Kawasaki Sportsbike Riders Club - Australia - Online Forum

who's had their head ported/polished, who did it and what did it cost you, and do you know what the power gains were?

no, this is not a result of the gixxer's somewhat lacklustre dyno day showing...

I, being the engineer I am, always get confused about this polishing of ports............
surely the idea of the ports is to allow a premixed fuel / air mixture into the combustion chamber.........therefore the rougher the casting the more turbulent the air flow hence the better the mixing ???

Rossi wrote:I, being the engineer I am, always get confused about this polishing of ports............
surely the idea of the ports is to allow a premixed fuel / air mixture into the combustion chamber.........therefore the rougher the casting the more turbulent the air flow hence the better the mixing ???

on the contrary.. the more turbulence the less efficient the bang is.. if i'm right, the air/fuel gets mixed a certain way and goes into the combustion chamber nice and smooth or something like that and then you have a bang which creates the most power. i'm no expert in this topic, just going on memory from what i've read in automotive articles so i could either be wrong on some counts or all!

i've had a few quick cars but never got round to having such a thing done so i'm giving some thought to getting the gixxer's done at some point, more out of curiousity as to the hp gain really, than to win dyno shootouts...

I believe that 4 strokes are diiferent to 2 strokes with regards to porting and polishing. With 2 strokes the generally preferred method at the moment is to have the porting done, but leave the polishing.

I'm no expert on such matters, but my understanding is that a rougher surface promotes fuel atomization. If the port is polished then the air/fuel turbulence in the port is massively reduced and can cause the fuel to pool on the walls of the ports.

It's far more complicated than it my first seem and simply taking to it with a die grinder isn't really the best option. Once you add fuel injection into the mix, then it complicates things even further.

Dave, if you want the work done, make sure you find someone who is experienced in such matters and that they have a flow meter.

oh i wasnt planning on doing it myself! im just doing as much homework as i can before i commit to anything.

Go and speak to Col Linney at 10/10ths Performance - I think it is near Liverpool ?? He can do the sort of modifications you are looking for, and can tailor the mods to suit *your* particular needs.

Porting - generally refers to the removal of any casting imperfections in the inlet tract ( both 2T and 4T). May include enlarging and/or reshaping the inlet tract for bigger carbies etc. Also refers to the re-shaping / removing of cylinder wall material (2T only}, to change the 'timing' of the ports. In 4T motors, can include re-shaping of the inlet tract around the valve-guide casting. There are often a lot of power gains to be had by re-shaping the area directly behind the valve head, and around the area of the valve-guide casting.

Polishing - exhaust ports can benefit from polishing, to remove old carbon deposits (both 2T and 4T). But re-shaping the exhaust port (generally but not always filling up the 'floor' of the port) results in more power gains. In 2T engines, polishing the exhaust port will help reduce the build-up of carbon (which can eventually restrict exhaust flow and cause significant power losses), so polishing the zorst is more of a 'preventative' measure than a 'horsepower' measure.

Polishing inlet tracts on either 2T or 4T is not recommended, for reasons already covered in previous posts.

I had Dave McClurg from Albion bike wreckers do the head on my 12 (no polishing was done, as aardvark said it aids fuel atomisation) the inlets are like looking into a bucket with the bottom cut out there just massive there was a fair bit of work done around the valve a supposedly special valve job, the way he cuts and reseats the valves, and alot of effort to get the exh. to flow better thats were they're let down. Sheet from the flow bench, cams profiled, basically organised the rest of the motor, supplied JE pistons all for 2k. This is the first bike engine that i've had work like this done on and it sounded more than reasonable to me.

So what difference did it make Chuffed?

Still waiting on my rods, ordered them from the states and they stuffed up the order they're supposed to be here by the end of the week, then we can start putting it back together No idea what sort of power its gunna make...... just cant wait to get out there and wring its neck, after ive run it in.

gixxerdave wrote: on the contrary.. the more turbulence the less efficient the bang is.. if i'm right, the air/fuel gets mixed a certain way and goes into the combustion chamber nice and smooth or something like that and then you have a bang which creates the most power.

Ok, im simple terms. The bigger the bang, the less power you get. What we're are is a fast and hot, but controlled burn. A bang is detonation which will b eterminal. Ok, pedantic rant over.

In reallity you are both right. The rough casting of a stock engine does help keep the mixture mixed, paricularly at lower engine speeds. However ultimatley an engine is only an air pump. The more air you can get in and out, the more power you can potentially make. so to make the most grunt you need to get a nice smooth flow of air through the ports. But this smooth flow will highlight any insufficentcies in jetting or injector timing. Once an engine has been polished, let alone ported, fuel metering needs to be spot on. There is no point polishing the ports if you're not going to re-tune fuel metering. It is possible, i know coz I've done it, to polish ports a find the engine becomes wooly at lower speeds.
It's also worth noting that if you increase the max air flow of the ports, the air spped will drop at lower engine sppeeds and my result i the fuel seperting from the air again. As with mosthings, it's about compremise. the more max grunt you make, the less drivability you get.

Then you can play with runner lengths, velocity stacks, swirled valves, piston crown shapes primary header length and the list goes on and on and on. For the money involved, I'd recomend bying a stat write off thou and retro fitting the engine and electronics. As much if not more grunt, and factory reliabilty, and probably less. Plus it'll still be a breeze to service and get parts for.

To make my point, I'm currently trying to secure a 10r gumby motor and electronics to shoe horn into one of my 7r's.

just my two cents. But good luck no matter what ypou decide. It's great to have some real threads on here from time to time.

Let us know how you go.

Hmmm.... upgrade if ur mot on a thou already though. For some reason i thought you were on a middle weight gixxer.