"Old Fashoned" tuning/performance?

[Matthew Duncan]

So, nowadays if you want more performance you go to a shop and get a remapped CDI, powercommander, performance de-cat exhaust etc..

What are the old fashoned style tips to get the most out of an engine in your own garage?

Stuff like valve lapping/polishing, Porting and Polishing.... the stuff that doesnt reley on fancy electronics and computer software.

Just out of curiousity cos i have an old 125 engine that im looking to put into a go kart - and i know im not going to get 120 mph out it...

thanks,

Matt

[JimR]

Get a copy of tuning for speed by Phil Iriving well worth a read

[DaftAlly]

You didn't say how old the engine is but if it's less than 20-30 years old It probably has transistorized ignition which means the box of tricks holds the ignition map.

Generally, nobody went to the trouble of creating a new map, burning it onto the chip and the soldering the new chip into the circuit board. Only professional tuners may go to these lengths and even then that would be valid only if cams and possibly pistons were changed.

Generally speaking an ignition advancer rotor and a session on a dynamometer which may involve adjustments or jet changes to the carburettors would be the equivalent of a remap.

The ignition advance rotor is used to advance the static ignition timing for higher octane fuel as many engines were built to accept as low as 91 RON fuel for countries where only low octane was available or to take account of altitude variations.

Machining and different camshaft lift and duration is still performed to significantly alter 4 stroke engine characteristics.

[slice]

What you did Matthew was get out the drill & polish all the crap off the inside of the ports then hone your valves to within an inch of their lives (if you have any) polish the pistons get the barrels chromed and drill the con rods to make them lighter, used to be called STAGE 5 TUNING I think, at least when I was racing anyway, then go lay down and try not to cry when you got the bill .

[dt502001]

Most mods only shorten the life of the eng. but a good cleaning of any flashing in the intake and exhaust,shave the head to bump compression, reseating the valves is a fairly safe and cheap way to get a small hp increase. If it has a spring type of mechanical advance for the ignition you can play with different spring tension to speed the advance or slow. Slotting the cam sprocket so you can alter the cam timming. lighting the piston by removing material from the inside or shorting the length,indexing the spark plug so that the open part of the electrode is facing the intake valve ( shims required). Change the length of the intake short for quick high reving eng's and long for low rev torquey motors,pollishing the intake and bore of the carb.

2t's stuffing the crank case with cork and altering port heights/timming has been played with to the point nobody has a1 rule that works for all

But most mods you loose something to gain something so first you need to know where you want the eng to work better,like are you going to be on a track where it will be at red line most of the time or a short track where you will need alot of bottem end torque to get out of corners.

The easiets way to get 2-3 hp is to run true race fuel expensive but if your not using it for transportation not that bad here about 2x the cost of pump,just dont leave it in the carb ,only put in what you will use and drain every time what you dont use and store in the steel container.

Or for some real fun add NoX and watch parts melt,grenade when you throw a 15 hp shot of NoX on a 125

windage trays in the sump,scrapers to keep oil from flinging around,knifeing the crank to get it to cut through the oil easier.Shot peening and pollishing the rods to harden,lighting the stator to get it to rev quicker or making it heavier for more torque in the bottom rev range all this stuff is for building a motor to work better in a single application.

[Cynic]

The most effective tuning I have found is a decent service.

Then make sure the chassis is good. Dragging brakes and a bad chain could eat 30% of your power.