Scooter main bearings

[Ichy]

The main bearing on my boys scooter need changing, or at least thats why I think its rattling, banging, and squeaking. I took the side cover off to have a look and noticed a fair bit of play in the main shaft.

It a typhoon 80 and since I know little to nothing about auto scooters I'm looking for advice. Scoot appears to be running fine, just noisy. The bike had partially seized due to the oil pump belt breaking.


Does my description sound like dodgy bearings?
How much work is involved with changing them?
Any advice on the best way to go about removing them from the crank and then getting them back on?
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[baldy]

There should be no movement in the main shaft. When my bro's speedfight 100 seized up, it used to rattle and rumble after. It also did it when the main bearing collapsed.

They are fairly easy to change, but while you're in there you might as well change the piston and rings along with the small end bearing. All you have to do it take the top end off, remove the flywheel, stator coils and other electrical crap in there, remove the six or eight bolts from the casing and pull it apart. Try not to bash the casings apart with anything other than a wooden or rubber mallet or you can break the casings. Once yo have split the casings, remove the seals carefully unless you are replacing them (i would, as the movement in the shaft would cause accelerated wear) and tap the bearing out (i always use a socket for this). Do the same for the other side but you have to remove the variator and belt first. Don't hammer the end of the crank shaft because it will fold the end of the threads over and fuck them up.
Assembly is the reverse of removal, but make sure that everything is clean, and there is no old gasket material left on the mating faces. I find that the bearings are easier to get in the casings if you cover them in 2 stroke oil first. Make sure that you drive them in squarely, otherwise they will just go again after 50 miles. When you put the crank in, coer everything in a coating of 2 stroke, as the engine will be dry of oil untill the pump gets working. Use all new gaskets, it's not worth having to strip the engine down again because one of the old ones is leaking. Also try to find a manual, (i know haynes do a general scooter manual that has all the data in it, i have one) as it will have all the torque values in it for the various bolts. And don't forget to run it in if you fit a new piston.

Hope this helps.
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One day i will rule the world, just not today.

[lonner]

[Ichy]

Cheers Baldy. It took longer to source parts than it did to strip down

Good general advice. Only thing I would add is that I prefer to heat up the bearing and drop them onto the crank then heat up the cases to ease the bearings in. At the end of the day, whatever works for you is best.

Mr Ion, it was just a test
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[chillpill]

i say just put a typhoon 125 engine in it , 80 engines are rare and parts will be expenisve , i know exactly what needs to be done for the conversion if you want more info its easy

[Ichy]

Thanks for the offer, I'll save it for next time. Surprising how easy it was to get parts, only one that caused problems was the oil pump drive belt.
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[chillpill]

fair enuff

putting the main bearings and the crank in a sealy bag and whack them in the frezzer overnight will make them much easier to fit

heat up the cases with a hot air gun before you put the bearings in and theyll slot in without any fuss , its not a really technical job but is time consuming

as for the oil pump id just leave that out , run it on 33:1 premix an oilpump is just another thing that could break

[Ichy]

Tell me about it, the failed belt is what caused all the problems in the first place.
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