3 on top of each other and then connect them

Yeah it and that one transfer were horrible

Doesnt look like much, and it isn't, but the ports were lowered and widened, giving probably 10% more intake area, to go with the mild increase in transfer and exhaust flow volume

This is the transfer port (inside radius) that was 30% blocked

I love blasters. They are fun, agile and it literally takes 15 minutes to get the jug off

Probably a good 5 hp on top

Yep. Huge difference from just a clean up port job

Thats a stock cheap chinese cylindedr as evidenced by the excessive blockages in the ports

Ok for some reason I cant upload any more pics. What the hell

Transfer before

Intake before

So my sons blaster was 100% stock. The power came on super early and had a nice midrange punch but fell FLAT on its face in the top end. So I was bored yesterday and decided to do a little grinding to wake up the top end. Upon removing the cylinder I discovered that 2 transfer ports has a decent amount of mismatch and that one of them was about 30% blocked with aluminum. Horrible. The exhaust port also had a LOT of aluminum where it shouldnt have been, mainly along the roof. I bet it affected the timing by about 3-5 degrees. So what I did was: -lowered the intake port about 3mm, narrowed the bridge about 2-3 mm -Smoothed out the transfer entrancesm cleaned up the area near the windows and made sure everything matched up nicely. Didn't change transfer timing at all -cleaned up the flashing from the exhaust, and raised the roof about 2mm in the center and about 4mm on the corners (squared it up a bit) You wouldnt believe how much better the top end is. Fro having a stock pipe it revs out nicely, and once on the pipe the powerband feels super linear. I bet its as fast as a piped blaster with no port work, and has a MUCH wider powerband I tried to take before and after pics but they didnt come out too great, I'll post them up in a minute

Well, I have read bell's book as well as the other one, back in the day, so I have at least a basic understanding lol. And when I cut transfers, I use that "pole" on a set of dial calipers to make sure they are the exact height

So essentially you dont spend much time opening up the area near the windows, correct? I have done this once. All I did was raised the transfer roof and hogged out as much as i could reach from the entrance. And the exhaust port wasnt even big at all. And it revved like a mofo

Yeah it does seem pretty conservative. If it were me I would widen it 1-2mm on each side, at the top, then taper it down to the current width at the bottom

Am I wrong in assuming that large boysen ports help the transfers charge more effectively?

Just increasing transfer port and exhaust port timing and doing nothing else will get you a bunch of HP. If I were to do a DIY port I would use a 2mm spacer to raise the cylinder, take 2mm off the deck to compensate and do this to the exhaust port (raise it another 1-2mm at the highest point: