rs125 help needed..

[neatbik]

hi, a friend of mine bought an rs125 (aprilia) last week, all was well till it started boiling over. i bled the system with no luck, and also removed the thermostat but its still boiling over - at this point im thinking the headgasket might have gone - but today another problem arose... suddenly the bike started vibrating badly and nasty noises were coming from the bottom end. i drained the gearbox oil to check the condition of it and found small pieces of what looked like plastic. im thinking maybe the plastic gears have knackered up, but thought i'd post on here to see if anyone can give me some pointers before i start stripping it down.
cheers

[Kickstart]

Hi

With plastic in the gearbox oil and a load of vibration then I would say it is likely the gears driving the balance shaft have died. These are a service item.

Also possible it is the drive for the water pump / oil pump. From memory this is plastic as well.

All the best

Keith
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[neatbik]

hi, we stripped it down and found 2 of the plastic gears had self destructed, so we replaced them. Then after putting the engine back together and test riding it started smoking like a trooper. We pulled out the spark plug and smoke came out of the combustion chamber - im thinking the rings have gone, but it still doesent explain (i think) the very bad vibrations coming from the bottom end. Im a bit stumped with this, or at least hesitant to take the engine to pieces..

[Timmeh]

To me, trashed rings, stripped cog teeth and noise from bottom end indicates that the bike's been thrashed until it seized, so a complete rebuild will be required.

Right, Keith?
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GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
20:22:30 BLUEX5: i would love to be forced to undergo a**l plugging with different sizes
20:48:18 Temeluchus: comp you hunk of smouldering homos3x you

[neatbik]

thats what ive been thinking... im not really keen on trying to rebuild it to be honest as i have neither the spare time, or the knowledge.. can anyone reccomend someone good to do it?
cheers

[Kickstart]

Hi

The cogs stripping is not that unusual. They should be replaced at 15000km, but I suspect most get ignored. Make sure you have set the balance shaft up correctly, otherwise you will make the vibration even worse.

I change rings on my RS125 at 6000km. Service schedule says to check them at 8000km, but to check them means pulling the engine apart far enough that you may as well replace them. However not sure why you think worn rings would have any effect on smoke coming out of the spark plug hole when you remove the plug from a hot engine (it is a 2 stroke, rings are not there to keep the oil in the bottom end of the engine).

All the best

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