Vespa VBA is quieter when clutch is engaged
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Lurker
Vespa VBA1T, 1960.
Joined: 21 Apr 2016
Posts: 4
Location: Sweden
Sun Jun 28, 2020 1:47 am quote
Hi!

I have been struggling to understand why the engine becomes quieter when the clutch is engaged. The sound becomes deeper and less "open". Bought the VBA, split the engine and changed everything from oil seals, to cylinder. It is almost like new beside the engine casing. With that said, I've no reference if this is normal or not.

If it is not normal, do you guys have any ideas why and what could be the cause? I like it when it's quieter so I would love to have that always and not just when the clutch is engaged

Any advice is helpful!
Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '64 VBB
Joined: 27 Mar 2013
Posts: 620
Location: S.Salem, NY
Sun Jun 28, 2020 2:28 am quote
The crank turns the clutch bell and through the clamped pressure of the plates, the input shaft ( X-mas tree) turns all the loose gears on the output shaft or axle. This is a constant-mesh transmission. The only thing not turning is the axle itself. When you engage the lever , which disengages the clutch, the only things turning are the crank and the clutch bell.
Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1423
Location: Siam
Sun Jun 28, 2020 5:23 am quote
I think it is normal. It happens that way on all my bikes, most noticeably so the GS160.
Lurker
Vespa VBA1T, 1960.
Joined: 21 Apr 2016
Posts: 4
Location: Sweden
Mon Jun 29, 2020 7:33 pm quote
Moto64 wrote:
The crank turns the clutch bell and through the clamped pressure of the plates, the input shaft ( X-mas tree) turns all the loose gears on the output shaft or axle. This is a constant-mesh transmission. The only thing not turning is the axle itself. When you engage the lever , which disengages the clutch, the only things turning are the crank and the clutch bell.
Simplicity is beautiful. Thank you!
Addicted
2007 Stella 150
Joined: 02 Nov 2019
Posts: 616
Location: Rochester, Minnesota
Tue Jun 30, 2020 5:07 am quote
Out of pure curiosity what oil are you using? Maybe a better oil or thicker oil if allowed in our gear box would quieten it down a bit? Maybe a modern gear oil made for that purpose if your not using one already? I don't notice much noise over all the vibration on mine, but I'm curious next time I go out I'm going to listen and see if I can tell the difference. If all else fails get a louder muffler it'll cover up the gear noise.
Banned
2:6
Joined: 11 Jan 2007
Posts: 7566
Location: San Francisco
Tue Jun 30, 2020 5:37 am quote
if there is play in the main bearings, then pulling the clutch applies a side load that will make it run quieter.

If you press in on the flywheel with your hand (engine not running), and then pull the clutch you may feel the flywheel move out as the clutch is pulled.

how much is too much? I have no idea, but there is near none on a fresh rebuild.
Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '64 VBB
Joined: 27 Mar 2013
Posts: 620
Location: S.Salem, NY
Tue Jun 30, 2020 6:50 am quote
I see this often mentioned but I can't understand how an axial load on the clutch bell can transfer to the crank.
bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5299
Location: So Cal
Tue Jun 30, 2020 10:40 am quote
Moto64 wrote:
I see this often mentioned but I can't understand how an axial load on the clutch bell can transfer to the crank.
Load transfers from bell—> springs—> thrust washer—> clutch cog—> spacer —> crank
Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '64 VBB
Joined: 27 Mar 2013
Posts: 620
Location: S.Salem, NY
Tue Jun 30, 2020 11:08 am quote
Oh boy, I am sorry... I had small frames in my mind.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Tue Jun 30, 2020 11:28 am quote
Over filling the gear oil will help. A modern JASO MA2 oil will help even more.

Correct me if I'm wrong but I think the VBA had a really low oil level filler and on subsequent models the filler was moved higher.
Banned
2:6
Joined: 11 Jan 2007
Posts: 7566
Location: San Francisco
Tue Jun 30, 2020 11:34 am quote
Moto64 wrote:
Oh boy, I am sorry... I had small frames in my mind.
yup, smallframes are "normal"
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