HELP! Lambretta Gearbox noise

[The Hiwatts]

Hi all,

SX 200 casing with new rear hub bearing - Layshaft in, SX200 gearbox, new roller bearing and shim under Christmas tree, Gears in correct way and sit appropriately higher than the layshaft, shim and end plate roller bearing new, and large end plate bearing new, gear shim 2.5mm, with correct amount of tolerance between plate and shim! Gearbox turns nicely!!!

Wheel was on and not touching ground when I tightened it all up to take pressure of layshaft and gears etc etc!!!

Start scooter sounds like Keith Moon is smashing my gearbox up!!???

Can anyone help as I have now stripped and rebuilt the gearbox approximately 7 times and I am getting close to setting the thing on fire, and putting it out with a bat!!!!!!!!!

HEEEELLLLP!!!!!

Thanks in advance

[mick1]

Why the gearbox ? If it's making the noises when you start up then that's before the gearbox is engaged ?

Does the noise disappear when clutch engaged ?

[The Hiwatts]

Yes the usual disappears when clutch in - I've built loads of engines and I've either been lucky to never come across this, or something is drastically wrong??

[The Hiwatts]

And when I Mean start, as in scooter starts and on tick over!!!!

[The Hiwatts]

I'm going to change the chain and tighten it on the guides a bit more check alignment - it's definitely not the kick start teeth engaging on gear either just to narrow the issue down!!

[The Hiwatts]

Still no better - I'm sat here stumped now!!
I can't physically build the gear box any different? New bearings too!!
What a ball ache this has become!!!

[Doom Patrol]

Is it the chain chattering on a nylon tensioner?

[The Hiwatts]

Hi Doom, I have thought this as I have metal chain guides with rubber
Silencing material on them, not Nylon type?? However these were in engine before
Rebuild and I didn't have this noise?? Only thing I've not replaced
Is the layshaft??

[dapper]

If it's making the racket you say it is then there should be signs of wear somewhere or bits of metal/filings showing up. Are you sure it's not the top clutch plate being ground down by the kickstart shaft as the gap between these is minimal. Just be very methodical. It's only a feckin Lambretta for Gawd's sake. Rebuild the gearbox and check that it turns freely by hand in all gears. Install clutch without chain and check again that the gearbox/clutch turn freely by hand and no excessive rock in the rear sprocket. Try to check the chain alignment once reinstated. Check that your front sprocket is not grinding on your side casing and that it's installed correctly on the turretsIt's a case of elimination, my Dear Holmes

[coaster]

Yes the usual disappears when clutch in - I've built loads of engines and I've either been lucky to never come across this, or something is drastically wrong??

Disengaging the clutch just stops the Christmas tree from turning but might also stabilise the clutch assembly if it is 'wobbling' Check that the rear of the rear sprocket isn't able to catch on anything.

Did you check/replace the xmas tree bearings/end float? and clutch bush or bearings?