Porting - are you actually taking advantage of it?

Skarrd

Member
Oct 13, 2010
501
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Chandler, AZ
the pocket bikes are nice but i like being able to bump start & having a clutch.
i had a cop follow me over two miles through a residential neighbourhood the other day.
he pulled up aside me & started chatting. i think he really appreciated that when i came up to an ice cream truck & i went from motor to pedalling around the truck . then back to motor w/o skipping a beat.
man the police around me would probably just b**** me out, even though i can still pedal the bike.
 
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ToxicAz520

New Member
Mar 11, 2011
288
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Tucson,Arizona
My first motor I didn't know what is was doing at all. It seized on me but it wasn't my fault. The first mods I did were just port matching and it made a great difference. I will have to add though that I really didn't see a difference it made till after I got a better air fiter to allow the port match to work. I know this cause I ran it with filter off before port match then again after port match. I can tell you that you don't have to be in rocket science to do it either. It is well worth the 30 to 60 min of grinding to have a smoother, better breathing china girl.(More Breath=more Power) And Of course we all know none of this matters with out being properly tuned that's a given.
 
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Edrockmcboy

New Member
Jul 6, 2011
20
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Arizona
I have never ported anything, however i would love to feel that power you guys talk about. I'm not exactly sure how powerful mine is as i just got it and its my first motorized bike. However im pretty sure it can top out at around 35-40 cause i ride on the main roads, on the side walks and bike lanes of course, and almost can keep up with the cars haha and the speed limit is 45. I always have people riding next to me and giving me thumbs up. They're and I am suprised at how powerful it is i havent ported it though like i said. I'm pretty sure its AN 80CC-66CC Engine cause the jug looks bigger then most peoples. Can someone make and put up like a list of things to get ported and mess with inside the engine cause i really want to port it and take a look inside the block,not much of a block but still haha. However i wouldnt want to take it apart do something then want to take it apart to do something else you know i just wanna do everything once its taken apart with testing it in between of coarse.
 

Edrockmcboy

New Member
Jul 6, 2011
20
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Arizona
Also I am in Mesa,Az i was just wondering if anyone in the area could help me port and tune the engine as I'm sixteen and my Dad says i shouldnt try porting anything from lack of experience. I dont know to much about engines but its really not hard to figure small engines like this out with a little common sense, that most kids at my school in my auto classes dont have haha. Also what are some tips about porting so that i dont destroy the structure of anything for example if i port, i mean when i port, my exhaust i plan on reinforcing how its affixed to the engine so it doesnt break things like that.
 

Tohri

New Member
Aug 28, 2010
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People's Republik of Massachusetts
Make certain you have a full set of tools, and I mean FULL. it's not so much a step by step process as the kind of thing you learn the theory on, and extrapolate.

Right now my motor case is split and cleaned in front of me, with the case transfers ground out and patched with JBweld putty, repacked the 'sealed' bearings with super lube grease, the inside of the crank case has been textured with a high speed steel cutter, the crank has been balanced (Albeit barbarian style) the CDI is being replaced with a high RPM puch CDI, the head has been replaced with a puch high comp head, and the cylinder has been ported out somewhat, with proper piston skirt clearance at TDC. On the next motor I do, there will be a high performance walkthrough made up.
 

rustycase

Gutter Rider
May 26, 2011
2,746
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Left coast
Great pep talk on improvement ! Are the specs all in the porting and tuning thread with how they should be set up with a degree wheel?

DTG is spot on comparing this to guitar tuning. It's a back and forth adjustment process... one thing changed always leads to other adjustments that must be made before you get the most from the first change. Then it sings!

LOL
I just had to laugh...
'this is not so much precision work as fixing the horrid work by the mfg'
lol
THAT, comes very close to truth of the matter!

I'm sure any amount of cleanup work done in these motors will be beneficial.
Even if done somewhat improperly it could increase the life of the motor, by preventing a bit of casting slag from dropping into the chamber at 4krpm.

Best
rc
 

Chrisflik

New Member
Apr 2, 2011
23
0
0
California
The last few guys are absolutely right.
My last motor build where I did the whole cha-cha runs sick! It was the best mod I did.
All the aftermarket parts help too. But the motor work I did. Pssssh. Forget about it! Basically. Port it all. These motors are gonna break in one way or another after about a 1000 miles. Enjoy it while it lasts.
That's if you wanna do 35+ consistently.
 

Skarrd

Member
Oct 13, 2010
501
1
18
30
Chandler, AZ
If you have the tools, just do it yourself, its pretty easy. If not then buy the piston since a decent dremel might run you the same or more in the end
 

CarpsCustoms

New Member
Jan 27, 2014
108
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Waterbury, Connecticut
Gotcha, how would i know how much to cut off? I just want a little more top end, not too much so i dont lose much pressure or torque. thanks btw

And since every jug is different, isnt it really impossible for Jake's piston to have the same results with every motor
 

Racin8de

New Member
Jun 15, 2018
2
0
1
47
porting should not be attempted without the proper tooling and definitely without the proper knowledge

example: a quality degree wheel(for port duration, blowdown, etc.), a means for measuring volumes before/after porting to establish the correct pressure ratios based off volume and also determining desired compression(cylinder/crankcase compression), a high quality grinder with diamond bits for around the ports and carbide for the aluminum, and these are just the starter tools

I have intrinsic knowledge with RC nitro engines which are extremely precise and sensitive motors when it comes to calculating power output and porting which I consider myself to be quite adept when it comes to this type of work, and besides these Chinese motors will not benefit from any porting as the motors themselves are not built for power, but for economy, do not waste time porting and blowing parts up

the exhaust port is responsible for your final rpm and some people go crazy with its size and wonder why the engine blew up, leave these engines alone, because they are fine for modest gains with a cylinder head compression boost and really good carburetor needle tuning with a decent tuned pipe setup

look towards a gilardoni 75cc hybrid set up and have some safe fun there
Really, don't waste time porting these engines. lol you're making me laugh cuz you think you know what you're talking about when in fact you don't have a clue.There are big gains in porting these motors, everyone does it because it works..
 

