View Full Version : Has anyone tried the 300cc conversion ?

11-22-2011, 04:41 AM

If as it seems the TSS-500 thing is all in a mess, I'm wondering if this might be a safer / cheaper / more sensible alternative.

Questions :

1. will it work with the standard airbox / carbs / ignition ?

2. how about exhausts, would we need new ones for this ?



11-22-2011, 01:47 PM
it seems very expensive that 300cc kit, better do it in your own

a bigger airbox is very useful for the 250cc,i guess it should be considered.

search the Wiseco pistons for bigger overbore (300cc) and Woessner for light version (270cc)

11-22-2011, 02:12 PM
I have the Stan Stephens stage 3, 300 kit. I think this is the exact same one that tuning works is offering.
The only issue i have had is dealing with high temps so i have egt's and cht guages. Shouldn't be a problem in colder climates.
I'm not sure this kit is worth the effort for a street bike!

11-22-2011, 04:18 PM
I've also had the Stan Stephens 300cc mod done. Works like a charm! Only minor when overboring an engine is that it runs flat on overrev. A visit to Carmo Electronics in Helmond (Holland) solved this problem. They adjusted the CDI unit by stretching the advance curve (with 1.500 RPM) which made the bike rev better than before (also works like a charm on standard 250cc engines)!
http://www.carmo.nl/index.php?language=en Just contact them by giving them an e-mail, and get good service from Robert!
Also look here for an earlier reply from me: http://www.apriliaforum.com/forums/showthread.php?t=162276&highlight=300&page=2 with a dynoprint of a standard engine.

11-22-2011, 08:31 PM
cheaper / more sensible alternative.From what I've seen, to be truly effective, it requires larger carbs, airbox, and a programmable ignition system. Those don't really add a lot to the cost, but they're worth factoring in.

Most of the failures they suffer appear to be related to ignoring those things. Much like most RS250 failures relate to ignoring maintenance/tuning.

12-02-2011, 02:57 AM
I have the Stan Stephens stage 3, 300 kit. I think this is the exact same one that tuning works is offering.

You're right. Stan asked me to carry them on now he has stopped doing them, enabling a bit of support for those who already bought his kit over the years.