Porting!

Mini Dirt Bikes & Pit Bikes Forum

Help Support Mini Dirt Bikes & Pit Bikes Forum:

kesman20

Member
Joined
Jul 1, 2008
Messages
8
Reaction score
0
new design. ok?
very good performance 1/8 mile 10 seg
my.php

ImageShack - Image Hosting :: p1030729x.jpg
 
Last edited:

KVracing

Member
Joined
Apr 20, 2009
Messages
8
Reaction score
0
There! Now I have read this whole fucking topic! hehe xD You will really learn a lot of porting by reading this topic. And thanks to Mack for gd input! But about the "homework" link, I think this motoman from mototuneusa has ritierd, I think it's a old website..

I read about porting at wikipedia, and exept from a lot of words, it really was gd, so chekk it out; en.wikipedia.org/wiki/Porting_(engine)

Peace to us tuners xP
 

robbo23

Active Member
Joined
Jun 4, 2009
Messages
35
Reaction score
0
hey guys could someone put some pics up to help me with the porting process.cheers
 

KVracing

Member
Joined
Apr 20, 2009
Messages
8
Reaction score
0
Lol, there is like 16 pages of gd info and a lot of pics xD

Stupid quesion..
 

sean01

Legend Spanner Spinner
Joined
May 27, 2007
Messages
5,934
Reaction score
120
Location
burpengary, brisbane
good to see alot of ppl giving it a go.

but i see alot of ppl are polishing the hell out of there intake ports.....

ppl stop polishing your intake ports, your doin nothing more than destroying your port work...
use no less than 120grit paper, ideally 60-80grit should be used.

the rough port walls are used to atomize the fuel...
 

50 nut

Well-Known Member
Joined
Apr 16, 2009
Messages
133
Reaction score
2
Dude that head wont last long before you drop a valve, you have taken all the meat away from valve allowing it to float under big revs meaning it will be tears....
 

no_crf50_here

Well-Known Member
Joined
Oct 7, 2007
Messages
2,342
Reaction score
37
Location
Brisbane, QLd Australia
Dafunk has his head the same way for months with out issue in his 140cc motard and still going strong. so time will tell. :)

I feel my motors last ages considering how i ride :)

I have more dyno time on thrus & friday, so might try that head on friday
 

dafunk

Well-Known Member
Joined
Jan 19, 2008
Messages
445
Reaction score
6
Location
qld
my head is similar not the same .true it hasnt had problems yet .the 125 has been similar for a long time with no problems , but it has much smaller valves.
but yeah some of the valve guide is gone. i dont think there will be a problem .
will be great to see dyno results.
 

no_crf50_here

Well-Known Member
Joined
Oct 7, 2007
Messages
2,342
Reaction score
37
Location
Brisbane, QLd Australia
This is the head i got from Akuna the other day and is currently fitted to my bike
Exhaust
SNC00331_small.jpg

Intake
SNC00334_small.jpg


Valve sizes only 1mm bigger but seems to make a nice little difference over the stock YX head (Intake 28mm exhaust 24mm) Left Stock YX on right
SNC00329_small.jpg
 
Last edited:

sean01

Legend Spanner Spinner
Joined
May 27, 2007
Messages
5,934
Reaction score
120
Location
burpengary, brisbane
i did a yx150 last week. did the same on the guide boss's as that left the standard size valves tho.i polished up the exhaust port a little more tho...didnt have time to take pics as it was for a bike that was getting a new engine for the hri rd 6.

ported it Wednesday and engine was built and running thursday night..
195cc....man its got some stink...
shame we were having carb troubles on race day....
 

sean01

Legend Spanner Spinner
Joined
May 27, 2007
Messages
5,934
Reaction score
120
Location
burpengary, brisbane
is that your own port work?

seems they have been semi polished on the intake and chamber...was there a reason for that? methanol?
 

Cactus Jack

Master Spanner Spinner
Joined
Jan 18, 2007
Messages
2,743
Reaction score
53
No it's not my own work ... but he knows exactly what he's doing since he's a professional head porter ...

http://tinyurl.com/HEAD-ON-FLOW-BENCH

http://tinyurl.com/HEAD-ON-FLOW-BENCH-2

I do my heads pretty similar ... I learnt to how to do them gradually in stages using stop watch testing of the engine in an actual bike ... no imaginary power gains ... IF fuel was falling out and clinging to the port walls as some people claim ... they'd be brown stained or coated with carbon ... instead there's only a very small stained patch on the valve throat ... right behind the valve stem ...

http://tinyurl.com/XR75-STOCK-VS-PORTED

http://tinyurl.com/XR75-PORTED-INTAKE

http://tinyurl.com/XR75-COMBUSTION-CHAMBERS
 

sean01

Legend Spanner Spinner
Joined
May 27, 2007
Messages
5,934
Reaction score
120
Location
burpengary, brisbane
very nice work.
i remember the dayz of the xr75...not many getting around my neck of the woods anymore...tho i do know of 1 that is highly modified...xr100 head...and some cdi ignition from some other engine.. not sure on the engine size, but on a flat track it keeps up with cr85's (hard to believe i know)and the kid riding it is the heaviest kid there...
lol to look at it its hard to see the xr75 there..
 

themountain

Well-Known Member
Joined
Mar 2, 2007
Messages
1,334
Reaction score
25
looking good...intake is almost square...nicely done....did you work on the valve seats also??
 

sean01

Legend Spanner Spinner
Joined
May 27, 2007
Messages
5,934
Reaction score
120
Location
burpengary, brisbane
nah no valve seat work, head is only about 5hrs old i think...but the ports/inserts are taken out nearly to the valve seat

just re-lapped them in before assembly
 

Latest posts

Top