OP
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Hello All! I finally got my hands on a Scooter - 1977 Bajaj 150, which's a clone of Vespa 150. The scooter is in pretty good shape and I have been working on it since a fortnight.

The issue is this though - when I kick start the scooter, there is this low noise from the engine bay which dies down when the clutch is pulled in.
Other than this, the scooter rides decently, neat acceleration as well.

Could you guys help me out in figuring out the problem?
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Hooked
66 50s mildly tickled, 65 Bajaj 150 8" of fun
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Location: Aucks.... deep dirty south
 
Hooked
66 50s mildly tickled, 65 Bajaj 150 8" of fun
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Posts: 177
Location: Aucks.... deep dirty south
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what do you mean by a low noise is it a rattling grinding whining??? also any other symptoms is the clutch releasing fully? not dragging.

I assume the gearbox has oil in it?.... have you had the engine apart??
@rob_hodge avatar
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Molto Verboso
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Molto Verboso
@rob_hodge avatar
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It's worn crankshaft bearings.

As they wear they get loose. When you pull the clutch lever, it compresses the clutch witc,h pushes on the main bearings, pushing them to one side and taking the slop out of them.

It's not necissarily the end of the world, nor worth srripping the engine just for that issue. Ple nty of vintage bikes have the same issue and as long as you take care of the engine andrun the propper oil mixture it rarely escalates or gets worse.
OP
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BFR wrote:
what do you mean by a low noise is it a rattling grinding whining??? also any other symptoms is the clutch releasing fully? not dragging.

I assume the gearbox has oil in it?.... have you had the engine apart??
Its more of a whining and not so apparent unless one carefully listens. Clutch engages smoothly and no drag.
Still haven't had the chance to check the gear oil. Am just trying to evaluate the state of the machine by doing a few occasional runs and splitting the engine is certainly in the cards - in about a month or so.
rob hodge wrote:
It's worn crankshaft bearings.

As they wear they get loose. When you pull the clutch lever, it compresses the clutch witc,h pushes on the main bearings, pushing them to one side and taking the slop out of them.

It's not necissarily the end of the world, nor worth srripping the engine just for that issue. Ple nty of vintage bikes have the same issue and as long as you take care of the engine andrun the propper oil mixture it rarely escalates or gets worse.
Although I work on my motorcycle, scooters are totally new to me and what you say does make sense. But my idea is to turn the scoot into a fair bit of tourer that can do decent speeds. So my question is, with the engine untouched, can I ride it at speeds of 70-80kmph? Would it survive the stress?

Thank you all for you inputs!
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Ossessionato
a lambretta or two
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Ossessionato
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a lambretta or two
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"Turning it into a tourer" by doing nothing other than riding as if it were a "tourer?" It's like magic!!


Put your hand on the flywheel. Use your other hand to pull in the clutch lever. Do you feel the flywheel move? If so, at the very least you will need new bearings. At the most you will need new bearings AND a new crank.
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SFvsr wrote:
"Turning it into a tourer" by doing nothing other than riding as if it were a "tourer?" It's like magic!!


Put your hand on the flywheel. Use your other hand to pull in the clutch lever. Do you feel the flywheel move? If so, at the very least you will need new bearings. At the most you will need new bearings AND a new crank.
Haha, I certainly do not want magic here!
Well, I did clean up the scoot, carb, lubed the cables and cleaned up the engine.
Tried wiggling the flywheel sideways and there s no slack.
So does that mean the bearings are okay? Sorry if am being too naive here.

About getting the hands dirty, office sucks right now and hence its gonna be a while before I completely tear apart the engine to check the state of affairs.
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Veni, Vidi, Posti
a not so normal vbb2 '64, a weirdo vbx '86, a not so normal pts100 '82 and a yellow sunshine '74 sprint
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Veni, Vidi, Posti
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a not so normal vbb2 '64, a weirdo vbx '86, a not so normal pts100 '82 and a yellow sunshine '74 sprint
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it appear ur clutch basket get worn, but are u sure ur bearing is oke ?
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