Porting

GoldenMotor.com

john8460

New Member
Aug 16, 2009
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USA
Hi everyone, I was just wondering what porting is, how it works, and also how to do it.

Thanks for any help,
John
 

Extinction

New Member
May 20, 2010
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Estonia
Stock motors suck tbh. To get the engine running good, slight porting (and crank balancing, crankcase and cylinder matching, exhaust and intake modifications, setting up the carb precisely etc) helps a lot if done correctly. And if you are after (a lot) more power then there is hundreds of other things to do than porting as well.

But one thing is sure, if you ask what porting is, what it gives you and how its done, then you definitely are not the man for the job (yet).

I've noticed that some of these chinese engines are of very poor quality (explains why they're so cheap). Some tuners are using pistons other than the original part, sleeved the cylinders and so on, all that to get the long lasting high output engine.
 
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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
I totally disagree with the above statement- "Some tuners are using pistons other than the original part, sleeved the cylinders and so on, all that to get the long lasting high output engine."
Almost every 'frankenstein' engine I've seen built here has blown up!

I concur with Barely! ;)
 

Extinction

New Member
May 20, 2010
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Estonia
The question "will the engine run or blow up" depends a lot on how its made and put together.
For example, the clutch on a "80cc" engine is totally ****, starts slipping as soon as you put a tuned pipe on the bike, next thing is that nicasil starts to flake off the cylinder wall, what the heck... Yeah I'm sure those engines have blown up, absolutely no doubt. :D That's because there is so many things to do when you want them to stay in one piece when tuned. May be that our opinions are so different because the build quality of some engines are so different but after all they are all made cheap.
BTW the people I know don't tune them for street use, its all for racing.
 

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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www.sickbikeparts.com
You can open the ports up a tiny bit and get a bit more perf without making a grenade.

But what is REALLY worth it for the DIY bike weasel, is at least matching the exhaust and intake manifold to the head. Pretty simple, and fun. New gaskets to match as well. Hello Freddy!!! Throw a pipe on the beast and watch the frack out.
 
Sep 20, 2008
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Clearwater, FL
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Unless you have the right tools and you know what you are doing:

Do not work the ports anywhere near the cylinder bore, where the chrome is. You need extremely fine diamond infused tools to finish the area around the inside of the ports. If it isn't done right the piston rings will catch the chrome and peel it resulting in broken rings and a blown motor!

There is nothing wrong with matching the ports to the intake and exhaust. Shape and blend them to about half way. It will make a little bit of difference in overall performance...maybe more depending on how bad the ports are initially.

Jim
 

BarelyAWake

New Member
Jul 21, 2009
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Maine
Reading the above statements, I gotta say that much of this must be variance frm manufacturer to manufacturer, even engine to engine as I've (lightly) ported a couple now with great success without the problems mentioned... but I'd not be surprised in the least if there were "bad batches" w/liner problems etc...

Tho I may be one of the few that does "tune for street" and not all-out racing lol and there's the old truism - the more ya tune, the harder ya ride ;)
 

PaulFlorida

New Member
Dec 4, 2009
52
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central florida
I have had a lot of fun with my fully ported motor. I've put 2 gallons of premium at 20:1 through it with the "frankenstein" setup. The clutch is beginning to slip in lower gears when accelerating hard, and the bearings are sounding reeeeaaally bad right now. One week of riding it. It was fun, but dang if I didn't learn from it. For general riding around, keep it simple for reliability.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I'll add my latest experience to this thread... I fully match ported the engine on my new red boardie. I split the cases & smoothed, enlarged & match ported the inside transfer ports & base gasket. I also did the same to the intake & exaust areas; & last I smoothed the inside of the carb.
I DID NOT TOUCH the heights of the cylinder ports, I only made the exaust port a little wider.
So far the engine runs very smooth & has a lot more power than any of my other bikes.
I'll post on how long it lasts. :rolleyes:
 

WildAlaskan

New Member
Sep 30, 2010
578
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alaska
just be carefull grinding away i ground thru my case and now my motor sits in a box waiting for justin at pirate cycle to send some fixer parts but i dont regret tryin it its a learning experience and i learned alot plus taking apart my motor was fun

but i do have a working reliable stock motor right now im not taking that baby apart untill i have another reliable ride setup cause i use my bike for main transportation
 

FlyGuy

New Member
Apr 1, 2011
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Corry, PA
I agree with all of you in certin instances.

I also belive that if you drop a super power port job on a stock bottom end the bottom end will not last. If you take a close look at various 2 strokes it is certinly possible to push much more power out of similar sized engines.

The question being if one was to build a bottom end with the best quality parts and attached a high power cylinder what would be the result.

Are there aftermarket bottom ends available?
 

DaveC

Member
Jul 14, 2010
969
1
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Boise, ID
Not really but there is up-grades to bearings and seals to consider. Daniel Maia's thread has the part numbers you need to up-grade.

http://motorbicycling.com/f13/66cc-engine-tear-down-setting-high-27007.html

When I get my new 49cc the 66cc is getting the treatment.

A stronger bottom end is key to longevity and the stock Chinese parts are barely adequate for the job. With them it's a matter of luck in the combination of parts more than anything else..bf.
 
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WildAlaskan

New Member
Sep 30, 2010
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alaska
im not sure if this is better but i think instead of skirt trimming ur piston, wouldnt it b better to raise the jug to clear the skirt and then shave the top of the jug down to u[p compression.
 

Goat Herder

Gutter Rider
Apr 28, 2008
6,237
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N.M.
im not sure if this is better but i think instead of skirt trimming ur piston, wouldnt it b better to raise the jug to clear the skirt and then shave the top of the jug down to u[p compression.
I think you have a point. As long as the transfers line up. The transfer ports on some of these motors are not clearing the piston that well if you look closely anyway.