Lis 125 starting issues

[Kristof Lammy pie]

Right Barrel off. BAD news I think. I'm no pro but I'm guessing that there shouldn't be this much play in the big end bearing or small end.

[johnnyXS]

my spare engine has play like that on the big and small ends but that engine was well worn.
I'm sure that there needs to be some play but that looks like rather a lot on the face of it considering it was supposed to have been rebuilt so recently.
I haven't been able to find out what the acceptable tolerance is yet but I suspect it will be in the workshop manual if it isn't in Stickys guide.

Unless you are planning on rebuilding the entire crankcase I would just remove the piston and give it a good clean especially the ring lands and measure the ring gap in the cylinder bore. if that is within tolerance I'd be tempted to decoke it and stick it all back with some new gaskets . If you decide to do the big end bearings you'll need to remove the crank ...then you might as well recondition the entire engine and gearbox which is ging to be a lot of money and time .

[Kristof Lammy pie]

Not sure what to do now, kind of getting out of my depth a bit.

Need to sit down, have a beer and think what to do next.

[johnnyXS]

sorry Kris I added to my previous post after your last post so you may not have seen my ps.

Don't get disheartened . These engines often work perfectly well without being reconditioned for 30+ years .
This is what I added
'Unless you are planning on rebuilding the entire crankcase I would just remove the piston and give it a good clean especially the ring lands and measure the ring gap in the cylinder bore. if that is within tolerance I'd be tempted to decoke it and stick it all back with some new gaskets . If you decide to do the big end bearings you'll need to remove the crank ...then you might as well recondition the entire engine and gearbox which is ging to be a lot of money and time .'

[Kristof Lammy pie]

Drinking a Doom and looking at Stickys manual.

[Kristof Lammy pie]

The barrel feels smooth with gouges or nick's





Slight mark on the barrel but you can't feel it



I'm confused as this looks like an original barrel and head?

Any ideas anyone?

[johnnyXS]

have a look at the top of the piston Chris It should be marked if its oversized .
If the bore is ok and the piston is not scored I would be tempted to hone the cylinder very lightly with some 250 grade wet n dry to remove the glaze and fit new standard rings to the piston and put it back together.
Its a pity you didn't test the compression before you removed the head because that would have told you something about the state of the engine components

[Kristof Lammy pie]

Before I took the barrel off if I put my fingers on top of the piston and t there was slight lateral movement which makes me think there is just too much movement from the bearings.

There is no up and down movement though.

The problem is the scoot is pretty much mint and I dont want to put a buggered motor in it. I'd rather do it properly at the start.

[Kristof Lammy pie]

The piston has 53 on the Crown.

[HxPaul]

If its the original crank,it wont have any shims,if the top end isn't shimmed you will get a lot of side play.

[Kristof Lammy pie]

If its the original crank,it wont have any shims,if the top end isn't shimmed you will get a lot of side play.

Sorry, so what's the best course of action then?

[HxPaul]

Get some piston shims,Scooter restorations stock them
http://www.scooterrestorations.com/lamb ... er-washer/

[Kristof Lammy pie]

Ok cheers.

Would you not worry about the lateral movement at the big end?

[HxPaul]

If you shim the piston,then you hardly get any sideplay.Innocenti used this method.

[Kristof Lammy pie]

Ok will whip the piston off tomorrow and clean it all up.


Am I right in thinking standard size piston is 52mm for a 125 and mine is a 53mm is that one size up?

[HxPaul]

52mm is the standard size for a 125cc. Scooter restorations sell pistons for 125 cc up to 53.4.

[rossclark]

Side float is acceptable in the big end if the small end is shimmed. It is acceptable in the small end if the big end is shimmed. It's not recommended to shim both ends.

There should not be any appreciable up and down play in the big or small end bearings.

[Kristof Lammy pie]

Right I couldn't wait. So I've taken the piston off.

There is lateral play in the big end but certainly no up down play at all.

The piston has been shimmed 1.2mm either side. And the piston is bang on 53mm.

Where do I go from here? Up shim on the piston and replace the rings?

[HxPaul]

I've just looked again at your video and there doesn't seem to be a lot of play at the piston end.When the cylinder is fitted the play you can see at the big end will be very much reduced.

[Kristof Lammy pie]

There's a tiny bit at the piston but not a lot.

Would you suggest using the same shims an just replacing the rings?