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Coljones
01-09-2009, 09:15 AM
My Euro3 spec bike has a VHST carb fitted with a Throttle Position Sensor, but as it's fitted to a carb instead of a fuel injector this can only be telling the ecu to trim the ignition according to throttle openings, "I think" but don't know, as I'm in the dark about what it actually does as it's fitted by Aprilia and not Dellorto!

I'd like to know if it only helps to control the idle or the additional air system as I'd like to run without it for racing.

Any suggestions appreciated.

HONDARACER
01-09-2009, 05:32 PM
http://www3.telus.net/smokeskull/RS125-RACE.PDF
Theofficial race setup guide for the new style RS

Coljones
01-09-2009, 07:39 PM
http://www3.telus.net/smokeskull/RS125-RACE.PDF
Theofficial race setup guide for the new style RS

Thanks but I de-restricted the bike according to that document.

I suppose I could run the engine at fixed revs with a timing light attached to the HT lead and the TPS detached from the carb and manipulate it's lever to see what happens to the ignition point.

It's one of those frustrating things where you can't form a judgment because you lack the information on which to base one.

bourney2007
01-10-2009, 09:09 AM
not meaning to take the piss or anything and i'm probably wrong but are you sure it's a throttle position sensor and not a carb heater??

I have never seen the carb before so i'm just stabbing in the dark really. Just a suggestion.

Like you say i can't think of a reason that a throttle position sensor would be fitted to it. As you say the only thing it could be doing is trimming the ignition timing.

I'm not sure but i'd really like to know lol. Let me know when you find out what it does.

williamr
01-10-2009, 09:27 AM
Used to be that with distributor ignition systems a vacum take off from the manifold was used to move the points mounting plate to retard the ignition when the throttle was opened for acceleration.

I always thought that using a TPS in addition to the revs as inputs to the ignition map was a good idea. Could be what this is for. On a carb without an accelerator pump (most small bike carbs) it could add a useful boost to the throttle response.

Rob

Coljones
01-11-2009, 09:45 AM
Thanks for the interest.

It is a TPS (shown as part number 8 and on top of the carb in the attached line drawing) it has a lever, not shown, which is actuated by movement of the slide.

My VHST carb also has a choke and a heater. I'm trying to get more information on this but can't find any yet on Dellorto's site!!??

HONDARACER
01-11-2009, 01:07 PM
I guess we need someone with a dyno to make a run or 2 with it unhooked to see if it makes any difference.

random0082
01-11-2009, 03:45 PM
Id just fit a 34mm carb and get rid of all that crap. same with a lot of things on the RS, strip it all out if you dont need it, simpler and less to go wrong

Raceboy
08-14-2009, 09:14 PM
http://www3.telus.net/smokeskull/RS125-RACE.PDF
Theofficial race setup guide for the new style RS

This link is broken, anyone know the new link or post the info.

Cheers,
Raceboy

STEPHEND161
04-03-2010, 06:56 PM
this should work hopefully

http://www.scribd.com/doc/8522656/Rs125-Race-Derestrict-an-aprilia-rs-125-2006-Euro-3