HP gain?

[BoDaddy87]

Im just starting out learning how to "clean up" the cylinder. Like polishing the exhaust and transfer ports. If nicely cleaned up about how much gain will it be? Thanks for your time.
Other mods in case you need to know..
-Fmf powercore 2
-Fmf fatty
-67mm wiseco piston
-Vito's .018 high comp head gasket
-hotrod crank
-bigger jet
-boyesen dual stage reeds

 

[blasterboy91]

Im just starting out learning how to "clean up" the cylinder. Like polishing the exhaust and transfer ports.

If you're going to do your own Porting, I'd suggest getting the crank welded. Just piece of mind.

As for gains, KOR has riders claiming high 20's - low 30's. Without dyno runs, it's all taken on word of mouth. You'll probolt be in the middle of those numbers. Maybe 23-28? It's good power considering stock the bike is 17 or 18 HP.

You need to have as much info as possible. Here's a link to the best info you can get on the web IMO.


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

 

[blasterboy91]

Stay away from 'template' port jobs. They're considered hack jobs. You need to know numbers, squish, deck heights, blah blah blah. Know what you're doing, what does what, what needs to be removed, and what needs to be cleaned up. I would also see if you can grab a spare 'practice' cylinder to hone your skills on. That way if something happens you have your original head laying around.

Good luck and have fun

 

[BoDaddy87]

Great thanks guys! Iv been practicing, iv got 4 cylinders lol. I feel like it's going good, iv got a good buddy thats showing me the ropes and also watching all the Kon Oconnor vids on youtube.

 

[BoDaddy87]

Heres some before and after, still alot of work to do but waiting for my blue stones and polishers to come in

 

[best]

I've done some of the polishing tricks one at a time to see what the gain is.
Porting the exhaust only at the cylinder (as to a template) delivered a sizable improvement.
Polishing the exhaust to a mirror finish delivered no noticeable improvement over rough finish.
Porting the exhaust larger leading up to the pipe killed mid-range torque with no max rpm gain.
Polishing and knife-edging the case to transfer port entrance delivered no noticeable gain.
Thinning the intake and piston bridge reduced piston longevity.

I don't have access to a dyno, but I do have a Blaster with a 32hp DT200 engine and another with a 45-50hp KTM 250 engine. With head and porting mods we have been able to exceed the power of theDT200 engine but have not yet come close to the power of the KTM250. The stock Vito's 240cc stroker crank and big bore kit comes close but does not have the revs and power of the DT200. A modifed head and aftermarket pipe brought it to about equal to the DT200, maybe.

I've posted this before, and the numbers may differ, but (done in this order) I'd estimate:
Stock Blaster = 17hp
Rechambered head with squish set = 22 hp
Aftermarket pipe and airbox opened up = 26hp
Exhaust port raised 1mm and 2-3mm wider = 28hp (at 8000rpm)
Intake port 2mm wider = 30hp
Better air filter, fine tune timing and jetting = equal DT200 at 32hp at 500 rpm lower.

Filling the reed box in with epoxy has helped gain power across the rpm band.
Hogging out the exhaust roof, exhaust port, intake port or larger carb might make marginally more top rpm power at the expense of mid-range power. More compression gives more low rpm power at the expense of reliability. All of these numbers depend on how well you do the work and how well you jet it.

 

[Awk08]

Stay away from 'template' port jobs. They're considered hack jobs.

That's bullshiit, and comes from the banshee guys who think only a bansheehq sponsor can port a cylinder.
The sport port templates are a proven way to learn porting skills, while not butchering a cylinder, and make decent gains for the $.
Sure it's nice to learn the timings of it all, which can be done while using the templates.

There are plenty of 30-40+ hp. Blasters around here running perfectly fine for years without welded cranks, again that's banshee stuff.

 

[Larry's Shee]

Best thing about templates is they keep you out of trouble !! It makes it far easier to keep thing symetrical. Plus you don't have to read up on the hows and whys of porting and two strokes in general, although you'll need the knowledge to go further. This especially true when it comes to raising/modifying the exhaust port. (more to follow)

In reality, it wouldn't surprise me if someone doing dozens of port jobs a year didn't use a template, poor man's CNC.

Welding on Banshee cranks is done to keep them in phase, exactly 180* of difference in stroke,.

But, then again, there are some Banshee owners that think the Niche cylinders are OK .........


When modifying the exhaust port, AVOID making the roof flat, a nice arc/radius is better. While a flat roof delivers a more "concentrated" hit of the powerband, but is extremely hard on the rings.

I'm actually going to be De-tuning/ re-tuning my Blaster, might have raised the exhaust a bit to much. Then adding a 3mil crank raised it more with the spacer plate. My plan is to do a little measuring with a degree to see if I gain enough when removing the plate to justifiey having a a custom head cut. Not that there's anything wrong with the way the powerband is, it's that I'm getting old and slowing down a bit

 

[best]

Hey Larry's Shee, I hear ya!
My Vito's BBK stroker does not make the power of my son's high reving port'n polish Blaster but it makes its power in the range I can use. His PnP is a screamer. It has a higher top speed, will pull wheelies at speed and will haul butt if you keep the revs up, but you gotta keep the revs up! Mine has an old guy's power band. I can lug it and run in a lazy and leisurely way, and easily scoot off with a bit of throttle. I love it.

My son and I are going to work on his Shee. It is a total rev machine. He followed the advice of the Banshee HQ crowd. Taller exhausts, more compression, big ports, big pipes, big carb. Gotta rev da piss outa her to get her moving and yet it is still not that impressive on top end. I'm hoping some epoxy and lowering the cylinder can make it sane again.

You don't need to remove the spacer plate. You still need some space with a stroker. Just swapping the 2 basegaskets for hand cut ones out of thin paper will gain you 0.040"-0.060".

 

[Awk08]

He followed the advice of the Banshee HQ crowd

From what I see over there, that was a mistake, if you're not building a sand drag big hp machine, the advice is limited at best for a woods machine.