Aprilia rs 125 rotax 123 engine help please :)

[jez125]

Hello i have just purchaced a non runner it a 123 rotax 1996 Aprilia 125, the top end is all new with good compresion and spark

Bad points

Bottom end, not entirly sure what is wrong

will not select gear have tryed adjusting gear selecter (didnt work)

Engine is now out of the bike i removed the casing on the clutch side to find where the rev counter cable goes in (white plastic gear was broken)

erm but yeah not to sure and ideas cheers

also i have been offered a swap for my whole engine 123 rotax and £190 cash, for a fully working rebuilt 2006 rotax 122 engine with wiring loom is that worth it? and would i need the carb of the new one cheers Jez

[Kickstart]

Hi

Forget the 122 for now. It is not a direct bolt in job (front mount is different), the 122 has no cable rev counter drive and the ignition is totally different. While it would be possible to do a conversion you would need every bit of the wiring, including the clocks and cdi unit.

Who did the rebuild? Did it ever change gear since then?

All the best

Keith
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[jez125]

ok erm just asked the people I got it off and waiting for a reply from them

[Kickstart]

Hi

Entirely possible to screw up assembling the gearbox so it won't change gear. If it were rebuilt by someone reputable then I would expect them to warrant their rebuild.

If it were rebuilt by some random bod with a big hammer I would be inclined to just have it rebuilt again by someone reputable to avoid the main bearings committing suicide within a few hundred km (*).

All the best

Keith

(*) You need special tools to pull the crank into the crankcases, NOT just press the cases together over the crank. If you do the lattor then you put a large sideways force onto the main bearings and they will rapidly fail.
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[jez125]

k the previous owners bought the bike with out a top end and he himself put the new top end on but bottom end wasnt working bit silly putting all that on knowing bottom end wasnt working so thats all i know from them if thats any help

[jez125]

which do you recon would be more cost effective to have the bottom end rebuilt or to get the 122 engine which he said he would give me the cdi + all wiring loom and clocks etc

[thomp1983]

the fact your having to ask would make me suspect your mechanical skills aren't the best so id stay away from buying an engine that isn't a straight bolt in job a if you have to pay someone to sort it out it will get expensive very quickly.
you say the bike won't change gear but is it currently in neutral at the minute? if it's in neutral and the engine turns over freely by hand you should be able to get it started or find the reason it won't

chris

[Kickstart]

Hi

Depends on how much work you can do yourself and the condition of the 122 engine.

If you can do everything yourself (including fitting the new subframe under the front of the engine, welding on a mount for the cdi unit, modifying the front fairing mount for the new clocks, etc) then the 122 engine might be more cost effective. However if the 122 needs a new piston and rings then that probably counts out the saving.

All the best

Keith
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