Problematic RX125

[Mik_RX125]

I've got a Aprilia RX125 and it has problems getting past 5000rpm if I have just been ticking over the engine (i.e. at traffic lights) then want to go fast. It only seems to have this problem in the first 3 gears, then it seems to "unstick" and will pull wheelies at 60mph.
Can anyone help please?
btw its a 1995 import which has a Rotax 123 engine like the older RS's.
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Yamaha FZ6 Fazer S2 owner
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[Kickstart]

Hi

Tends to suggest the power valve might be sticking, but that would tend to limit it to around a useful 8000rpm.

Probably worth giving it a good going over, cleaning the carb out, checking the timing, checking the compression, cleaning the exhaust out.

All the best

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

[Mik_RX125]

This bike has been stripped nearly every other weekend when I have had the time so these are all the things I have done since I bought it in November:
Stripped the carb, floats set, jets blasted.
New racing plug (only cos the bike shop recomends them)
Rave valve removed, cleaned, and replaced several times.
Gear shaft seals replaced
Brakes stripped
New chain and sprockets

My bike should have 2 powerbands one at 5000rpm and another more powerful one at around 7000rpm, but at the moment I only get the more powerful one with the first one becoming a barrier which stops me accelerating for about 5-10 secs before getting any power.
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Kickstart]

Hi

The powervalve opens at about 8000rpm, and there will not be much of a pick up in the power delivery until then.

Does it have the electronic or the pneumatic power valve? I would guess the electronic but just making sure.

One thing you can try is to disconnect the kill switch circuit. Find the orange wire that goes from the coil (joins to a red / white wire) and disconnect it and tape it up. Then try riding it. Note that when you flick the kill switch or turn off the ignition it will continue to run like this. The kill switch / ignition switch turn the engine off by grounding this wire, but if they are breaking down then they can have odd effects on the bike. Had a Gilera doing much the same as your bike due to an ignition switch.

Also check the jetting in the carb. Is it the 34mm carb? Which position is the clip on the needle jet?

All the best

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

[Mik_RX125]

It has an electronic solenoid powervalve on it.
I'll try that thing with the coil tomorrow after college hopefully. Though my bike doesn't have a kill switch as this is a basic off-roader really.
The carb is the VHSB 34LD but again I'll have to check the clip tomorrow or Wednesday.
Thanks for the tips
Mik
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Mik_RX125]

I found part of the problem, the powervalve was covered in carbon and so it was sticking. Had to chizzel it off then just use copper grease on it. Works like a dream now. I'll just have to clean it every other week to keep it in tip-top condition.
Also got my side stand fixed as it snapped on the way to college when it was raining last week.
I disconnected the kill switch but it just stopped me from turning the bike off. I would check the clip on the carb but tbh I can't be bothered till at least the weekend.
Thanks for the help

Mik
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Kickstart]

Hi

The sticking power valve might well be the problem. Think you are meant to lube them with 2 stroke oil. Make sure it is in the right way up (dealers get it wrong sometimes as it is different to the way the restricted blanking plate goes).

All the best

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

[Mik_RX125]

ARGH!! Its so annoying!!
Started my bike outside college today and it was fine. Just about to set off, knocked it into gear and it just died! It did this 4 times, so I had to keep the revs up all the way home, but still had to bump start it 4-5 times on the 7 mile trip.
I think it could be the kill switch shorting with it being in the rain all day.
I have no idea which way round the Powervalve is meant to go, but I have always put it in the same way it came out. Which is where the side with the slanted bottom is facing the engine block.
I'll probably strip the engine this summer after the Accrington MCC Rally in May, as I don't think is has every been done before, just to clean all the muck out. Ready for the many trips to Rivington over the summer

Mik
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Kickstart]

Hi

It should be shorter side down, longer side up, so the bit at the end is horizontal rather than vertical. I think this is the opposite way to how you have it at the moment.

\ \
\_\ = OK

\ \
\¦ = Wrong

If it is playing up in the rain consider replacing the plug cap and lead as these are cheap and easy to do, and less painful than finding out that it is shorting out in the rain .

All the best

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

[Mik_RX125]

I'm not quite sure what your pics mean but this is how it is at the moment:
[1]
._
| | This side
| | goes to the
.\| exhaust

But it could go like this, but it makes it impossible to attach the cable to the RAVE solenoid.

[2]
._
| | This side
| | goes to the
|/ exhaust

Mik
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Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Mik_RX125]

Could someone please tell me which way round the powervalve goes in to the engine ?

Mik
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Kickstart]

Hi

Sorry I did not reply earlier. I was away for a long weekend.

It is the wrong way round.

When you connect it up push the blade into the house so that you can see the small space for the end of the cable through the cut out in the housing (the bit that is normally covered with the rubber boot). Hook the cable into place. Then rotate the power valve 180 degrees in the housing. Now the cable cannot slip out.

All the best

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

[Mik_RX125]

Thanks I'll sort that out this weekend!!

Maybe it'll work properly as my new floats should arrive soon (Ordered them 22nd Nov 04!!)

Mik
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Yamaha FZ6 Fazer S2 owner
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[Mik_RX125]

BLOODY HELL!
Got a new cable for the powervalve today and a new gasket. Put the valve in the correct way round after covering it with 2st oil. An took it for a spin.

That little bastard almost threw me off rite away. Thought I'd beat a bigger bike at the lights but my front wheel had other ideas and lifted right away!!
It holds its speed better and has much more power at lower revs.

I just can't believe that switching it around could make such a difference.

Thanks for all the help Kickstart (Keith)

Mik
____________________
Yamaha FZ6 Fazer S2 owner
See all my Bikes

[Kickstart]

Hi

No problem. Glad it has improved things.

It is quite common for the power valves to be put in the wrong way. I have seen dealers put them in wrong on new bikes.

All the best

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