Aprilia Classic 125

[Erikas]

Hey guys, as you see I'm new here. I just got into this biking stuff, it was a dream since I was little.

So as you can see from the title, for my first bike I got Aprilia Classic 125cc. I had some fuel problems, but its resolved now.

Is there anybody who has this motorcycle as well? (its a 2t motor)
Sometimes driving I get really bad max speed, etc sometimes in 3rd gear it can reach around 60-70km/h, and other times when I get my Revs up high, it does not do it. 5th gear 80km/h. Its like sometimes it gets a boost, and sometimes it does not. Any ideas?

[Kickstart]

Hi

Does it have a power valve fitted? The blade for the power valve used in many Aprilias can stick (especially if used at low speed a lot - such as running in). If it is still a bit free then generally easy to remove and clean up.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Erikas]

[Erikas]

Figured it out, but im afraid to take the engine apart.

[Kickstart]

Hi

The power valve is a blade that does into the barrel above the exhaust, at about a 45 degree angle. It moves to open at about 8000rpm, and works to effectively move the top of the exhaust port (variable valve timing).

On early versions of the power valve system (plus those used in some karts) it is pneumatic, and works off exhaust gas pressure. Later versions have a solenoid to open the valve, and with these you will find a cable from the valve to the solenoid.

I am not sure if the Aprilia Classic had a power valve or not (they were fitted to the Red Rose which was the older cruiser style bike). But if they stick then performance will tail off at about 8000rpm, while when working the power would pick up around then. They can also stick open, at which point you have little low down power, but then the power kicks in at higher revs (when you are in the mood for it, quite fun that way).

To clean it you don't need to take the engine apart. 2 allen key bolts and it should pull out. Then push the valve into its housing and turn 180 degrees and you can unhook the blade from the cable (there is window in the housing to enable you to do this, which should be covered by a rubber boot)

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Erikas]

As I've heard that Classic 125 motor is the same (or almost) as an RS125. So I wondered, are there any minor improvements for the motor to increase its power? Now its a 125cc 8kw motor.

[Kickstart]

Hi

Is it a 122 or 123 engine? I suspect it is a fairly recent bike (last 15 years or so) and so a 122 engine. If 8kW and fairly recent I suspect it has no power valve (and possibly no provision for one to be fitted).

With a 2 stroke the exhaust is the important bit.

The power valve would likely help. I would suspect that even without the provision for one you could swap the complete top end of the engine for one with provision for a power valve. It would likely be difficult to fit a later electronic valve (ie, trying to wire it in), but the older pneumatic valve would likely be easy (they are fairly easy to buy as they are used on the Rotax Max kart engine).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Erikas]

[Erikas]

Or i might been mislead. The problem is im currently not able to go to the garage on my own. When I will be able to, I'll ask some more questions.

[Erikas]

https://i1371.photobucket.com/albums/ag313/Igoriz/2014-05-19141125_zps5521be81.jpg

What could be the problem, it got stuck in this posistion. Should I just pull it out?

[Erikas]

https://i1371.photobucket.com/albums/ag313/Igoriz/2014-05-19140358_zpsf22052e6.jpg

This is the engine. Dont know if its a 122 or a 123.

[Kickstart]

Hi

Probably a 123 (check the coil - if it is blue then that pretty much confirms it).

As to the power valve, spray a bit of penetrating oil on the blade and push it back in. Then pull out again, and keep at it. Better to move it many times that try and pull it hard (it is not unknown for the pin to snap off the blade). Keeping pushing it in and out and it should come lose fairly easily. Then give it a good clean up.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Erikas]

Cleaned it up, all good. Thanks.

Are there any other things/improvements/clean ups I could do to improve driving performance?

[Erikas]

Another questions, should the valve's blade should be pointing up, or down?

Edit:

Is there any way to put in a RPM gauge?

[Kickstart]

Hi

Not much. Exhaust is the important bit, but without ruining the look not sure you can change that easily and not sure how good the standard one is. It isn't really a bike designed for performance.

The blade should go in such that the engine end of it is horizontal. Ie like this \_\ not like this \|

As to a rev counter, the 123 engine was normally set up for a cable one. Short of an inductive one off the HT lead that is probably the easiest way to go but not sure how you can get it to look neat.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Erikas]

Does my bake have CDI?

https://i1371.photobucket.com/albums/ag313/Igoriz/2014-05-20105545_zpsf0a7edc2.jpg And is this the right way?

[stevo as b4]

I would have thought a Rotax 123 of this age with working powervalve and the std 28mm carb would be around 28bhp or more at the crank? I can't see why Aprilia would de-tune it much over std if they were sticking this engine into a cruiser style bike? And from what I've seen they have a nice fat expansion chamber lie the RS125, just with a different stinger/tailpipe and silencer.

If it's running right and not restricted it should feel quite exciting and pokey for a 125cc, If the way my 24bhp KMX125 feels is anything to go by?

[andy_uk]

[Kickstart]

Hi

If a 123 engine then it probably has the SEM ignition and no separate cdi unit.

Can't tell from the photo which way up the blade is in that photo I am afraid.

As to the 123 engine, in the Sintesi with a standard 28mm carb they made about 22hp at the back wheel.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stevo as b4]

A 2smoke cruiser with 22bhp at the rear tyre should feel lively and fun enough for 125cc. I know it would probably be a bit heavier than my KMX, but 24bhp (say 20bhp r/w) and 98kg dry, means it feels light and quite eager when you give it some. I'm not disappointed at all, and indeed on std gearing it pulls well enough to make the front wheel go light at 5-6k rpm and is useful from under 4000rpm.

In some ways the laid back position of a cruiser should feel oddly quick with 22bhp more so than an AF1 with its far more capable chassis and grippy fat tyres etc.

[Kickstart]

Hi

Suspect the classic is a fair bit heavier (only figure I have is 145kg dry), and not sure they used the 28mm carb rather than something smaller.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[andy_uk]

The unrestricted versions use the PHBH28 and the restricted ones have a PHBL24
I'm not sure of the BHP of the full power version, but the restricted one is supposed to be 15bhp (11KW).

As far as weight goes...they're around 150kg wet.

(also just checked the engines and they only ever used the Rotax 122)
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[Erikas]

[Erikas]

https://www.youtube.com/watch?v=9R--adlTXhM The speed on this one is incredible, mines max is 100...

[Erikas]

https://i1371.photobucket.com/albums/ag313/Igoriz/2014-05-21215903_zpsbdd1498b.jpg Whats this? It says DUCATI Energia on the side.

https://i1371.photobucket.com/albums/ag313/Igoriz/2014-05-21215929_zpsc148a0b8.jpg This also?