Skarrd

Member
Oct 13, 2010
501
1
18
30
Chandler, AZ
Really, don't waste time porting these engines. lol you're making me laugh cuz you think you know what you're talking about when in fact you don't have a clue.There are big gains in porting these motors, everyone does it because it works..
Nice contradiction there. "Don't waste time porting these engines"
Followed by
"There are big gains in porting these motors"


Um... Wat???
 

javy mcdees

Active Member
Jul 30, 2018
143
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Nice contradiction there. "Don't waste time porting these engines"
Followed by
"There are big gains in porting these motors"


Um... Wat???
dance1 the unported cylinder makes good torque for half the engine rpm if you have it tuned up good. yea 40 mph tops vibrating up a storm but will cruise nice at 25/30 mph all day, with that being said who da fuh wants that nonsense! xct2 Found a decent/not perfect $15 dollar ported cylinder on a shelf with 20 other ones to pick out of cleaned it up a bit and grinded up a piston and she has a power band now like it should and vibrations way down. Fun project! FYI those 415H chains the master links fall off so better to mod the chain and weld the pins
 

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Racin8de

New Member
Jun 15, 2018
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i said it earlier, match porting the intake and exhaust flanges will give you a big increase in performance. or at least, in drive-ability.

i've matched transfer ports, and cleaned up burrs on engines, but i haven't gone as far as trimming piston skirts, or other internal mods. i'm not afraid to, i just haven't had to. there's simple mods you can do, and you don't even have to finesse it with special tools. i mean, i use a dewalt cordless drill and some grinder bits for everything. i don't even trace out the amount of meat i have to grind off an intake anymore, i just go at it with the drill.

like DTG said, these ain't RC motors with high tolerances. they're 1900's technology, stolen by the russians, then copied by the chinese. it's an (at least) 3rd bastardized generation stump puller motor. and it's cheap. don't be afraid to experiment with it.

i build, ride, and race, the fastest 2 stroke china dolls around right now, and it really ain't that easy to make it go fast, last a long time, and exceed all your expectations.

and, for the record, the only major mods on my race bike is reversing the jug, so the carb's in front and the exhaust is out back,, then matching the ports, and "blueprinting" it all. i still have the NT carb and the stock exhaust. yeah, i tweaked everything a bit, but i lapped everyone at the deathrace with their shift kits, expansion chambers, etc...

and i'm just getting started. wait till the willow springs race...:)
**** Yes, I agree with Bairdco 100%, so far I only matched my exhaust and intake and I've seen a pretty decent amount of response with my 120.00 China Girl.. They are cheap but also to have fun with & experiment....I've seen guys make some ridiculously silly mods with upgraded parts and they run like absolute sht..
 

Tool Dog

New Member
Dec 14, 2018
2
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Hartford CT
I hear people talking about porting all the time. I see pictures of ported motors - and they're using stock exhaust and stock intakes.

If you're going to port, wouldn't you need to use a modified exhaust and intake that actually matched the head porting?

I plan to first modify my exhaust to match the original intake port, then modify the intake to match the intake port, noting performance increase from each.
The first thing you want to do is blue print the engine to the manufactures specifications.
 

Tool Dog

New Member
Dec 14, 2018
2
0
1
48
Hartford CT
In my personal case, and I've heard this a lot of other places, The 'porting' I did to my HT motor was mainly corrective. In it's stock setup, There was almost a 1/4" difference in BDC piston height vs the floor of the exhaust port. And at the other end of the stroke, the piston skirt was covering almost half my intake port.
On top of that, the transfer cutouts on the piston didn't match the cylinder cutouts at all, The transfers had massive amounts of slag and plating flaws in their ceilings, the exhaust port had a bad ridge on the ceiling, the intake was slagged up, and there was no bevel on ANY of the ports.
After correcting all of that and enlarging the intake and exhaust manifold throats, I've gone from a motor that's adequite in the low and mid ranges, and anemic at the top end (In some cases, nearly dead approaching top end) to a motor that needs help getting up to speed but has a power band that feels like it's never going to end.

This is with the stock pipe and a modified stock carb. Had to fabricate an aluminum spacer for the bottom end and copper gaskets all around. I have a puch HiHi 50cc moped head coming in from treatland that I'm going to experiment with next, and work my way up from there. My trike needs to be dismantled, and I could theoretically snag the Dellorto clone carb and tuned exhaust off that.

Long story way short: Porting and cleanup on these motors should be done even if you're using stock parts. Heh. Especially if you're using stock parts. I've noticed a dramatic increase in usable power and this is the first motor I've ever ported. My belief now is that the bottleneck lies not with the carb or exhaust, but with the sloppy castings and Zero finish work these engines receive.

The additude that performance comes from expensive aftermarket parts has always puzzled me. I'll rack it up to the aftermarket stuff being shinier.
Before you go out and buy expensive after market you must first know what you have to work with the only way to do this is to go through your stock motor and make sure everything lines up ports and to remove casting defects. You also want to make sure your engine is up to manufactures specifications before starting any modifications.