series 2 200 weird noise/gearing

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bishopsfinger
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Hi all! i have a series 2 with a stage 4 sil 200 motor and i have 2 queries
1) there is a strange noise rather like a slipping fanbelt on a car emanating from the flywheel side,its not the flywheel scraping the cowl,its intermittent and very annoying!
2) Top gear seems very low and its screaming its balls off at 60,the rest of the box is nice,if a little jumpy,3rd and fourth are very close together,would changing the front sprocket make all the difference? thanks!
bristolmod
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need to establish:-

1) what gear box is installed in said engine
2) what size front sprocket is fitted
3) what size rear sprocket is fitted

Which means a strip down and count I'm afraid.

The fact that 3 and 4 are "very close" is a tad worrying- is this related to the odd noises emanating? Odd gears fitted??

Chris
Scootering since 1968.
bishopsfinger
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hi chris,thanks for your reply,i believe the engine is standard and untampered with but ill have a butchers in there when i get a min,the noise is deff from the flywheel side and worse on tickover,not overly loud,i would have thought any noisy gears would be silenced with the clutch in
bishopsfinger
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done a bit more research and the consensus is that the sil gp200 box has a very close gap between 3rd and 4th,great for accelaration but im more of a cruiser!
bristolmod
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assuming its a standard SIL cogbox, then a larger front sprocket may be beneficial if there's sufficient power to pull it- obviously need to see what sprocket is on at the mo and go up, say, one tooth.( care re chain length)

As for the noise.......... poorly fitted flywheel? (try lapping in flywheel to crank); flywheel catching on pickup/ stator area?? Hard to diagnose without being there I'm afraid

Chris
Scootering since 1968.
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GP240
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same as Chris,

Fly-wheel rubbing on stator. (if electronic, magnet coming loose in flywheel).
Old Lambretta's never die, they get tuned..................
steeleyscoot
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Saw something very similar on a mates Lammy recently, turned out the caged needle-roller bearing assembly on the gearbox end-plate that the 'xmas tree' fits into was knackered, made an awful screeching noise and stumped us to begin with, I replaced all the gearbox bearings and the screeching noise went away.
bishopsfinger
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hi all and thanks for your help,im going to try a slightly larger sprocket,will going up one tooth need a change of chain? as for the noise it seems to be coming from the top end.Small end bearing?
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RICSPEED
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im more concerned about the noise .. is there any evidence of chain catching end plate studs ??
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bishopsfinger
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I would have thought that would be noisy all the time,I was out on it earlier and te noise was coming and going,no pattern at all,whatever it's doing it's doing it gently ! Sounds like the whirring noise a sports bike makes if that makes sense?
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