Anyone got any advice for porting.

[Powerwheelie]

Iv already had a mild tune done on my Rotax 122 Cylinder.

But a few people said i should have a go myself.

So i read up on it and i just want to make more power in the same powerband so that means i dont make the ports taller but still got any advice.

Bikes a Aprilia RS 125

Spec atm is: Mild ported cylinder, VHM Flat top head, Wiseco Flat top single ring piston, Arrow full exhaust and a Dellorto VHSB 34mm Carb.

Any advice for making more power please. And the bike is a track bike.

[cagimaha]

Rather than getting into the porting you may be better off "blueprinting" the engine if this hasnt been done already. This involves correcting any innacuracies that may have occured during the engines initial manufacture. This includes: setting the squish (distance between the piston crown and head at TDC), checking that the combustion chamber is centered on the cylinder, trimming gaskets so that transfers and reeds are not masked by any excess gasket, smoothing any ridges left on the intake rubber from casting, matching the transfer ports in the barrel to those in the crankcases, polishing the exhaust port to reduce carbon build up and make it easier to remove the carbon when it does build up, making sure the crank is within tolerance. If you have done this then I would reccomend having a look at "Performance Two-Stroke Tuning" by Alexander Bell which goes through all of the principles of porting a two-stroke. Most of the examples he uses are a little out of date now but the principles still stand. Hope this helps, Ben.

[Powerwheelie]

Cheers iv had most of them done but they made little difference. I'll have a look at the book mate cheers.

[spacemonkey]

Cheers iv had most of them done but they made little difference. I'll have a look at the book mate cheers.

A bit of nitrous?

Or a decent ignition.... I reckon there would be quite a bit to be gained on the ignition side of things.

[mgtkr1]

not familiar with thew rotax engines but getting the head/squish correct for the fuel you run helps reliability aswell as power. anything that isnt smooth want smoothing for better spread and power delivery. this inc steps where the cases meet the barrel and also the lugs on the bottopm of the barrel can be reshaped to aid the charge toward the transfers rather than just been there doing nothing in particular. it applies to a lot of crank case inducted 2 strokes. the ports should not be polished rather have a frosted finish to improve the charge mixing up and flow. polishing ports for hp is mythical although polishing the combustion chamber/ex port reduces carbon build up. often raising ports, widening them gives more power but do things bit at a time. easy to forget that metal cannot be put back but can be removed at a later date. unl;ess you have experience, never remover the limit port area/bore size. a good idea is to look at gp port maps of engines the same cc and just as important bore/stroke. remember to account for your high rev killing std ignition though. no use having a motor that makes its best power beyond were the ignition wants to play. a good ignition may be a good idea as would a pipe designed top work with your engines requirement. id get a spare motor and have a play with than. ex with heads/porting configurations ect and be prepared for tears/smiles and a super fast responsive lefdt hand!! as also pointed out, have a good read of as many two stroke tuning books/articles as poss. john robinson and graham bell's books are legendry in that there full of good old tuning priciples. any self respecting 2 stroke owner is aware of these books.

[Powerwheelie]

Well atm it makes peak power at about 11000 RPM and dies off at about 12500 which is where the ignition is killed.

On my last trackday the bike was totally standard and over the winter months i bought all that and only rode it on the road.

Still having problems setting the carb up as it's just oiling plugs up atm but i think thats because its got too much oil as im running Pre-Mix.

Does anyone have experiance with 125 2 Stroke ports and any idea what ports need opening up ?

Do you reckon bob farnham would give me some tips or will he keep his magic to himself.

[spacemonkey]

Do you reckon bob farnham would give me some tips or will he keep his magic to himself.

Hehe.. What do you reckon you'd do if you were in his shoes?

[mgtkr1]

bob farnham? nah he wont help. stan stevens on the other hand, just be sure to ring his lower rate number, he really gets monk on whenm you ring his 3.00 a min line just to chat tuning....